TS-7840 GPIO Usage

The Armada 385 and FPGA GPIO are exposed using a kernel character device. This interface provides a set of files and directories for interacting with GPIO which can be used from any language that interact with special files in linux using ioctl() or similar. For our platforms, we pre-install the "libgpiod" library and binaries. Documentation on these tools can be found here. This section only covers using these userspace tools and does not provide guidance on using the libgpiod library in end applications. Please see the libgpiod documentation for this purpose.

A user with suitable permissions to read and write /dev/gpiochip* files can immediately interact with GPIO pins. For example, to read the push switch:

gpioget 2 31

Multiple pins in the same chip can be read simultaneously by passing multiple pin numbers separated by spaces.

To write to a pin, the 'gpioset' command is used. For example, to set mikro_int_pad:

gpioset 3 26=0

Multiple pins in the same chip can be set simultaneously by passing multiple pin=value pairs separated by spaces.

If a call with 'gpioset' or 'gpioget' fails with "Device or resource busy," that means that specific GPIO is claimed by another device. The command 'cat /sys/kernel/debug/gpio' can be used to get a list of all of the system GPIO and what has claimed them.