by
jjm » Tue Aug 23, 2016 8:47 am
tadvi wrote:
What Linux GPIO numbers do single row Pins 6 and 7 correspond to?
6 GPIOL11/IR-RX - Linux GPIO # ?
7 SPDIF-OUT/GPIOA17 - Linux GPIO # ?
Hello，
Accessing the GPIO pins through sysfs with mainline kernel The GPIO pins can be accessed from user space using sysfs. To enabled this you need the following kernel option enabled: CONFIG_GPIO_SYSFS
Device Drivers ---> GPIO Support ---> /sys/class/gpio/... (sysfs interface)
To access a GPIO pin you first need to export it with
echo XX > /sys/class/gpio/export
with XX being the number of the desired pin. To obtain the correct number you have to calculate it from the pin name (like PH18)[1]:
(position of letter in alphabet - 1) * 32 + pin number
E.g for PH18 this would be ( 8 - 1) * 32 + 18 = 224 + 18 = 242 (since 'h' is the 8th letter).
After you have successfully exported the pin you can access it through /sys/class/gpio/gpio*NUMBER* (in case of PH18 it's /sys/class/gpio/gpio242).
With /sys/class/gpio/gpio*NUMBER*/direction you can set the pin to out or in using
echo "out" > /sys/class/gpio/gpio*NUMBER*/direction
and you can read/write the value with /sys/class/gpio/gpio*NUMBER*/value.
When you are done unexport the pin with
echo XX > /sys/class/gpio/unexport
