GY-21 HTU21D temperature + humidity with ESP32

Pins and ESP32 wiring

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(0x40);
  bool found = Wire.endTransmission() == 0;
  Serial.println(found ? "GY-21 HTU21D temperature + humidity found at 0x40" : "Not found: check power, GND and SDA/SCL");
}

void loop() {}

Sources

• TE Connectivity HTU21D(F) datasheet, I2C address 0x40 (fixed)

Related parts

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