MCP23017 16-bit I/O expander with ESP32

Supply 3.3-5 V Bus I2C I2C address 0x20 / 0x21 / 0x22 / 0x23 / 0x24 / 0x25 / 0x26 / 0x27

Pins and ESP32 wiring

Pin	Role	ESP32 pin	Notes
VCC	Power	3V3
GND	Ground	GND
SCL	I2C clock (SCL)	D22
SDA	I2C data (SDA)	D21
RESET	Input (the ESP32 drives it)	D25	Must be HIGH to run: tie to VCC
INTA	Interrupt	D35
INTB	Interrupt	VP
A0	Not wired to the ESP32	—	Address bit 0
A1	Not wired to the ESP32	—	Address bit 1
A2	Not wired to the ESP32	—	Address bit 2. Expander I/O pins GPA0-7 and GPB0-7 go to your LEDs or buttons

Suggested wiring for the 30-pin ESP32 DevKit, avoiding flash, input-only and strapping pins. BoardPilot checks it for you as you wire.

Starter code (Arduino)

#include <Wire.h>

void setup() {
  Serial.begin(115200);
  Wire.begin(21, 22);  // SDA = GPIO 21, SCL = GPIO 22
  Wire.beginTransmission(0x20);
  bool found = Wire.endTransmission() == 0;
  Serial.println(found ? "MCP23017 16-bit I/O expander found at 0x20" : "Not found: check power, GND and SDA/SCL");
}

void loop() {}

Sources

Microchip MCP23017 datasheet, Hardware address pins A0-A2: 0x20 to 0x27
Microchip MCP23017 datasheet, RESET is active LOW

Try it in 3D in BoardPilot

BoardPilot Part data (JSON)

Part data: CC BY 4.0, free to reuse with credit to BoardPilot.

MCP23017 16-bit I/O expander with ESP32

Pins and ESP32 wiring

Starter code (Arduino)

Sources

Try it in 3D in BoardPilot

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