PCF8574 I/O expander module with ESP32

Supply 3.3-5 V Bus I2C I2C address 0x20 / 0x21 / 0x22 / 0x23 / 0x24 / 0x25 / 0x26 / 0x27 / 0x38 / 0x39 / 0x3A / 0x3B / 0x3C / 0x3D / 0x3E / 0x3F

Pins and ESP32 wiring

Pin	Role	ESP32 pin	Notes
GND	Ground	GND
VCC	Power	3V3
SDA	I2C data (SDA)	D21
SCL	I2C clock (SCL)	D22
INT	Interrupt	D35	Interrupt output, optional
P0	Not wired to the ESP32	—	Expander I/O pins go to your LEDs or buttons, not to the ESP32
P1	Not wired to the ESP32	—
P2	Not wired to the ESP32	—
P3	Not wired to the ESP32	—
P4	Not wired to the ESP32	—
P5	Not wired to the ESP32	—
P6	Not wired to the ESP32	—
P7	Not wired to the ESP32	—

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 ? "PCF8574 I/O expander module found at 0x20" : "Not found: check power, GND and SDA/SCL");
}

void loop() {}

Sources

NXP PCF8574 / PCF8574A datasheet, Address 0x20 to 0x27 (PCF8574) or 0x38 to 0x3F (PCF8574A) via A0-A2

Try it in 3D in BoardPilot

BoardPilot Part data (JSON)

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

PCF8574 I/O expander module with ESP32

Pins and ESP32 wiring

Starter code (Arduino)

Sources

Try it in 3D in BoardPilot

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