GPIOlib

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With recent Linux kernel (> 2.6.3x), there is an abstraction layer meant to ease GPIO usage: gpiolib. We will explain here how to use it.

Installation

• If not already done:

$ make linux26-menuconfig

Device Drivers  --->
    -*- GPIO Support  --->
        [*]   /sys/class/gpio/... (sysfs interface)

$ make

• reflash your kernel (if needed)

Usage

• Find your GPIO number, eg for PF14 -> PortF (n°6) pin 14 -> (6-1)*32 + 14 -> 174
• Ask kernel to export the GPIO:

# echo 174 > /sys/class/gpio/export

• Access functions are created:

# ls /sys/class/gpio/gpio174/
active_low  edge        subsystem   value
direction   power       uevent

• Check GPIO direction and put in output:

# cat /sys/class/gpio/gpio174/direction
in
# echo out > /sys/class/gpio/gpio174/direction
# cat /sys/class/gpio/gpio174/direction
out

• Play with GPIO value:

# echo 1 > /sys/class/gpio/gpio146/value
# echo 0 > /sys/class/gpio/gpio146/value

Links

• http://www.kernel.org/doc/Documentation/gpio.txt