SI1145 UV index / IR / visible light with ESP32

Supply 3.3-5 V Bus I2C I2C address 0x60 Measures uv, light, proximity

Pins and ESP32 wiring

Pin	Role	ESP32 pin	Notes
VIN	Power	3V3
GND	Ground	GND
3VO	Not wired to the ESP32	—	3.3 V output of the on-board regulator. Leave unconnected
SCL	I2C clock (SCL)	D22
SDA	I2C data (SDA)	D21
INT	Interrupt	D35	Interrupt output, optional
LED	Not wired to the ESP32	—	For an external IR LED (proximity). Leave unconnected

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 0x00: a genuine part answers 0x45. 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(0x60);
  bool found = Wire.endTransmission() == 0;
  Serial.println(found ? "SI1145 UV index / IR / visible light found at 0x60" : "Not found: check power, GND and SDA/SCL");
}

void loop() {}

Sources

Silicon Labs Si1145/46/47 datasheet, Register 0x00 PART_ID (0x45 = Si1145, 0x46 = Si1146, 0x47 = Si1147); I2C address 0x60
Silicon Labs Si1145/46/47 datasheet, UV index is calculated from visible and IR light, it has no real UV photodiode

Try it in 3D in BoardPilot

BoardPilot Part data (JSON)

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