home-assistant.io/source/hassio/enable_i2c.markdown

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Enable I2C on the Home Assistant Operating System	Instructions on how to enable I2C on a Raspberry Pi

Home Assistant using the Home Assistant Operating System is a managed environment, which means you can't use existing methods to enable the I2C bus on a Raspberry Pi.

Step by step instructions

You will need:

• SD card reader
• SD card with Home Assistant Operating System flashed on it

Step 1 - Access the Home Assistant OS boot partition

Shutdown/turn-off your Home Assistant installation and unplug the SD card. Plug the SD card into an SD card reader and find a drive/file system named hassos-boot. The file system might be shown/mounted automatically. If not, use your operating systems disk management utility to find the SD card reader and make sure the first partition is available.

Step 2 - Add files to enable I2C

• In the root of the hassos-boot partition, add a new folder called CONFIG.
• In the CONFIG folder, add another new folder called modules.
• Inside the modules folder add a text file called rpi-i2c.conf with the following content:

  i2c-dev
  

• In the root of the hassos-boot partition, edit the file called config.txt add two lines to it:

  dtparam=i2c_vc=on
  dtparam=i2c_arm=on
  

Step 3 - Start with the new configuration

• Insert the SD card back into your Raspberry Pi.
• On startup, the hassos-config.service will automatically pickup the new rpi-i2c.conf configuration.
• Another reboot might be necessary to make sure the just imported rpi-i2c.conf is present at boot time.

The I2C devices should now be present under /dev.