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Update enable_i2c.md (#17005)

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Co-authored-by: Stefan Agner <stefan@agner.ch>
Co-authored-by: Franck Nijhof <frenck@frenck.nl>
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source/_includes/common-tasks/enable_i2c.md
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## Enable I2C
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.
Home Assistant using the Home Assistant Operating System which is a managed environment, which means you can't use existing methods to enable the I2C bus on a Raspberry Pi. In order to use I2C devices you will have to
- Enable I2C for the Home Assistant Operating System
- Setup I2C devices e.g. sensors
### Step by step instructions
### Enable I2C with an SD card reader
#### Access the boot partition
You will need:
- SD card reader
- SD card with Home Assistant Operating System flashed on it
#### Step 1 - Access the Home Assistant Operating System 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
#### 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`.
@ -32,7 +33,7 @@ and make sure the first partition is available.
dtparam=i2c_arm=on
```
#### Step 3 - Start with the new configuration
#### Start with the new OS configuration
- Insert the SD card back into your Raspberry Pi.
- On startup, the `hassos-config.service` will automatically pickup the new
@ -40,9 +41,7 @@ and make sure the first partition is available.
- 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.
### From Home Assistant Operating System Terminal
### Enable I2C via Home Assistant Operating System Terminal
Alternatively, by attaching a keyboard and screen to your device, you can access the physical terminal to the Home Assistant Operating System.
@ -62,3 +61,9 @@ You can enable i2c via this terminal:
sync
reboot
```
### Troubleshooting
After rebooting the host there should be `i2c-0` and similar device files in `/dev`. If such device files are missing, enabling I2C failed for some reason. You can check the status of I2C kernel modules by using `lsmod | grep i2c` in the terminal. If they are loaded, you should find at least the entry `i2c_dev`. Active usage of the modules is indicated by a number, e.g. `i2c_dev 20480 2` would indicate two active I2C device files.
An active I2C can also be check with a multi meter showing 3.3 V on the I2C pins GPIO2 and GPIO3.