GPIO without root

[paviro]

I am currently writing a module which uses the GPIO Pins for that the script has to be started as root. I tried running MM with DISPLAY=:0 sudo npm startbut all I get this way is a No protocol specifiederror on startup. Any idea how to fix this or how to use wiring-pi without root? Wasn’t there an Raspbian update recently that allowed GPIO access without root? I don’t remember it exactly…

[KirAsh4]

First Google result brings this up:
https://dissectionbydavid.wordpress.com/2013/10/21/raspberry-pi-using-gpio-wiringpi-without-root-sudo-access/

[paviro]

That’s nice and all but too complicated for people to setup…
Adding a sudo somewhere is one thing but that would make installing the module so complicated :confused:
Seems like it might be possible by using usermod -a -G gpio pi will check and report.

[paviro]

Found a workaround! Use the shell within node to export the pins. Works without root if the user is added to the gpio group, to do that execute sudo useradd -g pi gpio.

---

Setup the pins

const exec = require('child_process').exec;

exec("echo '22' > /sys/class/gpio/export", null);
exec("echo 'in' > /sys/class/gpio/gpio22/direction", null);

exec("echo '17' > /sys/class/gpio/export", null);
exec("echo 'out' > /sys/class/gpio/gpio17/direction", null);

Control the pins

gpio.setup('sys');

gpio.wiringPiISR(22, gpio.INT_EDGE_BOTH, function(delta) {
	if (gpio.digitalRead(22) == 1) {
		console.log("High");
		gpio.digitalWrite(17, 1)
	}
	else if (gpio.digitalRead(22) == 0) {
		console.log("Low");
		gpio.digitalWrite(17, 0)
	}
});