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====== GPIO Header ======

====== GPIO Usage Examples ======

<WRAP important >
Before using a GPIO, ensure it is not configured for another function (e.g., I2C, SPI). If it is, you can reconfigure it as a standard GPIO by applying a [[products:sbc:common:configurations:device-tree-overlay|Device Tree Overlay]]. 
</WRAP>

Once you have identified the correct GPIO number (e.g., 465), follow these steps to control it via the sysfs interface.

===== Export GPIO =====

Make the GPIO accessible to user space:
```shell
$ echo 465 | sudo tee /sys/class/gpio/export
```

===== Set GPIO Direction =====

Configure the GPIO as either an input or an output:

```shell
# Set GPIO output
$ echo out | sudo tee /sys/class/gpio/gpio465/direction 

# Set GPIO input
$ echo in  | sudo tee /sys/class/gpio/gpio465/direction 
```

===== Set GPIO value =====
If configured as an output, you can set its logic level:

```shell
# Set GPIO output high
$ echo 1 | sudo tee /sys/class/gpio/gpio465/value 

# Set GPIO output low
$ echo 0 | sudo tee /sys/class/gpio/gpio465/value 
```

===== Read GPIO Input value =====

If configured as an input, read its current logic level:
```shell
$ cat /sys/class/gpio/gpio465/value
```
The command returns 0 (low) or 1 (high).

===== Unexport GPIO ===== 

When finished, release the GPIO:
```shell
$ echo 465 | sudo tee /sys/class/gpio/unexport
```

===== Troubleshooting =====
If you encounter an error similar to the following when exporting, the GPIO pin is likely reserved for another function (e.g., by the device tree):

```shell
echo 465 | sudo tee /sys/class/gpio/export
tee: /sys/class/gpio/export: Invalid argument
```

**Solution**: Modify the [[products:sbc:common:configurations:device-tree-overlay|Device Tree Overlay]] configuration to free the pin and define it as a standard GPIO.