MCP23017.ino

MCP23017

This example demonstrates the use of MCP23017 IO expanders as if they were just normal IO pins.

Boards: 🛈

AVR, AVR USB, Nano Every, Nano 33 IoT, Nano 33 BLE, UNO R4, Pi Pico, Due, Teensy 3.x, ESP8266, ESP32

Connections

• SDA: MCP23017 SDA
• SCK: MCP23017 SCK
• 2: MCP23017 INT A or INT B

Connect an LED (and series resistor) between pin GPA0 of the MCP and ground. Connect a push button between pin GPB0 of the MCP and ground. The internal pull-up resistor will be used.

Tie the three address lines of the MCP to ground.

Behavior

When the push button is pressed, the LED turns on.

Written by PieterP, 2020-11-20
https://github.com/tttapa/Arduino-Helpers

 
#include <Wire.h>
 
#include <Arduino_Helpers.h>
 
#include <AH/Hardware/ExtendedInputOutput/MCP23017.hpp>
 
using namespace ExtIO; // Use the extended input/output functions
 
using WireType = decltype(Wire); // The type of the I²C driver to use
MCP23017<WireType> mcp {
  Wire, // The I²C driver to use
  0x0,  // The I²C address offset (depends on the state of the address pins)
  2,    // Optional: interrupt pin to detect input changes
};
 
pin_t ledPin = mcp.pinA(0);    // GPIOA0
pin_t buttonPin = mcp.pinB(0); // GPIOB0
 
void setup() {
  Wire.begin();          // Initialize the I²C interface
  Wire.setClock(800000); // Faster I²C clock
  mcp.begin();           // Initialize the MCP23017
 
  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT_PULLUP);
}
 
void loop() {
  auto buttonState = digitalRead(buttonPin);
  digitalWrite(ledPin, buttonState ? LOW : HIGH);
}
 
// Note:
// The “interrupt” pin is not used to trigger an actual interrupt on the
// microcontroller. It is just used to check whether any of the inputs of
// the MCP23017 changed without having to do an I²C transaction. Using this
// pin can speed up your code, but it's not necessary, you can leave it out
// in the MCP23017 construction at the top of the sketch.