GPIO pin control on Tinker OS android

There are two basic ways of controlling the GPIO pins

1. Via ADB on a seperate machine

• Enable developer options on the tinker board's android OS by selecting the about phone/tinker board in settings and clicking on the build number at the bottom repeatedly untill it tells you that you are a developer

• Go into developer options inside settings and turn on USB debugging

• on the PC, download android platform tools for your operating system and extract it somewhere in your computer which can be easily accessed.

• Make sure that the tinker board and the PC are connected to the same network or preferably connected to each other via ethernet.

• Open the "android platform tools" directory on the PC and right click while pressing L-shift.

• Select "open power shell window here" (the option name might vary) or open CMD/Powershell and cd into the "android platform tools" directory.

• Find the IP address of the tinker board by running ip a in termux on the android OS.

or go into "about phone" and into "status", here you will find the IP addr also.

• in the powershell run

> adb connect 192.168.xxx.xxx:5555     (replace the tinke rboard IP address in place of the 'x')

> adb root

> adb connect 192.168.xxx.xxx:5555     (again)

> adb shell

• Now you will get a root shell of the android system, in the root shell run

# cd /sys/class/gpio

• This is where the GPIO pin directories are stored, by default no GPIO pins are not initialized

• To init the GPIO pins we need to type the following commands (The directories must have the CPU IDs for the GPIO pins, not the wPi numbers)

# echo 17 > /sys/class/gpio/export

This will create a directory called gpio17 with the required files in it

Similarly you can add all the GPIO pins you want to use, for example I am using gpio17(CPU) or gpio7(wPi) or pin number 7

• Then we need to assign its direction which is out

# echo "out" > /sys/class/gpio/gpio17/direction

• Now we can write to the value file to switch the pin on and off

# echo 1 > /sys/class/gpio/gpio17/value

# echo 0 > /sys/class/gpio/gpio17/value

• Finally you can write a shell script to automate the processes and for several GPIO pins

2. In android OS, involves rooting

• Firstly obtain root access by following the steps mentioned here

• Then open termux on android and cd into /sys/class/gpio

• From there the steps are the same as before starting from altering the export file

• Finally you can write a shell script to automate the process