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Introducing Adafruit ItsyBitsy M4 Created by lady ada https://learn.adafruit.com/introducing-adafruit-itsybitsy-m4 Last updated on 2022-06-06 04:39:43 PM EDT ©Adafruit Industries Page 1 of 215 Table of Contents Overview Update the UF2 Bootloader 7 10 • Updating Your Bootloader 10 Pinouts 14 • • • • Power Pins Logic pins QSPI Flash and DotStar Other Pins 15 16 20 21 Arduino IDE Setup 21 Using with Arduino IDE 23 • • • • • • • • Install SAMD Support Install Adafruit SAMD Install Drivers (Windows 7 & 8 Only) Blink Successful Upload Compilation Issues Manually bootloading Ubuntu & Linux Issue Fix 24 24 26 28 29 29 30 30 Adapting Sketches to M0 & M4 31 • • • • • • • • • • • • • • • • • • • 31 31 31 32 33 34 34 34 35 35 36 36 36 37 37 38 38 38 39 Analog References Pin Outputs & Pullups Serial vs SerialUSB AnalogWrite / PWM on Feather/Metro M0 analogWrite() PWM range analogWrite() DAC on A0 Missing header files Bootloader Launching Aligned Memory Access Floating Point Conversion How Much RAM Available? Storing data in FLASH Pretty-Printing out registers M4 Performance Options CPU Speed (overclocking) Optimize Cache Max SPI and Max QSPI Enabling the Buck Converter on some M4 Boards What is CircuitPython? 39 • CircuitPython is based on Python • Why would I use CircuitPython? 40 40 CircuitPython on ItsyBitsy 41 • Set up CircuitPython Quick Start! • Further Information 41 41 ©Adafruit Industries Page 2 of 215 Installing the Mu Editor • Download and Install Mu • Starting Up Mu • Using Mu Creating and Editing Code • • • • Creating Code Editing Code Back to Editing Code... Naming Your Program File 43 44 45 45 46 47 49 50 51 Connecting to the Serial Console 51 • • • • 52 53 53 54 Are you using Mu? Serial Console Issues or Delays on Linux Setting Permissions on Linux Using Something Else? Interacting with the Serial Console 54 The REPL 57 • Entering the REPL • Interacting with the REPL • Returning to the Serial Console CircuitPython Libraries • • • • • • • • • • • • • The Adafruit Learn Guide Project Bundle The Adafruit CircuitPython Library Bundle Downloading the Adafruit CircuitPython Library Bundle The CircuitPython Community Library Bundle Downloading the CircuitPython Community Library Bundle Understanding the Bundle Example Files Copying Libraries to Your Board Understanding Which Libraries to Install Example: ImportError Due to Missing Library Library Install on Non-Express Boards Updating CircuitPython Libraries and Examples CircUp CLI Tool 58 59 61 62 63 65 65 66 66 67 67 68 68 71 72 72 73 Frequently Asked Questions 73 Welcome to the Community! 76 • • • • • Adafruit Discord CircuitPython.org Adafruit GitHub Adafruit Forums Read the Docs Advanced Serial Console on Windows • Windows 7 and 8.1 • What's the COM? • Install Putty Advanced Serial Console on Mac • What's the Port? ©Adafruit Industries 77 78 82 84 85 85 85 86 87 89 89 Page 3 of 215 • Connect with screen 90 "Uninstalling" CircuitPython 91 • Backup Your Code • Moving Circuit Playground Express to MakeCode • Moving to Arduino 91 92 93 Troubleshooting 94 • • • • • • • • • • • • • • • • • • • • • • • • • • • • 94 95 95 96 97 97 97 98 99 100 100 101 102 102 103 105 105 105 107 108 108 109 109 109 109 110 111 112 Always Run the Latest Version of CircuitPython and Libraries I have to continue using CircuitPython 5.x or earlier. Where can I find compatible libraries? Bootloader (boardnameBOOT) Drive Not Present Windows Explorer Locks Up When Accessing boardnameBOOT Drive Copying UF2 to boardnameBOOT Drive Hangs at 0% Copied CIRCUITPY Drive Does Not Appear or Disappears Quickly Device Errors or Problems on Windows Serial Console in Mu Not Displaying Anything code.py Restarts Constantly CircuitPython RGB Status Light CircuitPython 7.0.0 and Later CircuitPython 6.3.0 and earlier Serial console showing ValueError: Incompatible .mpy file CIRCUITPY Drive Issues Safe Mode To erase CIRCUITPY: storage.erase_filesystem() Erase CIRCUITPY Without Access to the REPL For the specific boards listed below: For SAMD21 non-Express boards that have a UF2 bootloader: For SAMD21 non-Express boards that do not have a UF2 bootloader: Running Out of File Space on SAMD21 Non-Express Boards Delete something! Use tabs On MacOS? Prevent & Remove MacOS Hidden Files Copy Files on MacOS Without Creating Hidden Files Other MacOS Space-Saving Tips Device Locked Up or Boot Looping CircuitPython Essentials 113 CircuitPython Pins and Modules 113 • • • • • • CircuitPython Pins import board I2C, SPI, and UART What Are All the Available Names? Microcontroller Pin Names CircuitPython Built-In Modules 114 114 115 117 118 118 CircuitPython Built-Ins 119 • • • • • • • 119 119 119 120 120 120 120 Thing That Are Built In and Work Flow Control Math Tuples, Lists, Arrays, and Dictionaries Classes, Objects and Functions Lambdas Random Numbers ©Adafruit Industries Page 4 of 215 CircuitPython Digital In & Out • Find the pins! • Read the Docs CircuitPython Analog In • • • • • • Creating the analog input get_voltage Helper Main Loop Changing It Up Wire it up Reading Analog Pin Values CircuitPython Analog Out • • • • Creating an analog output Setting the analog output Main Loop Find the pin CircuitPython PWM • • • • • • PWM with Fixed Frequency Create a PWM Output Main Loop PWM Output with Variable Frequency Wire it up Where's My PWM? CircuitPython Servo 120 122 125 125 126 126 126 127 127 131 132 132 132 133 133 137 137 139 139 139 140 146 147 • Servo Wiring • Standard Servo Code • Continuous Servo Code 147 149 150 CircuitPython Internal RGB LED 151 • • • • • 152 153 153 154 155 Create the LED Brightness Main Loop Making Rainbows (Because Who Doesn't Love 'Em!) Circuit Playground Express Rainbow CircuitPython NeoPixel • • • • • • • Wiring It Up The Code Create the LED NeoPixel Helpers Main Loop NeoPixel RGBW Read the Docs CircuitPython DotStar • • • • • • • Wire It Up The Code Create the LED DotStar Helpers Main Loop Is it SPI? Read the Docs ©Adafruit Industries 156 157 158 159 159 160 160 162 162 162 163 165 166 167 167 168 Page 5 of 215 CircuitPython UART Serial • • • • The Code Wire It Up Where's my UART? Trinket M0: Create UART before I2C CircuitPython I2C • • • • Wire It Up Find Your Sensor I2C Sensor Data Where's my I2C? CircuitPython HID Keyboard and Mouse • • • • • • • • CircuitPython Keyboard Emulator Create the Objects and Variables The Main Loop Non-US Keyboard Layouts CircuitPython Mouse Emulator Create the Objects and Variables CircuitPython HID Mouse Helpers Main Loop CircuitPython CPU Temp • Microcontroller Location • Reading the Microcontroller Temperature CircuitPython Storage • Logging the Temperature 168 170 171 173 175 175 176 179 180 181 183 183 185 185 186 186 188 189 189 190 190 190 192 194 CircuitPython Expectations 196 197 • • • • • • • 197 198 198 198 199 199 200 Always Run the Latest Version of CircuitPython and Libraries I have to continue using CircuitPython 3.x or 2.x, where can I find compatible libraries? Switching Between CircuitPython and Arduino The Difference Between Express And Non-Express Boards Non-Express Boards: Gemma, Trinket, and QT Py Differences Between CircuitPython and MicroPython Differences Between CircuitPython and Python UF2 Bootloader Details • • • • • • • • Entering Bootloader Mode Using the Mass Storage Bootloader Using the BOSSA Bootloader Running bossac on the command line Updating the bootloader Getting Rid of Windows Pop-ups Making your own UF2 Installing the bootloader on a fresh/bricked board Downloads • Files • Schematic & Fabrication Print ©Adafruit Industries 201 202 204 205 208 210 212 213 213 213 213 214 Page 6 of 215 Overview What's smaller than a Feather but larger than a Trinket? It's an Adafruit ItsyBitsy M4 Express featuring the Microchip ATSAMD51! Small, powerful, with a ultra fast ATSAMD51 Cortex M4 processor running at 120 MHz - this microcontroller board is perfect when you want something very compact, with a ton of horsepower and a bunch of pins. This Itsy is like a bullet train, with it's 120MHz Cortex M4 with floating point support and 512KB Flash and 192KB RAM. Your code will zig and zag and zoom, and with a bunch of extra peripherals for support, this will for sure be your favorite new chipset. ItsyBitsy M4 Express is only is only 1.4" long by 0.7" wide, but has 6 power pins, 23 digital GPIO pins (7 of which can be analog in, 2 x 1 MSPS analog out DACs, and 18 x PWM out). It's the same basic chip as the Adafruit Metro M4 (https://adafru.it/A5S) but really really small. So it's great once you've finished up a prototype on a Metro M4 or (the upcoming) Feather M4, and want to make the project much smaller. It even comes with 2MB of SPI Flash built in, for data logging, file storage, or CircuitPython code. The most exciting part of the ItsyBitsy M4 is that while you can use it with the Arduino IDE, we are shipping it with CircuitPython on board. When you plug it in, it will show up as a very small disk drive with main.py on it. Edit main.py with your favorite text editor to build your project using Python, the most popular programming language. No installs, IDE or compiler needed, so you can use it on any computer, even ©Adafruit Industries Page 7 of 215 ChromeBooks or computers you can't install software on. When you're done, unplug the Itsy' and your code will go with you. You can also use MakeCode (https://adafru.it/C9N)'s block-based GUI coding environment on this board. Here are some of the updates you can look forward to when using ItsyBitsy M4: • Same size, form-factor as the ItsyBitsy 32u4 (https://adafru.it/BjC) and ItsyBitsy M0 (https://adafru.it/Bl9), and nearly-identical pinout as both • ATSAMD51G19A 32-bit Cortex M4 core running at 120 MHz • Hardware DSP and floating point support • 512 KB flash, 192 KB RAM • 2 MB SPI FLASH chip for storing files and CircuitPython code storage. • 32-bit, 3.3V logic and power • Tons of GPIO! 23 x GPIO pins with following capabilities: ◦ Dual 1 MSPS 12 bit true analog DAC (A0 and A1) - can be used to play 12-bit stereo audio clips ◦ Dual 1 MSPS 12 bit ADC (7 analog pins some on ADC1 and some on ADC2) ◦ 6 x hardware SERCOM - Native hardware SPI, I2C and Serial all available ◦ 18 x PWM outputs - for servos, LEDs, etc ◦ No I2S. We have no idea why but I2S is only supported on the 64 pin version of this chip (ATSAMD51J19A) and we could only fit the 48 pin version (the ATSAMD51G19A) on this board. But there's a stereo DAC you could use? ◦ 8-bit Parallel capture controller (for camera/video in) ©Adafruit Industries Page 8 of 215 ◦ 1 x Special Vhigh output pin gives you the higher voltage from VBAT or VUSB, for driving NeoPixels, servos, and other 5V-logic devices. Digital 5 level-shifted output for high-voltage logic level output. ◦ Can drive NeoPixels or DotStars on any pins, with enough memory to drive 60,000+ pixels. DMA-NeoPixel support on the VHigh pin  (https://adafru.it/ xYD)so you can drive pixels without having to spend any processor time on it. • Built in crypto engines with AES (256 bit), true RNG, Pubkey controller • Native USB supported by every OS - can be used in Arduino or CircuitPython as USB serial console, Keyboard/Mouse HID, even a little disk drive for storing Python scripts. • Can be used with Arduino IDE or CircuitPython • Built in red pin #13 LED • Built in RGB DotStar LED • Reset button and pin • Power with either USB or external output (such as a battery) - it'll automatically switch over • Comes pre-loaded with the UF2 bootloader (https://adafru.it/wbC), which looks like a USB storage key. Simply drag firmware on to program, no special tools or drivers needed! It can be used to load up CircuitPython or Arduino IDE (it is bossa v1.8 compatible) Each order comes with one assembled and tested ItsyBitsy M4, with headers that can be soldered in for use with a breadboard. ItsyBitsy M4 comes with CircuitPython programmed in, but you can replace the code with Arduino if you like. ©Adafruit Industries Page 9 of 215 So what are you waiting for? Pick up a ItsyBitsy M4 today and be amazed at how easy and fast it is to get started with CircuitPython! Update the UF2 Bootloader Update the Bootloader on your SAMD51 M4 board to prevent a somewhat rare problem of parts of internal flash being overwritten on power-up. Your SAMD51 M4 board bootloader may need to be updated to fix an intermittent bug that can erase parts of internal flash. Updating Your Bootloader To see if you need to update your bootloader, get the UF2 boot drive to appear as a mounted drive on your computer, in a file browser window. If you're running MakeCode, click the reset button once. If you're running CircuitPython or an Arduino program, double-click the reset button. When you see the ...BOOT drive (FEATHERBOOT, METROM4BOOT, ITSYM4BOOT, PO RTALBOOT, etc.) , click the drive in the file browser window and then double-click the INFO_UF2.TXT file to see what's inside. The example screenshots below are for a PyGamer. What you see for your board will be largely the same except for the board name and the BOOT drive name. ©Adafruit Industries Page 10 of 215 The bootloader version is listed in INFO_UF2.TXT. In this example, the version is v3.6. 0. If the bootloader version you see is older than v3.9.0, you need to update. For instance, the bootloader above needs to be upgraded. Download the latest version of the bootloader updater from the circuitpython.org Downloads page for your board. ©Adafruit Industries Page 11 of 215 Latest board downloads https://adafru.it/Em8 • The bootloader updater will be named update-bootloadername_of_your_board-v3.9.0.uf2 or some later version. Drag that file from your D ownloads folder onto the BOOT drive: ©Adafruit Industries Page 12 of 215 After you drag the updater onto the boot drive, the red LED on the board will flicker and then blink slowly about five times. A few seconds later, the BOOT will appear in the Finder. After that, you can click on the BOOT drive and double-click INFO_UF2.TX T again to confirm you've updated the bootloader. ©Adafruit Industries Page 13 of 215 Pinouts Click here to view a PDF version of the pinout diagram (https://adafru.it/-Ar) ©Adafruit Industries Page 14 of 215 Power Pins The ItsyBitsy M4 Express has BAT G USB on the top left, right next to the micro USB port These pins are: BAT - battery input for an alternative power source to USB, the voltage can only be from 3.5V to 6VDC GND - Power/data ground USB - This is the same pin as the MicroUSB connector's 5V USB power pin. This should be used as an output to get 5V power from the USB port. Say if you need to power a bunch of NeoPixels or servos. You can always put any voltage you like into BAT and the circuitry will switch between BAT and USB dynamically for you. That means you can have a Batter backup that only gets enabled when USB is disconnected. If you want to add rechargeable power, a LiPoly backpack can be soldered into these three pins that will let you have a battery that is automatically recharged whenever USB is plugged in, then switches to LiPoly when on the go: Adafruit LiIon/LiPoly Backpack Add-On for Pro Trinket/ItsyBitsy If you have an ItsyBitsy or Pro Trinket you probably know it's the perfect little size for a portable project. This LiPoly backpack makes it really easy to do! Instead of wiring 2... https://www.adafruit.com/product/2124 ©Adafruit Industries Page 15 of 215 In addition to the three standard power pins, the ItsyBitsy M4 Express has a few more pins available for power sourcing: • 3V - this is the regulated output from the onboard regulator. You can draw 500mA whether powered by USB or battery. • Vhi - this is a special pin! It is a dual-Schottkey-diode connected output from BA T and USB. This means this will always have the higher-of-the-two voltages, but will always have power output. The voltage will about 5VDC when powered by USB, but can range from 3.5-6VDC when powered from battery. It's not regulated, but it is high-current, great for driving servos and NeoPixels. • EN - connected to the regulator enable, it will let you shut off power - when running on battery only. But at least you don't have to cut a trace or wire to  your battery. This pin does not affect power when using USB Logic pins This is the general purpose I/O pin set for the microcontroller. All logic is 3.3V. You can usually use 3V logic as an input to 5V, but the 3V Itsy pins should not be connected to 5V! Nearly all pins can do PWM output All pins can be interrupt inputs Please note this chip has hardware support for Serial, I2C and SPI but does not support I2S. We have no idea why but Atmel disabled I2S on the 48 QFN version of this chip. If you need I2S please pick up a Metro or Feather M4 as those use the I2Scapable 64-QFN  ¯\_(ツ)_/¯ ©Adafruit Industries Page 16 of 215 Along the right edge • #0 / RX - GPIO #0, also receive (input) pin for Serial1. PWM output • #1 / TX - GPIO #1, also transmit (output) pin for Serial1. PWM output • SDA and SCL - these are the I2C hardware interface pins. There's no pull up on this pin by default so when using with I2C, you may need a 2.2K-10K pullup on each to 3.3V. PWM output • #5 - GPIO #5. This is a special OUTPUT-only pin that can PWM. It is level-shifted up to Vhi voltage, so its perfect for driving NeoPixels that want a ~5V logic level input. You can use this with our NeoPixel DMA control library to automatically write NeoPixel data without needing any processor time (https://adafru.it/BkV). • #7 - GPIO #7 can PWM • #9 - GPIO #9 can PWM • #10 - GPIO #10 can PWM • #11 - GPIO #11 can PWM • #12 - GPIO #12 can PWM • #13 - GPIO #13 can PWM, is connected to the red LED next to the Reset button ©Adafruit Industries Page 17 of 215 Along the left edge • A0 - This pin is analog input  A0 but is also an analog output due to having a DAC (digital-to-analog converter). This is the first DAC, and is 'independent' of A1. You can set the raw voltage to anything from 0 to 3.3V, unlike PWM outputs this is a true analog output • A1 - This pin is analog input  A1 but is also an analog output due to having a DAC (digital-to-analog converter). This is the second DAC, and is 'independent' of A0. You can set the raw voltage to anything from 0 to 3.3V, unlike PWM outputs this is a true analog output • A2 thru A5 - These are each analog input as well as digital I/O pins. A4 and A5 have PWM output. (A4 and A5 cannot be used for PWM in CircuitPython.) • SCK/MOSI/MISO - These are the hardware SPI pins, you can use them as everyday GPIO pins but recommend keeping them free as they are best used for hardware SPI connections for high speed. MOSI and SCK have PWM output. (MOSI cannot be used for PWM in CircuitPython.) ©Adafruit Industries Page 18 of 215 Along the short edge: • #2 - GPIO #2, also analog input A6 and has PWM output. • #3 - GPIO #3. • #4 - GPIO #4. Can also do PWM output • SWCLK & SWDIO - These are the debug-interface pins, used if you want to reprogram the chip directly or attach a debugger. These pins are available in CircuitPython under the board module. Names that start with # are prefixed with D and other names are as is. So #0 / RX above is available as board.D0 and board.RX for example. Parallel Capture Peripheral There's a 'camera' input peripheral you can use with some camera chips to capture video with 8-bit data width. We thought this was neat so we made sure all those pins were available. Here are the PCC pins (left) and the Itsy M4 pins it's mapped to. Unlike other peripherals, you cannot mux these signals to other pins! • DEN1: SDA • DEN2: SCL • CLK: D4 • D0: RX • D1: TX • D2: D7 ©Adafruit Industries Page 19 of 215 • D3: D9 • D4: D10 • D5: D11 • D6: D13 • D7: D12 QSPI Flash and DotStar As part of the 'Express' series of boards, this ItsyBitsy is designed for use with CircuitPython. To make that easy, we have added two extra parts: a mini DotStar (RGB LED) and a 2 MB QSPI (Quad SPI) Flash chip The DotStar is connected to pin #6 (clock) and #8 (data) in Arduino, so just use our DotStar library (https://adafru.it/zbD) and set it up as a single-LED strand on pins 6 & 8. The DotStar is powered by the 3.3V power supply but that hasn't shown to make a big difference in brightness or color. The DotStar is also used by the bootloader to let you know if the device has enumerated correctly (green) or USB failure (red). In CircuitPython, the LED is used to indicate the run time status. The QSPI Flash is connected to 6 pins that are not brought out on the GPIO pads. This way you don't have to worry about the SPI flash colliding with other devices on the main SPI connection. QSPI is neat because it allows you to have 4 data in/out lines instead of just SPI's single line in and single line out. This means that QSPI is at least 4 times faster. But in reality is at least 10x faster because you can clock the QSPI peripheral much faster than a plain SPI peripheral However, the QSPI port is not also on an SERCOM. So, you have to either use the QSPI peripheral or bit-bang SPI if you want to talk to the chip. We have an Arduino library here which provides QSPI interfacing for Arduino (https://adafru.it/BeX). In CircuitPython, the QSPI flash is used natively by the interpreter and is read-only to user code, instead the Flash just shows up as the writable disk drive! ©Adafruit Industries Page 20 of 215 Other Pins RST - this is the Reset pin, tie to ground to manually reset the ATSAMD51, as well as launch the bootloader manually ARef - the analog reference pin. Normally the reference voltage is the same as the chip logic voltage (3.3V) but if you need an alternative analog reference, connect it to this pin and select the external AREF in your firmware. Can't go higher than 3.3V! Arduino IDE Setup The first thing you will need to do is to download the latest release of the Arduino IDE. You will need to be using version 1.8 or higher for this guide Arduino IDE Download https://adafru.it/f1P After you have downloaded and installed the latest version of Arduino IDE, you will need to start the IDE and navigate to the Preferences menu. You can access it from the File menu in Windows or Linux, or the Arduino menu on OS X. ©Adafruit Industries Page 21 of 215 A dialog will pop up just like the one shown below. We will be adding a URL to the new Additional Boards Manager URLs option. The list of URLs is comma separated, and you will only have to add each URL once. New Adafruit boards and updates to existing boards will automatically be picked up by the Board Manager each time it is opened. The URLs point to index files that the Board Manager uses to build the list of available & installed boards. To find the most up to date list of URLs you can add, you can visit the list of third party board URLs on the Arduino IDE wiki (https://adafru.it/f7U). We will only need to add one URL to the IDE in this example, but you can add multiple URLS by separating them with commas. Copy and paste the link below into the Additional Boards Manager URLs option in the Arduino IDE preferences. https://adafruit.github.io/arduino-board-index/ package_adafruit_index.json ©Adafruit Industries Page 22 of 215 Here's a short description of each of the Adafruit supplied packages that will be available in the Board Manager when you add the URL: • Adafruit AVR Boards - Includes support for Flora, Gemma, Feather 32u4, ItsyBitsy 32u4, Trinket, & Trinket Pro. • Adafruit SAMD Boards - Includes support for Feather M0 and M4, Metro M0 and M4, ItsyBitsy M0 and M4, Circuit Playground Express, Gemma M0 and Trinket M0 • Arduino Leonardo & Micro MIDI-USB - This adds MIDI over USB support for the Flora, Feather 32u4, Micro and Leonardo using the arcore project (https:// adafru.it/eSI). If you have multiple boards you want to support, say ESP8266 and Adafruit, have both URLs in the text box separated by a comma (,) Once done click OK to save the new preference settings. Next we will look at installing boards with the Board Manager. Now continue to the next step to actually install the board support package! Using with Arduino IDE The Feather/Metro/Gemma/QTPy/Trinket M0 and M4 use an ATSAMD21 or ATSAMD51 chip, and you can pretty easily get it working with the Arduino IDE. Most libraries (including the popular ones like NeoPixels and display) will work with the M0 and M4, especially devices & sensors that use I2C or SPI. Now that you have added the appropriate URLs to the Arduino IDE preferences in the previous page, you can open the Boards Manager by navigating to the Tools->Board  menu. ©Adafruit Industries Page 23 of 215 Once the Board Manager opens, click on the category drop down menu on the top left hand side of the window and select All. You will then be able to select and install the boards supplied by the URLs added to the preferences. Remember you need SETUP the Arduino IDE to support our board packages see the previous page on how to add adafruit's URL to the preferences Install SAMD Support First up, install the latest Arduino SAMD Boards (version 1.6.11 or later) You can type Arduino SAMD in the top search bar, then when you see the entry, click I nstall Install Adafruit SAMD Next you can install the Adafruit SAMD package to add the board file definitions Make sure you have Type All selected to the left of the Filter your search... box You can type Adafruit SAMD in the top search bar, then when you see the entry, click I nstall ©Adafruit Industries Page 24 of 215 Even though in theory you don't need to - I recommend rebooting the IDE Quit and reopen the Arduino IDE to ensure that all of the boards are properly installed. You should now be able to select and upload to the new boards listed in the Tools->Board menu. Select the matching board, the current options are: • Feather M0 (for use with any Feather M0 other than the Express) • Feather M0 Express • Metro M0 Express • Circuit Playground Express • Gemma M0 • Trinket M0 • QT Py M0 • ItsyBitsy M0 • Hallowing M0 • Crickit M0 (this is for direct programming of the Crickit, which is probably not what you want! For advanced hacking only) • Metro M4 Express • Grand Central M4 Express • ItsyBitsy M4 Express • Feather M4 Express • Trellis M4 Express • PyPortal M4 • PyPortal M4 Titano • PyBadge M4 Express • Metro M4 Airlift Lite • PyGamer M4 Express • MONSTER M4SK ©Adafruit Industries Page 25 of 215 • Hallowing M4 • MatrixPortal M4 • BLM Badge Install Drivers (Windows 7 & 8 Only) When you plug in the board, you'll need to possibly install a driver Click below to download our Driver Installer Download Latest Adafruit Drivers package https://adafru.it/mb8 Download and run the installer Run the installer! Since we bundle the SiLabs and FTDI drivers as well, you'll need to click through the license ©Adafruit Industries Page 26 of 215 Select which drivers you want to install, the defaults will set you up with just about every Adafruit board! Click Install to do the installin' ©Adafruit Industries Page 27 of 215 Blink Now you can upload your first blink sketch! Plug in the M0 or M4 board, and wait for it to be recognized by the OS (just takes a few seconds). It will create a serial/COM port, you can now select it from the dropdown, it'll even be 'indicated' as Trinket/Gemma/Metro/Feather/ItsyBitsy/Trellis! Please note, the QT Py and Trellis M4 Express are two of our very few boards that does not have an onboard pin 13 LED so you can follow this section to practice uploading but you wont see an LED blink! Now load up the Blink example // the setup function runs once when you press reset or power the board void setup() { // initialize digital pin 13 as an output. pinMode(13, OUTPUT); } // the loop function runs over and over again forever ©Adafruit Industries Page 28 of 215 void loop() { digitalWrite(13, HIGH); delay(1000); digitalWrite(13, LOW); delay(1000); } // // // // turn wait turn wait the for the for LED on (HIGH is the voltage level) a second LED off by making the voltage LOW a second And click upload! That's it, you will be able to see the LED blink rate change as you adapt the delay() calls. If you are having issues, make sure you selected the matching Board in the menu that matches the hardware you have in your hand. Successful Upload If you have a successful upload, you'll get a bunch of red text that tells you that the device was found and it was programmed, verified & reset After uploading, you may see a message saying "Disk Not Ejected Properly" about the ...BOOT drive. You can ignore that message: it's an artifact of how the bootloader and uploading work. Compilation Issues If you get an alert that looks like Cannot run program "{runtime.tools.arm-none-eabi-gcc.path}\bin\arm-non-eabi-g++" ©Adafruit Industries Page 29 of 215 Make sure you have installed the Arduino SAMD boards package, you need both Ard uino & Adafruit SAMD board packages Manually bootloading If you ever get in a 'weird' spot with the bootloader, or you have uploaded code that crashes and doesn't auto-reboot into the bootloader, click the RST button twice (like a double-click)to get back into the bootloader. The red LED will pulse and/or RGB LED will be green, so you know that its in bootloader mode. Once it is in bootloader mode, you can select the newly created COM/Serial port and re-try uploading. You may need to go back and reselect the 'normal' USB serial port next time you want to use the normal upload. Ubuntu & Linux Issue Fix  Follow the steps for installing Adafruit's udev rules on this page. (https://adafru.it/iOE) ©Adafruit Industries Page 30 of 215 Adapting Sketches to M0 & M4 The ATSAMD21 and 51 are very nice little chips, but fairly new as Arduino-compatible cores go. Most sketches & libraries will work but here’s a collection of things we noticed. The notes below cover a range of Adafruit M0 and M4 boards, but not every rule will apply to every board (e.g. Trinket and Gemma M0 do not have ARef, so you can skip the Analog References note!). Analog References If you'd like to use the ARef pin for a non-3.3V analog reference, the code to use is analogReference(AR_EXTERNAL) (it's AR_EXTERNAL not EXTERNAL) Pin Outputs & Pullups The old-style way of turning on a pin as an input with a pullup is to use pinMode(pin, INPUT) digitalWrite(pin, HIGH) This is because the pullup-selection register on 8-bit AVR chips is the same as the output-selection register. For M0 & M4 boards, you can't do this anymore! Instead, use: pinMode(pin, INPUT_PULLUP) Code written this way still has the benefit of being backwards compatible with AVR. You don’t need separate versions for the different board types. Serial vs SerialUSB 99.9% of your existing Arduino sketches use Serial.print to debug and give output. For the Official Arduino SAMD/M0 core, this goes to the Serial5 port, which isn't exposed on the Feather. The USB port for the Official Arduino M0 core is called SerialUSB instead. ©Adafruit Industries Page 31 of 215 In the Adafruit M0/M4 Core, we fixed it so that Serial goes to USB so it will automatically work just fine. However, on the off chance you are using the official Arduino SAMD core and not the Adafruit version (which really, we recommend you use our version because it’s been tuned to our boards), and you want your Serial prints and reads to use the USB port, use SerialUSB instead of Serial in your sketch. If you have existing sketches and code and you want them to work with the M0 without a huge find-replace, put #if defined(ARDUINO_SAMD_ZERO) && defined(SERIAL_PORT_USBVIRTUAL)   // Required for Serial on Zero based boards   #define Serial SERIAL_PORT_USBVIRTUAL #endif right above the first function definition in your code. For example: AnalogWrite / PWM on Feather/Metro M0 After looking through the SAMD21 datasheet, we've found that some of the options listed in the multiplexer table don't exist on the specific chip used in the Feather M0. For all SAMD21 chips, there are two peripherals that can generate PWM signals: The Timer/Counter (TC) and Timer/Counter for Control Applications (TCC). Each SAMD21 has multiple copies of each, called 'instances'. Each TC instance has one count register, one control register, and two output channels. Either channel can be enabled and disabled, and either channel can be inverted. The pins connected to a TC instance can output identical versions of the same PWM waveform, or complementary waveforms. ©Adafruit Industries Page 32 of 215 Each TCC instance has a single count register, but multiple compare registers and output channels. There are options for different kinds of waveform, interleaved switching, programmable dead time, and so on. The biggest members of the SAMD21 family have five TC instances with two 'waveform output' (WO) channels, and three TCC instances with eight WO channels: • TC[0-4],WO[0-1] • TCC[0-2],WO[0-7] And those are the ones shown in the datasheet's multiplexer tables. The SAMD21G used in the Feather M0 only has three TC instances with two output channels, and three TCC instances with eight output channels: • TC[3-5],WO[0-1] • TCC[0-2],WO[0-7] Tracing the signals to the pins broken out on the Feather M0, the following pins can't do PWM at all: • Analog pin A5 The following pins can be configured for PWM without any signal conflicts as long as the SPI, I2C, and UART pins keep their protocol functions: • Digital pins 5, 6, 9, 10, 11, 12, and 13 • Analog pins A3 and A4 If only the SPI pins keep their protocol functions, you can also do PWM on the following pins: • TX and SDA (Digital pins 1 and 20) analogWrite() PWM range On AVR, if you set a pin's PWM with analogWrite(pin, 255) it will turn the pin fully HIGH. On the ARM cortex, it will set it to be 255/256 so there will be very slim but ©Adafruit Industries Page 33 of 215 still-existing pulses-to-0V. If you need the pin to be fully on, add test code that checks if you are trying to analogWrite(pin, 255) and, instead, does a digitalWrite(pin, HIGH) analogWrite() DAC on A0 If you are trying to use analogWrite() to control the DAC output on A0, make sure you do not have a line that sets the pin to output. Remove: pinMode(A0, OUTPUT) . Missing header files There might be code that uses libraries that are not supported by the M0 core. For example if you have a line with #include you'll get an error that says fatal error: util/delay.h: No such file or directory   #include                          ^ compilation terminated. Error compiling. In which case you can simply locate where the line is (the error will give you the file name and line number) and 'wrap it' with #ifdef's so it looks like: #if !defined(ARDUINO_ARCH_SAM) && !defined(ARDUINO_ARCH_SAMD) && ! defined(ESP8266) && !defined(ARDUINO_ARCH_STM32F2) #include <util/delay.h> #endif The above will also make sure that header file isn't included for other architectures If the #include is in the arduino sketch itself, you can try just removing the line. Bootloader Launching For most other AVRs, clicking reset while plugged into USB will launch the bootloader manually, the bootloader will time out after a few seconds. For the M0/M4, you'll need ©Adafruit Industries Page 34 of 215 to double click the button. You will see a pulsing red LED to let you know you're in bootloader mode. Once in that mode, it wont time out! Click reset again if you want to go back to launching code. Aligned Memory Access This is a little less likely to happen to you but it happened to me! If you're used to 8bit platforms, you can do this nice thing where you can typecast variables around. e.g. uint8_t mybuffer[4]; float f = (float)mybuffer; You can't be guaranteed that this will work on a 32-bit platform because mybuffer might not be aligned to a 2 or 4-byte boundary. The ARM Cortex-M0 can only directly access data on 16-bit boundaries (every 2 or 4 bytes). Trying to access an oddboundary byte (on a 1 or 3 byte location) will cause a Hard Fault and stop the MCU. Thankfully, there's an easy work around ... just use memcpy! uint8_t mybuffer[4]; float f; memcpy(&f, mybuffer, 4) Floating Point Conversion Like the AVR Arduinos, the M0 library does not have full support for converting floating point numbers to ASCII strings. Functions like sprintf will not convert floating point.  Fortunately, the standard AVR-LIBC library includes the dtostrf function which can handle the conversion for you. Unfortunately, the M0 run-time library does not have dtostrf.  You may see some references to using #include to get dtostrf in your code.  And while it will compile, it does not work. Instead, check out this thread to find a working dtostrf function you can include in your code: http://forum.arduino.cc/index.php?topic=368720.0 (https://adafru.it/lFS) ©Adafruit Industries Page 35 of 215 How Much RAM Available? The ATSAMD21G18 has 32K of RAM, but you still might need to track it for some reason. You can do so with this handy function: extern "C" char *sbrk(int i); int FreeRam () { char stack_dummy = 0; return &stack_dummy - sbrk(0); } Thx to http://forum.arduino.cc/index.php?topic=365830.msg2542879#msg2542879 (h ttps://adafru.it/m6D) for the tip! Storing data in FLASH If you're used to AVR, you've probably used PROGMEM to let the compiler know you'd like to put a variable or string in flash memory to save on RAM. On the ARM, its a little easier, simply add const before the variable name: const char str[] = "My very long string"; That string is now in FLASH. You can manipulate the string just like RAM data, the compiler will automatically read from FLASH so you dont need special progmemknowledgeable functions. You can verify where data is stored by printing out the address: Serial.print("Address of str $"); Serial.println((int)&str, HEX); If the address is $2000000 or larger, its in SRAM. If the address is between $0000 and $3FFFF Then it is in FLASH Pretty-Printing out registers There's a lot of registers on the SAMD21, and you often are going through ASF or another framework to get to them. So having a way to see exactly what's going on is handy. This library from drewfish will help a ton! https://github.com/drewfish/arduino-ZeroRegs (https://adafru.it/Bet) ©Adafruit Industries Page 36 of 215 M4 Performance Options As of version 1.4.0 of the Adafruit SAMD Boards package in the Arduino Boards Manager, some options are available to wring extra performance out of M4-based devices. These are in the Tools menu. All of these performance tweaks involve a degree of uncertainty. There’s no guarantee of improved performance in any given project, and some may even be detrimental, failing to work in part or in whole. If you encounter trouble, select the default performance settings and re-upload. Here’s what you get and some issues you might encounter… CPU Speed (overclocking) This option lets you adjust the microcontroller core clock…the speed at which it processes instructions…beyond the official datasheet specifications. Manufacturers often rate speeds conservatively because such devices are marketed for harsh industrial environments…if a system crashes, someone could lose a limb or worse. But most creative tasks are less critical and operate in more comfortable settings, and we can push things a bit if we want more speed. There is a small but nonzero chance of code locking up or failing to run entirely. If this happens, try dialing back the speed by one notch and re-upload, see if it’s more stable. Much more likely, some code or libraries may not play well with the nonstandard CPU speed. For example, currently the NeoPixel library assumes a 120 MHz CPU speed and won’t issue the correct data at other settings (this will be worked on). Other ©Adafruit Industries Page 37 of 215 libraries may exhibit similar problems, usually anything that strictly depends on CPU timing…you might encounter problems with audio- or servo-related code depending how it’s written. If you encounter such code or libraries, set the CPU speed to the default 120 MHz and re-upload. Optimize There’s usually more than one way to solve a problem, some more resource-intensive than others. Since Arduino got its start on resource-limited AVR microcontrollers, the C++ compiler has always aimed for the smallest compiled program size. The “Optimize” menu gives some choices for the compiler to take different and often faster approaches, at the expense of slightly larger program size…with the huge flash memory capacity of M4 devices, that’s rarely a problem now. The “Small” setting will compile your code like it always has in the past, aiming for the smallest compiled program size. The “Fast” setting invokes various speed optimizations. The resulting program should produce the same results, is slightly larger, and usually (but not always) noticably faster. It’s worth a shot! “Here be dragons” invokes some more intensive optimizations…code will be larger still, faster still, but there’s a possibility these optimizations could cause unexpected behaviors. Some code may not work the same as before. Hence the name. Maybe you’ll discover treasure here, or maybe you’ll sail right off the edge of the world. Most code and libraries will continue to function regardless of the optimizer settings. If you do encounter problems, dial it back one notch and re-upload. Cache This option allows a small collection of instructions and data to be accessed more quickly than from flash memory, boosting performance. It’s enabled by default and should work fine with all code and libraries. But if you encounter some esoteric situation, the cache can be disabled, then recompile and upload. Max SPI and Max QSPI These should probably be left at their defaults. They’re present mostly for our own experiments and can cause serious headaches. ©Adafruit Industries Page 38 of 215 Max SPI determines the clock source for the M4’s SPI peripherals. Under normal circumstances this allows transfers up to 24 MHz, and should usually be left at that setting. But…if you’re using write-only SPI devices (such as TFT or OLED displays), this option lets you drive them faster (we’ve successfully used 60 MHz with some TFT screens). The caveat is, if using any read/write devices (such as an SD card), this will not work at all…SPI reads absolutely max out at the default 24 MHz setting, and anything else will fail. Write = OK. Read = FAIL. This is true even if your code is using a lower bitrate setting…just having the different clock source prevents SPI reads. Max QSPI does similarly for the extra flash storage on M4 “Express” boards. Very few Arduino sketches access this storage at all, let alone in a bandwidth-constrained context, so this will benefit next to nobody. Additionally, due to the way clock dividers are selected, this will only provide some benefit when certain “CPU Speed” settings are active. Our PyPortal Animated GIF Display (https://adafru.it/EkO) runs marginally better with it, if using the QSPI flash. Enabling the Buck Converter on some M4 Boards If you want to reduce power draw, some of our boards have an inductor so you can use the 1.8V buck converter instead of the built in linear regulator. If the board does have an inductor (see the schematic) you can add the line SUPC->VREG.bit.SEL = 1; to your code to switch to it. Note it will make ADC/DAC reads a bit noisier so we don't use it by default. You'll save ~4mA (https://adafru.it/F0H). What is CircuitPython? CircuitPython is a programming language designed to simplify experimenting and learning to program on low-cost microcontroller boards. It makes getting started easier than ever with no upfront desktop downloads needed. Once you get your board set up, open any text editor, and get started editing code. It's that simple. ©Adafruit Industries Page 39 of 215 CircuitPython is based on Python Python is the fastest growing programming language. It's taught in schools and universities. It's a high-level programming language which means it's designed to be easier to read, write and maintain. It supports modules and packages which means it's easy to reuse your code for other projects. It has a built in interpreter which means there are no extra steps, like compiling, to get your code to work. And of course, Python is Open Source Software which means it's free for anyone to use, modify or improve upon. CircuitPython adds hardware support to all of these amazing features. If you already have Python knowledge, you can easily apply that to using CircuitPython. If you have no previous experience, it's really simple to get started! Why would I use CircuitPython? CircuitPython is designed to run on microcontroller boards. A microcontroller board is a board with a microcontroller chip that's essentially an itty-bitty all-in-one computer. The board you're holding is a microcontroller board! CircuitPython is easy to use because all you need is that little board, a USB cable, and a computer with a USB connection. But that's only the beginning. Other reasons to use CircuitPython include: • You want to get up and running quickly. Create a file, edit your code, save the file, and it runs immediately. There is no compiling, no downloading and no uploading needed. • You're new to programming. CircuitPython is designed with education in mind. It's easy to start learning how to program and you get immediate feedback from the board. ©Adafruit Industries Page 40 of 215 • Easily update your code. Since your code lives on the disk drive, you can edit it whenever you like, you can also keep multiple files around for easy experimentation. • The serial console and REPL. These allow for live feedback from your code and interactive programming. • File storage. The internal storage for CircuitPython makes it great for datalogging, playing audio clips, and otherwise interacting with files. • Strong hardware support. There are many libraries and drivers for sensors, breakout boards and other external components. • It's Python! Python is the fastest-growing programming language. It's taught in schools and universities. CircuitPython is almost-completely compatible with Python. It simply adds hardware support. This is just the beginning. CircuitPython continues to evolve, and is constantly being updated. Adafruit welcomes and encourages feedback from the community, and incorporate it into the development of CircuitPython. That's the core of the open source concept. This makes CircuitPython better for you and everyone who uses it! CircuitPython on ItsyBitsy CircuitPython (https://adafru.it/tB7) is a derivative of MicroPython (https://adafru.it/BeZ) designed to simplify experimentation and education on low-cost microcontrollers. It makes it easier than ever to get prototyping by requiring no upfront desktop software downloads. Simply copy and edit files on the CIRCUITPY drive to iterate. Set up CircuitPython Quick Start! Follow this quick step-by-step for super-fast Python power :) Download the latest version of CircuitPython for this board via CircuitPython.org https://adafru.it/Emj Further Information For more detailed info on installing CircuitPython, check out Installing CircuitPython (h ttps://adafru.it/Amd). ©Adafruit Industries Page 41 of 215 Click the link above and download the latest UF2 file. Download and save it to your desktop (or wherever is handy). Plug your Itsy M4 into your computer using a known-good USB cable. A lot of people end up using charge-only USB cables and it is very frustrating! So make sure you have a USB cable you know is good for data sync. Double-click the Reset button on your board, and you will see the DotStar RGB LED turn green. If it turns red, check the USB cable, try another USB port, etc. If double-clicking doesn't work the first time, try again. Sometimes it can take a few tries to get the rhythm right! ©Adafruit Industries Page 42 of 215 You will see a new disk drive appear called ITSYBOOT. Drag the adafruit_circuitpython_etc.uf2 file to ITSYBOOT. The LED will flash. Then, the ITSYBOOT drive will disappear and a new disk drive called CIRCUITPY will appear. That's it, you're done! :) Installing the Mu Editor Mu is a simple code editor that works with the Adafruit CircuitPython boards. It's written in Python and works on Windows, MacOS, Linux and Raspberry Pi. The serial console is built right in so you get immediate feedback from your board's serial output! ©Adafruit Industries Page 43 of 215 Mu is our recommended editor - please use it (unless you are an experienced coder with a favorite editor already!). Download and Install Mu Download Mu from https:// codewith.mu (https://adafru.it/Be6). Click the Download link for downloads and installation instructions. Click Start Here to find a wealth of other information, including extensive tutorials and and how-to's.   Windows users: due to the nature of MSI installers, please remove old versions of Mu before installing the latest version. Ubuntu users: Mu currently (checked May 4, 2022) does not install properly on Ubuntu 22.04. See https://github.com/mu-editor/mu/issues to track this issue. See https://learn.adafruit.com/welcome-to-circuitpython/recommended-editors and https://learn.adafruit.com/welcome-to-circuitpython/pycharm-andcircuitpython for other editors to use. ©Adafruit Industries Page 44 of 215 Starting Up Mu The first time you start Mu, you will be prompted to select your 'mode' - you can always change your mind later. For now please select CircuitPython! The current mode is displayed in the lower right corner of the window, next to the "gear" icon. If the mode says "Microbit" or something else, click the Mode button in the upper left, and then choose "CircuitPython" in the dialog box that appears. Mu attempts to auto-detect your board on startup, so if you do not have a CircuitPython board plugged in with a CIRCUITPY drive available, Mu will inform you where it will store any code you save until you plug in a board. To avoid this warning, plug in a board and ensure that the CIRCUITPY drive is mounted before starting Mu. Using Mu You can now explore Mu! The three main sections of the window are labeled below; the button bar, the text editor, and the serial console / REPL. ©Adafruit Industries Page 45 of 215 Now you're ready to code! Let's keep going... Creating and Editing Code One of the best things about CircuitPython is how simple it is to get code up and running. This section covers how to create and edit your first CircuitPython program. To create and edit code, all you'll need is an editor. There are many options. Adafruit strongly recommends using Mu! It's designed for CircuitPython, and it's really simple and easy to use, with a built in serial console! If you don't or can't use Mu, there are a number of other editors that work quite well. The Recommended Editors page (https://adafru.it/Vue) has more details. Otherwise, make sure you do "Eject" or "Safe Remove" on Windows or "sync" on Linux after writing a file if you aren't using Mu. (This is not a problem on MacOS.) ©Adafruit Industries Page 46 of 215 Creating Code Installing CircuitPython generates a code.py file on your CIRCUITPY drive. To begin your own program, open your editor, and load the code.py file from the CIRCUITPY drive. If you are using Mu, click the Load button in the button bar, navigate to the CIRCUITPY drive, and choose code.py. Copy and paste the following code into your editor: import board import digitalio import time led = digitalio.DigitalInOut(board.LED) led.direction = digitalio.Direction.OUTPUT while True: led.value = True time.sleep(0.5) led.value = False time.sleep(0.5) The KB2040, QT Py and the Trinkeys do not have a built-in little red LED! There is an addressable RGB NeoPixel LED. The above example will NOT work on the KB2040, QT Py or the Trinkeys! If you're using a KB2040, QT Py or a Trinkey, please download the NeoPixel blink example (https://adafru.it/UDU). The NeoPixel blink example uses the onboard NeoPixel, but the time code is the same. You can use the linked NeoPixel Blink example to follow along with this guide page. ©Adafruit Industries Page 47 of 215 It will look like this. Note that under the while True: line, the next four lines begin with four spaces to indent them, and they're indented exactly the same amount. All the lines before that have no spaces before the text. Save the code.py file on your CIRCUITPY drive. The little LED should now be blinking. Once per half-second. Congratulations, you've just run your first CircuitPython program! On most boards you'll find a tiny red LED. On the ItsyBitsy nRF52840, you'll find a tiny blue LED. On QT Py M0, QT Py RP2040, and the Trinkey series, you will find only an RGB NeoPixel LED. ©Adafruit Industries Page 48 of 215 Editing Code To edit code, open the code.py file on your CIRCUITPY drive into your editor.   Make the desired changes to your code. Save the file. That's it! Your code changes are run as soon as the file is done saving. There's one warning before you continue... Don't click reset or unplug your board! The CircuitPython code on your board detects when the files are changed or written and will automatically re-start your code. This makes coding very fast because you save, and it re-runs. If you unplug or reset the board before your computer finishes writing the file to your board, you can corrupt the drive. If this happens, you may lose the code you've written, so it's important to backup your code to your computer regularly. There are a couple of ways to avoid filesystem corruption. 1. Use an editor that writes out the file completely when you save it. Check out the Recommended Editors page (https://adafru.it/Vue) for details on different editing options. If you are dragging a file from your host computer onto the CIRCUITPY drive, you still need to do step 2. Eject or Sync (below) to make sure the file is completely written. ©Adafruit Industries Page 49 of 215 2. Eject or Sync the Drive After Writing If you are using one of our not-recommended-editors, not all is lost! You can still make it work. On Windows, you can Eject or Safe Remove the CIRCUITPY drive. It won't actually eject, but it will force the operating system to save your file to disk. On Linux, use the sync command in a terminal to force the write to disk. You also need to do this if you use Windows Explorer or a Linux graphical file manager to drag a file onto CIRCUITPY. Oh No I Did Something Wrong and Now The CIRCUITPY Drive Doesn't Show Up!!! Don't worry! Corrupting the drive isn't the end of the world (or your board!). If this happens, follow the steps found on the Troubleshooting (https://adafru.it/Den) page of every board guide to get your board up and running again. Back to Editing Code... Now! Let's try editing the program you added to your board. Open your code.py file into your editor. You'll make a simple change. Change the first 0.5 to 0.1 . The code should look like this: import board import digitalio import time led = digitalio.DigitalInOut(board.LED) led.direction = digitalio.Direction.OUTPUT while True: led.value = True time.sleep(0.1) led.value = False time.sleep(0.5) Leave the rest of the code as-is. Save your file. See what happens to the LED on your board? Something changed! Do you know why? You don't have to stop there! Let's keep going. Change the second 0.5 to 0.1 so it looks like this: ©Adafruit Industries Page 50 of 215 while True: led.value = True time.sleep(0.1) led.value = False time.sleep(0.1) Now it blinks really fast! You decreased the both time that the code leaves the LED on and off! Now try increasing both of the 0.1 to 1 . Your LED will blink much more slowly because you've increased the amount of time that the LED is turned on and off. Well done! You're doing great! You're ready to start into new examples and edit them to see what happens! These were simple changes, but major changes are done using the same process. Make your desired change, save it, and get the results. That's really all there is to it! Naming Your Program File CircuitPython looks for a code file on the board to run. There are four options: code.tx t, code.py, main.txt and main.py. CircuitPython looks for those files, in that order, and then runs the first one it finds. While code.py is the recommended name for your code file, it is important to know that the other options exist. If your program doesn't seem to be updating as you work, make sure you haven't created another code file that's being read instead of the one you're working on. Connecting to the Serial Console One of the staples of CircuitPython (and programming in general!) is something called a "print statement". This is a line you include in your code that causes your code to output text. A print statement in CircuitPython (and Python) looks like this: print("Hello, world!") This line in your code.py would result in: Hello, world! However, these print statements need somewhere to display. That's where the serial console comes in! ©Adafruit Industries Page 51 of 215 The serial console receives output from your CircuitPython board sent over USB and displays it so you can see it. This is necessary when you've included a print statement in your code and you'd like to see what you printed. It is also helpful for troubleshooting errors, because your board will send errors and the serial console will display those too. The serial console requires an editor that has a built in terminal, or a separate terminal program. A terminal is a program that gives you a text-based interface to perform various tasks. Are you using Mu? If so, good news! The serial console is built into Mu and will autodetect your board making using the serial console really really easy. First, make sure your CircuitPython board is plugged in. If you open Mu without a board plugged in, you may encounter the error seen here, letting you know no CircuitPython board was found and indicating where your code will be stored until you plug in a board. If you are using Windows 7, make sure you installed the drivers (https://adafru.it/VuB). Once you've opened Mu with your board plugged in, look for the Serial button in the button bar and click it. The Mu window will split in two, horizontally, and display the serial console at the bottom. ©Adafruit Industries Page 52 of 215 If nothing appears in the serial console, it may mean your code is done running or has no print statements in it. Click into the serial console part of Mu, and press CTRL+D to reload. Serial Console Issues or Delays on Linux If you're on Linux, and are seeing multi-second delays connecting to the serial console, or are seeing "AT" and other gibberish when you connect, then the modemmanager service might be interfering. Just remove it; it doesn't have much use unless you're still using dial-up modems. To remove modemmanager , type the following command at a shell: sudo apt purge modemmanager Setting Permissions on Linux On Linux, if you see an error box something like the one below when you press the S erial button, you need to add yourself to a user group to have permission to connect to the serial console. On Ubuntu and Debian, add yourself to the dialout group by doing: sudo adduser $USER dialout After running the command above, reboot your machine to gain access to the group. On other Linux distributions, the group you need may be different. See the Advanced ©Adafruit Industries Page 53 of 215 Serial Console on Linux (https://adafru.it/VAO) for details on how to add yourself to the right group. Using Something Else? If you're not using Mu to edit, are using or if for some reason you are not a fan of its built in serial console, you can run the serial console from a separate program. Windows requires you to download a terminal program. Check out the Advanced Serial Console on Windows page for more details. (https://adafru.it/AAH) MacOS has Terminal built in, though there are other options available for download. C heck the Advanced Serial Console on Mac page for more details. (https://adafru.it/ AAI) Linux has a terminal program built in, though other options are available for download. Check the Advanced Serial Console on Linux page for more details. (https: //adafru.it/VAO) Once connected, you'll see something like the following. Interacting with the Serial Console Once you've successfully connected to the serial console, it's time to start using it. The code you wrote earlier has no output to the serial console. So, you're going to edit it to create some output. Open your code.py file into your editor, and include a print statement. You can print anything you like! Just include your phrase between the quotation marks inside the parentheses. For example: import board import digitalio import time ©Adafruit Industries Page 54 of 215 led = digitalio.DigitalInOut(board.LED) led.direction = digitalio.Direction.OUTPUT while True: print("Hello, CircuitPython!") led.value = True time.sleep(1) led.value = False time.sleep(1) Save your file. Now, let's go take a look at the window with our connection to the serial console. Excellent! Our print statement is showing up in our console! Try changing the printed text to something else. import board import digitalio import time led = digitalio.DigitalInOut(board.LED) led.direction = digitalio.Direction.OUTPUT while True: print("Hello back to you!") led.value = True time.sleep(1) led.value = False time.sleep(1) Keep your serial console window where you can see it. Save your file. You'll see what the serial console displays when the board reboots. Then you'll see your new change! ©Adafruit Industries Page 55 of 215 The Traceback (most recent call last): is telling you the last thing your board was doing before you saved your file. This is normal behavior and will happen every time the board resets. This is really handy for troubleshooting. Let's introduce an error so you can see how it is used. Delete the e at the end of True from the line led.value = True so that it says le d.value = Tru import board import digitalio import time led = digitalio.DigitalInOut(board.LED) led.direction = digitalio.Direction.OUTPUT while True: print("Hello back to you!") led.value = Tru time.sleep(1) led.value = False time.sleep(1) Save your file. You will notice that your red LED will stop blinking, and you may have a colored status LED blinking at you. This is because the code is no longer correct and can no longer run properly. You need to fix it! Usually when you run into errors, it's not because you introduced them on purpose. You may have 200 lines of code, and have no idea where your error could be hiding. This is where the serial console can help. Let's take a look! The Traceback (most recent call last): is telling you that the last thing it was able to run was line 10 in your code. The next line is your error: NameError: name 'Tru' is not defined . This error might not mean a lot to you, but combined with knowing the issue is on line 10, it gives you a great place to start! ©Adafruit Industries Page 56 of 215 Go back to your code, and take a look at line 10. Obviously, you know what the problem is already. But if you didn't, you'd want to look at line 10 and see if you could figure it out. If you're still unsure, try googling the error to get some help. In this case, you know what to look for. You spelled True wrong. Fix the typo and save your file. Nice job fixing the error! Your serial console is streaming and your red LED Is blinking again. The serial console will display any output generated by your code. Some sensors, such as a humidity sensor or a thermistor, receive data and you can use print statements to display that information. You can also use print statements for troubleshooting, which is called "print debugging". Essentially, if your code isn't working, and you want to know where it's failing, you can put print statements in various places to see where it stops printing. The serial console has many uses, and is an amazing tool overall for learning and programming! The REPL The other feature of the serial connection is the Read-Evaluate-Print-Loop, or REPL. The REPL allows you to enter individual lines of code and have them run immediately. It's really handy if you're running into trouble with a particular program and can't figure out why. It's interactive so it's great for testing new ideas. ©Adafruit Industries Page 57 of 215 Entering the REPL To use the REPL, you first need to be connected to the serial console. Once that connection has been established, you'll want to press CTRL+C. If there is code running, in this case code measuring distance, it will stop and you'll see Press any key to enter the REPL. Use CTRL-D to reload. Follow those instructions, and press any key on your keyboard. The Traceback (most recent call last): is telling you the last thing your board was doing before you pressed Ctrl + C and interrupted it. The KeyboardInterrupt is you pressing CTRL+C. This information can be handy when troubleshooting, but for now, don't worry about it. Just note that it is expected behavior. If your code.py file is empty or does not contain a loop, it will show an empty output and Code done running. . There is no information about what your board was doing before you interrupted it because there is no code running. If you have no code.py on your CIRCUITPY drive, you will enter the REPL immediately after pressing CTRL+C. Again, there is no information about what your board was doing before you interrupted it because there is no code running. ©Adafruit Industries Page 58 of 215 Regardless, once you press a key you'll see a >>> prompt welcoming you to the REPL! If you have trouble getting to the >>> prompt, try pressing Ctrl + C a few more times. The first thing you get from the REPL is information about your board. This line tells you the version of CircuitPython you're using and when it was released. Next, it gives you the type of board you're using and the type of microcontroller the board uses. Each part of this may be different for your board depending on the versions you're working with. This is followed by the CircuitPython prompt. Interacting with the REPL From this prompt you can run all sorts of commands and code. The first thing you'll do is run help() . This will tell you where to start exploring the REPL. To run code in the REPL, type it in next to the REPL prompt. Type help() next to the prompt in the REPL. Then press enter. You should then see a message. ©Adafruit Industries Page 59 of 215 First part of the message is another reference to the version of CircuitPython you're using. Second, a URL for the CircuitPython related project guides. Then... wait. What's this? To list built-in modules type `help("modules")`. Remember the modules you learned about while going through creating code? That's exactly what this is talking about! This is a perfect place to start. Let's take a look! Type help("modules") into the REPL next to the prompt, and press enter. This is a list of all the core modules built into CircuitPython, including board . Remember, board contains all of the pins on the board that you can use in your code. From the REPL, you are able to see that list! Type import board into the REPL and press enter. It'll go to a new prompt. It might look like nothing happened, but that's not the case! If you recall, the import statement simply tells the code to expect to do something with that module. In this case, it's telling the REPL that you plan to do something with that module. Next, type dir(board) into the REPL and press enter. This is a list of all of the pins on your board that are available for you to use in your code. Each board's list will differ slightly depending on the number of pins available. Do you see LED ? That's the pin you used to blink the red LED! ©Adafruit Industries Page 60 of 215 The REPL can also be used to run code. Be aware that any code you enter into the REPL isn't saved anywhere. If you're testing something new that you'd like to keep, make sure you have it saved somewhere on your computer as well! Every programmer in every programming language starts with a piece of code that says, "Hello, World." You're going to say hello to something else. Type into the REPL: print("Hello, CircuitPython!") Then press enter. That's all there is to running code in the REPL! Nice job! You can write single lines of code that run stand-alone. You can also write entire programs into the REPL to test them. Remember that nothing typed into the REPL is saved. There's a lot the REPL can do for you. It's great for testing new ideas if you want to see if a few new lines of code will work. It's fantastic for troubleshooting code by entering it one line at a time and finding out where it fails. It lets you see what modules are available and explore those modules. Try typing more into the REPL to see what happens! Everything typed into the REPL is ephemeral. Once you reload the REPL or return to the serial console, nothing you typed will be retained in any memory space. So be sure to save any desired code you wrote somewhere else, or you'll lose it when you leave the current REPL instance! Returning to the Serial Console When you're ready to leave the REPL and return to the serial console, simply press CT RL+D. This will reload your board and reenter the serial console. You will restart the program you had running before entering the REPL. In the console window, you'll see any output from the program you had running. And if your program was affecting anything visual on the board, you'll see that start up again as well. ©Adafruit Industries Page 61 of 215 You can return to the REPL at any time! CircuitPython Libraries As CircuitPython development continues and there are new releases, Adafruit will stop supporting older releases. Visit https://circuitpython.org/downloads to download the latest version of CircuitPython for your board. You must download the CircuitPython Library Bundle that matches your version of CircuitPython. Please update CircuitPython and then visit https://circuitpython.org/libraries to download the latest Library Bundle. Each CircuitPython program you run needs to have a lot of information to work. The reason CircuitPython is so simple to use is that most of that information is stored in other files and works in the background. These files are called libraries. Some of them are built into CircuitPython. Others are stored on your CIRCUITPY drive in a folder called lib. Part of what makes CircuitPython so great is its ability to store code separately from the firmware itself. Storing code separately from the firmware makes it easier to update both the code you write and the libraries you depend. Your board may ship with a lib folder already, it's in the base directory of the drive. If not, simply create the folder yourself. When you first install CircuitPython, an empty lib directory will be created for you. CircuitPython libraries work in the same way as regular Python modules so the Python docs (https://adafru.it/rar) are an excellent reference for how it all should work. In ©Adafruit Industries Page 62 of 215 Python terms, you can place our library files in the lib directory because it's part of the Python path by default. One downside of this approach of separate libraries is that they are not built in. To use them, one needs to copy them to the CIRCUITPY drive before they can be used. Fortunately, there is a library bundle. The bundle and the library releases on GitHub also feature optimized versions of the libraries with the .mpy file extension. These files take less space on the drive and have a smaller memory footprint as they are loaded. Due to the regular updates and space constraints, Adafruit does not ship boards with the entire bundle. Therefore, you will need to load the libraries you need when you begin working with your board. You can find example code in the guides for your board that depends on external libraries. Either way, as you start to explore CircuitPython, you'll want to know how to get libraries on board. The Adafruit Learn Guide Project Bundle The quickest and easiest way to get going with a project from the Adafruit Learn System is by utilising the Project Bundle. Most guides now have a Download Project Bundle button available at the top of the full code example embed. This button downloads all the necessary files, including images, etc., to get the guide project up and running. Simply click, open the resulting zip, copy over the right files, and you're good to go! The first step is to find the Download Project Bundle button in the guide you're working on. The Download Project Bundle button is only available on full demo code embedded from GitHub in a Learn guide. Code snippets will NOT have the button available. ©Adafruit Industries Page 63 of 215 When you copy the contents of the Project Bundle to your CIRCUITPY drive, it will replace all the existing content! If you don't want to lose anything, ensure you copy your current code to your computer before you copy over the new Project Bundle content! The Download Project Bundle button downloads a zip file. This zip contains a series of directories, nested within which is the code.py, any applicable assets like images or audio, and the lib/ folder containing all the necessary libraries. The following zip was downloaded from the Piano in the Key of Lime guide (https://adafru.it/-cW). When you open the zip, you'll find some nested directories. Navigate through them until you find what you need. You'll eventually find a directory for your CircuitPython version (in this case, 7.x). In the version directory, you'll find the file and directory you need: code.py and lib/. Once you find the content you need, you can copy it all over to your CIRCUITPY drive, replacing any files already on the drive with the files from the freshly downloaded zip. ©Adafruit Industries Page 64 of 215 In some cases, there will be other files such as audio or images in the same directory as code.py and lib/. Make sure you include all the files when you copy things over! Once you copy over all the relevant files, the project should begin running! If you find that the project is not running as expected, make sure you've copied ALL of the project files onto your microcontroller board. That's all there is to using the Project Bundle! The Adafruit CircuitPython Library Bundle Adafruit provides CircuitPython libraries for much of the hardware they provide, including sensors, breakouts and more. To eliminate the need for searching for each library individually, the libraries are available together in the Adafruit CircuitPython Library Bundle. The bundle contains all the files needed to use each library. Downloading the Adafruit CircuitPython Library Bundle You can download the latest Adafruit CircuitPython Library Bundle release by clicking the button below. The libraries are being constantly updated and improved, so you'll always want to download the latest bundle.  Match up the bundle version with the version of CircuitPython you are running. For example, you would download the 6.x library bundle if you're running any version of CircuitPython 6, or the 7.x library bundle if you're running any version of CircuitPython 7, etc. If you mix libraries with major CircuitPython versions, you will get incompatible mpy errors due to changes in library interfaces possible during major version changes. Click to visit circuitpython.org for the latest Adafruit CircuitPython Library Bundle https://adafru.it/ENC Download the bundle version that matches your CircuitPython firmware version. If you don't know the version, check the version info in boot_out.txt file on the CIRCUITPY drive, or the initial prompt in the CircuitPython REPL. For example, if you're running v7.0.0, download the 7.x library bundle. ©Adafruit Industries Page 65 of 215 There's also a py bundle which contains the uncompressed python files, you probably don't want that unless you are doing advanced work on libraries. The CircuitPython Community Library Bundle The CircuitPython Community Library Bundle is made up of libraries written and provided by members of the CircuitPython community. These libraries are often written when community members encountered hardware not supported in the Adafruit Bundle, or to support a personal project. The authors all chose to submit these libraries to the Community Bundle make them available to the community. These libraries are maintained by their authors and are not supported by Adafruit. As you would with any library, if you run into problems, feel free to file an issue on the GitHub repo for the library. Bear in mind, though, that most of these libraries are supported by a single person and you should be patient about receiving a response. Remember, these folks are not paid by Adafruit, and are volunteering their personal time when possible to provide support. Downloading the CircuitPython Community Library Bundle You can download the latest CircuitPython Community Library Bundle release by clicking the button below. The libraries are being constantly updated and improved, so you'll always want to download the latest bundle. Click for the latest CircuitPython Community Library Bundle release https://adafru.it/VCn The link takes you to the latest release of the CircuitPython Community Library Bundle on GitHub. There are multiple versions of the bundle available. Download the bundle version that matches your CircuitPython firmware version. If you don't know the version, check the version info in boot_out.txt file on the CIRCUITPY drive, or the initial prompt in the CircuitPython REPL. For example, if you're running v7.0.0, download the 7.x library bundle. ©Adafruit Industries Page 66 of 215 Understanding the Bundle After downloading the zip, extract its contents. This is usually done by double clicking on the zip. On Mac OSX, it places the file in the same directory as the zip. Open the bundle folder. Inside you'll find two information files, and two folders. One folder is the lib bundle, and the other folder is the examples bundle. Now open the lib folder. When you open the folder, you'll see a large number of .mpy files, and folders. Example Files All example files from each library are now included in the bundles in an examples directory (as seen above), as well as an examples-only bundle. These are included for two main reasons: • Allow for quick testing of devices. • Provide an example base of code, that is easily built upon for individualized purposes. ©Adafruit Industries Page 67 of 215 Copying Libraries to Your Board First open the lib folder on your CIRCUITPY drive. Then, open the lib folder you extracted from the downloaded zip. Inside you'll find a number of folders and .mpy files. Find the library you'd like to use, and copy it to the lib folder on CIRCUITPY. If the library is a directory with multiple .mpy files in it, be sure to copy the entire folder to CIRCUITPY/lib. This also applies to example files. Open the examples folder you extracted from the downloaded zip, and copy the applicable file to your CIRCUITPY drive. Then, rename it to code.py to run it. If a library has multiple .mpy files contained in a folder, be sure to copy the entire folder to CIRCUITPY/lib. Understanding Which Libraries to Install You now know how to load libraries on to your CircuitPython-compatible microcontroller board. You may now be wondering, how do you know which libraries you need to install? Unfortunately, it's not always straightforward. Fortunately, there is an obvious place to start, and a relatively simple way to figure out the rest. First up: the best place to start. When you look at most CircuitPython examples, you'll see they begin with one or more import statements. These typically look like the following: • import library_or_module ©Adafruit Industries Page 68 of 215 However, import statements can also sometimes look like the following: • from library_or_module import name • from library_or_module.subpackage import name • from library_or_module import name as local_name They can also have more complicated formats, such as including a try / except block, etc. The important thing to know is that an import statement will always include the name of the module or library that you're importing. Therefore, the best place to start is by reading through the import statements. Here is an example import list for you to work with in this section. There is no setup or other code shown here, as the purpose of this section involves only the import list. import time import board import neopixel import adafruit_lis3dh import usb_hid from adafruit_hid.consumer_control import ConsumerControl from adafruit_hid.consumer_control_code import ConsumerControlCode Keep in mind, not all imported items are libraries. Some of them are almost always built-in CircuitPython modules. How do you know the difference? Time to visit the REPL. In the Interacting with the REPL section (https://adafru.it/Awz) on The REPL page (http s://adafru.it/Awz) in this guide, the help("modules") command is discussed. This command provides a list of all of the built-in modules available in CircuitPython for your board. So, if you connect to the serial console on your board, and enter the REPL, you can run help("modules") to see what modules are available for your board. Then, as you read through the import statements, you can, for the purposes of figuring out which libraries to load, ignore the statement that import modules. The following is the list of modules built into CircuitPython for the Feather RP2040. Your list may look similar or be anything down to a significant subset of this list for smaller boards. ©Adafruit Industries Page 69 of 215 Now that you know what you're looking for, it's time to read through the import statements. The first two, time and board , are on the modules list above, so they're built-in. The next one, neopixel , is not on the module list. That means it's your first library! So, you would head over to the bundle zip you downloaded, and search for neopixel. There is a neopixel.mpy file in the bundle zip. Copy it over to the lib folder on your CI RCUITPY drive. The following one, adafruit_lis3dh , is also not on the module list. Follow the same process for adafruit_lis3dh, where you'll find adafruit_lis3dh.mpy, and copy that over. The fifth one is usb_hid , and it is in the modules list, so it is built in. Often all of the built-in modules come first in the import list, but sometimes they don't! Don't assume that everything after the first library is also a library, and verify each import with the modules list to be sure. Otherwise, you'll search the bundle and come up empty! The final two imports are not as clear. Remember, when import statements are formatted like this, the first thing after the from is the library name. In this case, the library name is adafruit_hid . A search of the bundle will find an adafruit_hid folder. When a library is a folder, you must copy the entire folder and its contents as it is in the bundle to the lib folder on your CIRCUITPY drive. In this case, you would copy the entire adafruit_hid folder to your CIRCUITPY/lib folder. Notice that there are two imports that begin with adafruit_hid . Sometimes you will need to import more than one thing from the same library. Regardless of how many times you import the same library, you only need to load the library by copying over the adafruit_hid folder once. That is how you can use your example code to figure out what libraries to load on your CircuitPython-compatible board! ©Adafruit Industries Page 70 of 215 There are cases, however, where libraries require other libraries internally. The internally required library is called a dependency. In the event of library dependencies, the easiest way to figure out what other libraries are required is to connect to the serial console and follow along with the ImportError printed there. The following is a very simple example of an ImportError , but the concept is the same for any missing library. Example: ImportError Due to Missing Library If you choose to load libraries as you need them, or you're starting fresh with an existing example, you may end up with code that tries to use a library you haven't yet loaded.  This section will demonstrate what happens when you try to utilise a library that you don't have loaded on your board, and cover the steps required to resolve the issue. This demonstration will only return an error if you do not have the required library loaded into the lib folder on your CIRCUITPY drive. Let's use a modified version of the Blink example. import board import time import simpleio led = simpleio.DigitalOut(board.LED) while True: led.value = True time.sleep(0.5) led.value = False time.sleep(0.5) Save this file. Nothing happens to your board. Let's check the serial console to see what's going on. ©Adafruit Industries Page 71 of 215 You have an ImportError . It says there is no module named 'simpleio' . That's the one you just included in your code! Click the link above to download the correct bundle. Extract the lib folder from the downloaded bundle file. Scroll down to find simpleio.mpy. This is the library file you're looking for! Follow the steps above to load an individual library file. The LED starts blinking again! Let's check the serial console. No errors! Excellent. You've successfully resolved an ImportError ! If you run into this error in the future, follow along with the steps above and choose the library that matches the one you're missing. Library Install on Non-Express Boards If you have an M0 non-Express board such as Trinket M0, Gemma M0, QT Py M0, or one of the M0 Trinkeys, you'll want to follow the same steps in the example above to install libraries as you need them. Remember, you don't need to wait for an ImportEr ror if you know what library you added to your code. Open the library bundle you downloaded, find the library you need, and drag it to the lib folder on your CIRCUITPY drive. You can still end up running out of space on your M0 non-Express board even if you only load libraries as you need them. There are a number of steps you can use to try to resolve this issue. You'll find suggestions on the Troubleshooting page (https:// adafru.it/Den). Updating CircuitPython Libraries and Examples Libraries and examples are updated from time to time, and it's important to update the files you have on your CIRCUITPY drive. ©Adafruit Industries Page 72 of 215 To update a single library or example, follow the same steps above. When you drag the library file to your lib folder, it will ask if you want to replace it. Say yes. That's it! A new library bundle is released every time there's an update to a library. Updates include things like bug fixes and new features. It's important to check in every so often to see if the libraries you're using have been updated. CircUp CLI Tool There is a command line interface (CLI) utility called CircUp (https://adafru.it/Tfi) that can be used to easily install and update libraries on your device. Follow the directions on the install page within the CircUp learn guide (https://adafru.it/-Ad). Once you've got it installed you run the command circup update in a terminal to interactively update all libraries on the connected CircuitPython device. See the usage page in the CircUp guide (https://adafru.it/-Ah) for a full list of functionality Frequently Asked Questions These are some of the common questions regarding CircuitPython and CircuitPython microcontrollers. As CircuitPython development continues and there are new releases, Adafruit will stop supporting older releases. Visit https://circuitpython.org/downloads to download the latest version of CircuitPython for your board. You must download the CircuitPython Library Bundle that matches your version of CircuitPython. Please update CircuitPython and then visit https://circuitpython.org/libraries to download the latest Library Bundle. I have to continue using CircuitPython 6.x or earlier. Where can I find compatible libraries? We are no longer building or supporting the CircuitPython 6.x or earlier library bundles. We highly encourage you to update CircuitPython to the latest version (https://adafru.it/Em8) and use the current version of the libraries (https:// adafru.it/ENC). However, if for some reason you cannot update, here are the last available library bundles for older versions: • 2.x bundle (https://adafru.it/FJA) • 3.x bundle (https://adafru.it/FJB) • 4.x bundle (https://adafru.it/QDL) • 5.x bundle (https://adafru.it/QDJ) ©Adafruit Industries Page 73 of 215 • 6.x bundle (https://adafru.it/Xmf) Is ESP8266 or ESP32 supported in CircuitPython? Why not? We dropped ESP8266 support as of 4.x - For more information please read about it here (https://adafru.it/CiG)! We do not support ESP32 because it does not have native USB. We do support ESP32-S2, which has native USB. How do I connect to the Internet with CircuitPython? If you'd like to include WiFi in  your project, check out this guide (https://adafru.it/ F5X) on using AirLift with CircuitPython. For further project examples, and guides about using AirLift with specific hardware, check out the Adafruit Learn System (https://adafru.it/VBr). Is there asyncio support in CircuitPython? There is preliminary support for asyncio starting with CircuitPython 7.1.0. Read about using it in the Cooperative Multitasking in CircuitPython (https://adafru.it/ XnA) Guide. My RGB NeoPixel/DotStar LED is blinking funny colors what does it mean? The status LED can tell you what's going on with your CircuitPython board. Read more here for what the colors mean! (https://adafru.it/Den) What is a MemoryError? Memory allocation errors happen when you're trying to store too much on the board. The CircuitPython microcontroller boards have a limited amount of memory available. You can have about 250 lines of code on the M0 Express boards. If you try to import too many libraries, a combination of large libraries, or run a program with too many lines of code, your code will fail to run and you will receive a MemoryError in the serial console. ©Adafruit Industries Page 74 of 215 What do I do when I encounter a MemoryError? Try resetting your board. Each time you reset the board, it reallocates the memory. While this is unlikely to resolve your issue, it's a simple step and is worth trying. Make sure you are using .mpy versions of libraries. All of the CircuitPython libraries are available in the bundle in a .mpy format which takes up less memory than .py format. Be sure that you're using the latest library bundle (https://adafru.it/uap) for your version of CircuitPython. If that does not resolve your issue, try shortening your code. Shorten comments, remove extraneous or unneeded code, or any other clean up you can do to shorten your code. If you're using a lot of functions, you could try moving those into a separate library, creating a .mpy of that library, and importing it into your code. You can turn your entire file into a .mpy and import that into code.py. This means you will be unable to edit your code live on the board, but it can save you space. Can the order of my import statements affect memory? It can because the memory gets fragmented differently depending on allocation order and the size of objects. Loading .mpy files uses less memory so its recommended to do that for files you aren't editing. How can I create my own .mpy files? You can make your own .mpy versions of files with mpy-cross . You can download mpy-cross for your operating system from here (https:// adafru.it/QDK). Builds are available for Windows, macOS, x64 Linux, and Raspberry Pi Linux. Choose the latest mpy-cross whose version matches the version of CircuitPython you are using. To make a .mpy file, run ./mpy-cross path/to/yourfile.py to create a yourfile.mpy in the same directory as the original file. How do I check how much memory I have free? Run the following to see the number of bytes available for use: import gc gc.mem_free() ©Adafruit Industries Page 75 of 215 Does CircuitPython support interrupts? No. CircuitPython does not currently support interrupts. We do not have an estimated time for when they will be included Does Feather M0 support WINC1500? No, WINC1500 will not fit into the M0 flash space. Can AVRs such as ATmega328 or ATmega2560 run CircuitPython? No. Commonly Used Acronyms CP or CPy = CircuitPython (https://adafru.it/KJD) CPC = Circuit Playground Classic (https://adafru.it/ncE) CPX = Circuit Playground Express (https://adafru.it/wpF) CPB = Circuit Playground Bluefruit (https://adafru.it/Gpe) Welcome to the Community! CircuitPython is a programming language that's super simple to get started with and great for learning. It runs on microcontrollers and works out of the box. You can plug it in and get started with any text editor. The best part? CircuitPython comes with an amazing, supportive community. ©Adafruit Industries Page 76 of 215 Everyone is welcome! CircuitPython is Open Source. This means it's available for anyone to use, edit, copy and improve upon. This also means CircuitPython becomes better because of you being a part of it. Whether this is your first microcontroller board or you're a seasoned software engineer, you have something important to offer the Adafruit CircuitPython community. This page highlights some of the many ways you can be a part of it! Adafruit Discord The Adafruit Discord server is the best place to start. Discord is where the community comes together to volunteer and provide live support of all kinds. From general discussion to detailed problem solving, and everything in between, Discord is a digital maker space with makers from around the world. There are many different channels so you can choose the one best suited to your needs. Each channel is shown on Discord as "#channelname". There's the #help-withprojects channel for assistance with your current project or help coming up with ideas for your next one. There's the #show-and-tell channel for showing off your newest creation. Don't be afraid to ask a question in any channel! If you're unsure, #general is a great place to start. If another channel is more likely to provide you with a better answer, someone will guide you. The help with CircuitPython channel is where to go with your CircuitPython questions. #help-with-circuitpython is there for new users and developers alike so feel free to ask a question or post a comment! Everyone of any experience level is welcome to join in on the conversation. Your contributions are important! The #circuitpython-dev channel is available for development discussions as well. ©Adafruit Industries Page 77 of 215 The easiest way to contribute to the community is to assist others on Discord. Supporting others doesn't always mean answering questions. Join in celebrating successes! Celebrate your mistakes! Sometimes just hearing that someone else has gone through a similar struggle can be enough to keep a maker moving forward. The Adafruit Discord is the 24x7x365 hackerspace that you can bring your granddaughter to. Visit https://adafru.it/discord  ()to sign up for Discord. Everyone is looking forward to meeting you! CircuitPython.org Beyond the Adafruit Learn System, which you are viewing right now, the best place to find information about CircuitPython is circuitpython.org (https://adafru.it/KJD). Everything you need to get started with your new microcontroller and beyond is available. You can do things like download CircuitPython for your microcontroller (http s://adafru.it/Em8) or download the latest CircuitPython Library bundle (https://adafru.it/ ENC), or check out which single board computers support Blinka (https://adafru.it/ EA8). You can also get to various other CircuitPython related things like Awesome CircuitPython or the Python for Microcontrollers newsletter. This is all incredibly useful, but it isn't necessarily community related. So why is it included here? The Cont ributing page (https://adafru.it/VD7). ©Adafruit Industries Page 78 of 215 CircuitPython itself is written in C. However, all of the Adafruit CircuitPython libraries are written in Python. If you're interested in contributing to CircuitPython on the Python side of things, check out circuitpython.org/contributing (https://adafru.it/VD7). You'll find information pertaining to every Adafruit CircuitPython library GitHub repository, giving you the opportunity to join the community by finding a contributing option that works for you. Note the date on the page next to Current Status for: If you submit any contributions to the libraries, and do not see them reflected on the Contributing page, it could be that the job that checks for new updates hasn't yet run for today. Simply check back tomorrow! Now, a look at the different options. Pull Requests The first tab you'll find is a list of open pull requests. GitHub pull requests, or PRs, are opened when folks have added something to an Adafruit CircuitPython library GitHub repo, and are asking for Adafruit to add, or merge, their changes into the main library code. For PRs to be merged, they must first be reviewed. Reviewing is a great way to contribute! Take a look at the list of open pull requests, and pick one that interests you. If you have the hardware, you can test code changes. If you don't, you can still check the code updates for syntax. In the case of documentation updates, you can verify the information, or check it for spelling and grammar. Once you've checked out the update, you can leave a comment letting us know that you took a look. Once you've done that for a while, and you're more comfortable with it, you can consider joining the CircuitPythonLibrarians review team. ©Adafruit Industries Page 79 of 215 The more reviewers we have, the more authors we can support. Reviewing is a crucial part of an open source ecosystem, CircuitPython included. Open Issues The second tab you'll find is a list of open issues. GitHub issues are filed for a number of reasons, including when there is a bug in the library or example code, or when someone wants to make a feature request. Issues are a great way to find an opportunity to contribute directly to the libraries by updating code or documentation. If you're interested in contributing code or documentation, take a look at the open issues and find one that interests you. If you're not sure where to start, you can search the issues by label. Labels are applied to issues to make the goal easier to identify at a first glance, or to indicate the difficulty level of the issue. Click on the dropdown next to "Sort by issue labels" to see the list of available labels, and click on one to choose it. If you're new to everything, new to contributing to open source, or new to contributing to the CircuitPython project, you can choose "Good first issue". Issues ©Adafruit Industries Page 80 of 215 with that label are well defined, with a finite scope, and are intended to be easy for someone new to figure out. If you're looking for something a little more complicated, consider "Bug" or "Enhancement". The Bug label is applied to issues that pertain to problems or failures found in the library. The Enhancement label is applied to feature requests. Don't let the process intimidate you. If you're new to Git and GitHub, there is a guide ( https://adafru.it/Dkh) to walk you through the entire process. As well, there are always folks available on Discord () to answer questions. Library Infrastructure Issues The third tab you'll find is a list of library infrastructure issues. This section is generated by a script that runs checks on the libraries, and then reports back where there may be issues. It is made up of a list of subsections each containing links to the repositories that are experiencing that particular issue. This page is available mostly for internal use, but you may find some opportunities to contribute on this page. If there's an issue listed that sounds like something you could help with, mention it on Discord, or file an issue on GitHub indicating you're working to resolve that issue. Others can reply either way to let you know what the scope of it might be, and help you resolve it if necessary. CircuitPython Localization The fourth tab you'll find is the CircuitPython Localization tab. ©Adafruit Industries Page 81 of 215 If you speak another language, you can help translate CircuitPython! The translations apply to informational and error messages that are within the CircuitPython core. It means that folks who do not speak English have the opportunity to have these messages shown to them in their own language when using CircuitPython. This is incredibly important to provide the best experience possible for all users. CircuitPython uses Weblate to translate, which makes it much simpler to contribute translations. You will still need to know some CircuitPython-specific practices and a few basics about coding strings, but as with any CircuitPython contributions, folks are there to help. Regardless of your skill level, or how you want to contribute to the CircuitPython project, there is an opportunity available. The Contributing page (https://adafru.it/VD7) is an excellent place to start! Adafruit GitHub Whether you're just beginning or are life-long programmer who would like to contribute, there are ways for everyone to be a part of the CircuitPython project. The CircuitPython core is written in C. The libraries are written in Python. GitHub is the best source of ways to contribute to the CircuitPython core (https://adafru.it/tB7), and the CircuitPython libraries (https://adafru.it/VFv). If you need an account, visit https:// github.com/ (https://adafru.it/d6C) and sign up. ©Adafruit Industries Page 82 of 215 If you're new to GitHub or programming in general, there are great opportunities for you. For the CircuitPython core, head over to the CircuitPython repository on GitHub, click on "Issues (https://adafru.it/tBb)", and you'll find a list that includes issues labeled "good first issue (https://adafru.it/Bef)". For the libraries, head over to the Contributing page Issues list (https://adafru.it/VFv), and use the drop down menu to search for "goo d first issue (https://adafru.it/VFw)". These issues are things that have been identified as something that someone with any level of experience can help with. These issues include options like updating documentation, providing feedback, and fixing simple bugs. If you need help getting started with GitHub, there is an excellent guide on Cont ributing to CircuitPython with Git and GitHub (https://adafru.it/Dkh). Already experienced and looking for a challenge? Checkout the rest of either issues list and you'll find plenty of ways to contribute. You'll find all sorts of things, from new driver requests, to library bugs, to core module updates. There's plenty of opportunities for everyone at any level! When working with or using CircuitPython or the CircuitPython libraries, you may find problems. If you find a bug, that's great! The team loves bugs! Posting a detailed issue to GitHub is an invaluable way to contribute to improving CircuitPython. For CircuitPython itself, file an issue here (https://adafru.it/tBb). For the libraries, file an issue on the specific library repository on GitHub. Be sure to include the steps to replicate the issue as well as any other information you think is relevant. The more detail, the better! Testing new software is easy and incredibly helpful. Simply load the newest version of CircuitPython or a library onto your CircuitPython hardware, and use it. Let us know about any problems you find by posting a new issue to GitHub. Software testing on both stable and unstable releases is a very important part of contributing CircuitPython. The developers can't possibly find all the problems themselves! They need your help to make CircuitPython even better. On GitHub, you can submit feature requests, provide feedback, report problems and much more. If you have questions, remember that Discord and the Forums are both there for help! ©Adafruit Industries Page 83 of 215 Adafruit Forums The Adafruit Forums (https://adafru.it/jIf) are the perfect place for support. Adafruit has wonderful paid support folks to answer any questions you may have. Whether your hardware is giving you issues or your code doesn't seem to be working, the forums are always there for you to ask. You need an Adafruit account to post to the forums. You can use the same account you use to order from Adafruit. While Discord may provide you with quicker responses than the forums, the forums are a more reliable source of information. If you want to be certain you're getting an Adafruit-supported answer, the forums are the best place to be. There are forum categories that cover all kinds of topics, including everything Adafruit. The Adafruit CircuitPython (https://adafru.it/xXA) category under "Supported Products & Projects" is the best place to post your CircuitPython questions. Be sure to include the steps you took to get to where you are. If it involves wiring, post a picture! If your code is giving you trouble, include your code in your post! These are great ways to make sure that there's enough information to help you with your issue. You might think you're just getting started, but you definitely know something that someone else doesn't. The great thing about the forums is that you can help others too! Everyone is welcome and encouraged to provide constructive feedback to any of ©Adafruit Industries Page 84 of 215 the posted questions. This is an excellent way to contribute to the community and share your knowledge! Read the Docs Read the Docs (https://adafru.it/Beg) is a an excellent resource for a more detailed look at the CircuitPython core and the CircuitPython libraries. This is where you'll find things like API documentation and example code. For an in depth look at viewing and understanding Read the Docs, check out the CircuitPython Documentation (https:// adafru.it/VFx) page! Advanced Serial Console on Windows Windows 7 and 8.1 If you're using Windows 7 (or 8 or 8.1), you'll need to install drivers. See the Windows 7 and 8.1 Drivers page (https://adafru.it/VuB) for details. You will not need to install drivers on Mac, Linux or Windows 10. You are strongly encouraged to upgrade to Windows 10 if you are still using Windows 7 or Windows 8 or 8.1. Windows 7 has reached end-of-life and no longer receives ©Adafruit Industries Page 85 of 215 security updates. A free upgrade to Windows 10 is still available (https://adafru.it/ RWc). What's the COM? First, you'll want to find out which serial port your board is using. When you plug your board in to USB on your computer, it connects to a serial port. The port is like a door through which your board can communicate with your computer using USB. You'll use Windows Device Manager to determine which port the board is using. The easiest way to determine which port the board is using is to first check without the board plugged in. Open Device Manager. Click on Ports (COM & LPT). You should find something already in that list with (COM#) after it where # is a number. Now plug in your board. The Device Manager list will refresh and a new item will appear under Ports (COM & LPT). You'll find a different (COM#) after this item in the list. ©Adafruit Industries Page 86 of 215 Sometimes the item will refer to the name of the board. Other times it may be called something like USB Serial Device, as seen in the image above. Either way, there is a new (COM#) following the name. This is the port your board is using. Install Putty If you're using Windows, you'll need to download a terminal program. You're going to use PuTTY. The first thing to do is download the latest version of PuTTY (https://adafru.it/Bf1). You'll want to download the Windows installer file. It is most likely that you'll need the 64-bit version. Download the file and install the program on your machine. If you run into issues, you can try downloading the 32-bit version instead. However, the 64-bit version will work on most PCs. Now you need to open PuTTY. • Under Connection type: choose the button next to Serial. • In the box under Serial line, enter the serial port you found that your board is using. • In the box under Speed, enter 115200. This called the baud rate, which is the speed in bits per second that data is sent over the serial connection. For boards with built in USB it doesn't matter so much but for ESP8266 and other board ©Adafruit Industries Page 87 of 215 with a separate chip, the speed required by the board is 115200 bits per second. So you might as well just use 115200! If you want to save those settings for later, use the options under Load, save or delete a stored session. Enter a name in the box under Saved Sessions, and click the Save button on the right. Once your settings are entered, you're ready to connect to the serial console. Click "Open" at the bottom of the window. A new window will open. ©Adafruit Industries Page 88 of 215 If no code is running, the window will either be blank or will look like the window above. Now you're ready to see the results of your code. Great job! You've connected to the serial console! Advanced Serial Console on Mac Connecting to the serial console on Mac does not require installing any drivers or extra software. You'll use a terminal program to find your board, and screen to connect to it. Terminal and screen both come installed by default. What's the Port? First you'll want to find out which serial port your board is using. When you plug your board in to USB on your computer, it connects to a serial port. The port is like a door through which your board can communicate with your computer using USB. The easiest way to determine which port the board is using is to first check without the board plugged in. Open Terminal and type the following: ls /dev/tty.* Each serial connection shows up in the /dev/ directory. It has a name that starts with tty. . The command ls shows you a list of items in a directory. You can use * as a wildcard, to search for files that start with the same letters but end in something different. In this case, you're asking to see all of the listings in /dev/ that start with t ty. and end in anything. This will show us the current serial connections. ©Adafruit Industries Page 89 of 215 Now, plug your board. In Terminal, type: ls /dev/tty.* This will show you the current serial connections, which will now include your board. A new listing has appeared called /dev/tty.usbmodem141441 . The  tty.usbmodem1 41441 part of this listing is the name the example board is using. Yours will be called something similar. Using Linux, a new listing has appeared called /dev/ttyACM0 . The ttyACM0 part of this listing is the name the example board is using. Yours will be called something similar. Connect with screen Now that you know the name your board is using, you're ready connect to the serial console. You're going to use a command called screen . The screen command is included with MacOS. To connect to the serial console, use Terminal. Type the following command, replacing board_name with the name you found your board is using: screen /dev/tty.board_name 115200 The first part of this establishes using the screen command. The second part tells screen the name of the board you're trying to use. The third part tells screen what baud rate to use for the serial connection. The baud rate is the speed in bits per second that data is sent over the serial connection. In this case, the speed required by the board is 115200 bits per second. ©Adafruit Industries Page 90 of 215 Press enter to run the command. It will open in the same window. If no code is running, the window will be blank. Otherwise, you'll see the output of your code. Great job! You've connected to the serial console! "Uninstalling" CircuitPython A lot of our boards can be used with multiple programming languages. For example, the Circuit Playground Express can be used with MakeCode, Code.org CS Discoveries, CircuitPython and Arduino. Maybe you tried CircuitPython and want to go back to MakeCode or Arduino? Not a problem. You can always remove or reinstall CircuitPython whenever you want! Heck, you can change your mind every day! There is nothing to uninstall. CircuitPython is "just another program" that is loaded onto your board. You simply load another program (Arduino or MakeCode) and it will overwrite CircuitPython. Backup Your Code Before replacing CircuitPython, don't forget to make a backup of the code you have on the CIRCUITPY drive. That means your code.py any other files, the lib folder etc. You may lose these files when you remove CircuitPython, so backups are key! Just drag the files to a folder on your laptop or desktop computer like you would with any USB drive. ©Adafruit Industries Page 91 of 215 Moving Circuit Playground Express to MakeCode On the Circuit Playground Express (this currently does NOT apply to Circuit Playground Bluefruit), if you want to go back to using MakeCode, it's really easy. Visit makecode.adafruit.com (https://adafru.it/wpC) and find the program you want to upload. Click Download to download the .uf2 file that is generated by MakeCode. Now double-click your CircuitPython board until you see the onboard LED(s) turn green and the ...BOOT directory shows up. Then find the downloaded MakeCode .uf2 file and drag it to the CPLAYBOOT drive. ©Adafruit Industries Page 92 of 215 Your MakeCode is now running and CircuitPython has been removed. Going forward you only have to single click the reset button to get to CPLAYBOOT. This is an idiosyncrasy of MakeCode. Moving to Arduino If you want to use Arduino instead, you just use the Arduino IDE to load an Arduino program. Here's an example of uploading a simple "Blink" Arduino program, but you don't have to use this particular program. Start by plugging in your board, and double-clicking reset until you get the green onboard LED(s). Within Arduino IDE, select the matching board, say Circuit Playground Express. Select the correct matching Port: Create a new simple Blink sketch example: // the setup function runs once when you press reset or power the board void setup() { // initialize digital pin 13 as an output. pinMode(13, OUTPUT); ©Adafruit Industries Page 93 of 215 } // the loop function runs over and over again forever void loop() { digitalWrite(13, HIGH); // turn the LED on (HIGH is the voltage level) delay(1000); // wait for a second digitalWrite(13, LOW); // turn the LED off by making the voltage LOW delay(1000); // wait for a second } Make sure the LED(s) are still green, then click Upload to upload Blink. Once it has uploaded successfully, the serial Port will change so re-select the new Port! Once Blink is uploaded you should no longer need to double-click to enter bootloader mode. Arduino will automatically reset when you upload. Troubleshooting From time to time, you will run into issues when working with CircuitPython. Here are a few things you may encounter and how to resolve them. As CircuitPython development continues and there are new releases, Adafruit will stop supporting older releases. Visit https://circuitpython.org/downloads to download the latest version of CircuitPython for your board. You must download the CircuitPython Library Bundle that matches your version of CircuitPython. Please update CircuitPython and then visit https://circuitpython.org/libraries to download the latest Library Bundle. Always Run the Latest Version of CircuitPython and Libraries As CircuitPython development continues and there are new releases, Adafruit will stop supporting older releases. You need to update to the latest CircuitPython. (https:/ /adafru.it/Em8). You need to download the CircuitPython Library Bundle that matches your version of CircuitPython. Please update CircuitPython and then download the latest bundle (http s://adafru.it/ENC). As new versions of CircuitPython are released, Adafruit will stop providing the previous bundles as automatically created downloads on the Adafruit CircuitPython Library Bundle repo. If you must continue to use an earlier version, you can still ©Adafruit Industries Page 94 of 215 download the appropriate version of mpy-cross from the particular release of CircuitPython on the CircuitPython repo and create your own compatible .mpy library files. However, it is best to update to the latest for both CircuitPython and the library bundle. I have to continue using CircuitPython 5.x or earlier. Where can I find compatible libraries? Adafruit is no longer building or supporting the CircuitPython 5.x or earlier library bundles. You are highly encourged to update CircuitPython to the latest version (https ://adafru.it/Em8) and use the current version of the libraries (https://adafru.it/ENC). However, if for some reason you cannot update, links to the previous bundles are available in the FAQ (https://adafru.it/FwY). Bootloader (boardnameBOOT) Drive Not Present You may have a different board. Only Adafruit Express boards and the SAMD21 non-Express boards ship with the UF2 bootloader  (https://adafru.it/zbX)installed. The Feather M0 Basic, Feather M0 Adalogger, and similar boards use a regular Arduino-compatible bootloader, which does not show a boardnameBOOT drive. MakeCode If you are running a MakeCode (https://adafru.it/zbY) program on Circuit Playground Express, press the reset button just once to get the CPLAYBOOT drive to show up. Pressing it twice will not work. MacOS DriveDx and its accompanything SAT SMART Driver can interfere with seeing the BOOT drive. See this forum post (https://adafru.it/sTc) for how to fix the problem. ©Adafruit Industries Page 95 of 215 Windows 10 Did you install the Adafruit Windows Drivers package by mistake, or did you upgrade to Windows 10 with the driver package installed? You don't need to install this package on Windows 10 for most Adafruit boards. The old version (v1.5) can interfere with recognizing your device. Go to Settings -> Apps and uninstall all the "Adafruit" driver programs. Windows 7 or 8.1 To use a CircuitPython-compatible board with Windows 7 or 8.1, you must install a driver. Installation instructions are available here (https://adafru.it/VuB). It is recommended (https://adafru.it/Amd) that you upgrade to Windows 10 if possible; an upgrade is probably still free for you. Check here (https://adafru.it/Amd). The Windows Drivers installer was last updated in November 2020 (v2.5.0.0) . Windows 7 drivers for CircuitPython boards released since then, including RP2040 boards, are not yet available. The boards work fine on Windows 10. A new release of the drivers is in process. You should now be done! Test by unplugging and replugging the board. You should see the CIRCUITPY drive, and when you double-click the reset button (single click on Circuit Playground Express running MakeCode), you should see the appropriate boar dnameBOOT drive. Let us know in the Adafruit support forums (https://adafru.it/jIf) or on the Adafruit Discord () if this does not work for you! Windows Explorer Locks Up When Accessing boardnameBOOT Drive On Windows, several third-party programs that can cause issues. The symptom is that you try to access the boardnameBOOT drive, and Windows or Windows Explorer seems to lock up. These programs are known to cause trouble: • AIDA64: to fix, stop the program. This problem has been reported to AIDA64. They acquired hardware to test, and released a beta version that fixes the ©Adafruit Industries Page 96 of 215 problem. This may have been incorporated into the latest release. Please let us know in the forums if you test this. • Hard Disk Sentinel • Kaspersky anti-virus: To fix, you may need to disable Kaspersky completely. Disabling some aspects of Kaspersky does not always solve the problem. This problem has been reported to Kaspersky. • ESET NOD32 anti-virus: There have been problems with at least version 9.0.386.0, solved by uninstallation. Copying UF2 to boardnameBOOT Drive Hangs at 0% Copied On Windows, a Western DIgital (WD) utility that comes with their external USB drives can interfere with copying UF2 files to the boardnameBOOT drive. Uninstall that utility to fix the problem. CIRCUITPY Drive Does Not Appear or Disappears Quickly Kaspersky anti-virus can block the appearance of the CIRCUITPY drive. There has not yet been settings change discovered that prevents this. Complete uninstallation of Kaspersky fixes the problem. Norton anti-virus can interfere with CIRCUITPY. A user has reported this problem on Windows 7. The user turned off both Smart Firewall and Auto Protect, and CIRCUITPY then appeared. Sophos Endpoint security software can cause CIRCUITPY to disappear (https:// adafru.it/ELr) and the BOOT drive to reappear. It is not clear what causes this behavior. Device Errors or Problems on Windows Windows can become confused about USB device installations. This is particularly true of Windows 7 and 8.1. It is recommended (https://adafru.it/Amd) that you upgrade to Windows 10 if possible; an upgrade is probably still free for you: see this link (https: //adafru.it/V2a). ©Adafruit Industries Page 97 of 215 If not, try cleaning up your USB devices. Use Uwe Sieber's Device Cleanup Tool (https ://adafru.it/RWd). Download and unzip the tool. Unplug all the boards and other USB devices you want to clean up. Run the tool as Administrator. You will see a listing like this, probably with many more devices. It is listing all the USB devices that are not currently attached. Select all the devices you want to remove, and then press Delete. It is usually safe just to select everything. Any device that is removed will get a fresh install when you plug it in. Using the Device Cleanup Tool also discards all the COM port assignments for the unplugged boards. If you have used many Arduino and CircuitPython boards, you have probably seen higher and higher COM port numbers used, seemingly without end. This will fix that problem. Serial Console in Mu Not Displaying Anything There are times when the serial console will accurately not display anything, such as, when no code is currently running, or when code with no serial output is already running before you open the console. However, if you find yourself in a situation where you feel it should be displaying something like an error, consider the following. Depending on the size of your screen or Mu window, when you open the serial console, the serial console panel may be very small. This can be a problem. A basic CircuitPython error takes 10 lines to display! Auto-reload is on. Simply save files over USB to run them or enter REPL to disable. code.py output: Traceback (most recent call last): File "code.py", line 7 ©Adafruit Industries Page 98 of 215 SyntaxError: invalid syntax Press any key to enter the REPL. Use CTRL-D to reload. More complex errors take even more lines! Therefore, if your serial console panel is five lines tall or less, you may only see blank lines or blank lines followed by Press any key to enter the REPL. Use CTRL-D to reload. . If this is the case, you need to either mouse over the top of the panel to utilise the option to resize the serial panel, or use the scrollbar on the right side to scroll up and find your message. This applies to any kind of serial output whether it be error messages or print statements. So before you start trying to debug your problem on the hardware side, be sure to check that you haven't simply missed the serial messages due to serial output panel height. code.py Restarts Constantly CircuitPython will restart code.py if you or your computer writes to something on the CIRCUITPY drive. This feature is called auto-reload, and lets you test a change to your program immediately. Some utility programs, such as backup, anti-virus, or disk-checking apps, will write to the CIRCUITPY as part of their operation. Sometimes they do this very frequently, causing constant restarts. Acronis True Image and related Acronis programs on Windows are known to cause this problem. It is possible to prevent this by disabling the " (https://adafru.it/XDZ)Acro nis Managed Machine Service Mini" (https://adafru.it/XDZ). If you cannot stop whatever is causing the writes, you can disable auto-reload by putting this code in boot.py or code.py: ©Adafruit Industries Page 99 of 215 import supervisor supervisor.disable_autoreload() CircuitPython RGB Status Light Nearly all CircuitPython-capable boards have a single NeoPixel or DotStar RGB LED on the board that indicates the status of CircuitPython. A few boards designed before CircuitPython existed, such as the Feather M0 Basic, do not. Circuit Playground Express and Circuit Playground Bluefruit have multiple RGB LEDs, but do NOT have a status LED. The LEDs are all green when in the bootloader. In versions before 7.0.0, they do NOT indicate any status while running CircuitPython. CircuitPython 7.0.0 and Later The status LED blinks were changed in CircuitPython 7.0.0 in order to save battery power and simplify the blinks. These blink patterns will occur on single color LEDs when the board does not have any RGB LEDs. Speed and blink count also vary for this reason. On start up, the LED will blink YELLOW multiple times for 1 second. Pressing reset during this time will restart the board and then enter safe mode. On Bluetooth capable boards, after the yellow blinks, there will be a set of faster blue blinks. Pressing reset during the BLUE blinks will clear Bluetooth information and start the device in discoverable mode, so it can be used with a BLE code editor. Once started, CircuitPython will blink a pattern every 5 seconds when no user code is running to indicate why the code stopped: • 1 GREEN blink: Code finished without error. • 2 RED blinks: Code ended due to an exception. Check the serial console for details. • 3 YELLOW blinks: CircuitPython is in safe mode. No user code was run. Check the serial console for safe mode reason. When in the REPL, CircuitPython will set the status LED to WHITE. You can change the LED color from the REPL. The status indicator will not persist on non-NeoPixel or DotStar LEDs. ©Adafruit Industries Page 100 of 215 CircuitPython 6.3.0 and earlier Here's what the colors and blinking mean: • steady GREEN: code.py (or code.txt, main.py, or main.txt) is running • pulsing GREEN: code.py (etc.) has finished or does not exist • steady YELLOW at start up: (4.0.0-alpha.5 and newer) CircuitPython is waiting for a reset to indicate that it should start in safe mode • pulsing YELLOW: Circuit Python is in safe mode: it crashed and restarted • steady WHITE: REPL is running • steady BLUE: boot.py is running Colors with multiple flashes following indicate a Python exception and then indicate the line number of the error. The color of the first flash indicates the type of error: • GREEN: IndentationError • CYAN: SyntaxError • WHITE: NameError • ORANGE: OSError • PURPLE: ValueError • YELLOW: other error These are followed by flashes indicating the line number, including place value. WHIT E flashes are thousands' place, BLUE are hundreds' place, YELLOW are tens' place, ©Adafruit Industries Page 101 of 215 and CYAN are one's place. So for example, an error on line 32 would flash YELLOW three times and then CYAN two times. Zeroes are indicated by an extra-long dark gap. Serial console showing ValueError: Incompatible .mpy file This error occurs when importing a module that is stored as a .mpy binary file that was generated by a different version of CircuitPython than the one its being loaded into. In particular, the mpy binary format changed between CircuitPython versions 6.x and 7.x, 2.x and 3.x, and 1.x and 2.x. So, for instance, if you upgraded to CircuitPython 7.x from 6.x you’ll need to download a newer version of the library that triggered the error on import . All libraries are available in the Adafruit bundle (https://adafru.it/y8E). CIRCUITPY Drive Issues You may find that you can no longer save files to your CIRCUITPY drive. You may find that your CIRCUITPY stops showing up in your file explorer, or shows up as NO_NAM E. These are indicators that your filesystem has issues. When the CIRCUITPY disk is not safely ejected before being reset by the button or being disconnected from USB, it may corrupt the flash drive. It can happen on Windows, Mac or Linux, though it is more common on Windows. ©Adafruit Industries Page 102 of 215 Be aware, if you have used Arduino to program your board, CircuitPython is no longer able to provide the USB services. You will need to reload CircuitPython to resolve this situation. The easiest first step is to reload CircuitPython. Double-tap reset on the board so you get a boardnameBOOT drive rather than a CIRCUITPY drive, and copy the latest version of CircuitPython (.uf2) back to the board. This may restore CIRCUITPY functionality. If reloading CircuitPython does not resolve your issue, the next step is to try putting the board into safe mode. Safe Mode Whether you've run into a situation where you can no longer edit your code.py on your CIRCUITPY drive, your board has gotten into a state where CIRCUITPY is readonly, or you have turned off the CIRCUITPY drive altogether, safe mode can help. Safe mode in CircuitPython does not run any user code on startup, and disables autoreload. This means a few things. First, safe mode bypasses any code in boot.py (where you can set CIRCUITPY read-only or turn it off completely). Second, it does not run the code in code.py. And finally, it does not automatically soft-reload when data is written to the CIRCUITPY drive. Therefore, whatever you may have done to put your board in a non-interactive state, safe mode gives you the opportunity to correct it without losing all of the data on the CIRCUITPY drive. Entering Safe Mode in CircuitPython 7.x To enter safe mode when using CircuitPython 7.x, plug in your board or hit reset (highlighted in red above). Immediately after the board starts up or resets, it waits 1000ms. On some boards, the onboard status LED will blink yellow during that time. If you press reset during that 1000ms, the board will start up in safe mode. It can be difficult to react to the yellow LED, so you may want to think of it simply as a "slow" double click of the reset button. (Remember, a fast double click of reset enters the bootloader.) ©Adafruit Industries Page 103 of 215 Entering Safe Mode in CircuitPython 6.x To enter safe mode when using CircuitPython 6.x, plug in your board or hit reset (highlighted in red above). Immediately after the board starts up or resets, it waits 700ms. On some boards, the onboard status LED (highlighted in green above) will turn solid yellow during this time. If you press reset during that 700ms, the board will start up in safe mode. It can be difficult to react to the yellow LED, so you may want to think of it simply as a slow double click of the reset button. (Remember, a fast double click of reset enters the bootloader.) In Safe Mode Once you've entered safe mode successfully in CircuitPython 6.x, the LED will pulse yellow. If you successfully enter safe mode on CircuitPython 7.x, the LED will intermittently blink yellow three times. If you connect to the serial console, you'll find the following message. Auto-reload is off. Running in safe mode! Not running saved code. CircuitPython is in safe mode because you pressed the reset button during boot. Press again to exit safe mode. Press any key to enter the REPL. Use CTRL-D to reload. You can now edit the contents of the CIRCUITPY drive. Remember, your code will not run until you press the reset button, or unplug and plug in your board, to get out of safe mode. At this point, you'll want to remove any user code in code.py and, if present, the boot. py file from CIRCUITPY. Once removed, tap the reset button, or unplug and plug in your board, to restart CircuitPython. This will restart the board and may resolve your drive issues. If resolved, you can begin coding again as usual. If safe mode does not resolve your issue, the board must be completely erased and CircuitPython must be reloaded onto the board. You WILL lose everything on the board when you complete the following steps. If possible, make a copy of your code before continuing. ©Adafruit Industries Page 104 of 215 To erase CIRCUITPY: storage.erase_filesystem() CircuitPython includes a built-in function to erase and reformat the filesystem. If you have a version of CircuitPython older than 2.3.0 on your board, you can update to the newest version (https://adafru.it/Amd) to do this. 1. Connect to the CircuitPython REPL (https://adafru.it/Bec) using Mu or a terminal program. 2. Type the following into the REPL: >>> import storage >>> storage.erase_filesystem() CIRCUITPY will be erased and reformatted, and your board will restart. That's it! Erase CIRCUITPY Without Access to the REPL If you can't access the REPL, or you're running a version of CircuitPython previous to 2.3.0 and you don't want to upgrade, there are options available for some specific boards. The options listed below are considered to be the "old way" of erasing your board. The method shown above using the REPL is highly recommended as the best method for erasing your board. If at all possible, it is recommended to use the REPL to erase your CIRCUITPY drive. The REPL method is explained above. For the specific boards listed below: If the board you are trying to erase is listed below, follow the steps to use the file to erase your board.        1.  Download the correct erase file: Circuit Playground Express https://adafru.it/AdI Feather M0 Express ©Adafruit Industries Page 105 of 215 https://adafru.it/AdJ Feather M4 Express https://adafru.it/EVK Metro M0 Express https://adafru.it/AdK Metro M4 Express QSPI Eraser https://adafru.it/EoM Trellis M4 Express (QSPI) https://adafru.it/DjD Grand Central M4 Express (QSPI) https://adafru.it/DBA PyPortal M4 Express (QSPI) https://adafru.it/Eca Circuit Playground Bluefruit (QSPI) https://adafru.it/Gnc Monster M4SK (QSPI) https://adafru.it/GAN PyBadge/PyGamer QSPI Eraser.UF2 https://adafru.it/GAO CLUE_Flash_Erase.UF2 https://adafru.it/Jat Matrix_Portal_M4_(QSPI).UF2 https://adafru.it/Q5B        2.  Double-click the reset button on the board to bring up the boardnameBOOT drive.        3.  Drag the erase .uf2 file to the boardnameBOOT drive. ©Adafruit Industries Page 106 of 215        4.  The status LED will turn yellow or blue, indicating the erase has started.        5.  After approximately 15 seconds, the status LED will light up green. On the NeoTrellis M4 this is the first NeoPixel on the grid        6.  Double-click the reset button on the board to bring up the boardnameBOOT d rive.        7.  Drag the appropriate latest release of CircuitPython (https://adafru.it/Em8) .uf2 file to the boardnameBOOT drive. It should reboot automatically and you should see CIRCUITPY in your file explorer again. If the LED flashes red during step 5, it means the erase has failed. Repeat the steps starting with 2. If you haven't already downloaded the latest release of CircuitPython for your board, check out the installation page (https://adafru.it/Amd). You'll also need to load your code and reinstall your libraries! For SAMD21 non-Express boards that have a UF2 bootloader: Any SAMD21-based microcontroller that does not have external flash available is considered a SAMD21 non-Express board. Non-Express boards that have a UF2 bootloader include Trinket M0, GEMMA M0, QT Py M0, and the SAMD21-based Trinkey boards. If you are trying to erase a SAMD21 non-Express board, follow these steps to erase your board.        1.  Download the erase file: SAMD21 non-Express Boards https://adafru.it/VB       2.  Double-click the reset button on the board to bring up the boardnameBOOT drive.        3.  Drag the erase .uf2 file to the boardnameBOOT drive.        4.  The boot LED will start flashing again, and the boardnameBOOT drive will reappear.        5.  Drag the appropriate latest release CircuitPython (https://adafru.it/Em8) .uf2 file to the boardnameBOOT drive. ©Adafruit Industries Page 107 of 215 It should reboot automatically and you should see CIRCUITPY in your file explorer again. If you haven't already downloaded the latest release of CircuitPython for your board, check out the installation page (https://adafru.it/Amd) YYou'll also need to load your code and reinstall your libraries! For SAMD21 non-Express boards that do not have a UF2 bootloader: Any SAMD21-based microcontroller that does not have external flash available is considered a SAMD21 non-Express board. Non-Express boards that do not have a UF2 bootloader include the Feather M0 Basic Proto, Feather Adalogger, or the Arduino Zero. If you are trying to erase a non-Express board that does not have a UF2 bootloader, f ollow these directions to reload CircuitPython using bossac  (https://adafru.it/Bed), which will erase and re-create CIRCUITPY. Running Out of File Space on SAMD21 NonExpress Boards Any SAMD21-based microcontroller that does not have external flash available is considered a SAMD21 non-Express board. This includes boards like the Trinket M0, GEMMA M0, QT Py M0, and the SAMD21-based Trinkey boards. The file system on the board is very tiny. (Smaller than an ancient floppy disk.) So, its likely you'll run out of space but don't panic! There are a number of ways to free up space. ©Adafruit Industries Page 108 of 215 Delete something! The simplest way of freeing up space is to delete files from the drive. Perhaps there are libraries in the lib folder that you aren't using anymore or test code that isn't in use. Don't delete the lib folder completely, though, just remove what you don't need. The board ships with the Windows 7 serial driver too! Feel free to delete that if you don't need it or have already installed it. It's ~12KiB or so. Use tabs One unique feature of Python is that the indentation of code matters. Usually the recommendation is to indent code with four spaces for every indent. In general, that is recommended too. However, one trick to storing more human-readable code is to use a single tab character for indentation. This approach uses 1/4 of the space for indentation and can be significant when you're counting bytes. On MacOS? MacOS loves to generate hidden files. Luckily you can disable some of the extra hidden files that macOS adds by running a few commands to disable search indexing and create zero byte placeholders. Follow the steps below to maximize the amount of space available on macOS. Prevent & Remove MacOS Hidden Files First find the volume name for your board.  With the board plugged in run this command in a terminal to list all the volumes: ls -l /Volumes Look for a volume with a name like CIRCUITPY (the default for CircuitPython).  The full path to the volume is the /Volumes/CIRCUITPY path. Now follow the steps from this question (https://adafru.it/u1c) to run these terminal commands that stop hidden files from being created on the board: mdutil -i off /Volumes/CIRCUITPY cd /Volumes/CIRCUITPY rm -rf .{,_.}{fseventsd,Spotlight-V*,Trashes} ©Adafruit Industries Page 109 of 215 mkdir .fseventsd touch .fseventsd/no_log .metadata_never_index .Trashes cd - Replace /Volumes/CIRCUITPY in the commands above with the full path to your board's volume if it's different.  At this point all the hidden files should be cleared from the board and some hidden files will be prevented from being created. Alternatively, with CircuitPython 4.x and above, the special files and folders mentioned above will be created automatically if you erase and reformat the filesystem. WARNING: Save your files first! Do this in the REPL: >>> import storage >>> storage.erase_filesystem() However there are still some cases where hidden files will be created by MacOS.  In particular if you copy a file that was downloaded from the internet it will have special metadata that MacOS stores as a hidden file.  Luckily you can run a copy command from the terminal to copy files without this hidden metadata file.  See the steps below. Copy Files on MacOS Without Creating Hidden Files Once you've disabled and removed hidden files with the above commands on macOS you need to be careful to copy files to the board with a special command that prevents future hidden files from being created.  Unfortunately you cannot use drag and drop copy in Finder because it will still create these hidden extended attribute files in some cases (for files downloaded from the internet, like Adafruit's modules). To copy a file or folder use the -X option for the cp command in a terminal.  For example to copy a file_name.mpy file to the board use a command like: cp -X file_name.mpy /Volumes/CIRCUITPY (Replace file_name.mpy with the name of the file you want to copy.) Or to copy a folder and all of the files and folders contained within, use a command like: cp -rX folder_to_copy /Volumes/CIRCUITPY ©Adafruit Industries Page 110 of 215 If you are copying to the lib folder, or another folder, make sure it exists before copying. # if lib does not exist, you'll create a file named lib ! cp -X file_name.mpy /Volumes/CIRCUITPY/lib # This is safer, and will complain if a lib folder does not exist. cp -X file_name.mpy /Volumes/CIRCUITPY/lib/ Other MacOS Space-Saving Tips If you'd like to see the amount of space used on the drive and manually delete hidden files here's how to do so. First, move into the Volumes/ directory with cd /Volumes/ , and then list the amount of space used on the CIRCUITPY drive with the df command. That's not very much space left! The next step is to show a list of the files currently on the CIRCUITPY drive, including the hidden files, using the ls command. You cannot use Finder to do this, you must do it via command line! There are a few of the hidden files that MacOS loves to generate, all of which begin with a ._ before the file name. Remove the ._ files using the rm command. You can remove them all once by running rm CIRCUITPY/._* . The * acts as a wildcard to apply the command to everything that begins with ._ at the same time. Finally, you can run df again to see the current space used. ©Adafruit Industries Page 111 of 215 Nice! You have 12Ki more than before! This space can now be used for libraries and code! Device Locked Up or Boot Looping In rare cases, it may happen that something in your code.py or boot.py files causes the device to get locked up, or even go into a boot loop. A boot loop occurs when the board reboots repeatedly and never fully loads. These are not caused by your everyday Python exceptions, typically it's the result of a deeper problem within CircuitPython. In this situation, it can be difficult to recover your device if CIRCUITPY is not allowing you to modify the code.py or boot.py files. Safe mode is one recovery option. When the device boots up in safe mode it will not run the code.py or boot.py scripts, but will still connect the CIRCUITPY drive so that you can remove or modify those files as needed. The method used to manually enter safe mode can be different for different devices. It is also very similar to the method used for getting into bootloader mode, which is a different thing. So it can take a few tries to get the timing right. If you end up in bootloader mode, no problem, you can try again without needing to do anything else. For most devices: Press the reset button, and then when the RGB status LED blinks yellow, press the reset button again. Since your reaction time may not be that fast, try a "slow" double click, to catch the yellow LED on the second click. For ESP32-S2 based devices: Press and release the reset button, then press and release the boot button about 3/4 of a second later. Refer to the diagrams above for boot sequence details. ©Adafruit Industries Page 112 of 215 CircuitPython Essentials You've gone through the Welcome to CircuitPython guide (https://adafru.it/cpywelcome). You've already gotten everything setup, and you've gotten CircuitPython running. Great! Now what? CircuitPython Essentials! There are a number of core modules built into CircuitPython and commonly used libraries available. This guide will introduce you to these and show you an example of how to use each one. Each section will present you with a piece of code designed to work with different boards, and explain how to use the code with each board. These examples work with any board designed for CircuitPython, including Circuit Playground Express, Trinket M0, Gemma M0, QT Py, ItsyBitsy M0 Express, ItsyBitsy M4 Express, Feather M0 Express, Feather M4 Express, Metro M4 Express,  Metro M0 Express, Trellis M4 Express, and Grand Central M4 Express. Some examples require external components, such as switches or sensors. You'll find wiring diagrams where applicable to show you how to wire up the necessary components to work with each example. Let's get started learning the CircuitPython Essentials! CircuitPython Pins and Modules CircuitPython is designed to run on microcontrollers and allows you to interface with all kinds of sensors, inputs and other hardware peripherals. There are tons of guides showing how to wire up a circuit, and use CircuitPython to, for example, read data from a sensor, or detect a button press. Most CircuitPython code includes hardware setup which requires various modules, such as board or digitalio . You import these modules and then use them in your code. How does CircuitPython know to look ©Adafruit Industries Page 113 of 215 for hardware in the specific place you connected it, and where do these modules come from? This page explains both. You'll learn how CircuitPython finds the pins on your microcontroller board, including how to find the available pins for your board and what each pin is named. You'll also learn about the modules built into CircuitPython, including how to find all the modules available for your board. CircuitPython Pins When using hardware peripherals with a CircuitPython compatible microcontroller, you'll almost certainly be utilising pins. This section will cover how to access your board's pins using CircuitPython, how to discover what pins and board-specific objects are available in CircuitPython for your board, how to use the board-specific objects, and how to determine all available pin names for a given pin on your board. import board When you're using any kind of hardware peripherals wired up to your microcontroller board, the import list in your code will include import board . The board module is built into CircuitPython, and is used to provide access to a series of board-specific objects, including pins. Take a look at your microcontroller board. You'll notice that next to the pins are pin labels. You can always access a pin by its pin label. However, there are almost always multiple names for a given pin. To see all the available board-specific objects and pins for your board, enter the REPL ( >>> ) and run the following commands: import board dir(board) Here is the output for the QT Py. You may have a different board, and this list will vary, based on the board. ©Adafruit Industries Page 114 of 215 The following pins have labels on the physical QT Py board: A0, A1, A2, A3, SDA, SCL, TX, RX, SCK, MISO, and MOSI. You see that there are many more entries available in board than the labels on the QT Py. You can use the pin names on the physical board, regardless of whether they seem to be specific to a certain protocol. For example, you do not have to use the SDA pin for I2C - you can use it for a button or LED. On the flip side, there may be multiple names for one pin. For example, on the QT Py, pin A0 is labeled on the physical board silkscreen, but it is available in CircuitPython as both A0 and D0 . For more information on finding all the names for a given pin, see the What Are All the Available Pin Names? (https://adafru.it/QkA) section below. The results of dir(board) for CircuitPython compatible boards will look similar to the results for the QT Py in terms of the pin names, e.g. A0, D0, etc. However, some boards, for example, the Metro ESP32-S2, have different styled pin names. Here is the output for the Metro ESP32-S2. Note that most of the pins are named in an IO# style, such as IO1 and IO2. Those pins on the physical board are labeled only with a number, so an easy way to know how to access them in CircuitPython, is to run those commands in the REPL and find the pin naming scheme. If your code is failing to run because it can't find a pin name you provided, verify that you have the proper pin name by running these commands in the REPL. I2C, SPI, and UART You'll also see there are often (but not always!) three special board-specific objects included: I2C , SPI , and UART - each one is for the default pin-set used for each of the three common protocol busses they are named for. These are called singletons. ©Adafruit Industries Page 115 of 215 What's a singleton? When you create an object in CircuitPython, you are instantiating ('creating') it. Instantiating an object means you are creating an instance of the object with the unique values that are provided, or "passed", to it. For example, When you instantiate an I2C object using the busio module, it expects two pins: clock and data, typically SCL and SDA. It often looks like this: i2c = busio.I2C(board.SCL, board.SDA) Then, you pass the I2C object to a driver for the hardware you're using. For example, if you were using the TSL2591 light sensor and its CircuitPython library, the next line of code would be: tsl2591 = adafruit_tsl2591.TSL2591(i2c) However, CircuitPython makes this simpler by including the I2C singleton in the boa rd module. Instead of the two lines of code above, you simply provide the singleton as the I2C object. So if you were using the TSL2591 and its CircuitPython library, the two above lines of code would be replaced with: tsl2591 = adafruit_tsl2591.TSL2591(board.I2C()) The board.I2C(), board.SPI(), and board.UART() singletons do not exist on all boards. They exist if there are board markings for the default pins for those devices. This eliminates the need for the busio module, and simplifies the code. Behind the scenes, the board.I2C()   object is instantiated when you call it, but not before, and on subsequent calls, it returns the same object. Basically, it does not create an object until you need it, and provides the same object every time you need it. You can call board.I2C() as many times as you like, and it will always return the same object. The UART/SPI/I2C singletons will use the 'default' bus pins for each board - often labeled as RX/TX (UART), MOSI/MISO/SCK (SPI), or SDA/SCL (I2C). Check your board documentation/pinout for the default busses. ©Adafruit Industries Page 116 of 215 What Are All the Available Names? Many pins on CircuitPython compatible microcontroller boards have multiple names, however, typically, there's only one name labeled on the physical board. So how do you find out what the other available pin names are? Simple, with the following script! Each line printed out to the serial console contains the set of names for a particular pin. On a microcontroller board running CircuitPython, connect to the serial console. Then, save the following as code.py on your CIRCUITPY drive. # SPDX-FileCopyrightText: 2021 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials Pin Map Script""" import microcontroller import board board_pins = [] for pin in dir(microcontroller.pin): if isinstance(getattr(microcontroller.pin, pin), microcontroller.Pin): pins = [] for alias in dir(board): if getattr(board, alias) is getattr(microcontroller.pin, pin): pins.append("board.{}".format(alias)) if len(pins) > 0: board_pins.append(" ".join(pins)) for pins in sorted(board_pins): print(pins) Here is the result when this script is run on QT Py: Each line represents a single pin. Find the line containing the pin name that's labeled on the physical board, and you'll find the other names available for that pin. For example, the first pin on the board is labeled A0. The first line in the output is board. A0 board.D0 . This means that you can access pin A0 with both board.A0 and board.D0 . ©Adafruit Industries Page 117 of 215 You'll notice there are two "pins" that aren't labeled on the board but appear in the list: board.NEOPIXEL and board.NEOPIXEL_POWER . Many boards have several of these special pins that give you access to built-in board hardware, such as an LED or an on-board sensor. The Qt Py only has one on-board extra piece of hardware, a NeoPixel LED, so there's only the one available in the list. But you can also control whether or not power is applied to the NeoPixel, so there's a separate pin for that. That's all there is to figuring out the available names for a pin on a compatible microcontroller board in CircuitPython! Microcontroller Pin Names The pin names available to you in the CircuitPython board module are not the same as the names of the pins on the microcontroller itself. The board pin names are aliases to the microcontroller pin names. If you look at the datasheet for your microcontroller, you'll likely find a pinout with a series of pin names, such as "PA18" or "GPIO5". If you want to get to the actual microcontroller pin name in CircuitPython, you'll need the microcontroller.pin module. As with board , you can run dir(mi crocontroller.pin) in the REPL to receive a list of the microcontroller pin names. CircuitPython Built-In Modules There is a set of modules used in most CircuitPython programs. One or more of these modules is always used in projects involving hardware. Often hardware requires installing a separate library from the Adafruit CircuitPython Bundle. But, if you try to find board or digitalio in the same bundle, you'll come up lacking. So, where do these modules come from? They're built into CircuitPython! You can find an comprehensive list of built-in CircuitPython modules and the technical details of their functionality from CircuitPython here (https://adafru.it/QkB) and the Python-like modules included here (https://adafru.it/QkC). However, not every module is available for every board due to size constraints or hardware limitations. How do you find out what modules are available for your board? There are two options for this. You can check the support matrix (https://adafru.it/ N2a), and search for your board by name. Or, you can use the REPL. ©Adafruit Industries Page 118 of 215 Plug in your board, connect to the serial console and enter the REPL. Type the following command. help("modules") That's it! You now know two ways to find all of the modules built into CircuitPython for your compatible microcontroller board. CircuitPython Built-Ins CircuitPython comes 'with the kitchen sink' - a lot of the things you know and love about classic Python 3 (sometimes called CPython) already work. There are a few things that don't but we'll try to keep this list updated as we add more capabilities! This is not an exhaustive list! It's simply some of the many features you can use. Thing That Are Built In and Work Flow Control All the usual if , elif , else , for , while work just as expected. Math import math will give you a range of handy mathematical functions. >>> dir(math) ['__name__', 'e', 'pi', 'sqrt', 'pow', 'exp', 'log', 'cos', 'sin', 'tan', 'acos', 'asin', 'atan', 'atan2', 'ceil', 'copysign', 'fabs', ©Adafruit Industries Page 119 of 215 'floor', 'fmod', 'frexp', 'ldexp', 'modf', 'isfinite', 'isinf', 'isnan', 'trunc', 'radians', 'degrees'] CircuitPython supports 30-bit wide floating point values so you can use int and flo at whenever you expect. Tuples, Lists, Arrays, and Dictionaries You can organize data in () ,  [] , and {} including strings, objects, floats, etc. Classes, Objects and Functions We use objects and functions extensively in our libraries so check out one of our many examples like this MCP9808 library (https://adafru.it/BfQ) for class examples. Lambdas Yep! You can create function-functions with lambda just the way you like em: >>> g = lambda x: x**2 >>> g(8) 64 Random Numbers To obtain random numbers: import random random.random() will give a floating point number from 0 to 1.0 . random.randint(min, max) will give you an integer number between min and ma x. CircuitPython Digital In & Out The first part of interfacing with hardware is being able to manage digital inputs and outputs. With CircuitPython, it's super easy! ©Adafruit Industries Page 120 of 215 This example shows how to use both a digital input and output. You can use a switch i nput with pullup resistor (built in) to control a digital output - the built in red LED. Copy and paste the code into code.py using your favorite editor, and save the file to run the demo. # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials Digital In Out example""" import time import board from digitalio import DigitalInOut, Direction, Pull # LED setup. led = DigitalInOut(board.LED) # For QT Py M0. QT Py M0 does not have a D13 LED, so you can connect an external LED instead. # led = DigitalInOut(board.SCK) led.direction = Direction.OUTPUT # For Gemma M0, Trinket M0, Metro M0 Express, ItsyBitsy M0 Express, Itsy M4 Express, QT Py M0 switch = DigitalInOut(board.D2) # switch = DigitalInOut(board.D5) # For Feather M0 Express, Feather M4 Express # switch = DigitalInOut(board.D7) # For Circuit Playground Express switch.direction = Direction.INPUT switch.pull = Pull.UP while True: # We could also do "led.value = not switch.value"! if switch.value: led.value = False else: led.value = True time.sleep(0.01) # debounce delay Note that we made the code a little less "Pythonic" than necessary. The if/else block could be replaced with a simple led.value = not switch.value but we wanted to make it super clear how to test the inputs. The interpreter will read the digital input when it evaluates switch.value . For Gemma M0, Trinket M0, Metro M0 Express, Metro M4 Express, ItsyBitsy M0 Express, ItsyBitsy M4 Express, no changes to the initial example are needed. Note: To "comment out" a line, put a # and a space before it. To "uncomment" a line, remove the # + space from the beginning of the line. For Feather M0 Express and Feather M4 Express, comment out switch = DigitalInOut(board.D2) (and/or switch = DigitalInOut(board.D7) ©Adafruit Industries Page 121 of 215 depending on what changes you already made), and uncomment switch = DigitalInOut(board.D5) . For Circuit Playground Express, you'll need to comment out switch = DigitalInOut(board.D2) (and/or switch = DigitalInOut(board.D5) depending on what changes you already made), and uncomment  switch = DigitalInOut(board.D7) . QT Py M0 does not have a little red LED built in. Therefore, you must connect an external LED for this example to work. See below for a wiring diagram illustrating how to connect an external LED to a QT Py M0. For QT Py M0, you'll need to comment out led = DigitalInOut(board.LED) and uncomment led = DigitalInOut(board.SCK) . The switch code remains the same. To find the pin or pad suggested in the code, see the list below. For the boards that require wiring, wire up a switch (also known as a tactile switch, button or pushbutton), following the diagram for guidance. Press or slide the switch, and the onboard red LED will turn on and off. Note that on the M0/SAMD based CircuitPython boards, at least, you can also have internal pulldowns with Pull.DOWN and if you want to turn off the pullup/pulldown just assign switch.pull = None. Find the pins! The list below shows each board, explains the location of the Digital pin suggested for use as input, and the location of the D13 LED. ©Adafruit Industries Page 122 of 215 Circuit Playground Express   We're going to use the switch, which is pin D7, and is located between the battery connector and the reset switch on the board. The LED is labeled D13 and is located next to the USB micro port.   To use D7, comment out the current pin setup line, and uncomment the line labeled for Circuit Playground Express. See the details above! Trinket M0   D2 is connected to the blue wire, labeled "2", and located between "3V" and "1" on the board. The LED is labeled "13" and is located next to the USB micro port. Gemma M0   D2 is an alligator-clip-friendly pad labeled both "D2" and "A1", shown connected to the blue wire, and is next to the USB micro port. The LED is located next to the "GND" label on the board, above the "On/Off" switch.   Use alligator clips to connect your switch to your Gemma M0! ©Adafruit Industries Page 123 of 215 QT Py M0 D2 is labeled A2, shown connected to the blue wire, and is near the USB port between A1 and A3. There is no little red LED built-in to the QT Py M0. Therefore, you must connect an external LED for this example to work. To wire up an external LED: LED + to QT Py SCK LED - to 470Ω resistor 470Ω resistor to QT Py GND The button and the LED share the same GND pin. To use the external LED, comment out the current LED setup line, and uncomment the line labeled for QT Py M0. See the details above! Feather M0 Express and Feather M4 Express   D5 is labeled "5" and connected to the blue wire on the board. The LED is labeled "#13" and is located next to the USB micro port.   To use D5, comment out the current pin setup line, and uncomment the line labeled for Feather M0 Express. See the details above! ©Adafruit Industries Page 124 of 215 ItsyBitsy M0 Express and ItsyBitsy M4 Express   D2 is labeled "2", located between the "MISO" and "EN" labels, and is connected to the blue wire on the board. The LED is located next to the reset button between the "3" and "4" labels on the board. Metro M0 Express and Metro M4 Express   D2 is located near the top left corner, and is connected to the blue wire. The LED is labeled "L" and is located next to the USB micro port. Read the Docs For a more in-depth look at what digitalio can do, check out the DigitalInOut page in Read the Docs (https://adafru.it/C4c). CircuitPython Analog In This example shows you how you can read the analog voltage on the A1 pin on your board. Copy and paste the code into code.py using your favorite editor, and save the file to run the demo. # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials Analog In example""" import time import board from analogio import AnalogIn ©Adafruit Industries Page 125 of 215 analog_in = AnalogIn(board.A1) def get_voltage(pin): return (pin.value * 3.3) / 65536 while True: print((get_voltage(analog_in),)) time.sleep(0.1) Make sure you're running the latest CircuitPython! If you are not, you may run into an error: "AttributeError: 'module' object has no attribute 'A1'". If you receive this error, first make sure you're running the latest version of CircuitPython! Creating the analog input analog1in = AnalogIn(board.A1) Creates an object and connects the object to A1 as an analog input. get_voltage Helper get_voltage(pin) is our little helper program. By default, analog readings will range from 0 (minimum) to 65535 (maximum). This helper will convert the 0-65535 reading from pin.value and convert it a 0-3.3V voltage reading. Main Loop The main loop is simple. It prints out the voltage as floating point values by calling get_voltage on our analog object. Connect to the serial console to see the results. ©Adafruit Industries Page 126 of 215 Changing It Up By default the pins are floating so the voltages will vary. While connected to the serial console, try touching a wire from A1 to the GND pin or 3Vo pin to see the voltage change. You can also add a potentiometer to control the voltage changes. From the potentiometer to the board, connect the left pin to ground, the middle pin to A1, and the right pin to 3V. If you're using Mu editor, you can see the changes as you rotate the potentiometer on the plotter like in the image above! (Click the Plotter icon at the top of the window to open the plotter.) When you turn the knob of the potentiometer, the wiper rotates left and right, increasing or decreasing the resistance. This, in turn, changes the analog voltage level that will be read by your board on A1. Wire it up The list below shows wiring diagrams to help find the correct pins and wire up the potentiometer, and provides more information about analog pins on your board! ©Adafruit Industries Page 127 of 215 Circuit Playground Express   A1 is located on the right side of the board. There are multiple ground and 3V pads (pins).   Your board has 7 analog pins that can be used for this purpose. For the full list, see the pinout page (https://adafru.it/AM9) on the main guide. Trinket M0   A1 is labeled as 2! It's located between "1~" and "3V" on the same side of the board as the little red LED. Ground is located on the opposite side of the board. 3V is located next to 2, on the same end of the board as the reset button.   You have 5 analog pins you can use. For the full list, see the pinouts page (https:// adafru.it/AMd) on the main guide. ©Adafruit Industries Page 128 of 215 Gemma M0   A1 is located near the top of the board of the board to the left side of the USB Micro port. Ground is on the other side of the USB port from A1. 3V is located to the left side of the battery connector on the bottom of the board.   Your board has 3 analog pins. For the full list, see the pinout page (https://adafru.it/ AMa) on the main guide. QT Py M0 A1, shown connected to the blue wire, is near the USB port between A0 and A2. Ground is on the opposite side of the QT Py, near the USB port, between 3V and 5V. 3V is the next pin, between GND and MO.   Your board has 10 analog pins. For the full list, see the pinouts page (https://adafru.it/ OeY) in the main guide. ©Adafruit Industries Page 129 of 215 Feather M0 Express and Feather M4 Express   A1 is located along the edge opposite the battery connector. There are multiple ground pins. 3V is located along the same edge as A1, and is next to the reset button.   Your board has 6 analog pins you can use. For the full list, see the pinouts page (https://adafru.it/AMc) on the main guide. ItsyBitsy M0 Express and ItsyBitsy M4 Express   A1 is located in the middle of the board, near the "A" in "Adafruit". Ground is labled "G" and is located next to "BAT", near the USB Micro port. 3V is found on the opposite side of the USB port from Ground, next to RST.   You have 6 analog pins you can use. For a full list, see the pinouts page (https:// adafru.it/BMg) on the main guide. ©Adafruit Industries Page 130 of 215 Metro M0 Express and Metro M4 Express   A1 is located on the same side of the board as the barrel jack. There are multiple ground pins available. 3V is labeled "3.3" and is located in the center of the board on the same side as the barrel jack (and as A1).   Your Metro M0 Express board has 6 analog pins you can use. For the full list, see the pinouts page (https://adafru.it/ AMb) on the main guide.   Your Metro M4 Express board has 6 analog pins you can use. For the full list, see the pinouts page (https://adafru.it/B1O) on the main guide. Reading Analog Pin Values The get_voltage() helper used in the potentiometer example above reads the raw analog pin value and converts it to a voltage level. You can, however, directly read an analog pin value in your code by using pin.value . For example, to simply read the raw analog pin value from the potentiometer, you would run the following code: import time import board from analogio import AnalogIn analog_in = AnalogIn(board.A1) while True: print(analog_in.value) time.sleep(0.1) This works with any analog pin or input. Use the .value to read the raw value and utilise it in your code. ©Adafruit Industries Page 131 of 215 CircuitPython Analog Out This example shows you how you can set the DAC (true analog output) on pin A0. A0 is the only true analog output on the M0 boards. No other pins do true analog output! Copy and paste the code into code.py using your favorite editor, and save the file. # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Analog Out example""" import board from analogio import AnalogOut analog_out = AnalogOut(board.A0) while True: # Count up from 0 to 65535, with 64 increment # which ends up corresponding to the DAC's 10-bit range for i in range(0, 65535, 64): analog_out.value = i Creating an analog output analog_out = AnalogOut(A0) Creates an object analog_out and connects the object to A0, the only DAC pin available on both the M0 and the M4 boards. (The M4 has two, A0 and A1.) Setting the analog output The DAC on the SAMD21 is a 10-bit output, from 0-3.3V. So in theory you will have a resolution of 0.0032 Volts per bit. To allow CircuitPython to be general-purpose enough that it can be used with chips with anything from 8 to 16-bit DACs, the DAC takes a 16-bit value and divides it down internally. For example, writing 0 will be the same as setting it to 0 - 0 Volts out. Writing 5000 is the same as setting it to 5000 / 64 = 78, and 78 / 1024 * 3.3V = 0.25V output. ©Adafruit Industries Page 132 of 215 Writing 65535 is the same as 1023 which is the top range and you'll get 3.3V output Main Loop The main loop is fairly simple, it goes through the entire range of the DAC, from 0 to 65535, but increments 64 at a time so it ends up clicking up one bit for each of the 10-bits of range available. CircuitPython is not terribly fast, so at the fastest update loop you'll get 4 Hz. The DAC isn't good for audio outputs as-is. Express boards like the Circuit Playground Express, Metro M0 Express, ItsyBitsy M0 Express, ItsyBitsy M4 Express, Metro M4 Express, Feather M4 Express, or Feather M0 Express have more code space and can perform audio playback capabilities via the DAC. QT Py M0, Gemma M0 and Trinket M0 cannot! Check out the Audio Out section of this guide (https://adafru.it/BRj) for examples! Find the pin Use the diagrams below to find the A0 pin marked with a magenta arrow! ©Adafruit Industries Page 133 of 215 Circuit Playground Express   A0 is located between VOUT and A1 near the battery port. Trinket M0   A0 is labeled "1~" on Trinket! A0 is located between "0" and "2" towards the middle of the board on the same side as the red LED. Gemma M0   A0 is located in the middle of the right side of the board next to the On/Off switch. ©Adafruit Industries Page 134 of 215 QT Py M0 A0 is located next to the USB port, by the "QT" label on the board silk. Feather M0 Express   A0 is located between GND and A1 on the opposite side of the board from the battery connector, towards the end with the Reset button. Feather M4 Express   A0 is located between GND and A1 on the opposite side of the board from the battery connector, towards the end with the Reset button, and the pin pad has left and right white parenthesis markings around it ©Adafruit Industries Page 135 of 215 ItsyBitsy M0 Express   A0 is located between VHI and A1, near the "A" in "Adafruit", and the pin pad has left and right white parenthesis markings around it. ItsyBitsy M4 Express   A0 is located between VHI and A1, and the pin pad has left and right white parenthesis markings around it. Metro M0 Express   A0 is between VIN and A1, and is located along the same side of the board as the barrel jack adapter towards the middle of the headers found on that side of the board. ©Adafruit Industries Page 136 of 215 Metro M4 Express   A0 is between VIN and A1, and is located along the same side of the board as the barrel jack adapter towards the middle of the headers found on that side of the board.   On the Metro M4 Express, there are TWO true analog outputs: A0 and A1. CircuitPython PWM Your board has pwmio support, which means you can PWM LEDs, control servos, beep piezos, and manage "pulse train" type devices like DHT22 and Infrared. Nearly every pin has PWM support! For example, all ATSAMD21 board have an A0 pin which is 'true' analog out and does not have PWM support. PWM with Fixed Frequency This example will show you how to use PWM to fade the little red LED on your board. The QT Py M0 does not have a little red LED. Therefore, you must connect an external LED and edit this example for it to work. Follow the wiring diagram and steps below to run this example on QT Py M0. The following illustrates how to connect an external LED to a QT Py M0. ©Adafruit Industries Page 137 of 215 LED + to QT Py SCK LED - to 470Ω resistor 470Ω resistor to QT Py GND Copy and paste the code into code.py using your favorite editor, and save the file. # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials: PWM with Fixed Frequency example.""" import time import board import pwmio # LED led = # LED # led setup for most CircuitPython boards: pwmio.PWMOut(board.LED, frequency=5000, duty_cycle=0) setup for QT Py M0: = pwmio.PWMOut(board.SCK, frequency=5000, duty_cycle=0) while True: for i in range(100): # PWM LED up and down if i < 50: led.duty_cycle = int(i * 2 * 65535 / 100) # Up else: led.duty_cycle = 65535 - int((i - 50) * 2 * 65535 / 100) time.sleep(0.01) # Down Remember: To "comment out" a line, put a # and a space before it. To "uncomment" a line, remove the # + space from the beginning of the line. To use with QT Py M0, you must comment out led = pwmio.PWMOut(board.LED, frequency=5000, duty_cycle=0) and uncomment led = pwmio.PWMOut(board.SCK, frequency=5000, duty_cycle=0) . Your setup lines should look like this for the example to work with QT Py M0: # LED # led # LED led = setup for most CircuitPython boards: = pwmio.PWMOut(board.LED, frequency=5000, duty_cycle=0) setup for QT Py M0: pwmio.PWMOut(board.SCK, frequency=5000, duty_cycle=0) ©Adafruit Industries Page 138 of 215 Create a PWM Output led = pwmio.PWMOut(board.LED, frequency=5000, duty_cycle=0) Since we're using the onboard LED, we'll call the object led , use pwmio.PWMOut to create the output and pass in the D13 LED pin to use. Main Loop The main loop uses range() to cycle through the loop. When the range is below 50, it PWMs the LED brightness up, and when the range is above 50, it PWMs the brightness down. This is how it fades the LED brighter and dimmer! The time.sleep() is needed to allow the PWM process to occur over a period of time. Otherwise it happens too quickly for you to see! PWM Output with Variable Frequency Fixed frequency outputs are great for pulsing LEDs or controlling servos. But if you want to make some beeps with a piezo, you'll need to vary the frequency. The following example uses pwmio to make a series of tones on a piezo. To use with any of the M0 boards, no changes to the following code are needed. Remember: To "comment out" a line, put a # and a space before it. To "uncomment" a line, remove the # + space from the beginning of the line. To use with the Metro M4 Express, ItsyBitsy M4 Express or the Feather M4 Express, you must comment out the piezo = pwmio.PWMOut(board.A2, duty_cycle=0, frequency=440, variable_frequency=True) line and uncomment the piezo = pwmio.PWMOut(board.A1, duty_cycle=0, frequency=440, variable_frequency=True) line. A2 is not a supported PWM pin on the M4 boards! # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials PWM with variable frequency piezo example""" import time import board import pwmio ©Adafruit Industries Page 139 of 215 # For the M0 boards: piezo = pwmio.PWMOut(board.A2, duty_cycle=0, frequency=440, variable_frequency=True) # For the M4 boards: # piezo = pwmio.PWMOut(board.A1, duty_cycle=0, frequency=440, variable_frequency=True) while True: for f in (262, 294, 330, 349, 392, 440, 494, 523): piezo.frequency = f piezo.duty_cycle = 65535 // 2 # On 50% time.sleep(0.25) # On for 1/4 second piezo.duty_cycle = 0 # Off time.sleep(0.05) # Pause between notes time.sleep(0.5) If you have simpleio library loaded into your /lib folder on your board, we have a nice little helper that makes a tone for you on a piezo with a single command. To use with any of the M0 boards, no changes to the following code are needed. To use with the Metro M4 Express, ItsyBitsy M4 Express or the Feather M4 Express, you must comment out the simpleio.tone(board.A2, f, 0.25) line and uncomment the simpleio.tone(board.A1, f, 0.25) line. A2 is not a supported PWM pin on the M4 boards! # SPDX-FileCopyrightText: 2017 Limor Fried for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials PWM piezo simpleio example""" import time import board import simpleio while True: for f in (262, 294, 330, 349, 392, 440, 494, 523): # For the M0 boards: simpleio.tone(board.A2, f, 0.25) # on for 1/4 second # For the M4 boards: # simpleio.tone(board.A1, f, 0.25) # on for 1/4 second time.sleep(0.05) # pause between notes time.sleep(0.5) As you can see, it's much simpler! Wire it up Use the diagrams below to help you wire up your piezo. Attach one leg of the piezo to pin A2 on the M0 boards or A1 on the M4 boards, and the other leg to ground. It doesn't matter which leg is connected to which pin. They're interchangeable! ©Adafruit Industries Page 140 of 215 Circuit Playground Express   Use alligator clips to attach A2 and any one of the GND to different legs of the piezo.   CPX has PWM on the following pins: A1, A2, A3, A6, RX, LIGHT, A8, TEMPERATURE, A9, BUTTON_B, D5, SLIDE_SWITCH, D7, D13, REMOTEIN, IR_RX, REMOTEOUT, IR_TX, IR_PROXIMITY, MICROPHONE_CLOCK, MICROPHONE_DATA, ACCELEROMETER_INTERRUPT, ACCELEROMETER_SDA, ACCELEROMETER_SCL, SPEAKER_ENABLE.   There is NO PWM on: A0, SPEAKER, A4, SCL, A5, SDA, A7, TX, BUTTON_A, D4, NEOPIXEL, D8, SCK, MOSI, MISO, FLASH_CS. ©Adafruit Industries Page 141 of 215 Trinket M0   Note: A2 on Trinket is also labeled Digital "0"!   Use jumper wires to connect GND and D0 to different legs of the piezo.   Trinket has PWM available on the following pins: D0, A2, SDA, D2, A1, SCL, MISO, D4, A4, TX, MOSI, D3, A3, RX, SCK, D13, APA102_MOSI, APA102_SCK.   There is NO PWM on: A0, D1. Gemma M0   Use alligator clips to attach A2 and GND to different legs on the piezo.   Gemma has PWM available on the following pins: A1, D2, RX, SCL, A2, D0, TX, SDA, L, D13, APA102_MOSI, APA102_SCK.   There is NO PWM on: A0, D1. ©Adafruit Industries Page 142 of 215 QT Py M0 Use jumper wires to attach A2 and GND to different legs of the piezo.   The QT Py M0 has PWM on the following pins: A2, A3, A6, A7, A8, A9, A10, D2, D3, D4, D5, D6, D7, D8, D9, D10, SCK, MISO, MOSI, NEOPIXEL, RX, TX, SCL, SDA. There is NO A0, A1, D0, D1, NEOPIXEL_POWER. Feather M0 Express   Use jumper wires to attach A2 and one of the two GND to different legs of the piezo.   Feather M0 Express has PWM on the following pins: A2, A3, A4, SCK, MOSI, MISO, D0, RX, D1, TX, SDA, SCL, D5, D6, D9, D10, D11, D12, D13, NEOPIXEL.   There is NO PWM on: A0, A1, A5. ©Adafruit Industries Page 143 of 215 Feather M4 Express   Use jumper wires to attach A1 and one of the two GND to different legs of the piezo.   To use A1, comment out the current pin setup line, and uncomment the line labeled for the M4 boards. See the details above!   Feather M4 Express has PWM on the following pins: A1, A3, SCK, D0, RX, D1, TX, SDA, SCL, D4, D5, D6, D9, D10, D11, D12, D13.   There is NO PWM on: A0, A2, A4, A5, MOSI, MISO. ItsyBitsy M0 Express   Use jumper wires to attach A2 and G to different legs of the piezo.   ItsyBitsy M0 Express has PWM on the following pins: D0, RX, D1, TX, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12, D13, L, A2, A3, A4, MOSI, MISO, SCK, SCL, SDA, APA102_MOSI, APA102_SCK.   There is NO PWM on: A0, A1, A5. ©Adafruit Industries Page 144 of 215 ItsyBitsy M4 Express   Use jumper wires to attach A1 and G to different legs of the piezo.   To use A1, comment out the current pin setup line, and uncomment the line labeled for the M4 boards. See the details above!   ItsyBitsy M4 Express has PWM on the following pins: A1, D0, RX, D1, TX, D2, D4, D5, D7, D9, D10, D11, D12, D13, SDA, SCL. There is NO PWM on: A2, A3, A4, A5, D3, SCK, MOSI, MISO. Metro M0 Express   Use jumper wires to connect A2 and any one of the GND to different legs on the piezo.   Metro M0 Express has PWM on the following pins: A2, A3, A4, D0, RX, D1, TX, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12, D13, SDA, SCL, NEOPIXEL, SCK, MOSI, MISO.   There is NO PWM on: A0, A1, A5, FLASH_CS. ©Adafruit Industries Page 145 of 215 Metro M4 Express   Use jumper wires to connect A1 and any one of the GND to different legs on the piezo.   To use A1, comment out the current pin setup line, and uncomment the line labeled for the M4 boards. See the details above! Metro M4 Express has PWM on: A1, A5, D0, RX, D1, TX, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12, D13, SDA, SCK, MOSI, MISO   There is No PWM on: A0, A2, A3, A4, SCL, AREF, NEOPIXEL, LED_RX, LED_TX. Where's My PWM? Want to check to see which pins have PWM yourself? We've written this handy script! It attempts to setup PWM on every pin available, and lets you know which ones work and which ones don't. Check it out! # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials PWM pin identifying script""" import board import pwmio for pin_name in dir(board): pin = getattr(board, pin_name) try: p = pwmio.PWMOut(pin) p.deinit() print("PWM on:", pin_name) # Prints the valid, PWM-capable pins! except ValueError: # This is the error returned when the pin is invalid. print("No PWM on:", pin_name) # Prints the invalid pins. except RuntimeError: # Timer conflict error. print("Timers in use:", pin_name) # Prints the timer conflict pins. ©Adafruit Industries Page 146 of 215 except TypeError: # Error returned when checking a non-pin object in dir(board). pass # Passes over non-pin objects in dir(board). CircuitPython Servo In order to use servos, we take advantage of pwmio . Now, in theory, you could just use the raw pwmio  calls to set the frequency to 50 Hz and then set the pulse widths. But we would rather make it a little more elegant and easy! So, instead we will use adafruit_motor which manages servos for you quite nicely! adafruit_motor is a library so be sure to grab it from the library bundle if you have not yet (https://adafru.it/zdx)! If you need help installing the library, check out the Circu itPython Libraries page (https://adafru.it/ABU). Servos come in two types:  • A standard hobby servo - the horn moves 180 degrees (90 degrees in each direction from zero degrees). • A continuous servo - the horn moves in full rotation like a DC motor. Instead of an angle specified, you set a throttle value with 1.0 being full forward, 0.5 being half forward, 0 being stopped, and -1 being full reverse, with other values between. Servo Wiring Servos will only work on PWM-capable pins! Check your board details to verify which pins have PWM outputs. The connections for a servo are the same for standard servos and continuous rotation servos. Connect the servo's brown or black ground wire to ground on the CircuitPython board. Connect the servo's red power wire to 5V power, USB power is good for a servo or two. For more than that, you'll need an external battery pack. Do not use 3.3V for powering a servo! ©Adafruit Industries Page 147 of 215 Connect the servo's yellow or white signal wire to the control/data pin, in this case A1 or A2 but you can use any PWM-capable pin. For example, to wire a servo to Trinket, connect the ground wire to GND, the power wire to USB, and the signal wire to 0.   Remember, A2 on Trinket is labeled "0".     For Gemma, use jumper wire alligator clips to connect the ground wire to GND, the power wire to VOUT, and the signal wire to A2. For Circuit Playground Express and Circuit Playground Bluefruit, use jumper wire alligator clips to connect the ground wire to GND, the power wire to VOUT, and the signal wire to A2. ©Adafruit Industries Page 148 of 215 For QT Py M0, connect the ground wire to GND, the power wire to 5V, and the signal wire to A2. For boards like Feather M0 Express, ItsyBitsy M0 Express and Metro M0 Express, connect the ground wire to any GND, the power wire to USB or 5V, and the signal wire to A2. For the Metro M4 Express, ItsyBitsy M4 Express and the Feather M4 Express, connect the ground wire to any G or GND, the power wire to USB or 5V, and the signal wire to A2. Standard Servo Code Here's an example that will sweep a servo connected to pin A2 from 0 degrees to 180 degrees (-90 to 90 degrees) and back: # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT ©Adafruit Industries Page 149 of 215 """CircuitPython Essentials Servo standard servo example""" import time import board import pwmio from adafruit_motor import servo # create a PWMOut object on Pin A2. pwm = pwmio.PWMOut(board.A2, duty_cycle=2 ** 15, frequency=50) # Create a servo object, my_servo. my_servo = servo.Servo(pwm) while True: for angle in range(0, 180, 5): # 0 - 180 degrees, 5 degrees at a time. my_servo.angle = angle time.sleep(0.05) for angle in range(180, 0, -5): # 180 - 0 degrees, 5 degrees at a time. my_servo.angle = angle time.sleep(0.05) Continuous Servo Code There are two differences with Continuous Servos vs. Standard Servos: 1. The servo object is created like  my_servo = servo.ContinuousServo(pwm) instead of  my_servo = servo.Servo(pwm) 2. Instead of using myservo.angle , you use my_servo.throttle using a throttle value from 1.0 (full on) to 0.0 (stopped) to -1.0 (full reverse). Any number between would be a partial speed forward (positive) or reverse (negative). This is very similar to standard DC motor control with the adafruit_motor library. This example runs full forward for 2 seconds, stops for 2 seconds, runs full reverse for 2 seconds, then stops for 4 seconds. # SPDX-FileCopyrightText: 2019 Anne Barela for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials Servo continuous rotation servo example""" import time import board import pwmio from adafruit_motor import servo # create a PWMOut object on Pin A2. pwm = pwmio.PWMOut(board.A2, frequency=50) # Create a servo object, my_servo. my_servo = servo.ContinuousServo(pwm) while True: print("forward") my_servo.throttle = 1.0 time.sleep(2.0) print("stop") my_servo.throttle = 0.0 time.sleep(2.0) print("reverse") ©Adafruit Industries Page 150 of 215 my_servo.throttle = -1.0 time.sleep(2.0) print("stop") my_servo.throttle = 0.0 time.sleep(4.0) Pretty simple! Note that we assume that 0 degrees is 0.5ms and 180 degrees is a pulse width of 2.5ms. That's a bit wider than the official 1-2ms pulse widths. If you have a servo that has a different range you can initialize the servo object with a different min_pulse and max_pulse . For example: my_servo = servo.Servo(pwm, min_pulse = 500, max_pulse = 2500)   For more detailed information on using servos with CircuitPython, check out the Circui tPython section of the servo guide (https://adafru.it/Bei)! CircuitPython Internal RGB LED Every board has a built in RGB LED. You can use CircuitPython to control the color and brightness of this LED. There are two different types of internal RGB LEDs: DotSta r (https://adafru.it/kDg) and NeoPixel (https://adafru.it/Bej). This section covers both and explains which boards have which LED. The first example will show you how to change the color and brightness of the internal RGB LED. Copy and paste the code into code.py using your favorite editor, and save the file. ©Adafruit Industries Page 151 of 215 # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials Internal RGB LED red, green, blue example""" import time import board # For Trinket M0, Gemma M0, ItsyBitsy M0 Express, and ItsyBitsy M4 Express import adafruit_dotstar led = adafruit_dotstar.DotStar(board.APA102_SCK, board.APA102_MOSI, 1) # For Feather M0 Express, Metro M0 Express, Metro M4 Express, Circuit Playground Express, QT Py M0 # import neopixel # led = neopixel.NeoPixel(board.NEOPIXEL, 1) led.brightness = 0.3 while True: led[0] = (255, 0, 0) time.sleep(0.5) led[0] = (0, 255, 0) time.sleep(0.5) led[0] = (0, 0, 255) time.sleep(0.5) Create the LED First, we create the LED object and attach it to the correct pin or pins. In the case of a NeoPixel, there is only one pin necessary, and we have called it NEOPIXEL for easier use. In the case of a DotStar, however, there are two pins necessary, and so we use the pin names  APA102_MOSI and  APA102_SCK to get it set up. Since we're using the single onboard LED, the last thing we do is tell it that there's only 1 LED! Trinket M0, Gemma M0, ItsyBitsy M0 Express, and ItsyBitsy M4 Express each have an onboard Dotstar LED, so no changes are needed to the initial version of the example. Remember: To "comment out" a line, put a # and a space before it. To "uncomment" a line, remove the # + space from the beginning of the line. QT Py M0, Feather M0 Express, Feather M4 Express, Metro M0 Express, Metro M4 Express, and Circuit Playground Express each have an onboard NeoPixel LED, so you must comment out  import adafruit_dotstar and led = adafruit_dotstar.DotStar(board.APA102_SCK, board.APA102_MOSI, 1) , and uncomment  import neopixel and led = neopixel.NeoPixel(board.NEOPIXEL, 1) . ©Adafruit Industries Page 152 of 215 Brightness To set the brightness you simply use the brightness attribute. Brightness is set with a number between 0 and 1 , representative of a percent from 0% to 100%. So, led.brightness = (0.3) sets the LED brightness to 30%. The default brightness is 1 or 100%, and at it's maximum, the LED is blindingly bright! You can set it lower if you choose. Main Loop LED colors are set using a combination of red, green, and blue, in the form of an (R, G, B) tuple. Each member of the tuple is set to a number between 0 and 255 that determines the amount of each color present. Red, green and blue in different combinations can create all the colors in the rainbow! So, for example, to set the LED to red, the tuple would be (255, 0, 0), which has the maximum level of red, and no green or blue. Green would be (0, 255, 0), etc. For the colors between, you set a combination, such as cyan which is (0, 255, 255), with equal amounts of green and blue. The main loop is quite simple. It sets the first LED to red using (255, 0, 0) , then gr een using (0, 255, 0) , and finally blue using (0, 0, 255) . Next, we give it a tim e.sleep() so it stays each color for a period of time. We chose time.sleep(0.5) , or half a second. Without the time.sleep() it'll flash really quickly and the colors will be difficult to see! Note that we set led[0] . This means the first, and in the case of most of the boards, the only LED. In CircuitPython, counting starts at 0. So the first of any object, list, etc will be 0 ! ©Adafruit Industries Page 153 of 215 Try changing the numbers in the tuples to change your LED to any color of the rainbow. Or, you can add more lines with different color tuples to add more colors to the sequence. Always add the time.sleep() , but try changing the amount of time to create different cycle animations! Making Rainbows (Because Who Doesn't Love 'Em!) Coding a rainbow effect involves a little math and a helper function called colorwhee l . For details about how wheel works, see this explanation here (https://adafru.it/ Bek)! ©Adafruit Industries Page 154 of 215 The last example shows how to do a rainbow animation on the internal RGB LED. Copy and paste the code into code.py using your favorite editor, and save the file. Re member to comment and uncomment the right lines for the board you're using, as exp lained above (https://adafru.it/Bel). # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials Internal RGB LED rainbow example""" import time import board from rainbowio import colorwheel # For Trinket M0, Gemma M0, ItsyBitsy M0 Express and ItsyBitsy M4 Express import adafruit_dotstar led = adafruit_dotstar.DotStar(board.APA102_SCK, board.APA102_MOSI, 1) # For Feather M0 Express, Metro M0 Express, Metro M4 Express, Circuit Playground Express, QT Py M0 # import neopixel # led = neopixel.NeoPixel(board.NEOPIXEL, 1) led.brightness = 0.3 i = 0 while True: i = (i + 1) % 256 # run from 0 to 255 led.fill(colorwheel(i)) time.sleep(0.01) We add the colorwheel function in after setup but before our main loop. And right before our main loop, we assign the variable i = 0 , so it's ready for use inside the loop. The main loop contains some math that cycles i from 0 to 255 and around again repeatedly. We use this value to cycle colorwheel() through the rainbow! The time.sleep() determines the speed at which the rainbow changes. Try a higher number for a slower rainbow or a lower number for a faster one! Circuit Playground Express Rainbow Note that here we use led.fill instead of led[0] . This means it turns on all the LEDs, which in the current code is only one. So why bother with fill ? Well, you may have a Circuit Playground Express, which as you can see has TEN NeoPixel LEDs built in. The examples so far have only turned on the first one. If you'd like to do a rainbow on all ten LEDs, change the 1 in: ©Adafruit Industries Page 155 of 215 led = neopixel.NeoPixel(board.NEOPIXEL, 1) to 10 so it reads: led = neopixel.NeoPixel(board.NEOPIXEL, 10) . This tells the code to look for 10 LEDs instead of only 1. Now save the code and watch the rainbow go! You can make the same 1 to 10 change to the previous examples as well, and use led.fill to light up all the LEDs in the colors you chose! For more details, check out the NeoPixel section of the CPX guide (https://adafru.it/Bem)! CircuitPython NeoPixel NeoPixels are a revolutionary and ultra-popular way to add lights and color to your project. These stranded RGB lights have the controller inside the LED, so you just push the RGB data and the LEDs do all the work for you. They're a perfect match for CircuitPython! You can drive 300 NeoPixel LEDs with brightness control (set brightness=1.0 in object creation) and 1000 LEDs without. That's because to adjust the brightness we have to dynamically recreate the data-stream each write. You'll need the neopixel.mpy library if you don't already have it in your /lib folder! You can get it from the CircuitPython Library Bundle (https://adafru.it/y8E). If you need help installing the library, check out the CircuitPython Libraries page (https://adafru.it/ ABU). ©Adafruit Industries Page 156 of 215 Wiring It Up You'll need to solder up your NeoPixels first. Verify your connection is on the DATA INPUT or DIN side. Plugging into the DATA OUT or DOUT side is a common mistake! The connections are labeled and some formats have arrows to indicate the direction the data must flow. For powering the pixels from the board, the 3.3V regulator output can handle about 500mA peak which is about 50 pixels with 'average' use. If you want really bright lights and a lot of pixels, we recommend powering direct from an external power source. • On Gemma M0 and Circuit Playground Express this is the Vout pad - that pad has direct power from USB or the battery, depending on which is higher voltage. • On Trinket M0, Feather M0 Express, Feather M4 Express, ItsyBitsy M0 Express and ItsyBitsy M4 Express the USB or BAT pins will give you direct power from the USB port or battery. • On Metro M0 Express and Metro M4 Express, use the 5V pin regardless of whether it's powered via USB or the DC jack. • On QT Py M0, use the 5V pin. If the power to the NeoPixels is greater than 5.5V you may have some difficulty driving some strips, in which case you may need to lower the voltage to 4.5-5V or use a level shifter. Do not use the VIN pin directly on Metro M0 Express or Metro M4 Express! The voltage can reach 9V and this can destroy your NeoPixels! Note that the wire ordering on your NeoPixel strip or shape may not exactly match the diagram above. Check the markings to verify which pin is DIN, 5V and GND ©Adafruit Industries Page 157 of 215 The Code This example includes multiple visual effects. Copy and paste the code into code.py using your favorite editor, and save the file. # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials NeoPixel example""" import time import board from rainbowio import colorwheel import neopixel pixel_pin = board.A1 num_pixels = 8 pixels = neopixel.NeoPixel(pixel_pin, num_pixels, brightness=0.3, auto_write=False) def color_chase(color, wait): for i in range(num_pixels): pixels[i] = color time.sleep(wait) pixels.show() time.sleep(0.5) def rainbow_cycle(wait): for j in range(255): for i in range(num_pixels): rc_index = (i * 256 // num_pixels) + j pixels[i] = colorwheel(rc_index & 255) pixels.show() time.sleep(wait) RED = (255, 0, 0) YELLOW = (255, 150, 0) GREEN = (0, 255, 0) CYAN = (0, 255, 255) BLUE = (0, 0, 255) PURPLE = (180, 0, 255) while True: pixels.fill(RED) pixels.show() # Increase or decrease to change the speed of the solid color change. time.sleep(1) pixels.fill(GREEN) pixels.show() time.sleep(1) pixels.fill(BLUE) pixels.show() time.sleep(1) color_chase(RED, 0.1) # Increase the number to slow down the color chase color_chase(YELLOW, 0.1) color_chase(GREEN, 0.1) color_chase(CYAN, 0.1) color_chase(BLUE, 0.1) color_chase(PURPLE, 0.1) ©Adafruit Industries Page 158 of 215 rainbow_cycle(0) # Increase the number to slow down the rainbow Create the LED The first thing we'll do is create the LED object. The NeoPixel object has two required arguments and two optional arguments. You are required to set the pin you're using to drive your NeoPixels and provide the number of pixels you intend to use. You can optionally set brightness and auto_write . NeoPixels can be driven by any pin. We've chosen A1. To set the pin, assign the variable pixel_pin to the pin you'd like to use, in our case board.A1 . To provide the number of pixels, assign the variable num_pixels to the number of pixels you'd like to use. In this example, we're using a strip of 8 . We've chosen to set brightness=0.3 , or 30%. By default, auto_write=True , meaning any changes you make to your pixels will be sent automatically. Since True is the default, if you use that setting, you don't need to include it in your LED object at all. We've chosen to set  auto_write=False . If you set auto_write=False , you must include pixels.show() each time you'd like to send data to your pixels. This makes your code more complicated, but it can make your LED animations faster! NeoPixel Helpers Next we've included a few helper functions to create the super fun visual effects found in this code. First is wheel() which we just learned with the Internal RGB LED ( https://adafru.it/Bel). Then we have color_chase() which requires you to provide a color and the amount of time in seconds you'd like between each step of the chase. Next we have rainbow_cycle() , which requires you to provide the mount of time in seconds you'd like the animation to take. Last, we've included a list of variables for our colors. This makes it much easier if to reuse the colors anywhere in the code, as well as add more colors for use in multiple places. Assigning and using RGB colors is explained in this section of the CircuitPython Internal RGB LED page (https://adafru.it/ Bel). ©Adafruit Industries Page 159 of 215 Main Loop Thanks to our helpers, our main loop is quite simple. We include the code to set every NeoPixel we're using to red, green and blue for 1 second each. Then we call color_c hase() , one time for each color on our list with 0.1 second delay between setting each subsequent LED the same color during the chase. Last we call rainbow_cycle( 0) , which means the animation is as fast as it can be. Increase both of those numbers to slow down each animation! Note that the longer your strip of LEDs, the longer it will take for the animations to complete. We have a ton more information on general purpose NeoPixel know-how at our NeoPixel UberGuide https://learn.adafruit.com/adafruit-neopixel-uberguide NeoPixel RGBW NeoPixels are available in RGB, meaning there are three LEDs inside, red, green and blue. They're also available in RGBW, which includes four LEDs, red, green, blue and white. The code for RGBW NeoPixels is a little bit different than RGB. If you run RGB code on RGBW NeoPixels, approximately 3/4 of the LEDs will light up and the LEDs will be the incorrect color even though they may appear to be changing. This is because NeoPixels require a piece of information for each available color (red, green, blue and possibly white). Therefore, RGB LEDs require three pieces of information and RGBW LEDs require FOUR pieces of information to work. So when you create the LED object for RGBW LEDs, you'll include pixel_order=(1, 0, 2, 3) , which sets the pixel order and indicates four pieces of information involved. Then, you must include an extra number in every color tuple you create. For example, red will be (255, 0, 0, 0) . This is how you send the fourth piece of information. Check out the example below to see how our NeoPixel code looks for using with RGBW LEDs! # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials NeoPixel RGBW example""" import time ©Adafruit Industries Page 160 of 215 import board import neopixel pixel_pin = board.A1 num_pixels = 8 pixels = neopixel.NeoPixel(pixel_pin, num_pixels, brightness=0.3, auto_write=False, pixel_order=(1, 0, 2, 3)) def colorwheel(pos): # Input a value 0 to 255 to get a color value. # The colours are a transition r - g - b - back to r. if pos < 0 or pos > 255: return (0, 0, 0, 0) if pos < 85: return (255 - pos * 3, pos * 3, 0, 0) if pos < 170: pos -= 85 return (0, 255 - pos * 3, pos * 3, 0) pos -= 170 return (pos * 3, 0, 255 - pos * 3, 0) def color_chase(color, wait): for i in range(num_pixels): pixels[i] = color time.sleep(wait) pixels.show() time.sleep(0.5) def rainbow_cycle(wait): for j in range(255): for i in range(num_pixels): rc_index = (i * 256 // num_pixels) + j pixels[i] = colorwheel(rc_index & 255) pixels.show() time.sleep(wait) RED = (255, 0, 0, 0) YELLOW = (255, 150, 0, 0) GREEN = (0, 255, 0, 0) CYAN = (0, 255, 255, 0) BLUE = (0, 0, 255, 0) PURPLE = (180, 0, 255, 0) while True: pixels.fill(RED) pixels.show() # Increase or decrease to change the speed of the solid color change. time.sleep(1) pixels.fill(GREEN) pixels.show() time.sleep(1) pixels.fill(BLUE) pixels.show() time.sleep(1) color_chase(RED, 0.1) # Increase the number to slow down the color chase color_chase(YELLOW, 0.1) color_chase(GREEN, 0.1) color_chase(CYAN, 0.1) color_chase(BLUE, 0.1) color_chase(PURPLE, 0.1) rainbow_cycle(0) ©Adafruit Industries # Increase the number to slow down the rainbow Page 161 of 215 Read the Docs For a more in depth look at what neopixel can do, check out NeoPixel on Read the Docs (https://adafru.it/C5m). CircuitPython DotStar DotStars use two wires, unlike NeoPixel's one wire. They're very similar but you can write to DotStars much faster with hardware SPI and they have a faster PWM cycle so they are better for light painting. Any pins can be used but if the two pins can form a hardware SPI port, the library will automatically switch over to hardware SPI. If you use hardware SPI then you'll get 4 MHz clock rate (that would mean updating a 64 pixel strand in about 500uS - that's 0.0005 seconds). If you use non-hardware SPI pins you'll drop down to about 3KHz, 1000 times as slow! You can drive 300 DotStar LEDs with brightness control (set brightness=1.0 in object creation) and 1000 LEDs without. That's because to adjust the brightness we have to dynamically recreate the data-stream each write. You'll need the adafruit_dotstar.mpy library if you don't already have it in your /lib folder! You can get it from the CircuitPython Library Bundle (https://adafru.it/y8E). If you need help installing the library, check out the CircuitPython Libraries page (https:/ /adafru.it/ABU). Wire It Up You'll need to solder up your DotStars first. Verify your connection is on the DATA INPUT or DI and CLOCK INPUT or CI side. Plugging into the DATA OUT/DO or CLOCK OUT/CO side is a common mistake! The connections are labeled and some formats ©Adafruit Industries Page 162 of 215 have arrows to indicate the direction the data must flow. Always verify your wiring with a visual inspection, as the order of the connections can differ from strip to strip! For powering the pixels from the board, the 3.3V regulator output can handle about 500mA peak which is about 50 pixels with 'average' use. If you want really bright lights and a lot of pixels, we recommend powering direct from an external power source. • On Gemma M0 and Circuit Playground Express this is the Vout pad - that pad has direct power from USB or the battery, depending on which is higher voltage. • On Trinket M0, Feather M0 Express, Feather M4 Express, ItsyBitsy M0 Express and ItsyBitsy M4 Express the USB or BAT pins will give you direct power from the USB port or battery. • On Metro M0 Express and Metro M4 Express, use the 5V pin regardless of whether it's powered via USB or the DC jack. • On QT Py M0, use the 5V pin. If the power to the DotStars is greater than 5.5V you may have some difficulty driving some strips, in which case you may need to lower the voltage to 4.5-5V or use a level shifter. Do not use the VIN pin directly on Metro M0 Express or Metro M4 Express! The voltage can reach 9V and this can destroy your DotStars! Note that the wire ordering on your DotStar strip or shape may not exactly match the diagram above. Check the markings to verify which pin is DIN, CIN, 5V and GND The Code This example includes multiple visual effects. Copy and paste the code into code.py using your favorite editor, and save the file. ©Adafruit Industries Page 163 of 215 # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials DotStar example""" import time from rainbowio import colorwheel import adafruit_dotstar import board num_pixels = 30 pixels = adafruit_dotstar.DotStar(board.A1, board.A2, num_pixels, brightness=0.1, auto_write=False) def color_fill(color, wait): pixels.fill(color) pixels.show() time.sleep(wait) def slice_alternating(wait): pixels[::2] = [RED] * (num_pixels // 2) pixels.show() time.sleep(wait) pixels[1::2] = [ORANGE] * (num_pixels // 2) pixels.show() time.sleep(wait) pixels[::2] = [YELLOW] * (num_pixels // 2) pixels.show() time.sleep(wait) pixels[1::2] = [GREEN] * (num_pixels // 2) pixels.show() time.sleep(wait) pixels[::2] = [TEAL] * (num_pixels // 2) pixels.show() time.sleep(wait) pixels[1::2] = [CYAN] * (num_pixels // 2) pixels.show() time.sleep(wait) pixels[::2] = [BLUE] * (num_pixels // 2) pixels.show() time.sleep(wait) pixels[1::2] = [PURPLE] * (num_pixels // 2) pixels.show() time.sleep(wait) pixels[::2] = [MAGENTA] * (num_pixels // 2) pixels.show() time.sleep(wait) pixels[1::2] = [WHITE] * (num_pixels // 2) pixels.show() time.sleep(wait) def slice_rainbow(wait): pixels[::6] = [RED] * (num_pixels // 6) pixels.show() time.sleep(wait) pixels[1::6] = [ORANGE] * (num_pixels // 6) pixels.show() time.sleep(wait) pixels[2::6] = [YELLOW] * (num_pixels // 6) pixels.show() time.sleep(wait) pixels[3::6] = [GREEN] * (num_pixels // 6) pixels.show() time.sleep(wait) pixels[4::6] = [BLUE] * (num_pixels // 6) ©Adafruit Industries Page 164 of 215 pixels.show() time.sleep(wait) pixels[5::6] = [PURPLE] * (num_pixels // 6) pixels.show() time.sleep(wait) def rainbow_cycle(wait): for j in range(255): for i in range(num_pixels): rc_index = (i * 256 // num_pixels) + j pixels[i] = colorwheel(rc_index & 255) pixels.show() time.sleep(wait) RED = (255, 0, 0) YELLOW = (255, 150, 0) ORANGE = (255, 40, 0) GREEN = (0, 255, 0) TEAL = (0, 255, 120) CYAN = (0, 255, 255) BLUE = (0, 0, 255) PURPLE = (180, 0, 255) MAGENTA = (255, 0, 20) WHITE = (255, 255, 255) while True: # Change this number to change how long it stays on each solid color. color_fill(RED, 0.5) color_fill(YELLOW, 0.5) color_fill(ORANGE, 0.5) color_fill(GREEN, 0.5) color_fill(TEAL, 0.5) color_fill(CYAN, 0.5) color_fill(BLUE, 0.5) color_fill(PURPLE, 0.5) color_fill(MAGENTA, 0.5) color_fill(WHITE, 0.5) # Increase or decrease this to speed up or slow down the animation. slice_alternating(0.1) color_fill(WHITE, 0.5) # Increase or decrease this to speed up or slow down the animation. slice_rainbow(0.1) time.sleep(0.5) # Increase this number to slow down the rainbow animation. rainbow_cycle(0) We've chosen pins A1 and A2, but these are not SPI pins on all boards. DotStars respond faster when using hardware SPI! Create the LED The first thing we'll do is create the LED object. The DotStar object has three required arguments and two optional arguments. You are required to set the pin you're using ©Adafruit Industries Page 165 of 215 for data, set the pin you'll be using for clock, and provide the number of pixels you intend to use. You can optionally set brightness and auto_write . DotStars can be driven by any two pins. We've chosen A1 for clock and A2 for data. To set the pins, include the pin names at the beginning of the object creation, in this case board.A1 and board.A2 . To provide the number of pixels, assign the variable num_pixels to the number of pixels you'd like to use. In this example, we're using a strip of 72 . We've chosen to set brightness=0.1 , or 10%. By default, auto_write=True , meaning any changes you make to your pixels will be sent automatically. Since True is the default, if you use that setting, you don't need to include it in your LED object at all. We've chosen to set  auto_write=False . If you set auto_write=False , you must include pixels.show() each time you'd like to send data to your pixels. This makes your code more complicated, but it can make your LED animations faster! DotStar Helpers We've included a few helper functions to create the super fun visual effects found in this code.  First is wheel() which we just learned with the Internal RGB LED (https://adafru.it/ Bel). Then we have color_fill() which requires you to provide a color and the length of time you'd like it to be displayed. Next, are slice_alternating() , slice_rainbow() , and rainbow_cycle() which require you to provide the amount of time in seconds you'd between each step of the animation. Last, we've included a list of variables for our colors. This makes it much easier if to reuse the colors anywhere in the code, as well as add more colors for use in multiple places. Assigning and using RGB colors is explained in this section of the CircuitPython Internal RGB LED page (https://adafru.it/Bel). The two slice helpers utilise a nifty feature of the DotStar library that allows us to use math to light up LEDs in repeating patterns. slice_alternating() first lights up the even number LEDs and then the odd number LEDs and repeats this back and forth. s lice_rainbow() lights up every sixth LED with one of the six rainbow colors until the strip is filled. Both use our handy color variables. This slice code only works when the total number of LEDs is divisible by the slice size, in our case 2 and 6. DotStars come ©Adafruit Industries Page 166 of 215 in strips of 30, 60, 72, and 144, all of which are divisible by 2 and 6. In the event that you cut them into different sized strips, the code in this example may not work without modification. However, as long as you provide a total number of LEDs that is divisible by the slices, the code will work. Main Loop Our main loop begins by calling color_fill() once for each color on our list and sets each to hold for 0.5 seconds. You can change this number to change how fast each color is displayed. Next, we call slice_alternating(0.1) , which means there's a 0.1 second delay between each change in the animation. Then, we fill the strip white to create a clean backdrop for the rainbow to display. Then, we call slice_rainbow(0.1) , for a 0.1 second delay in the animation. Last we call rainbow_cycle(0) , which means it's as fast as it can possibly be. Increase or decrease either of these numbers to speed up or slow down the animations! Note that the longer your strip of LEDs is, the longer it will take for the animations to complete. We have a ton more information on general purpose DotStar know-how at our DotStar UberGuide https://learn.adafruit.com/adafruit-dotstar-leds Is it SPI? We explained at the beginning of this section that the LEDs respond faster if you're using hardware SPI. On some of the boards, there are HW SPI pins directly available in the form of MOSI and SCK. However, hardware SPI is available on more than just those pins. But, how can you figure out which? Easy! We wrote a handy script. We chose pins A1 and A2 for our example code. To see if these are hardware SPI on the board you're using, copy and paste the code into code.py using your favorite editor, and save the file. Then connect to the serial console to see the results. To check if other pin combinations have hardware SPI, change the pin names on the line reading: if is_hardware_SPI(board.A1, board.A2): to the pins you want to use. Then, check the results in the serial console. Super simple! # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials Hardware SPI pin verification script""" ©Adafruit Industries Page 167 of 215 import board import busio def is_hardware_spi(clock_pin, data_pin): try: p = busio.SPI(clock_pin, data_pin) p.deinit() return True except ValueError: return False # Provide the two pins you intend to use. if is_hardware_spi(board.A1, board.A2): print("This pin combination is hardware SPI!") else: print("This pin combination isn't hardware SPI.") Read the Docs For a more in depth look at what dotstar can do, check out DotStar on Read the Docs (https://adafru.it/C4d). CircuitPython UART Serial In addition to the USB-serial connection you use for the REPL, there is also a hardwar e UART you can use. This is handy to talk to UART devices like GPSs, some sensors, or other microcontrollers! This quick-start example shows how you can create a UART device for communicating with hardware serial devices. To use this example, you'll need something to generate the UART data. We've used a GPS! Note that the GPS will give you UART data without getting a fix on your location. You can use this example right from your desk! You'll have data to read, it simply won't include your actual location. The QT Py M0 does not have a little red LED. Therefore, you must connect an external LED and edit this example for it to work. Follow the wiring diagram and steps below to run this example on QT Py M0. ©Adafruit Industries Page 168 of 215 LED + to QT Py SCK LED - to 470Ω resistor 470Ω resistor to QT Py GND Copy and paste the code into code.py using your favorite editor, and save the file. # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials UART Serial example""" import board import busio import digitalio # For most CircuitPython boards: led = digitalio.DigitalInOut(board.LED) # For QT Py M0: # led = digitalio.DigitalInOut(board.SCK) led.direction = digitalio.Direction.OUTPUT uart = busio.UART(board.TX, board.RX, baudrate=9600) while True: data = uart.read(32) # read up to 32 bytes # print(data) # this is a bytearray type if data is not None: led.value = True # convert bytearray to string data_string = ''.join([chr(b) for b in data]) print(data_string, end="") led.value = False Note: To "comment out" a line, put a # and a space before it. To "uncomment" a line, remove the # + space from the beginning of the line. For QT Py M0, you'll need to comment out led = DigitalInOut(board.LED) and uncomment led = DigitalInOut(board.SCK) . The UART code remains the same. ©Adafruit Industries Page 169 of 215 The Code First we create the UART object. We provide the pins we'd like to use, board.TX and board.RX , and we set the baudrate=9600 . While these pins are labeled on most of the boards, be aware that RX and TX are not labeled on Gemma, and are labeled on the bottom of Trinket. See the diagrams below for help with finding the correct pins on your board. Once the object is created you read data in with read(numbytes) where you can specify the max number of bytes. It will return a byte array type object if anything was received already. Note it will always return immediately because there is an internal buffer! So read as much data as you can 'digest'. If there is no data available, read() will return None , so check for that before continuing. The data that is returned is in a byte array, if you want to convert it to a string, you can use this handy line of code which will run chr() on each byte: datastr = ''.join([chr(b) for b in data]) # convert bytearray to string Your results will look something like this: ©Adafruit Industries Page 170 of 215 For more information about the data you're reading and the Ultimate GPS, check out the Ultimate GPS guide: https://learn.adafruit.com/adafruit-ultimate-gps Wire It Up You'll need a couple of things to connect the GPS to your board. For Gemma M0 and Circuit Playground Express, you can use use alligator clips to connect to the Flora Ultimate GPS Module. For Trinket M0, Feather M0 Express, Metro M0 Express and ItsyBitsy M0 Express, you'll need a breadboard and jumper wires to connect to the Ultimate GPS Breakout. We've included diagrams show you how to connect the GPS to your board. In these diagrams, the wire colors match the same pins on each board. • The black wire connects between the ground pins. • The red wire connects between the power pins on the GPS and your board. • The blue wire connects from TX on the GPS to RX on your board. • The white wire connects from RX on the GPS to TX on your board. Check out the list below for a diagram of your specific board! Watch out! A common mixup with UART serial is that RX on one board connects to TX on the other! However, sometimes boards have RX labeled TX and vice versa. So, you'll want to start with RX connected to TX, but if that doesn't work, try the other way around! Circuit Playground Express and Circuit Playground Bluefruit Connect 3.3v on your CPX to 3.3v on your GPS. Connect GND on your CPX to GND on your GPS. Connect RX/A6 on your CPX to TX on your GPS. Connect TX/A7 on your CPX to RX on your GPS. ©Adafruit Industries Page 171 of 215 Trinket M0 Connect GPS. Connect GPS. Connect GPS. Connect GPS. USB on the Trinket to VIN on the Gnd on the Trinket to GND on the D3 on the Trinket to TX on the D4 on the Trinket to RX on the Gemma M0 Connect 3vo on the Gemma to 3.3v on the GPS. Connect GND on the Gemma to GND on the GPS. Connect A1/D2 on the Gemma to TX on the GPS. Connect A2/D0 on the Gemma to RX on the GPS. QT Py M0 Connect GPS. Connect GPS. Connect GPS. Connect GPS. ©Adafruit Industries 3V on the QT Py to VIN on the GND on the QT Py to GND on the RX on the QT Py to TX on the TX on the QT Py to RX on the Page 172 of 215 Feather M0 Express and Feather M4 Express Connect USB on the Feather to VIN on the GPS. Connect GND on the Feather to GND on the GPS. Connect RX on the Feather to TX on the GPS. Connect TX on the Feather to RX on the GPS. ItsyBitsy M0 Express and ItsyBitsy M4 Express Connect the GPS Connect GPS. Connect GPS. Connect GPS. USB on the ItsyBitsy to VIN on G on the ItsyBitsy to GND on the RX/0 on the ItsyBitsy to TX on the TX/1 on the ItsyBitsy to RX on the Metro M0 Express and Metro M4 Express Connect GPS. Connect GPS. Connect GPS. Connect GPS. 5V on the Metro to VIN on the GND on the Metro to GND on the RX/D0 on the Metro to TX on the TX/D1 on the Metro to RX on the Where's my UART? On the SAMD21, we have the flexibility of using a wide range of pins for UART. Compare this to some chips like the ESP8266 with fixed UART pins. The good news is you can use many but not all pins. Given the large number of SAMD boards we have, its impossible to guarantee anything other than the labeled 'TX' and 'RX'. So, if you ©Adafruit Industries Page 173 of 215 want some other setup, or multiple UARTs, how will you find those pins? Easy! We've written a handy script. All you need to do is copy this file to your board, rename it code.py, connect to the serial console and check out the output! The results print out a nice handy list of RX and TX pin pairs that you can use. These are the results from a Trinket M0, your output may vary and it might be very long. For more details about UARTs and SERCOMs check out our detailed guide here  (https://adafru.it/Ben) # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials UART possible pin-pair identifying script""" import board import busio from microcontroller import Pin def is_hardware_uart(tx, rx): try: p = busio.UART(tx, rx) p.deinit() return True except ValueError: return False def get_unique_pins(): exclude = ['NEOPIXEL', 'APA102_MOSI', 'APA102_SCK'] pins = [pin for pin in [ getattr(board, p) for p in dir(board) if p not in exclude] if isinstance(pin, Pin)] unique = [] for p in pins: if p not in unique: unique.append(p) return unique for tx_pin in get_unique_pins(): for rx_pin in get_unique_pins(): if rx_pin is tx_pin: continue if is_hardware_uart(tx_pin, rx_pin): print("RX pin:", rx_pin, "\t TX pin:", tx_pin) ©Adafruit Industries Page 174 of 215 Trinket M0: Create UART before I2C On the Trinket M0 (only), if you are using both UART and I2C, you must create the UART object first, e.g.: >>> import board >>> uart = board.UART() >>> i2c = board.I2C() # Uses pins 4 and 3 for TX and RX, baudrate 9600. # Uses pins 2 and 0 for SCL and SDA. # or alternatively, Creating the I2C object first does not work: >>> import board >>> i2c = board.I2C() # Uses pins 2 and 0 for SCL and SDA. >>> uart = board.UART() # Uses pins 4 and 3 for TX and RX, baudrate 9600. Traceback (most recent call last): File "", line 1, in ValueError: Invalid pins CircuitPython I2C I2C is a 2-wire protocol for communicating with simple sensors and devices, meaning it uses two connections for transmitting and receiving data. There are many I2C devices available and they're really easy to use with CircuitPython. We have libraries available for many I2C devices in the library bundle (https://adafru.it/uap). (If you don't see the sensor you're looking for, keep checking back, more are being written all the time!) In this section, we're going to do is learn how to scan the I2C bus for all connected devices. Then we're going to learn how to interact with an I2C device. We'll be using the Adafruit TSL2591 (https://adafru.it/dGE), a common, low-cost light sensor. While the exact code we're running is specific to the TSL2591 the overall process is the same for just about any I2C sensor or device. You'll need the adafruit_tsl2591.mpy library and adafruit_bus_device library folder if you don't already have it in your /lib folder! You can get it from the CircuitPython Library Bundle (https://adafru.it/y8E). If you need help installing the library, check out the CircuitPython Libraries page (https://adafru.it/ABU). These examples will use the TSL2591 lux sensor breakout. The first thing you'll want to do is get the sensor connected so your board has I2C to talk to. ©Adafruit Industries Page 175 of 215 Wire It Up You'll need a couple of things to connect the TSL2591 to your board. The TSL2591 comes with STEMMA QT / QWIIC connectors on it, which makes it super simple to wire it up. No further soldering required! For Gemma M0, Circuit Playground Express and Circuit Playground Bluefruit, you can use use the STEMMA QT to alligator clips cable (https://adafru.it/KKa) to connect to the TSL2591. For Trinket M0, Feather M0 and M4 Express, Metro M0 and M4 Express and ItsyBitsy M0 and M4 Express, you'll need a breadboard and STEMMA QT to male jumper wires cable (https://adafru.it/FA-) to connect to the TSL2591. For QT Py M0, you'll need a STEMMA QT cable (https://adafru.it/FNS) to connect to the TSL2591. We've included diagrams show you how to connect the TSL2591 to your board. In these diagrams, the wire colors match the STEMMA QT cables and connect to the same pins on each board. • The black wire connects from GND on the TSL2591 to ground on your board. • The red wire connects from VIN on the TSL2591 to power on your board. • The yellow wire connects from SCL on the TSL2591 to SCL on your board. • The blue wire connects from SDA on the TSL2591 to SDA on your board. Check out the list below for a diagram of your specific board! Be aware that the Adafruit microcontroller boards do not have I2C pullup resistors built in! All of the Adafruit breakouts do, but if you're building your own board or using a non-Adafruit breakout, you must add 2.2K-10K ohm pullups on both SDA and SCL to the 3.3V. ©Adafruit Industries Page 176 of 215 Circuit Playground Express and Circuit Playground Bluefruit   Connect 3.3v on your CPX to 3.3v on your TSL2591. Connect GND on your CPX to GND on your TSL2591. Connect SCL/A4 on your CPX to SCL on your TSL2591. Connect SDL/A5 on your CPX to SDA on your TSL2591. Trinket M0   Connect USB on the Trinket to VIN on the TSL2591. Connect Gnd on the Trinket to GND on the TSL2591. Connect D2 on the Trinket to SCL on the TSL2591. Connect D0 on the Trinket to SDA on the TSL2591. Gemma M0   Connect 3vo on the Gemma to 3V on the TSL2591. Connect GND on the Gemma to GND on the TSL2591. Connect A1/D2 on the Gemma to SCL on the TSL2591. Connect A2/D0 on the Gemma to SDA on the TSL2591. ©Adafruit Industries Page 177 of 215 QT Py M0 If using the STEMMA QT cable: Connect the STEMMA QT cable from the connector on the QT Py to the connector on the TSL2591. Alternatively, if using a breadboard: Connect 3V on the QT Py to VIN on the TSL2591. Connect GND on the QT Py to GND on the TSL2591. Connect SCL on the QT Py to SCL on the TSL2591. Connect SDA on the QT Py to SDA on the TSL2591. Feather M0 Express and Feather M4 Express   Connect USB on the Feather to VIN on the TSL2591. Connect GND on the Feather to GND on the TSL2591. Connect SCL on the Feather to SCL on the TSL2591. Connect SDA on the Feather to SDA on the TSL2591. ItsyBitsy M0 Express and ItsyBitsy M4 Express   Connect USB on the ItsyBitsy to VIN on the TSL2591 Connect G on the ItsyBitsy to GND on the TSL2591. Connect SCL on the ItsyBitsy to SCL on the TSL2591. Connect SDA on the ItsyBitsy to SDA on the TSL2591. ©Adafruit Industries Page 178 of 215 Metro M0 Express and Metro M4 Express   Connect 5V on the Metro to VIN on the TSL2591. Connect GND on the Metro to GND on the TSL2591. Connect SCL on the Metro to SCL on the TSL2591. Connect SDA on the Metro to SDA on the TSL2591. Find Your Sensor The first thing you'll want to do after getting the sensor wired up, is make sure it's wired correctly. We're going to do an I2C scan to see if the board is detected, and if it is, print out its I2C address. Copy and paste the code into code.py using your favorite editor, and save the file. # SPDX-FileCopyrightText: 2017 Limor Fried for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython I2C Device Address Scan""" # If you run this and it seems to hang, try manually unlocking # your I2C bus from the REPL with # >>> import board # >>> board.I2C().unlock() import time import board # To use default I2C bus (most boards) i2c = board.I2C() # # # # To create I2C bus on specific pins import busio i2c = busio.I2C(board.SCL1, board.SDA1) i2c = busio.I2C(board.GP1, board.GP0) # QT Py RP2040 STEMMA connector # Pi Pico RP2040 while not i2c.try_lock(): pass try: while True: print( "I2C addresses found:", [hex(device_address) for device_address in i2c.scan()], ) time.sleep(2) ©Adafruit Industries Page 179 of 215 finally: # unlock the i2c bus when ctrl-c'ing out of the loop i2c.unlock() First we create the i2c object, using board.I2C() . This convenience routine creates and saves a busio.I2C object using the default pins board.SCL and board.SDA . If the object has already been created, then the existing object is returned. No matter how many times you call board.I2C() , it will return the same object. This is called a singleton. To be able to scan it, we need to lock the I2C down so the only thing accessing it is the code. So next we include a loop that waits until I2C is locked and then continues on to the scan function. Last, we have the loop that runs the actual scan, i2c_scan() . Because I2C typically refers to addresses in hex form, we've included this bit of code that formats the results into hex format: [hex(device_address) for device_address in i2c.scan()] . Open the serial console to see the results! The code prints out an array of addresses. We've connected the TSL2591 which has a 7-bit I2C address of 0x29. The result for this sensor is I2C addresses found: ['0x29'] . If no addresses are returned, refer back to the wiring diagrams to make sure you've wired up your sensor correctly. I2C Sensor Data Now we know for certain that our sensor is connected and ready to go. Let's find out how to get the data from our sensor! Copy and paste the code into code.py using your favorite editor, and save the file. # SPDX-FileCopyrightText: 2017 Limor Fried for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials I2C sensor example using TSL2591""" import time import board import adafruit_tsl2591 i2c = board.I2C() # Lock the I2C device before we try to scan while not i2c.try_lock(): pass # Print the addresses found once print("I2C addresses found:", [hex(device_address) for device_address in i2c.scan()]) # Unlock I2C now that we're done scanning. ©Adafruit Industries Page 180 of 215 i2c.unlock() # Create library object on our I2C port tsl2591 = adafruit_tsl2591.TSL2591(i2c) # Use the object to print the sensor readings while True: print("Lux:", tsl2591.lux) time.sleep(0.5) This code begins the same way as the scan code. We've included the scan code so you have verification that your sensor is wired up correctly and is detected. It prints the address once. After the scan, we unlock I2C with i2c_unlock() so we can use the sensor for data. We create our sensor object using the sensor library. We call it tsl2591 and provide it the i2c object. Then we have a simple loop that prints out the lux reading using the sensor object we created. We add a time.sleep(1.0) , so it only prints once per second. Connect to the serial console to see the results. Try shining a light on it to see the results change! Where's my I2C? On the SAMD21, SAMD51 and nRF52840, we have the flexibility of using a wide range of pins for I2C. On the nRF52840, any pin can be used for I2C! Some chips, like the ESP8266, require using bitbangio, but can also use any pins for I2C. There's some other chips that may have fixed I2C pin.   ©Adafruit Industries Page 181 of 215 The good news is you can use many but not all pins. Given the large number of SAMD boards we have, its impossible to guarantee anything other than the labeled 'SDA' and 'SCL'. So, if you want some other setup, or multiple I2C interfaces, how will you find those pins? Easy! We've written a handy script. All you need to do is copy this file to your board, rename it code.py, connect to the serial console and check out the output! The results print out a nice handy list of SCL and SDA pin pairs that you can use. These are the results from an ItsyBitsy M0 Express. Your output may vary and it might be very long. For more details about I2C and SERCOMs, check out our detailed guide here (https://adafru.it/Ben). # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials I2C possible pin-pair identifying script""" import board import busio from microcontroller import Pin def is_hardware_I2C(scl, sda): try: p = busio.I2C(scl, sda) p.deinit() return True except ValueError: return False except RuntimeError: return True def get_unique_pins(): exclude = ['NEOPIXEL', 'APA102_MOSI', 'APA102_SCK'] pins = [pin for pin in [ getattr(board, p) for p in dir(board) if p not in exclude] if isinstance(pin, Pin)] unique = [] for p in pins: if p not in unique: ©Adafruit Industries Page 182 of 215 unique.append(p) return unique for scl_pin in get_unique_pins(): for sda_pin in get_unique_pins(): if scl_pin is sda_pin: continue if is_hardware_I2C(scl_pin, sda_pin): print("SCL pin:", scl_pin, "\t SDA pin:", sda_pin) CircuitPython HID Keyboard and Mouse One of the things we baked into CircuitPython is 'HID' (Human Interface Device) control - that means keyboard and mouse capabilities. This means your CircuitPython board can act like a keyboard device and press key commands, or a mouse and have it move the mouse pointer around and press buttons. This is really handy because even if you cannot adapt your software to work with hardware, there's almost always a keyboard interface - so if you want to have a capacitive touch interface for a game, say, then keyboard emulation can often get you going really fast! This section walks you through the code to create a keyboard or mouse emulator. First we'll go through an example that uses pins on your board to emulate keyboard input. Then, we will show you how to wire up a joystick to act as a mouse, and cover the code needed to make that happen. You'll need the adafruit_hid library folder if you don't already have it in your /lib folder! You can get it from the CircuitPython Library Bundle (https://adafru.it/y8E). If you need help installing the library, check out the CircuitPython Libraries page (https://adafru.it/ ABU). CircuitPython Keyboard Emulator Copy and paste the code into code.py using your favorite editor, and save the file. # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials HID Keyboard example""" import time import board import digitalio import usb_hid from adafruit_hid.keyboard import Keyboard from adafruit_hid.keyboard_layout_us import KeyboardLayoutUS from adafruit_hid.keycode import Keycode # A simple neat keyboard demo in CircuitPython ©Adafruit Industries Page 183 of 215 # The pins we'll use, each will have an internal pullup keypress_pins = [board.A1, board.A2] # Our array of key objects key_pin_array = [] # The Keycode sent for each button, will be paired with a control key keys_pressed = [Keycode.A, "Hello World!\n"] control_key = Keycode.SHIFT # The keyboard object! time.sleep(1) # Sleep for a bit to avoid a race condition on some systems keyboard = Keyboard(usb_hid.devices) keyboard_layout = KeyboardLayoutUS(keyboard) # We're in the US :) # Make all pin objects inputs with pullups for pin in keypress_pins: key_pin = digitalio.DigitalInOut(pin) key_pin.direction = digitalio.Direction.INPUT key_pin.pull = digitalio.Pull.UP key_pin_array.append(key_pin) # For most CircuitPython boards: led = digitalio.DigitalInOut(board.LED) # For QT Py M0: # led = digitalio.DigitalInOut(board.SCK) led.direction = digitalio.Direction.OUTPUT print("Waiting for key pin...") while True: # Check each pin for key_pin in key_pin_array: if not key_pin.value: # Is it grounded? i = key_pin_array.index(key_pin) print("Pin #%d is grounded." % i) # Turn on the red LED led.value = True while not key_pin.value: pass # Wait for it to be ungrounded! # "Type" the Keycode or string key = keys_pressed[i] # Get the corresponding Keycode or string if isinstance(key, str): # If it's a string... keyboard_layout.write(key) # ...Print the string else: # If it's not a string... keyboard.press(control_key, key) # "Press"... keyboard.release_all() # ..."Release"! # Turn off the red LED led.value = False time.sleep(0.01) Connect pin A1 or A2 to ground, using a wire or alligator clip, then disconnect it to send the key press "A" or the string "Hello world!" ©Adafruit Industries Page 184 of 215 This wiring example shows A1 and A2 connected to ground.   Remember, on Trinket, A1 and A2 are labeled 2 and 0! On other boards, you will have A1 and A2 labeled as expected. Create the Objects and Variables First, we assign some variables for later use. We create three arrays assigned to variables: keypress_pins , key_pin_array , and keys_pressed . The first is the pins we're going to use. The second is empty because we're going to fill it later. The third is what we would like our "keyboard" to output - in this case the letter "A" and the phrase, "Hello world!". We create our last variable assigned to control_key which allows us to later apply the shift key to our keypress. We'll be using two keypresses, but you can have up to six keypresses at once. Next keyboard and keyboard_layout objects are created. We only have US right now (if you make other layouts please submit a GitHub pull request!). The time.sleep(1) avoids an error that can happen if the program gets run as soon as the board gets plugged in, before the host computer finishes connecting to the board. Then we take the pins we chose above, and create the pin objects, set the direction and give them each a pullup. Then we apply the pin objects to key_pin_array so we can use them later. Next we set up the little red LED to so we can use it as a status light. The last thing we do before we start our loop is print , "Waiting for key pin..." so you know the code is ready and waiting! The Main Loop Inside the loop, we check each pin to see if the state has changed, i.e. you connected the pin to ground. Once it changes, it prints, "Pin # grounded." to let you know the ground state has been detected. Then we turn on the red LED. The code waits for the ©Adafruit Industries Page 185 of 215 state to change again, i.e. it waits for you to unground the pin by disconnecting the wire attached to the pin from ground. Then the code gets the corresponding keys pressed from our array. If you grounded and ungrounded A1, the code retrieves the keypress a , if you grounded and ungrounded A2, the code retrieves the string, "Hello world!" If the code finds that it's retrieved a string, it prints the string, using the keyboard_layout to determine the keypresses. Otherwise, the code prints the keypress from the control_key and the keypress "a", which result in "A". Then it calls keyboard.release_all() . You always want to call this soon after a keypress or you'll end up with a stuck key which is really annoying! Instead of using a wire to ground the pins, you can try wiring up buttons like we did in CircuitPython Digital In & Out (https://adafru.it/Beo). Try altering the code to add more pins for more keypress options! Non-US Keyboard Layouts The code above uses KeyboardLayoutUS. If you would like to emulate a non-US keyboard, a number of other keyboard layout classes are available (https://adafru.it/ UYD). CircuitPython Mouse Emulator Copy and paste the code into code.py using your favorite editor, and save the file. # SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials HID Mouse example""" import time import analogio import board import digitalio import usb_hid from adafruit_hid.mouse import Mouse mouse = Mouse(usb_hid.devices) x_axis = analogio.AnalogIn(board.A0) y_axis = analogio.AnalogIn(board.A1) select = digitalio.DigitalInOut(board.A2) select.direction = digitalio.Direction.INPUT select.pull = digitalio.Pull.UP pot_min = 0.00 pot_max = 3.29 ©Adafruit Industries Page 186 of 215 step = (pot_max - pot_min) / 20.0 def get_voltage(pin): return (pin.value * 3.3) / 65536 def steps(axis): """ Maps the potentiometer voltage range to 0-20 """ return round((axis - pot_min) / step) while True: x = get_voltage(x_axis) y = get_voltage(y_axis) if select.value is False: mouse.click(Mouse.LEFT_BUTTON) time.sleep(0.2) # Debounce delay if steps(x) > 11.0: # print(steps(x)) mouse.move(x=1) if steps(x) < 9.0: # print(steps(x)) mouse.move(x=-1) if steps(x) > 19.0: # print(steps(x)) mouse.move(x=8) if steps(x) < 1.0: # print(steps(x)) mouse.move(x=-8) if steps(y) > 11.0: # print(steps(y)) mouse.move(y=-1) if steps(y) < 9.0: # print(steps(y)) mouse.move(y=1) if steps(y) > 19.0: # print(steps(y)) mouse.move(y=-8) if steps(y) < 1.0: # print(steps(y)) mouse.move(y=8) For this example, we've wired up a 2-axis thumb joystick with a select button. We use this to emulate the mouse movement and the mouse left-button click. To wire up this joytick: • Connect d. • Connect • Connect • Connect VCC on the joystick to the 3V on your board. Connect ground to groun Xout on the joystick to pin A0 on your board. Yout on the joystick to pin A1 on your board. Sel on the joystick to pin A2 on your board. ©Adafruit Industries Page 187 of 215 Remember, Trinket's pins are labeled differently. Check the Trinket Pinouts page (https ://adafru.it/AMd) to verify your wiring.   To use this demo, simply move the joystick around. The mouse will move slowly if you move the joystick a little off center, and more quickly if you move it as far as it goes. Press down on the joystick to click the mouse. Awesome! Now let's take a look at the code. Create the Objects and Variables First we create the mouse object. Next, we set x_axis and y_axis to pins A0 and A1 . Then we set select to A2 , set it as input and give it a pullup. The x and y axis on the joystick act like 2 potentiometers. We'll be using them just like we did in CircuitPython Analog In (https://adafru.it/Bep). We set pot_min and pot_ma x to be the minimum and maximum voltage read from the potentiometers. We assign step = (pot_max - pot_min) / 20.0 to use in a helper function. ©Adafruit Industries Page 188 of 215 CircuitPython HID Mouse Helpers First we have the get_voltage() helper so we can get the correct readings from the potentiometers. Look familiar? We learned about it in Analog In (https://adafru.it/ Bep). Second, we have steps(axis) . To use it, you provide it with the axis you're reading. This is where we're going to use the step variable we assigned earlier. The potentiometer range is 0-3.29. This is a small range. It's even smaller with the joystick because the joystick sits at the center of this range, 1.66, and the + and - of each axis is above and below this number. Since we need to have thresholds in our code, we're going to map that range of 0-3.29 to while numbers between 0-20.0 using this helper function. That way we can simplify our code and use larger ranges for our thresholds instead of trying to figure out tiny decimal number changes. Main Loop First we assign x and y to read the voltages from x_axis and y_axis . Next, we check to see when the state of the select button is False . It defaults to True when it is not pressed, so if the state is False , the button has been pressed. When it's pressed, it sends the command to click the left mouse button. The time.sl eep(0.2) prevents it from reading multiple clicks when you've only clicked once. Then we use the steps() function to set our mouse movement. There are two sets of two if statements for each axis. Remember that 10 is the center step, as we've mapped the range 0-20 . The first set for each axis says if the joystick moves 1 step off center (left or right for the x axis and up or down for the y axis), to move the mouse the appropriate direction by 1 unit. The second set for each axis says if the joystick is moved to the lowest or highest step for each axis, to move the mouse the appropriate direction by 8 units. That way you have the option to move the mouse slowly or quickly! To see what step the joystick is at when you're moving it, uncomment the print statements by removing the #  from the lines that look like # print(steps(x)) , and connecting to the serial console to see the output. Consider only uncommenting one set at a time, or you end up with a huge amount of information scrolling very quickly, which can be difficult to read! ©Adafruit Industries Page 189 of 215 For more detail check out the documentation at https:// circuitpython.readthedocs.io/projects/hid/en/latest/ CircuitPython CPU Temp There is a temperature sensor built into the CPU on your microcontroller board. It reads the internal CPU temperature, which varies depending on how long the board has been running or how intense your code is. CircuitPython makes it really simple to read this data from the temperature sensor built into the microcontroller. Using the built-in microcontroller module, you can easily read the temperature. Microcontroller Location Reading the Microcontroller Temperature The data is read using two lines of code. All necessary modules are built into CircuitPython, so you don't need to download any extra files to get started. Connect to the serial console (https://adafru.it/Bec), and then update your code.py to the following and save. # SPDX-FileCopyrightText: 2021 Kattni Rembor for Adafruit Industries # SPDX-License-Identifier: MIT """CircuitPython CPU temperature example in Celsius""" import time import microcontroller while True: ©Adafruit Industries Page 190 of 215 print(microcontroller.cpu.temperature) time.sleep(0.15) The CPU temperature in Celsius is printed out to the serial console! Try putting your finger on the microcontroller to see the temperature change. The code is simple. First you import two modules: time and microcontroller . Then, inside the loop, you print the microcontroller CPU temperature, and the time.s leep() slows down the print enough to be readable. That's it! You can easily print out the temperature in Fahrenheit by adding a little math to your code, using this simple formula: Celsius * (9/5) + 32. Update your code.py to the following, and save. # SPDX-FileCopyrightText: 2021 Kattni Rembor for Adafruit Industries # SPDX-License-Identifier: MIT """CircuitPython CPU temperature example in Fahrenheit""" import time import microcontroller while True: print(microcontroller.cpu.temperature * (9 / 5) + 32) time.sleep(0.15) The CPU temperature in Fahrenheit is printed out to the serial console! That's all there is to reading the CPU temperature using CircuitPython! ©Adafruit Industries Page 191 of 215 CircuitPython Storage CircuitPython-compatible microcontrollers show up as a CIRCUITPY drive when plugged into your computer, allowing you to edit code directly on the board. Perhaps you've wondered whether or not you can write data from CircuitPython directly to the board to act as a data logger. The answer is yes! The  storage  module in CircuitPython enables you to write code that allows CircuitPython to write data to the CIRCUITPY drive. This process requires you to include a boot.py file on your CIRCUITPY drive, along side your code.py file. The boot.py file is special - the code within it is executed when CircuitPython starts up, either from a hard reset or powering up the board. It is not run on soft reset, for example, if you reload the board from the serial console or the REPL. This is in contrast to the code within code.py, which is executed after CircuitPython is already running. The CIRCUITPY drive is typically writable by your computer; this is what allows you to edit your code directly on the board. The reason you need a boot.py file is that you have to set the filesystem to be read-only by your computer to allow it to be writable by CircuitPython. This is because CircuitPython cannot write to the filesystem at the same time as your computer. Doing so can lead to filesystem corruption and loss of all content on the drive, so CircuitPython is designed to only allow one at at time. You can only have either your computer edit the CIRCUITPY drive files, or CircuitPython. You cannot have both write to the drive at the same time. (Bad Things Will Happen so we do not allow you to do it!) Save the following as boot.py on your CIRCUITPY drive. Click the Download Project Bundle button, open the resulting zip file, and copy the bo ot.py file to your CIRCUITPY drive.   The filesystem will NOT automatically be set to read-only on creation of this file! You'll still be able to edit files on CIRCUITPY after saving this boot.py. # SPDX-FileCopyrightText: 2017 Limor Fried for Adafruit Industries # # SPDX-License-Identifier: MIT ©Adafruit Industries Page 192 of 215 """CircuitPython Essentials Storage logging boot.py file""" import board import digitalio import storage # For Gemma M0, Trinket M0, Metro M0/M4 Express, ItsyBitsy M0/M4 Express switch = digitalio.DigitalInOut(board.D2) # For Feather M0/M4 Express # switch = digitalio.DigitalInOut(board.D5) # For Circuit Playground Express, Circuit Playground Bluefruit # switch = digitalio.DigitalInOut(board.D7) switch.direction = digitalio.Direction.INPUT switch.pull = digitalio.Pull.UP # If the switch pin is connected to ground CircuitPython can write to the drive storage.remount("/", switch.value) The  storage.remount()  command has a  readonly  keyword argument. This argument refers to the read/write state of CircuitPython. It does NOT refer to the read/ write state of your computer. When the physical pin is connected to ground, it returns  False . The  readonly  argu ment in boot.py is set to the  value  of the pin. When the  value=True , the CIRCUITPY drive is read-only to CircuitPython (and writable by your computer). When the  value=False , the CIRCUITPY drive is writable by CircuitPython (an read-only by your computer). For Gemma M0, Trinket M0, Metro M0 Express, Metro M4 Express, ItsyBitsy M0 Express and ItsyBitsy M4 Express, no changes to the initial code are needed. For Feather M0 Express and Feather M4 Express, comment out switch = digitalio.DigitalInOut(board.D2) , and uncomment switch = digitalio.DigitalInOut(board.D5) . For Circuit Playground Express and Circuit Playground Bluefruit, comment out switch = digitalio.DigitalInOut(board.D2) , and uncomment  switch = digitalio.DigitalInOut(board.D7) . Remember, D7 is the onboard slide switch, so there's no extra wires or alligator clips needed. On the Circuit Playground Express or Circuit Playground Bluefruit, the switch is in the right position (closer to the ear icon on the silkscreen) it returns False , and the CIRC UITPY drive will be writable by CircuitPython. If the switch is in the left position (closer to the music icon on the silkscreen), it returns True , and the CIRCUITPY drive will be writable by your computer. ©Adafruit Industries Page 193 of 215 Remember: To "comment out" a line, put a # and a space before it. To "uncomment" a line, remove the # + space from the beginning of the line. The following is your new code.py. Copy and paste the code into code.py using your favorite editor. # SPDX-FileCopyrightText: 2017 Limor Fried for Adafruit Industries # # SPDX-License-Identifier: MIT """CircuitPython Essentials Storage logging example""" import time import board import digitalio import microcontroller # For most CircuitPython boards: led = digitalio.DigitalInOut(board.LED) # For QT Py M0: # led = digitalio.DigitalInOut(board.SCK) led.switch_to_output() try: with open("/temperature.txt", "a") as fp: while True: temp = microcontroller.cpu.temperature # do the C-to-F conversion here if you would like fp.write('{0:f}\n'.format(temp)) fp.flush() led.value = not led.value time.sleep(1) except OSError as e: # Typically when the filesystem isn't writeable... delay = 0.5 # ...blink the LED every half second. if e.args[0] == 28: # If the file system is full... delay = 0.25 # ...blink the LED faster! while True: led.value = not led.value time.sleep(delay) Logging the Temperature The way boot.py works is by checking to see if the pin you specified in the switch setup in your code is connected to a ground pin. If it is, it changes the read-write state of the file system, so the CircuitPython core can begin logging the temperature to the board. For help finding the correct pins, see the wiring diagrams and information in the Find the Pins section of the CircuitPython Digital In & Out guide (https://adafru.it/Bes). Instead of wiring up a switch, however, you'll be connecting the pin directly to ground with alligator clips or jumper wires. ©Adafruit Industries Page 194 of 215 boot.py only runs on first boot of the device, not if you re-load the serial console with ctrl+D or if you save a file. You must EJECT the USB drive, then physically press the reset button! Once you copied the files to your board, eject it and unplug it from your computer. If you're using your Circuit Playground Express, all you have to do is make sure the switch is to the right. Otherwise, use alligator clips or jumper wires to connect the chosen pin to ground. Then, plug your board back into your computer. You will not be able to edit code on your CIRCUITPY drive anymore! The red LED should blink once a second and you will see a new temperature.txt file on CIRCUITPY. ©Adafruit Industries Page 195 of 215 This file gets updated once per second, but you won't see data come in live. Instead, when you're ready to grab the data, eject and unplug your board. For CPX, move the switch to the left, otherwise remove the wire connecting the pin to ground. Now it will be possible for you to write to the filesystem from your computer again, but it will not be logging data. We have a more detailed guide on this project available here: CPU Temperature Logging with CircuitPython. (https://adafru.it/zuF) If you'd like more details, check it out! There is a CPU temperature sensor built into every ATSAMD21, ATSAMD51 and nRF52840 chips. CircuitPython makes it really simple to read the data from this sensor. This works on the Adafruit CircuitPython boards it's built into the microcontroller used for these boards. The data is read using two simple commands. We're going to enter them in the REPL. Plug in your board, connect to the serial console (https://adafru.it/Bec), and enter the REPL (https://adafru.it/Awz). Then, enter the following commands into the REPL: import microcontroller microcontroller.cpu.temperature That's it! You've printed the temperature in Celsius to the REPL. Note that it's not exactly the ambient temperature and it's not super precise. But it's close! ©Adafruit Industries Page 196 of 215 If you'd like to print it out in Fahrenheit, use this simple formula: Celsius * (9/5) + 32. It's super easy to do math using CircuitPython. Check it out! Note that the temperature sensor built into the nRF52840 has a resolution of 0.25 degrees Celsius, so any temperature you print out will be in 0.25 degree increments. CircuitPython Expectations As we continue to develop CircuitPython and create new releases, we will stop supporting older releases. Visit https://circuitpython.org/downloads to download the latest version of CircuitPython for your board. You must download the CircuitPython Library Bundle that matches your version of CircuitPython. Please update CircuitPython and then visit https://circuitpython.org/libraries to download the latest Library Bundle. Always Run the Latest Version of CircuitPython and Libraries As we continue to develop CircuitPython and create new releases, we will stop supporting older releases. You need to update to the latest CircuitPython (https:// adafru.it/Em8). You need to download the CircuitPython Library Bundle that matches your version of CircuitPython. Please update CircuitPython and then download the latest bundle (http s://adafru.it/ENC). As we release new versions of CircuitPython, we will stop providing the previous bundles as automatically created downloads on the Adafruit CircuitPython Library Bundle repo. If you must continue to use an earlier version, you can still download the appropriate version of mpy-cross from the particular release of CircuitPython on the ©Adafruit Industries Page 197 of 215 CircuitPython repo and create your own compatible .mpy library files. However, it is best to update to the latest for both CircuitPython and the library bundle. I have to continue using CircuitPython 3.x or 2.x, where can I find compatible libraries? We are no longer building or supporting the CircuitPython 2.x and 3.x library bundles. We highly encourage you to update CircuitPython to the latest version (https:// adafru.it/Em8) and use the current version of the libraries (https://adafru.it/ENC). However, if for some reason you cannot update, you can find the last available 2.x build here (https://adafru.it/FJA) and the last available 3.x build here (https://adafru.it/ FJB). Switching Between CircuitPython and Arduino Many of the CircuitPython boards also run Arduino. But how do you switch between the two? Switching between CircuitPython and Arduino is easy. If you're currently running Arduino and would like to start using CircuitPython, follow the steps found in Welcome to CircuitPython: Installing CircuitPython (https://adafru.it/ Amd). If you're currently running CircuitPython and would like to start using Arduino, plug in your board, and then load your Arduino sketch. If there are any issues, you can double tap the reset button to get into the bootloader and then try loading your sketch. Always backup any files you're using with CircuitPython that you want to save as they could be deleted. That's it! It's super simple to switch between the two. The Difference Between Express And NonExpress Boards We often reference "Express" and "Non-Express" boards when discussing CircuitPython. What does this mean? ©Adafruit Industries Page 198 of 215 Express refers to the inclusion of an extra 2MB flash chip on the board that provides you with extra space for CircuitPython and your code. This means that we're able to include more functionality in CircuitPython and you're able to do more with your code on an Express board than you would on a non-Express board. Express boards include Circuit Playground Express, ItsyBitsy M0 Express, Feather M0 Express, Metro M0 Express and Metro M4 Express. Non-Express boards include Trinket M0, Gemma M0, QT Py, Feather M0 Basic, and other non-Express Feather M0 variants. Non-Express Boards: Gemma, Trinket, and QT Py CircuitPython runs nicely on the Gemma M0, Trinket M0, or QT Py M0 but there are some constraints Small Disk Space Since we use the internal flash for disk, and that's shared with runtime code, its limited! Only about 50KB of space. No Audio or NVM Part of giving up that FLASH for disk means we couldn't fit everything in. There is, at this time, no support for hardware audio playpack or NVM 'eeprom'. Modules audioi o  and bitbangio are not included. For that support, check out the Circuit Playground Express or other Express boards. However, I2C, UART, capacitive touch, NeoPixel, DotStar, PWM, analog in and out, digital IO, logging storage, and HID do work! Check the CircuitPython Essentials for examples of all of these. Differences Between CircuitPython and MicroPython For the differences between CircuitPython and MicroPython, check out the CircuitPyth on documentation (https://adafru.it/Bvz). ©Adafruit Industries Page 199 of 215 Differences Between CircuitPython and Python Python (also known as CPython) is the language that MicroPython and CircuitPython are based on. There are many similarities, but there are also many differences. This is a list of a few of the differences. Python Libraries Python is advertised as having "batteries included", meaning that many standard libraries are included. Unfortunately, for space reasons, many Python libraries are not available. So for instance while we wish you could import numpy , numpy isn't available (look for the ulab library for similar functions to numpy which works on many microcontroller boards). So you may have to port some code over yourself! Integers in CircuitPython On the non-Express boards, integers can only be up to 31 bits long. Integers of unlimited size are not supported. The largest positive integer that can be represented is 230-1, 1073741823, and the most negative integer possible is -2 30, -1073741824. As of CircuitPython 3.0, Express boards have arbitrarily long integers as in Python. Floating Point Numbers and Digits of Precision for Floats in CircuitPython Floating point numbers are single precision in CircuitPython (not double precision as in Python). The largest floating point magnitude that can be represented is about +/-3.4e38. The smallest magnitude that can be represented with full accuracy is about +/-1.7e-38, though numbers as small as +/-5.6e-45 can be represented with reduced accuracy. CircuitPython's floats have 8 bits of exponent and 22 bits of mantissa (not 24 like regular single precision floating point), which is about five or six decimal digits of precision. ©Adafruit Industries Page 200 of 215 Differences between MicroPython and Python For a more detailed list of the differences between CircuitPython and Python, you can look at the MicroPython documentation. We keep up with MicroPython stable releases, so check out the core 'differences' they document here. (https://adafru.it/ zwA) UF2 Bootloader Details This is an information page for advanced users who are curious how we get code from your computer into your Express board! Adafruit SAMD21 (M0) and SAMD51 (M4) boards feature an improved bootloader that makes it easier than ever to flash different code onto the microcontroller. This bootloader makes it easy to switch between Microsoft MakeCode, CircuitPython and Arduino. Instead of needing drivers or a separate program for flashing (say, bossac , jlink or avrdude ), one can simply drag a file onto a removable drive. The format of the file is a little special. Due to 'operating system woes' you cannot just drag a binary or hex file (trust us, we tried it, it isn't cross-platform compatible). Instead, the format of the file has extra information to help the bootloader know where the data goes. The format is called UF2 (USB Flashing Format). Microsoft MakeCode generates UF2s for flashing and CircuitPython releases are also available as UF2. You can also create your own UF2s from binary files using uf2tool, available here. (https://adafru.it/vPE) The bootloader is also BOSSA compatible, so it can be used with the Arduino IDE which expects a BOSSA bootloader on ATSAMD-based boards For more information about UF2, you can read a bunch more at the MakeCode blog (h ttps://adafru.it/w5A), then check out the UF2 file format specification.  (https:// adafru.it/vPE) Visit Adafruit's fork of the Microsoft UF2-samd bootloader GitHub repository (https:// adafru.it/Beu) for source code and releases of pre-built bootloaders on CircuitPython. org (https://adafru.it/Em8). ©Adafruit Industries Page 201 of 215 The bootloader is not needed when changing your CircuitPython code. Its only needed when upgrading the CircuitPython core or changing between CircuitPython, Arduino and Microsoft MakeCode. Entering Bootloader Mode The first step to loading new code onto your board is triggering the bootloader. It is easily done by double tapping the reset button. Once the bootloader is active you will see the small red LED fade in and out and a new drive will appear on your computer with a name ending in BOOT. For example, feathers show up as FEATHERBOOT, while the new CircuitPlayground shows up as CPLAYBOOT, Trinket M0 will show up as TRINKETBOOT, and Gemma M0 will show up as GEMMABOOT Furthermore, when the bootloader is active, it will change the color of one or more onboard neopixels to indicate the connection status, red for disconnected and green for connected. If the board is plugged in but still showing that its disconnected, try a different USB cable. Some cables only provide power with no communication. For example, here is a Feather M0 Express running a colorful Neopixel swirl. When the reset button is double clicked (about half second between each click) the NeoPixel will stay green to let you know the bootloader is active. When the reset button is clicked once, the 'user program' (NeoPixel color swirl) restarts. ©Adafruit Industries Page 202 of 215 If the bootloader couldn't start, you will get a red NeoPixel LED. That could mean that your USB cable is no good, it isn't connected to a computer, or maybe the drivers could not enumerate. Try a new USB cable first. Then try another port on your computer! Once the bootloader is running, check your computer. You should see a USB Disk drive... ©Adafruit Industries Page 203 of 215 Once the bootloader is successfully connected you can open the drive and browse the virtual filesystem. This isn't the same filesystem as you use with CircuitPython or Arduino. It should have three files: •  CURRENT.UF2 - The current contents of the microcontroller flash. •  INDEX.HTM - Links to Microsoft MakeCode. •  INFO_UF2.TXT - Includes bootloader version info. Please include it on bug reports. Using the Mass Storage Bootloader To flash something new, simply drag any UF2 onto the drive. After the file is finished copying, the bootloader will automatically restart. This usually causes a warning about an unsafe eject of the drive. However, its not a problem. The bootloader knows when everything is copied successfully. ©Adafruit Industries Page 204 of 215 You may get an alert from the OS that the file is being copied without it's properties. You can just click Yes You may also get get a complaint that the drive was ejected without warning. Don't worry about this. The drive only ejects once the bootloader has verified and completed the process of writing the new code Using the BOSSA Bootloader As mentioned before, the bootloader is also compatible with BOSSA, which is the standard method of updating boards when in the Arduino IDE. It is a command-line tool that can be used in any operating system. We won't cover the full use of the boss ac tool, suffice to say it can do quite a bit! More information is available at ShumaTech  (https://adafru.it/vQa). ©Adafruit Industries Page 205 of 215 Windows 7 Drivers If you are running Windows 7 (or, goodness, something earlier?) You will need a Serial Port driver file. Windows 10 users do not need this so skip this step. You can download our full driver package here: Download Latest Adafruit Driver Installer https://adafru.it/AB0 Download and run the installer. We recommend just selecting all the serial port drivers available (no harm to do so) and installing them. Verifying Serial Port in Device Manager If you're running Windows, its a good idea to verify the device showed up. Open your Device Manager from the control panel and look under Ports (COM & LPT) for a device called Feather M0 or Circuit Playground or whatever! ©Adafruit Industries Page 206 of 215 If you see something like this, it means you did not install the drivers. Go back and try again, then remove and re-plug the USB cable for your board ©Adafruit Industries Page 207 of 215 Running bossac on the command line If you are using the Arduino IDE, this step is not required. But sometimes you want to read/write custom binary files, say for loading CircuitPython or your own code. We recommend using bossac v 1.7.0 (or greater), which has been tested. The Arduino branch is most recommended (https://adafru.it/vQb). You can download the latest builds here. (https://adafru.it/s1B) The mingw32 version is for Windows, apple-darwin for Mac OSX and various linux options for Linux. Once downloaded, extract the files from the zip and open the command line to the directory with bossac . With bossac versions 1.9 or later, you must use the --offset parameter on the command line, and it must have the correct value for your board. With bossac version 1.9 or later, you must give an  --offset  parameter on the command line to specify where to start writing the firmware in flash memory. This ©Adafruit Industries Page 208 of 215 parameter was added in bossac 1.8.0 with a default of  0x2000 , but starting in 1.9, the default offset was changed to  0x0000 , which is not what you want in most cases. If you omit the argument for bossac 1.9 or later, you will probably see a "Verify Failed" error from bossac.  Remember to change the option for  -p  or  --port  to match the port on your Mac. Replace the filename below with the name of your downloaded  .bin : it will vary based on your board! Using bossac Versions 1.7.0, 1.8 There is no  --offset  parameter available. Use a command line like this: bossac -p=/dev/cu.usbmodem14301 -e -w -v -R adafruit-circuitpython-bo ardname-version.bin For example, bossac -p=/dev/cu.usbmodem14301 -e -w -v -R adafruit-circuitpythonfeather_m0_express-3.0.0.bin Using bossac Versions 1.9 or Later For M0 boards, which have an 8kB bootloader, you must specify  -offset=0x2000 , for example: bossac -p=/dev/cu.usbmodem14301 -e -w -v -R --offset=0x2000 adafruitcircuitpython-feather_m0_express-3.0.0.bin For M4 boards, which have a 16kB bootloader, you must specify  -offset=0x4000 , for example: bossac -p=/dev/cu.usbmodem14301 -e -w -v -R --offset=0x4000 adafruitcircuitpython-feather_m4_express-3.0.0.bin This will  e rase the chip,  w rite the given file,  v erify the write and  R eset the board. On Linux or MacOS you may need to run this command with  sudo ./bossac ... , or add yourself to the dialout group first. ©Adafruit Industries Page 209 of 215 Updating the bootloader The UF2 bootloader is relatively new and while we've done a ton of testing, it may contain bugs. Usually these bugs effect reliability rather than fully preventing the bootloader from working. If the bootloader is flaky then you can try updating the bootloader itself to potentially improve reliability. If you're using MakeCode on a Mac, you need to make sure to upload the bootloader to avoid a serious problem with newer versions of MacOS. See instructions and more details here (https://adafru.it/ECU). In general, you shouldn't have to update the bootloader! If you do think you're having bootloader related issues, please post in the forums or discord. Updating the bootloader is as easy as flashing CircuitPython, Arduino or MakeCode. Simply enter the bootloader as above and then drag the update bootloader uf2 file below. This uf2 contains a program which will unlock the bootloader section, update the bootloader, and re-lock it. It will overwrite your existing code such as CircuitPython or Arduino so make sure everything is backed up! After the file is copied over, the bootloader will be updated and appear again. The INF O_UF2.TXT file should show the newer version number inside. For example: UF2 Bootloader v2.0.0-adafruit.5 SFHWRO Model: Metro M0 Board-ID: SAMD21G18A-Metro-v0 Lastly, reload your code from Arduino or MakeCode or flash the latest CircuitPython core (https://adafru.it/Em8). ©Adafruit Industries Page 210 of 215 Below are the latest updaters for various boards. The latest versions can always be found here (https://adafru.it/Bmg).  Look for the update-bootloader... files, not the bootloader... files. Circuit Playground Express V3.7.0 update-bootloader.uf2 https://adafru.it/JcN Feather M0 Express v3.7.0 updatebootloader.uf2 https://adafru.it/JcO Metro M0 Express v3.7.0 updatebootloader.uf2 https://adafru.it/JcR Gemma M0 v3.7.0 updatebootloader.uf2 https://adafru.it/JcU Trinket M0 v3.7.0 updatebootloader.uf2 https://adafru.it/JcX Itsy Bitsy M0 v3.7.0 updatebootloader.uf2 https://adafru.it/Jc- Grand Central M4 v3.7.0 updatebootloader.uf2 https://adafru.it/Jd2 Latest version of updatebootloader.uf2 for other boards. Make sure you pick the right one. https://adafru.it/Bmg ©Adafruit Industries Page 211 of 215 Getting Rid of Windows Pop-ups If you do a lot of development on Windows with the UF2 bootloader, you may get annoyed by the constant "Hey you inserted a drive what do you want to do" pop-ups. Go to the Control Panel. Click on the Hardware and Sound header Click on the Autoplay header Uncheck the box at the top, labeled Use Autoplay for all devices ©Adafruit Industries Page 212 of 215 Making your own UF2 Making your own UF2 is easy! All you need is a .bin file of a program you wish to flash and the Python conversion script (https://adafru.it/vZb). Make sure that your program was compiled to start at 0x2000 (8k) for M0 boards or 0x4000 (16kB) for M4 boards. The bootloader takes up the first 8kB (M0) or 16kB (M4). CircuitPython's linker script (h ttps://adafru.it/CXh) is an example on how to do that. Once you have a .bin file, you simply need to run the Python conversion script over it. Here is an example from the directory with uf2conv.py. This command will produce a f irmware.uf2 file in the same directory as the source firmware.bin. The uf2 can then be flashed in the same way as above. # For programs with 0x2000 offset (default) uf2conv.py -c -o build-circuitplayground_express/firmware.uf2 buildcircuitplayground_express/firmware.bin # For programs needing 0x4000 offset (M4 boards) uf2conv.py -c -b 0x4000 -o build-metro_m4_express/firmware.uf2 buildmetro_M4_express/firmware.bin Installing the bootloader on a fresh/bricked board If you somehow damaged your bootloader or maybe you have a new board, you can use a JLink to re-install it. Here's a Learn Guide explaining how to fix the bootloader on a variety of boards using Atmel Studio (https://adafru.it/F5f) Here's a short writeup by turbinenreiter on how to do it for the Feather M4 (but adaptable to other boards) (https://adafru.it/ven) Downloads Files • ATSAMD51G19 Product page w/datasheets (https://adafru.it/BBf) (the main chip on the Metro M4) • Fritzing object in the Adafruit Fritzing Library (https://adafru.it/aP3) ©Adafruit Industries Page 213 of 215 • EagleCAD files on GitHub (https://adafru.it/BBg) • 3D Models on GitHub (https://adafru.it/GAr) • PDF for ItsyBitsy M4 Board Diagram on GitHub (https://adafru.it/-Ar) SVG for ItsyBitsy M4 Board Diagram https://adafru.it/-As Schematic & Fabrication Print ©Adafruit Industries Page 214 of 215 ©Adafruit Industries Page 215 of 215