MCP23017

Project MCP23017
Guide: Connecting MCP23017 to ESP8266
Status	Completed
Contact	sttc
Last Update	2020-02-15

Status

Status as of 2020/1/13:

• Completed

Introduction

MCP23017 is a GPIO expander runs on I2C. This page forms wiring and communication guide for MCP23017 on ESP8266.

Used components:

• MCP23017

MCP23017 I2C Interface 16bit I/O Extension Module Pin Board IIC to GIPO Converter https://www.aliexpress.com/item/32883688022.html?spm=a2g0s.9042311.0.0.5d3e4c4d6bMkco

• ESP8266:

LiLon NodeMCU V3 4MB flash ESP8266 12E More info on ESP8266: https://randomnerdtutorials.com/esp8266-pinout-reference-gpios/

Wiring

Setting up ESP8266 for I2C pins is not necessary in this code. SCL and SDA pins as below:

Pin on MCP23017	ESP8266
GND	GND
VCC	3V
SCL	D1 (GPIO5)
SDA	D2 (GPIO4)

Code

// MCP23017 Example: Slow key press reaction.
//
// Toggle LEDs and detect keypress.
//
// Example code showing slow reaction of 'button' 
// LED to keypress. Leading into why interrupts
// are useful (See next example).
//
// Copyright : John Main
// Free for non commercial use.

#include <Wire.h>
#include <Adafruit_MCP23017.h>

#define MCP_LED1 7
#define MCP_INPUTPIN 8
#define MCP_LEDTOG1 11 

Adafruit_MCP23017 mcp;
  
void setup() {  
  mcp.begin();      // Default device address 0

  mcp.pinMode(MCP_LEDTOG1, OUTPUT);  // LED for blinking
  
  mcp.pinMode(MCP_LED1, OUTPUT);     // LED output for button
  
  mcp.digitalWrite(MCP_LED1, HIGH);  // default > LED turn on

  mcp.pinMode(MCP_INPUTPIN,INPUT);   // Button i/p to GND
  mcp.pullUp(MCP_INPUTPIN,HIGH);     // Puled high to ~100k
}
 
void loop() {

  // blinking led
  delay(300);
  mcp.digitalWrite(MCP_LEDTOG1, HIGH); 
  delay(300);
  mcp.digitalWrite(MCP_LEDTOG1, LOW); 
  
  
  
  // Transfer input pin state to LED1
  if (mcp.digitalRead(MCP_INPUTPIN)) {
     mcp.digitalWrite(MCP_LED1,HIGH);
  } else {
     mcp.digitalWrite(MCP_LED1,LOW);
  }
  
}

MCP21017 GPIO

Number in IDE =
mcp.pinMode(Number in IDE, OUTPUT);

MCP21017	Number in IDE
PA0	0
PA1	1
PA2	2
PA3	3
PA4	4
PA5	5
PA6	6
PA7	7
PB0	8
PB1	9
PB2	10
PB3	11
PB4	12
PB5	13
PB6	14
PB7	15

Remarks

Pins of VCC,GND,SCL,SDA,RT,ITA,ITB line do not fit to the board together with GPIO pins (PA7, PA6...) > (Do not solder VCC... line pins)