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Roadrunner technical documentation

Manage GPIO lines using sysfs

GPIO sysfs is the legacy way to manage the GPIO lines under Linux from user space. It uses the directory /sys/class/gpio to set or read any GPIO line. replaced with the GPIO character device.

This ABI is deprecated and will be removed after 2020.

Inside this directory there are two directories called:

  • export
  • unexport

To manage a GPIO line you have to know its kernel ID. The Kernel IDs of any Acme Systems SoM are available on:

Check the port available by typing this command:

sudo less /sys/kernel/debug/pinctrl/fc038000.pinctrl-atmel_pinctrl/pinconf-pins

The Microchip chips have the GPIO lines organized by 32 bit port called PA,PB, etc.

Before set or read a port you have to export it. Follow an example on how to set, reset and read the port PA1 (Kernel ID 1) from the command line:

Set the line status of GPIO line PA1

sudo sh -c "echo 1 > /sys/class/gpio/export"
sudo sh -c "echo out > /sys/class/gpio/PA1/direction"
sudo sh -c "echo 1 > /sys/class/gpio/PA1/value"

Reset the line status of GPIO line PA1

sudo sh -c "echo 0 > /sys/class/gpio/PA1/value"

Read the line status of GPIO line PA1

sudo sh -c "echo in > /sys/class/gpio/PA1/direction"
cat /sys/class/gpio/PA1/value

The official documentation about the GPIO Sysfs interface is available on:

Roadrunner technical documentation