PCA9685 PWM driver with ESP32

Specifications

Power and logic levels

3.3 V: safe to connect directly

ESP32 pins, including those on a display board's connectors, work at 3.3 V and are not 5 V tolerant. Modules differ, so if in doubt, measure the signal before you connect it.

Wiring

Arduino code

#include <Wire.h>

const int SDA_PIN = 8, SCL_PIN = 9;
const uint8_t ADDR = 0x40;

void writeReg(uint8_t reg, uint8_t value) {
  Wire.beginTransmission(ADDR);
  Wire.write(reg); Wire.write(value);
  Wire.endTransmission();
}

void setPulse(uint8_t channel, uint16_t off) {
  Wire.beginTransmission(ADDR);
  Wire.write(0x06 + 4 * channel);    // LEDn_ON_L
  Wire.write(0); Wire.write(0);
  Wire.write(off & 0xFF); Wire.write(off >> 8);
  Wire.endTransmission();
}

void setup() {
  Wire.begin(SDA_PIN, SCL_PIN);
  writeReg(0x00, 0x10);              // sleep, needed to set the prescaler
  writeReg(0xFE, 121);               // 50 Hz
  writeReg(0x00, 0x20);              // wake, auto-increment
  delay(1);
  writeReg(0x00, 0xA0);              // restart
}

void loop() {
  setPulse(0, 300); delay(1000);
  setPulse(0, 400); delay(1000);
}

No extra library needed. Compiled for ESP32-S3 with arduino-esp32 3.x. Not yet tested by us on a physical sensor. Change the pins to match your board.

On a display

Read the value in your sketch and pass it to a label, or send it over MQTT and show it with an MQTT value in the editor.

Boards with a ready connector

Only boards whose connectors we have surveyed. Others may still work on free GPIOs.

Good to know

• Use a separate supply for the servos.
• All channels share one frequency.
• Check 0x40 for clashes with INA sensors.
• Find each servo's end stops carefully.

What it is good for

• Robot arms and hexapods
• Boards with no free PWM pins
• Banks of LEDs at one frequency

FAQ

Sources

• https://esp32.co.uk/pca9685-esp32-esphome-16-channel-pwm-servos-leds/
• https://espboards.dev/sensors/pca9685
• https://wiki.lckfb.com/en/esp32s3r8n8/module/control/16-ch-servo-drive-module.html

Related parts

• SG90 servo
• MCP23017 GPIO expander