# LED Brightness

For this example, we'll be using an LED on an Arduino board, and modifying it's
brightness to make it fade in and out. Before we start, make sure you've got the
`cylon-arduino` module installed.

Let's start by importing Cylon:

    var Cylon = require('cylon');

Once we've got that, we can start defining our robot:

    Cylon.robot({

We'll be using an Arduino, and communicating over the Firmata protocol. As well,
we'll let our robot know about the LED we'll be modifying, on pin #3 of the
Arduino.

      connections: {
        arduino: { adaptor: 'firmata', port: '/dev/ttyACM0' }
      },

      devices: {
        led: { driver: 'led', pin: 3 }
      },

Next up, we'll define our robot's work:

      work: function(my) {

We'll set some variables here: brightness will represent the LED's brightness,
from 1-255, and 'fade' will be the brightness change on each tick.

        var brightness = 0,
            fade = 5;

Every 50 milliseconds, we'll be incrementing the brightness by `fade`'s value,
setting the LED to that brightness, and reversing `fade`'s value if brightness
hits 0 or 255.

        every(0.05.seconds(), function() {
          brightness += fade;
          my.led.brightness(brightness);
          if ((brightness === 0) || (brightness === 255)) { fade = -fade; }
        });
      }

And with that done, we can now start our robot.

    }).start();
