I would like to use two GPIOs on a custom board that includes the Digi ConnectCard i.mx28 module; an output associated with pin 27 of the module and an input associated with pin 29 of the module. From the Digi hardware reference manual, these correspond to GPIO0_23 and GPIO0_22, respectively.
The GPIO as input (pin 27) works as expected when I configure it from the user space via sysfs. The GPIO as output (pin 29) does not report any errors when I set it up via sysfs, but I am unable to change the value. If I “cat” the value, it doesn’t follow what is assigned, and if I probe the pin with an oscilloscope, the signal shows no change either.
The documentation in the ConnectCard hardware reference manual is terse. From a literature review, it seems as if the issue might be related to a need to set up pin multiplexing to use the pin as GPIO and/or additionally configuring the GPIO in the device tree.
Any guidance on the details to do this within the framework of Digi Embedded Yocto is sincerely appreciated. I am working with the minimal, non-graphical build for the ConnectCard imx28js JumpStart platform as a baseline for Yocto.