BOB-13601

Page 1 of 16   SX1509 I/O Expander Breakout Hookup Guide Introduction Is your Arduino running low on GPIO? Looking to control the brightness of 16 LEDs individually? Maybe blink or breathe a few autonomously? Want to delegate scanning an 8x8 matrix of 64 buttons to another controller? These are all tasks the for which the SX1509 16-IO Expander was made! The SX1509 is a 16-channel GPIO expander with an I2C interface – that means with just two wires, your microcontroller can interface with 16 fully configurable digital input/output pins. But, the SX1509 can do so much more than just simple digital pin control. It can produce PWM signals, so you can dim LEDs. It can be set to blink or even breathe pins at varying rates. And, with a built-in keypad engine, it can interface with up to 64 buttons set up in an 8x8 matrix. An SX1509 controlling three LEDs, monitoring three buttons and a 12button keypad, and producing SPI signals to drive a Serial 7-Segment Display. It’s a really cool chip and a great tool for expanding the capability of your Arduino or any other I2C-capable microcontroller. Page 2 of 16 Covered In this Tutorial This tutorial will serve to familiarize you with all things SX1509 and the SparkFun Breakout. Then we’ll demonstrate how take advantage of all of the I/O expander’s features using an Arduino-compatible microcontroller and our SX1509 Arduino Library. The tutorial is split into the following sections: • SX1509 Breakout Board Overview – An overview of the features of the SX1509 and the SparkFun breakout. • Hardware Assembly – Tips and tricks for soldering headers or wires to the SX1509 Breakout. • Installing the SparkFun SX1509 Arduino Library – We’ve written an Arduino library to abstract all of the ugly register bit-operations. ◦ Example: Digital In/Out and PWM – An example circuit and Arduino sketch demonstrating some of the simpler I/O expander features. ◦ Example: LED Driving – Examples demonstrating how to autonomously blink and breathe LEDs. ◦ Example: Button Matrices – How to use the SX1509’s keypad engine to monitor a 12-button keypad. Suggested Reading Before delving into this tutorial, there are a few concepts you should already be somewhat familiar with. Check out these related tutorials: • I2C Communication – The SX1509 is controlled over an I2C interface. Learn all about this powerful 2-wire interface. • Logic Levels – While most Arduino’s operate at 5V, the SX1509 works at 3.3V. The GPIO are, at least, 5V tolerant! • Pulse-Width Modulation (PWM) – All of the SX1509’s output pins are capable of producing a PWM signal. That means you can control the brightness of LEDs! Pulse-width Modulation Logic Levels An introduction to the concept of pulse width modulation. Learn the difference between 3.3 V and 5 V devices. Light-emitting Diodes (LEDs) I2C Learn the basics about LEDs as well as some more advanced topics to help you calculate requirements for projects containing many LEDs. An introduction to I2C, one of the main embedded communications protocols in use today. Page 3 of 16 SX1509 Breakout Board Overview There’s a lot going on on the SX1509 Breakout. GPIO and power buses are broken out in every-which direction, and configurable jumpers cover most of the rest of the board. This section will cover all things SX1509 Breakout, so you can get the most out of the board’s features. I2C and Power Input Headers These two headers at the top and bottom of the breakout board are the input and control headers to the board. This is where you can supply power to the SX1509, and where your I2C signals – SDA and SCL – will terminate. These headers break out the following pins: Pin Label Type Description INT Output Active low programmable interrupt RST Input Active low reset (pulled high on-board) GND Power Ground (0V) 3V3 Power Main supply voltage (1.425-3.6V) SDA I2C I2C serial data line SCL I2C I2C serial clock line OSC Clock In/Out Optional clock input, or programmable clock signal output Page 4 of 16 The SDA and SCL pins each have 10kΩ resistors pulling them up to 3.3V. These resistors can be disconnected by cutting the SJ1 jumpers. RST – the SX1509’s active-low reset input – works just like an Arduino reset pin. If the pin is pulled LOW, the SX1509 will power down. When RST rises, the SX1509 will turn back on, but all of its settings will be cleared out. The breakout board includes a 10kΩ resistor pulling RST HIGH, so you ignore this pin if you don’t need the reset functionality. INT is a very handy interrupt output, especially if you’re using any SX1509 pins as inputs. It can be configured to go LOW whenever a pin state changes. The breakout board includes a 10kΩ resistor pulling INT HIGH. Finally, OSC breaks out the SX1509’s OSCIO pin – the oscillator input/output. This highly-configurable pin can be used as either the clock input for the SX1509 (if you don’t want to use its internal 2MHz clock), a clock output (producing an up to 2MHz square wave signal), or a simple digital I/O. Required and optional pins: The pairs of power and I2C pins are the only ones required for interfacing with the SX1509. RST, INT, and OSC are all optional, they can be left disconnected if you don't need the feature they provide. I/O and GND/VCC Breakouts The real meat of the breakout board are the pairs of rows breaking out all sixteen I/O pins plus the power rails. The SX1509 breaks its 16 I/O into two banks – bank A and bank B. Each bank can operate on a separate power supply, but by default they’re both set to 3.3V. Bank A is powered by VCC1, and bank B is supplied by VCC2. VCC1 and VCC2 can range between 1.2V and 3.6V, if you want to supply them externally. Check out the “Jumpers” section for more information on that. Every I/O pin is capable of PWM and blink outputs, but only half of them can be set to “breathe” (blink with smooth transitions from on to off). Also, if you plan on using the SX1509 keypad driver, each I/O is relegated to either a row or column interface. LED Driver Keypad I/O PWM Blink Breathe Row 0 ✓ ✓ ✓ 1 ✓ ✓ ✓ 2 ✓ ✓ ✓ 3 ✓ ✓ ✓ Column Page 5 of 16 4 ✓ ✓ ✓ ✓ 5 ✓ ✓ ✓ ✓ 6 ✓ ✓ ✓ ✓ 7 ✓ ✓ ✓ ✓ 8 ✓ ✓ ✓ 9 ✓ ✓ ✓ 10 ✓ ✓ ✓ 11 ✓ ✓ ✓ 12 ✓ ✓ ✓ ✓ 13 ✓ ✓ ✓ ✓ 14 ✓ ✓ ✓ ✓ 15 ✓ ✓ ✓ ✓ Ground (or Power) Rails Running alongside the I/O breakouts are a pair of power rails. These rails can be distinguished by the bars of white silkscreen running between each pad. By default, these rails are both set to ground – handy if you want to fan out some active-low buttons, or current-sourced LEDs. Jumpers on the back side allow you to switch the rails from GND to either VCC1 or VCC2. You’ll need to cut the jumper between GND and the rail, then blob solder between the rail and VCC. This bus is completely optional. Just don’t solder male pins into both rows of headers if you plan on using the breakout in a breadboard! Address-Select Jumpers Up to four SX1509’s can be connected to a single I2C bus, by configuring them to different addresses. The SX1509 has two pins devoted to I2C address selection: ADD0 and ADD1. Each of those pins are broken out to a jumper on the bottom of the board. Page 6 of 16 The board defaults each of those pins to GND, which sets the I2C address to 0x3E. To set either jumper to “1” (HIGH), grab a hobby knife, cut the trace connecting to “0”, and blob some solder between the center pad and “1”. The four configurable addresses are listed on the back of the board, but for quick reference, they are: ADD1 ADD0 I2C address 0 0 0x3E 0 1 0x3F 1 0 0x70 1 1 0x71 VCC1 and VCC2 Jumpers SJ1 and SJ2 on the back-side of the board connect VCC2 and VCC1, respectively, to the 3V3 voltage supply input. So, if you’re delivering 3.3V to the board, each of the I/O banks will operate at 3.3V. If you want to take advantage of the SX1509’s level-shifting capabilities by powering these banks at something other than VCC, cut the jumpers and plug any voltage between 1.2V and 3.6V into the VCC1 and/or VCC2 pins. These supply buses are completely independent – so they can operate at different voltages. Hardware Assembly You’ll need to solder something into the SX1509 Breakout to use it, whether that something is male or female headers or wire is completely up to you and your intended application. If you’ve never soldered before, check out our PTH soldering tutorial. One option we like, which keeps the board as breadboard-compatible as can be, is soldering male headers on the I/O banks, and female headers on either (or both) of the power/I2C headers. Page 7 of 16 Then you can use male-to-male jumper wires to connect between your microcontroller and the breakout, and breadboard the rest of the I/O. Installing the SparkFun SX1509 Arduino Library Now that you’ve got the hardware all mostly figured out, it’s time to start programming! To help make using the SX1509 as painless as possible, we’ve written an Arduino library to help interface with it. Visit the SparkFun SX1509 Arduino Library GitHub repository, or click the button below to download the latest version of the library. D O W N LO AD T H E S X1 5 0 9 A R D UI N O L I B RA R Y ! For help installing the library, check out our Installing an Arduino Library tutorial. If you downloaded the library as a ZIP, you can use Arduino’s Sketch > Include Library > Add .ZIP Library tool to automatically add it to your Arduino sketchbook. The SparkFun SX1509 Arduino library includes all sorts of examples, which demonstrate specific features of the I/O expander. Navigate to File > Examples > SparkFun SX1509 IO Expander to check them out. Quickly, we’ll walk you through a few quick examples that show off the I/O expander’s range of features. Example: Digital In/Out and PWM Page 8 of 16 As with almost any I/O expander, each of the SX1509’s GPIO can be configured as simple digital inputs or outputs. So you can toggle LEDs on or off, monitor for button presses, or even bit-bang more advanced digital interfaces like SPI (probably nothing that’s timing-dependent though). Here’s a quick example that shows how you can digitalWrite or digitalRead using the SX1509. If you want to follow along, hook up a circuit like below: Match up 3.3V, GND, SDA, and SCL between your Arduino and the SX1509 Breakout. Then connect an LED to I/O 15 – you can either configure it to source or sink current. And connect an active-low button to I/O 0. Then throw this code onto your Arduino: Page 9 of 16 #include  // Include the I2C library (required)  #include  // Include SX1509 library  SX1509 io; // Create an SX1509 object  // SX1509 pin definitions:  // Note: these aren't Arduino pins. They're the SX1509 I/O:  const int SX1509_LED_PIN = 15; // LED connected to 15 (source  ing current)  const int SX1509_BTN_PIN = 7; // Button connected to 0 (active ­low)  bool ledState = false;  void setup()   {    pinMode(13, OUTPUT); // Use pin 13 LED as debug output    digitalWrite(13, LOW); // Start it as low    // Call io.begin() to initialize the I/O    // expander. It'll return 1 on success, 0 on fail.    if (!io.begin(0x3E))    {      // If we failed to communicate, turn the pin 13 LED on      digitalWrite(13, HIGH);      while (1)        ; // And loop forever.    }    // Call io.pinMode(, ) to set any SX1509 pin as    // either an INPUT, OUTPUT, INPUT_PULLUP, or ANALOG_OUTPUT    io.pinMode(SX1509_LED_PIN, OUTPUT);    io.pinMode(SX1509_BTN_PIN, INPUT_PULLUP);    // Blink the LED a few times before we start:    for (int i=0; i