/*
 * WhiteLEDsThrob.INO 
 * Todd Andersen
 * 20-NOV-16
 *
 *Based on: "Throb"
 *http://playground.arduino.cc/Tutorials/Throb
 *
 * A variation on Blink.  This sketch presents the concept of PWM or
 * Pulse Width Modulation. It "throbs" the brightness of an LED, making it
 * gradually brighter and dimmer.
 */
int ledPin1 = 2;                     // White LEDs on board
int ledPin2 = 3;
int ledPin3 = 4;
int ledPin4 = 5;
int ledPin5 = 6;
int ledPin6 = 7;

int cycleTime = 100;                 // Total duration of single PWM cycle (100 or greater is best)
int changeSpeed = 3;                 // Throb speed, Change the onTimePerCycle per Cycle (mSec)
boolean brightnessGoingUp = true;    // Brightness up (true) / down (false)
int onTimePerCycle = 0;              // Milliseconds to turn the LED ON within a cycle

void setup(){                        // Run once, Start sketch
  pinMode(ledPin1, OUTPUT);          // Set digital pins as outputs
  pinMode(ledPin2, OUTPUT);
  pinMode(ledPin3, OUTPUT);
  pinMode(ledPin4, OUTPUT);
  pinMode(ledPin5, OUTPUT);
  pinMode(ledPin6, OUTPUT);
}

void loop(){                         // Continously runs
  digitalWrite(ledPin1, HIGH);       // LEDs on  
  digitalWrite(ledPin2, HIGH);
  digitalWrite(ledPin3, HIGH);
  digitalWrite(ledPin4, HIGH);
  digitalWrite(ledPin5, HIGH);
  digitalWrite(ledPin6, HIGH);
  delay(onTimePerCycle);             // Wait for onTimePerCycle (mSec)
  digitalWrite(ledPin1, LOW);        // LEDs off
  digitalWrite(ledPin2, LOW);
  digitalWrite(ledPin3, LOW);
  digitalWrite(ledPin4, LOW);
  digitalWrite(ledPin5, LOW);
  digitalWrite(ledPin6, LOW);
  delay(cycleTime - onTimePerCycle); // Wait for cycle to complete              

  // Adjust brightness up or down depending on current T / F state
  if (brightnessGoingUp){  
    onTimePerCycle += changeSpeed;
  }
  else{
    onTimePerCycle -= changeSpeed;
  }  
  // Full brightness, LEDs on for the complete cycle
  if (onTimePerCycle >= cycleTime){
    brightnessGoingUp = false;       // Brightness DOWN
    onTimePerCycle = cycleTime;      // Ensure brightness did not go over
  }
  // if we are at zero brightness, where the LED is not on at all in a cycle
  if (onTimePerCycle <= 0){        
    brightnessGoingUp = true;        // Brightness UP
    onTimePerCycle = 0;              // Ensure onTime didn't go bellow zero        
  }
}