Previously I tried out the pi-gpio package to get my led to flash, but wanted to explore other options. After a bit of searching around the internets I stumbled upon wiringPi and a corresponding node wrapper.

The documentation didn't have any apparent quick start examples but after reading a few examples. I clobbered together an example that worked with the latest version of the package. I loaded up web storm with automatic upload and pasted in the code.

var wpi = require('wiring-pi');
wpi.wiringPiSetup();
var pin = 0;
wpi.pinMode(pin, wpi.OUTPUT);
var value = 0;
setInterval(function() {
    wpi.digitalWrite(pin, value);
    value = +!value;
}, 500);

I needed to look at the pin layout table again to make sure I was using the right pin number.

I then ssh into the pi, ran sudo node led.js, and off went the flashing led. :-)

It was a success so I hit ctrl-c to terminate the app and the led stayed on, which thinking about it makes sense as I killed the application while the LED was on.

Time to research ways to run a function when a nodejs app terminates. As usual stack overflow was the go to place to learn how to execute a clean up function and also how to use Any key to exit.

Putting it all together

var wpi = require('wiring-pi');


wpi.wiringPiSetup();
var pin = 0;
wpi.pinMode(pin, wpi.OUTPUT);
var value = 0;
setInterval(function() {
    wpi.digitalWrite(pin, value);
    value = +!value;
}, 500);


function exitHandler(options, err) {
    if (options.cleanup) {
        if(wpi){
            wpi.digitalWrite(pin, 0);
        }
    }
    if (err) {
        console.log(err.stack);
    }
    if (options.exit) {
        process.exit();
    }
}

//do something when app is closing
process.on('exit', exitHandler.bind(null,{cleanup:true}));

//catches ctrl+c event
process.on('SIGINT', exitHandler.bind(null, {exit:true}));

//catches uncaught exceptions
process.on('uncaughtException', exitHandler.bind(null, {exit:true}));

console.log('Press any key to exit');

process.stdin.setRawMode(true);
process.stdin.resume();
process.stdin.on('data', process.exit.bind(process, 0));

Now when the app exits I can verify that the LED is in the off state.

Mental recap

• wiringPi seems like the way to go for future GPIO adventures
• clean up after yourself when your app terminates
• web storm is way easier compared to nano.