increase speed of LED blink on Raspberry Pi using node.js and onoff

Question

I'm trying to alter the interval by using a the variable 'counter'.

The Twitter stream is working and the LED is blinking.

I have removed all the twitter credentials.

Any help would be greatly appreciated!

Here is my code:

var Gpio = require('onoff').Gpio;
var Twit = require('twit');
var T = new Twit({
    consumer_key:         '' // Your Consumer Key
  , consumer_secret:      '' // Your Co$
  , access_token:         '' // Your Ac$
  , access_token_secret:  '' // Your Access $
});

var stream = T.stream('statuses/filter', { track: '#blessed, #peace'})

led = new Gpio(17, 'out'),
counter = 500;

stream.start();

var iv = setInterval(function(){
        led.writeSync(led.readSync() === 0 ? 1 : 0);
}, counter);


stream.on('tweet', function(tweet) {

        if(tweet.text.indexOf('#blessed') > -1) {
                console.log("blessed");

                counter += 100;

            }  else if (tweet.text.indexOf('#peace') > -1) {

                console.log("peace");
                counter -= 100;

            }

});

Answer 1

Once you've made the setInterval() call, the timer's locked in, you can't change it. This is how arguments to functions work: Changing them after the fact does nothing. There is no binding to the value supplied, numbers get passed in as a copy.

You'll need to clear and re-set the timer. setInterval() returns a handle you can pass through to clearInterval() to turn it off. You've captured this, so you just need to use it:

var iv;

function blink(interval) {
  if (iv) {
    clearInterval(iv);
  }

  iv = setInterval(function() {
    led.writeSync(led.readSync() === 0 ? 1 : 0);
  }, interval);
}

Then use this function to reset it:

counter -= 100;
blink(counter);

Just make sure you don't go negative.