I2C

I2C is a synchronous communication bus that supports multiple devices communicating over two wires. Each device on the bus will have an ID. Wikipedia

ESPHome

To use I2C bus for ESPHome, add the following configuration. Set scan to true to have ESPHome output device IDs in the logs.

# Example configuration entry for ESP32
i2c:
  sda: 21
  scl: 22
  scan: true
  id: bus_a

Full Documentation