Program to fade in and fade out LED

Write the following code in Cloud9 and save it as fadeLED.js. Run the program and you should see the LED fading in and out alternatively.

The code for fadeLED.js is as follows:

var b = require('bonescript');
var led = "P9_21";
var loopTime = 20;
var duty_cycle=0;
var increment = true;

var loopTimer = setInterval(fadeLED, loopTime);

function fadeLED()
{
    if(duty_cycle == 100 )
        increment = false;
    if(duty_cycle == 0)
        increment = true;

    if(increment == true)
        duty_cycle = duty_cycle + 1;
    else
        duty_cycle = duty_cycle - 1;

    console.log("duty_cycle = ",duty_cycle/100);
    b.analogWrite(led,duty_cycle/100);
}

Explanation

In Chapter 3, Blinking External LEDs we used the function digitalWrite() with a similar setup. Here, we are using the analogWrite() function. We are initializing the variable duty_cycle with a value of zero. We use the variable increment as a Boolean flag to keep track of fading in or fading out...