Reading Sensors over I2C

Wiring an I2C sensor, scanning the bus for its address, and pulling a first reading.

I2C is a two-wire bus that lets many sensors and chips share the same pair of connections, each identified by its own address. It's the most common way to add off-the-shelf sensors — temperature, pressure, motion — to an ESP32 project.

Finding a device's address

#include 

void setup() {
  Wire.begin(); // default SDA=21, SCL=22
  Serial.begin(115200);
  delay(200);

  for (byte addr = 1; addr < 127; addr++) {
    Wire.beginTransmission(addr);
    if (Wire.endTransmission() == 0) {
      Serial.print("Found device at 0x");
      Serial.println(addr, HEX);
    }
  }
}

void loop() {
}

Reading a sensor

Once you know a sensor's address, most sensor libraries handle the register-level reads and writes for you — you call something like sensor.readTemperature() and the library takes care of the I2C conversation underneath.