pulsing LED – fireflies on an Espruino

If you only want slow-ish PWM, you can do something like this:

Pin.prototype.pwm = function(dutyCycle, speed) {
  var pin = this;
  if (Pin.intervals===undefined)
    Pin.intervals = {};
  if (Pin.intervals[pin]!==undefined)
    clearInterval(Pin.intervals[pin]);
  var pulseLen = dutyCycle*1000/speed;
  Pin.intervals[pin] = setInterval(function() {
    digitalPulse(pin, 1, pulseLen);
  }, 1000/speed);
};

LED1.pwm(0.1, 100); // 100Hz

Note that because digitalPulse uses a timer, you're only having to run JavaScript once per pulse, and not once.

If you want to do that glowing effect then you could do something like this:

Pin.prototype.glow = function() {
  var pin = this;
  var pos = 0.001;
  var interval = setInterval(function() {
    digitalPulse(pin, 1, Math.sin(pos*Math.PI)*20); // up to 20ms
    pos += 0.01;
    if (pos>=1) clearInterval(interval);
  }, 20); // 50Hz
};

LED1.glow();

Which shouldn't halt Espruino while it's working.