OPT3001 ambient light (CJMCU-3001) with ESP32

Supply 3.3 V Bus I2C I2C address 0x44 / 0x45 / 0x46 / 0x47 Measures light

Pins and ESP32 wiring

Pin	Role	ESP32 pin	Notes
VCC	Power	3V3	Chip maximum is 3.6 V: use 3V3 only
GND	Ground	GND
SDA	I2C data (SDA)	D21
SCL	I2C clock (SCL)	D22
INT	Interrupt	D35	Interrupt output (open drain), optional
ADDR	Not wired to the ESP32	—	Address: GND = 0x44, VCC = 0x45, SDA = 0x46, SCL = 0x47

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

Check it is the real chip

Read register 0x7F: a genuine part answers 0x30. BoardPilot does this automatically in “Debug a problem”.

Starter code (Arduino)

#include <Wire.h>

void setup() {
  Serial.begin(115200);
  Wire.begin(21, 22);  // SDA = GPIO 21, SCL = GPIO 22
  Wire.beginTransmission(0x44);
  bool found = Wire.endTransmission() == 0;
  Serial.println(found ? "OPT3001 ambient light (CJMCU-3001) found at 0x44" : "Not found: check power, GND and SDA/SCL");
}

void loop() {}

Sources

TI OPT3001 datasheet, Device ID register 0x7F = 0x3001 (first byte read is 0x30)
TI OPT3001 datasheet, ADDR pin: GND, VDD, SDA, SCL = 0x44 to 0x47; supply 1.6 to 3.6 V

Try it in 3D in BoardPilot

BoardPilot Part data (JSON)

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