1

I was wondering if there is a way to find out that a GPIO is under voltage, say - the GPIO is set to HIGH. I need to be able to check this in a linux terminal, using a command or a script that simply returns true or false.

I tried to use the WiringPi library, but I can't seem to find a function in documentation that would be able to do this. Any help appreciated.

2

To control GPIO from the command line you can use the GPIO Sysfs Interface for Userspace. For example to monitor pin 26 you can do:

Prepair pin 26

rpi ~$ sudo -Es
rpi ~# echo 26 > /sys/class/gpio/export
rpi ~# echo "in" > /sys/class/gpio/gpio26/direction

Get status of pin 26

rpi ~# cat /sys/class/gpio/gpio26/value
0

Finish monitoring of pin 26

rpi ~# echo 26 > /sys/class/gpio/unexport
rpi ~# exit
rpi ~$

Here you can find a small script to Continuesly monitor GPIO input change/events in Bash with inotify.

1

Use wiringPi's gpio command.

man gpio for details.

Use pigpio's pigs command.

E.g.

sudo pigpiod # start the pigpio daemon

pigs r 4     # read GPIO 4
pigs w 4 1   # set GPIO 4 high

man pigs for details.

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