GPIO (in/out) for NanoPi[edit]

Note: the test environment is a NanoPi K1 Plus with FriendlyCore installed in eMMC, kernel 4.14.x .

To enable a pin, execute:

echo X > /sys/class/gpio/export

where X is the number of the linux gpio corresponding to the pin you want to enable.

For example, if we want to enable pin N. 37, according to the table in http://wiki.friendlyarm.com/wiki/index.php/NanoPi_K1_Plus#Diagram.2C_Layout_and_Dimension , we need to execute:

echo 9 > /sys/class/gpio/export

A new /sys/class/gpio/gpio9 directory will appear.

In the same way, to disable the pin we need to execute:

echo 9 > /sys/class/gpio/unexport

and the directory/symbolic link gpio9 will disappear.

To set the direction (input or output pin), we need to execute:

echo out > /sys/class/gpio/gpio9/direction

or

echo in > /sys/class/gpio/gpio9/direction

To set the value:

echo 0 > /sys/class/gpio/gpio9/value
echo 1 > /sys/class/gpio/gpio9/value

To read the value

cat /sys/class/gpio/gpio9/value

How to calculate linux gpio numbers[edit]

A0 = gpio0
A1 = gpio1
A2 = gpio2
....
B0 = gpio32
B1 = gpio33
...
C0 = gpio64
...