I²C Bus

This component sets up the I²C bus for your ESP32 or ESP8266. In order for these components to work correctly, you need to define the I²C bus in your configuration. Please note the ESP will enable its internal 10kΩ pullup resistors for these pins, so you usually don’t need to put on external ones. You can use multiple devices on one I²C bus as each device is given a unique address for communicating between it and the ESP. You can do this by hopping wires from the two lines (SDA and SCL) from each device board to the next device board or by connecting the wires from each device back to the two I²C pins on the ESP.

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

Configuration variables:

  • sda (Optional, Pin): The pin for the data line of the I²C bus. Defaults to the default of your board (usually GPIO21 for ESP32 and GPIO4 for ESP8266).

  • scl (Optional, Pin): The pin for the clock line of the I²C bus. Defaults to the default of your board (usually GPIO22 for ESP32 and GPIO5 for ESP8266).

  • scan (Optional, boolean): If ESPHome should do a search of the I²C address space on startup. Defaults to true.

  • frequency (Optional, float): Set the frequency the I²C bus should operate on. Defaults to 50kHz. Values are 10kHz, 50kHz, 100kHz, 200kHz, … 800kHz

  • id (Optional, ID): Manually specify the ID for this I²C bus if you need multiple I²C buses.


If the device can support multiple I²C buses (ESP32 has 2, ESP8266 does not support more than one) these buses need to be defined as below and sensors need to be setup specifying the correct bus:

 # Example configuration entry
   - id: bus_a
     sda: 13
     scl: 16
     scan: true
   - id: bus_b
     sda: 14
     scl: 15
     scan: true
# Sensors should be specified as follows
- platform: bme680
  i2c_id: bus_b
  address: 0x76
  # ...

For I2C multiplexing see TCA9548A I²C Multiplexer.

See Also