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Page 1 of 20 ATmega128RFA1 Dev Board Hookup Guide CONTR IBUTORS: J IM B 0 Overview The ATmega128RFA1 is a really nifty system-on-chip, which combines an ATmega128 microcontroller with a 2.4GHz, 802.15.4 RF transceiver. It’s what you might get if you smashed a wireless module, like Zigbee or Synapse, into an AVR microcontroller (like those on many Arduinos). We at SparkFun thought the chip was neat enough to warrant its own development board. This tutorial is focused on documenting the schematic and hardware layout of the development board. It’ll also explain how to program the board via the pre-programmed serial bootloader, from the comfy confines of the Arduino IDE. We’ll finish off the tutorial with some example code, detailing the basics of the ATmega128RFA1’s RF communication capabilities. ATmega128RFA1 Devlopment Board Features: • Arduino R3 Form Factor (Arduino shield compatible) • On-Board Chip Antenna • 33 Digital I/O’s ◦ SPI, TWI (I2C), and UART hardware interfaces • 8 Analog Inputs (10-bit resolution) • 16 MHz operating frequency • ATmegaBOOT bootloader pre-programmed (making it programmable with an FTDI Basic and the Arduino IDE) • On-board 3.3V regulator • Other standard ATmega128RFA1 features: ◦ 6 Timers ◦ 128 KB Flash Page 2 of 20 ◦ 16 KB SRAM ◦ 4096 Bytes EEPROM ◦ 2.4 GHz RF Transciever Required Materials In this tutorial, we’ll cover the basics of getting the ATmega128RFA1 Development Board up-and-running. There will be a focus on programming the board via the bootloader (in the Arduino IDE), using an FTDI Board. To follow along, you’ll need these materials: ATmega128RFA1 Development Board Hookup Guide SparkFun Wish List Break Away Male Headers - Right Angle PRT-00553 A row of right angle male headers - break to fit. 40 pins that can be cu… Break Away Headers - Straight PRT-00116 A row of headers - break to fit. 40 pins that can be cut to any size. Us… Female Headers PRT-00115 Single row of 40-holes, female header. Can be cut to size with a pair… SparkFun FTDI Basic Breakout - 3.3V DEV-09873 This is the newest revision of our [FTDI Basic](http://www.sparkfun.co… DC Barrel Power Jack/Connector PRT-00119 DC power jack/connector. This is a common barrel-type power jack fo… Male headers are useful for soldering into programming headers, while female headers help to add shield compatibility. A pair of ATmega128RFA1s – either the SparkFun board, or another development platform – are required to test communication between the chips. Required Tools This assembly will require some simple soldering, so you’ll need a soldering iron and a bit of solder. If you’ve never soldered before, check out our how to solder guide. Suggested Reading Page 3 of 20 This tutorial assumes some previous electronics knowledge to get along. If you’re not familiar with these concepts, consider checking out our tutorials on the subject! • What is an Arduino - While not directly using an Arduino platform, this tutorial will make use of the IDE. • Installing FTDI Drivers - If you’ve never used an FTDI cable or board before, you’ll need to install drivers. • Serial Communication - We’ll be using the ATmega128RFA1 boards as wireless bridges between two serial devices. • How to Use GitHub - All of the source code and design files are hosted on Github. About the ATmega128RFA1 The ATmega128RFA1 is a portmanteau of sorts – two separate components combined to form one device. Half microcontroller, half RF transceiver. ATmega128 Half of the ATmega128RFA1 is an ATmega128, an old mainstay of Atmel AVR microcontrollers. The 128 is an 8-bit microcontroller with 128kB of programmable flash, an abundance of I/O pins, an analog-to-digital converter, and much more. Low-Power 2.4GHz Transceiver The other half of the ATmega128RFA1 – the “RFA1” part – is what really makes it unique. That’s because built into the chip is a 2.4GHz wireless radio transceiver. So one ATmega128RFA1 could talk to another up to about 75m away, at speeds of up to 2 Mbps. Because it has built-in hardware support for IEEE 802.15.4, the chip can also talk to RF modules, like ZigBee’s, Synapse modules, and IPv6/6LoWPAN devices. 802.15.4 defines a personal area network (PAN) of wireless devices. It’s very similar to the Bluetooth standard (802.15.1) in that way. Unlike Bluetooth though, which can send data at around 3Mbps, 802.15.4 can’t achieve as high a data rate, maxing out at around 250kbps. Still, 802.15.4 is an excellent, cost-sensitive choice when you don’t need to quickly send huge chunks of wireless data. In comparison to the other wireless standards and protocols out there, the ATmega128RFA1’s transceiver is geared towards low-level, low-power, low-speed, low-data rate, low-range communication between devices. This isn’t like WiFi, where we need to stream video, while downloading pictures of cats, and syncing our dropboxes. 802.15.4 is for sending data between embedded devices. Maybe you want to periodically transmit data from a Page 4 of 20 weather station to a display in your house, or turn your coffee machine on from the bed. That’s the type of situation 802.15.4 works best in! That sounds like a job for the ATmega128RFA1 Dev Board! Schematic and Hardware The development board surrounds the ATmega128RFA1 with all of the supporting circuitry one might need to get up-and-running with the chip. Click the image to get a bigger view of the schematic. Or you can download a PDF of it. Power Input The power input section of the circuit includes a voltage regulator, which feeds 3.3V to the rest of the circuit. The following footprints are provided for power input: • • • • DC Barrel Jack JST connector (2-Pin, Right-Angle) 3.5mm 2-Pin Screw Terminal Standard 0.1"-spaced header The slide-switch on the side of the board controls the flow of the input power sources above to the regulator. The 3.3V and GND pins are also broken out along the side of the board. These nets are unregulated, but can be used to supply a clean, regulated 3.3V voltage source to the board. ATmega128RFA1 Circuitry The ATmega128RFA1 is supported by a 16MHz crystal and an assortment of decoupling caps. The RF section of the board has a crystal of its own, as well as a chip antenna and circuitry to support the RF interface. Try to avoid placing components near the antenna, as they may interfere with signal strength. Page 5 of 20 All digital I/O pins of the ATmega128RFA1 are broken out in some form or another. Two on-board LEDs are connected to the MCU’s pins B6 and B7. The remaining I/O’s are broken out to the outer headers of the board. The eight analog inputs on port F are available in the same place you’d expect to find an Arduino’s analog pins. Key digital pins, like the hardware SPI, I2C, and UART pins, are broken out to the same locations found on Arduinos as well. Programming Headers There are two programming headers on the board. One 6-pin (2x3) ICSP header, which can be used to program the chip using a standard AVR incircuit programmer. A 6-pin serial header near the power inputs can also be used to program the chip (assuming the bootloader’s still on there); this header should match up to common FTDI headers and cables (just make sure they’re the 3.3V variety). Powering the Board There are a variety of ways to power the development board. Input jacks are broken out for barrel jack, JST, screw, and 0.1" connectors. Whichever voltage supply you choose to power the board, it should be between 4.5 and 15V. Each of these power sources is fed into the voltage regulator, which drops the voltage down to 3.3V. If you’re using the barrel jack, a 5V or 9V wall-wart is a good choice for power source. Voltage can be fed directly to the chip, using the headers labeled “3.3V” – just make sure the voltage doesn’t exceed 3.6V. The ATmega128RFA1 can only operate at voltages between 1.8 and 3.6V. One of the ATmega128RFA1’s key features is its low power consumption. Sending or receiving RF data should only require 16 to 18mA of current. Idling, the chip should only require about 1-4.5mA. Each of the output pins can source/sink between 2-8mA. Check out the datasheet for more electrical specs. Page 6 of 20 How To Program Below, we’ll explain the two interfaces available for programming the ATmega128RFA1. There is a serial bootloader pre-programmed onto the board, or you can use the standard AVR 6-pin ISP header. In either case, you’ll probably need to solder headers onto the programming port pins to connect a programmer. ATmegaBOOT Serial Bootloader Bootloaders are small programs loaded onto a chip, which make uploading compiled code easier. Instead of requiring a specialized (often expensive) piece of hardware – a programmer – a more generalized tool can be used to upload to the board. The ATmega128RFA1 Development Board ships with a pre-programmed serial bootloader. Either an (archaic) serial port can be used to upload code to the board, or a more common USB-to-Serial converter can be used. We recommend the 3.3V FTDI Basic board, which interfaces directly to the 6-pin serial header of the dev board. A 3.3V FTDI Basic Board connected to the development board’s serial programming header. Right-angle headers were previously soldered to the header. As a bonus, the FTDI basic can also power the dev board. The bootloader on the ATmega128RFA1 Dev Board is a variation of the ATmegaBOOT serial bootloader, which was used on older Arduinos like the Duemilanove. This bootloader uses the UART0 of the ATmega128RFA1, and expects uploaded code at a baud rate of 57600. If you’re familiar with avrdude, a command like the one below should upload a compiled piece of code. avrdude ­p atmega128rfa1 ­c arduino ­P \\.\COM## ­b 57600 ­D ­V ­U flash:w:test­sketch.hex:i Page 7 of 20 Or, skip avrdude, and use the Arduino IDE with the bootloader, as we’ll explain in the following pages. ISP Programmer If you’ve got an AVR programmer and would rather skip working with the bootloader, the standard AVR 2x3 pin programming header is broken out on the board. Pin 1 of the programming port is marked with a silk-screened dash. An AVR Pocket Programmer connected to the development board’s ISP header. Straight headers were previously soldered to the header to allow for the connection. If you don’t have an AVR programmer but would still prefer using this method for uploading code, we’d recommend the USB Pocket AVR Programmer. Using that, an avrdude command like below can be used to upload a program: avrdude ­p atmega128rfa1 ­c usbtiny ­P usb ­D ­V ­U flash:w:test­sketch.hex:i If you have an Arduino, that can work as an alternative to the AVR programmer – check out the the ArduinoISP sketch under the examples menu. Arduino Compatibility Everyone loves Arduino! The simplified IDE and host of libraries and supporting code make it an awesome place to start prototyping. The ATmega128RFA1 shares a lot in common with the popular ATmega328 used on the Arduino Uno, so it seems reasonable that we should be able to program the board using the Arduino software. There are just a few extra steps which need to be taken to do so. First, if you haven’t already, download and install Arduino. Then… Update WinAVR (For Windows Users) Page 8 of 20 WinAVR is a wonderful, free, and open-source package of AVR utilities (including avr-gcc and avrdude) and definition files. It forms the backbone of most AVR development, including any AVR-based Arduino. Unfortunately, Arduino is (as of v1.0.5) packaged with an out-of-date version of WinAVR, which does not support the ATmega128RFA1. But it’s easy to upgrade! Download the most recent version of WinAVR (WinAVR-20100110 as of writing this) from the WinAVR project page. It should be installed over the old version of WinAVR included with Arduino, which is located in the Arduino\hardware\tools\avr directory. Follow these steps to update WinAVR: 1. Run the WinAVR installer (WinAVR-20100110-install.exe). 2. Cick "Run", Select your install Language, Click "Next", Click "I Agree" (unless you don't?), until you get to the install location screen. 3. On the install location screen, click Browse..., and navigate to the ../hardware/tools/avr directory inside your Arduino install (with the Arduino installer, it should go to the location seen in this image): 4. Click next. On the next screen, make sure Install files and Add Directories to PATH are selected. Install Programmers Notepad is optional. Page 9 of 20 5. Click Install and wait for the install to finish. Alternative to that method, you can install WinAVR to a standalone directory, and copy/paste it into the Arduino directory. Update AVRGCC, Etc. With CrossPack (For Mac Users) If you’re using the ATmega128RFA1 Dev Board with Mac, a similar set of steps is required to update your AVRGCC and AVR include files. CrossPack is an excellent source for up-to-date AVR development files. Go to their download page, and grab the most recent version. Once the disk image is downloaded, you can install the “CrossPackAVR.pkg” file. By default, the package will install to /usr/local/CrossPack­AVR­20131216 (the date part of that name is subject to change). Now you’ll need to copy everything from that directory into your Arduino application. To copy them into your Arduino app, right-click on the “Arduino” app and select Show Package Contents. Then navigate to the /Contents/Resources/Java/hardware/tools/avr folder within there. Finally, copy everything from the CrossPack download into that Arduino app directory. Voila! Onto the next step, adding the board definition. Add the Board Definitions File We also need to add a board definition file to be able to use the ATmega128RFA1 Dev Board within the Arduino environment. To begin, download the ATmega128RFA1 arduino addon. Page 10 of 20 The 128RFA1-DEV folder from that download should be added to a hardware directory within your Arduino sketchbook. Normally the sketchbook will install to your documents/Arduino folder. If a hardware folder isn’t already there, make it. This directory contains a boards.txt file which defines the ATmega128RFA1 Dev Board, and adds a selectable option under the Tools > Board menu. When you open the Arduino IDE (close and reopen it if it’s already open), this option should be added to the menu: When OS X prompts you, to ask what to do with merge conflicts, tell it to Keep Newer. This will keep any old, un-updated files, in place. Pin Mapping After you’ve added ATmega128RFA1-compatibility to your Arduino IDE, you can take advantage of all of the wonderful libraries you may have grown acustomed to, including Serial, SPI, and Wire. In addition to that each pin is mapped to a unique pin number, which you can invoke all of your digitalWrite , digitalRead , analogWrite , and analogRead needs upon. The addon defines all of the ATmega128RFA1’s pins as singular numbers. Just as Arduino has pins 0-13, and A0-A6, this development board has pins 0-25, and A0-A7. Here’s how the pins are mapped out: Page 11 of 20 There are a few pins with PWM functionality – 3, 4, 5, 8, 9, 19, 34, and 35 – which you can use for analogWrite . Note that pins 34 and 35 are not broken out to pins. They’re only connected to on-board LEDs. The SPI, UART, and I2C pins are where you’d expect them to be on an equivalent R3-or-later Arduino Uno. There is a second UART – UART1 – on pins D2 and D3. Example Code Example Sketch: RF Chat You can download the RF chat example here (or grab it from github). This is a simple example of how to make use of the RF functionality of the ATmega128RFA1. The radio-specific functions are split off into a secondary file – RadioFunctions.h. You’ll need two ATmega128RFA1’s for this example (it’s hard to demo the RF functionality without something to talk to!). They can be tied to the same computer, or a few rooms away. The maximum distance should be around 75m, but that’s with complete line-of-sight, walls will diminish the range. Upload the same sketch to each dev board. Then open up a serial monitor on each. You can use either the Arduino Serial Monitor, or a stand-alone terminal program (Tera Term is great for Windows users, Cool Term should work for Mac). Open up each serial port to 9600 bps (8 data bits, no parity, 1 stop bit), and start typing away! What’s typed into one terminal should pop up into another. Page 12 of 20 Understanding the Sketch There are a few key functions, and a few interrupt routines that are key to the workings of the RF transceiver. rfBegin() First, the radio must be initialized by calling the rfBegin() function. This is called in the setup() portion of the sketch. Check out the comments within the code for a line-by-line explanation. This function initializes the ATmega128RFA1’s radio. The lone parameter for this function sets the radio’s 2.4GHz channel, which should be some value between 11 and 26. Radios must be on the same channel to communicate with each other. Page 13 of 20 // Initialize the RFA1's low­power 2.4GHz transciever. // Sets up the state machine, and gets the radio into // the RX_ON state. Interrupts are enabled for RX // begin and end, as well as TX end. uint8_t rfBegin(uint8_t channel) {  for (int i=0; i