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ESPHome - Smart Home Made Simple 2026.5.2

I²C Bus

This component sets up the I²C bus for your esp32, esp8266, rp2040, nrf52, or host platform. In order for these components to work correctly, you need to define the I²C bus in your configuration. On ESP32 (both Arduino and ESP-IDF frameworks), internal pullup resistors are enabled by default. On ESP8266, the internal 10kΩ pullup resistors are always enabled. External pullups are still recommended for longer wire runs or multiple devices. 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
i2c:
  sda: GPIOXX
  scl: GPIOXX
  scan: true
  id: bus_a
# Example configuration entry for host platform
i2c:
  device: /dev/i2c-1
  scan: true

Configuration variables

Section titled “Configuration variables”

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

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

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

esp32, esp8266, rp2040, nrf52

Section titled “esp32, esp8266, rp2040, nrf52”

  • 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).

  • timeout (Optional, Time): Set the I²C bus timeout. Defaults to the framework defaults (100us on esp32, 1s on esp8266 and 1s on rp2040). Maximum on esp32 is 13ms.

esp32 only

Section titled “esp32 only”

  • sda_pullup_enabled (Optional, boolean): Enable the internal pullup resistor for the SDA pin. Defaults to true.

  • scl_pullup_enabled (Optional, boolean): Enable the internal pullup resistor for the SCL pin. Defaults to true.

  • low_power_mode (Optional, boolean): Enable the low-power (master only) I²C bus. Only available on ESP32C5, ESP32C6 and ESP32P4. Defaults to false unless required.

host

Section titled “host”
  • device (Required, string): The I²C device path to use (e.g., /dev/i2c-0, /dev/i2c-1).

Multiple I²C buses

Section titled “Multiple I²C buses”

If the device supports multiple I²C buses, they need to be defined separately and sensors need to be set up specifying the correct bus:

# Example configuration entry
i2c:
  - id: bus_a
    sda: GPIOXX
    scl: GPIOXX
    scan: true
  - id: bus_b
    sda: GPIOXX
    scl: GPIOXX
    scan: true
# Sensors should be specified as follows
sensor:
  - platform: bme680
    i2c_id: bus_b
    address: 0x76

For I²C multiplexing see Tca9548A.

See Also

Section titled “See Also”