.. _gpio-8X:

GPIO
======

This guide will show you how to connect to toggle a GPIO on the phyCORE-i.MX8X development kit.

.. tip::
    The GPIO pin numbering of the phyCORE-i.MX8X schematic is offset from the device name in sysfs.

    You can use the following equation to figure out what number the device is represented as in sysfs.

      *Hardware Signal = GPIO(Bank)_IO(num)*

      *sysfs GPIO Device = (Bank)*32 + num*

    Example:

    Hardware Signal = LSIO_GPIO0_IO19

    sysfs GPIO Device = (0)*32 + 19 = 19

    LSIO_GPIO0_IO19 is represented as GPIO19 in sysfs


Toggling User LED (D31)
--------------------------

The development kit has a user-configurable LED (D31) that is hooked up to LSIO_GPIO0_IO28 of the processor.

.. note:: This is named as X_SAI0_TXFS on the SOM schematic and changes to X_USER_LED on the carrier board schematic.

.. image:: ../../images/phycore-imx8x/pcm-065_gpio-d31.webp
   :width: 500px

* Now that we know the GPIO bank (0) and number (28) we can calculate which gpio to export in software.

  *(0x32) + 28 = 28*

* Export GPIO28

  .. code-block:: none
    :caption: Target (Linux)

    echo 28 > /sys/class/gpio/export

* Set GPIO28 as an output

  .. code-block:: none
    :caption: Target (Linux)

    echo out > /sys/class/gpio/gpio28/direction

* Turn ON the User_LED

  .. code-block:: none
    :caption: Target (Linux)

    echo 0 > /sys/class/gpio/gpio28/value


GPIO Expander (U90)
----------------------

The GPIO expander is connected to the I2C1 interface at address 0x20 and provides an additional 8 GPIOs that are used for various interfaces such as ETH, the displays, the cameras, and the fan.

To learn how to access the GPIO expander you can refer to our :ref:`i2c-8x` guide.