GPIO on 9210 EL - looking for steps on how to access GPIO 1 - not visible when using GPIO Module

If you can not access the pin it is probably taken by one of the enabled peripherals. In this case problably UART
Change your Uart to 2 wire only in kernel config and the pin should become free as GPIO

Thanks for the info.
I did finally do better reading of the documentation and realized I needed to correctly edit the makedevs.d resources.

I am having trouble trying to find appropriate examples of how to handle a pin to be interrupt driven. How to define the callback function.

There are two ways to work with GPIO

  1. using GPIO example app & sample gpio kernel module.
    Example app shows how to use interrupts.

  2. using sysfs (recommended):
    With actual C example here:

Another good article here: