MCP9808 precision temperature with ESP32

Supply 3.3-5 V Bus I2C I2C address 0x18 / 0x19 / 0x1A / 0x1B / 0x1C / 0x1D / 0x1E / 0x1F Measures temperature

Pins and ESP32 wiring

Pin	Role	ESP32 pin	Notes
VDD	Power	3V3
GND	Ground	GND
SCL	I2C clock (SCL)	D22
SDA	I2C data (SDA)	D21
ALERT	Interrupt	D35	Alert output (open drain), optional
A2	Not wired to the ESP32	—	Address bit 2. Pulled LOW on the board
A1	Not wired to the ESP32	—	Address bit 1. Pulled LOW on the board
A0	Not wired to the ESP32	—	Address bit 0. Pulled LOW on the board (0x18)

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 0x07: a genuine part answers 0x04. 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(0x18);
  bool found = Wire.endTransmission() == 0;
  Serial.println(found ? "MCP9808 precision temperature found at 0x18" : "Not found: check power, GND and SDA/SCL");
}

void loop() {}

Sources

Microchip MCP9808 datasheet, Device ID register 0x07 = 0x0400 (first byte read is 0x04)
Microchip MCP9808 datasheet, Address 0011 A2 A1 A0 = 0x18 to 0x1F; supply 2.7 to 5.5 V
Adafruit MCP9808 guide, Pinout Vdd, GND, SCL, SDA, Alert, A2, A1, A0

Try it in 3D in BoardPilot

BoardPilot Part data (JSON)

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