EPERM, operation not permitted while pin.value(true);

[kiddyfurby]

On both a raspberry pi (arch linux arm) and a beaglebone black (debian) I get a permission denied running test.js that came with npm install pi-pins
If I change index.js:46 to use a write() instead of writeSync() there will be no error, however I do want to make sure my write are not just buffered.

trace from node test.js

fs.js:540
return binding.write(fd, buffer, offset, length, position);
^
Error: EPERM, operation not permitted
at Object.fs.writeSync (fs.js:540:18)
at EventEmitter.gpio.value (/root/nrf/node_modules/nrf/node_modules/pi-pins/index.js:46:16)
at Object. (/root/nrf/node_modules/nrf/node_modules/pi-pins/test.js:9:6)

[natevw]

The Raspberry Pi GPIO device files are not available to users by default. You'll need to either start your script via sudo, or, setup your permissions so that your desired user can access. See Raspberry Pi – using GPIO / WiringPi without root (sudo) access or Stack Overflow: Accessing the GPIO (of a raspberry pi) without sudo for potential advice on the latter.

[natevw]

Actually, I'm reopening this issue as I review the non-sudo solutions. The device files themselves are "exported" (i.e. created) by this library during normal course of operations:

pi-pins/index.js

Line 28 in 79c0445

fs.writeFileSync("/sys/class/gpio/export", ''+pin);

So I'd like to add a CLI script to this package that can be used once (via sudo) to make the pins available, so that the script actually using them can be run non-privileged.

In the meantime the workaround would be to use the existing Python/C/whatever utilities that do this first. Thanks for the bug report, @kiddyfurby!

[kiddyfurby]

Thank you for your great library!

manually export the GPIO and chmod didn't help, actually, not even running as root helps.
chmod -R 777 /sys/class/gpio/gpio20
chmod -R 777 /sys/class/gpio/gpio21

[root@alarmpi pi-pins]# node test.js
Should be true: false
Should be false: false

fs.js:540
return binding.write(fd, buffer, offset, length, position);
^
Error: EPERM, operation not permitted
at Object.fs.writeSync (fs.js:540:18)
at EventEmitter.gpio.value (/root/pi-pins/node_modules/pi-pins/index.js:46:16)

[kiddyfurby]

I needed one line of change in pi-pins index.js

gpio.mode = function (mode) {       // 'in','out','low','high'
    fs.writeFileSync(pinPath+"/direction", mode);
    if (mode == 'high' || mode == 'low') this.value( mode == 'high' ); // add this line!
};

I do however still have problems with nrf (not sure if I should post here or there).
My logic analyzer suggest that the CE pin was set high too early, more precisely, before even W_TX_PAYLOAD is shifted out via SPI

Could it be that the GPIO and SPI handling of Linux has different timing?