Control GPIO pins on the PINE64 with C#

Similar to the Raspberry Pi, GPIO pins on the PINE64 can be controlled through sysfs. You can refer to my previous post which goes into the concept in detail, and the C# code remains the same for the PINE64. However, with the longsleep Ubuntu image, root access is required to control the GPIO pins. You will need to grant the necessary permissions in order to be able to control GPIO pins as a normal user.

Granting user permissions
We’ll assume that we want to be able to control the pins as the default ubuntu user. Follow these steps to grant the necessary permissions.

1. Create a user group called gpio.
   groupadd gpio
2. Add the ubuntu user to the gpio group.
   useradd -G gpio ubuntu
3. Add a udev rule to run chown on the sysfs files. The chown command will set group ownership to the gpio group. Adding the udev rule will run the chown command automatically whenever you export a pin. Create a file called 99-com.rules in /etc/dev/rules.d and paste the following contents.
   
   SUBSYSTEM=="gpio*", PROGRAM="/bin/sh -c 'chown -R root:gpio /sys/class/gpio && chmod -R 770 /sys/class/gpio; chown -R root:gpio /sys/devices/soc.0/1c20800.pinctrl/gpio && chmod -R 770 /sys/devices/soc.0/1c20800.pinctrl/gpio; chown -R root:gpio /sys/devices/soc.0/1f02c00.pinctrl/gpio && chmod -R 770 /sys/devices/soc.0/1f02c00.pinctrl/gpio'"

   1

   SUBSYSTEM=="gpio*", PROGRAM="/bin/sh -c 'chown -R root:gpio /sys/class/gpio && chmod -R 770 /sys/class/gpio; chown -R root:gpio /sys/devices/soc.0/1c20800.pinctrl/gpio && chmod -R 770 /sys/devices/soc.0/1c20800.pinctrl/gpio; chown -R root:gpio /sys/devices/soc.0/1f02c00.pinctrl/gpio && chmod -R 770 /sys/devices/soc.0/1f02c00.pinctrl/gpio'"

   
   Physical pin to GPIO number mapping
   I took some time to test the physical pins on the PINE in order to determine the sysfs gpio numbers and came up with this table. As an example, physical pin 22 on the Pi 2 pinout corresponds to /sys/class/gpio/gpio79.

   Pin #	GPIO #
   Pi 2 pinout
   3	227
   5	226
   8	32
   10	33
   11	71
   12	72
   13	233
   15	76
   16	77
   18	78
   19	64
   21	65
   22	79
   23	66
   24	67
   26	231
   27	361
   28	360
   29	229
   31	230
   32	68
   33	69
   35	73
   36	70
   37	80
   38	74
   40	75
   Euler pinout
   7	363
   10	232
   11	35
   12	36
   13	37
   15	38
   16	39
   18	100
   19	98
   21	99
   22	101
   23	97
   24	96
   26	102
   27	34
   28	103
   29	40
   30	41
   Exp pinout
   2	359
   7	40
   8	41