/* Blink without Delay
 
 Utilizziamo la funzione millis() al posto di delay()
 per poter gestire il lampeggio di un LED senza bloccare
 il processore.

 Questo esercizio e' strutturato in una serie di passaggi incrementali
 nei quali una versione minimale si evolve per introdurre
 programmazione ad oggetti, interrupts, pointers.

 Turns on and off a light emitting diode(LED) connected to a digital  
 pin, without using the delay() function.  This means that other code
 can run at the same time without being interrupted by the LED code.
 
 The circuit:
 * LED attached from pin 13 to ground.
 * Note: on most Arduinos, there is already an LED on the board
 that's attached to pin 13, so no hardware is needed for this example.
 
 
 created 2005
 by David A. Mellis
 modified 8 Feb 2010
 by Paul Stoffregen
 2015 modified by Andrea Manni
 
 This example code is in the public domain.

 
 http://www.arduino.cc/en/Tutorial/BlinkWithoutDelay
 */

// constants won't change. Used here to 
// set pin numbers:
const int ledPin =  13;      

// Variables will change:
int ledState = LOW;             // ledState used to set the LED
long previousMillis = 0;        // will store last time LED was updated

// the follow variables is a long because the time, measured in miliseconds,
// will quickly become a bigger number than can be stored in an int.
const long interval = 1000;           // interval at which to blink (milliseconds)

void setup() {
  // set the digital pin as output:
  pinMode(ledPin, OUTPUT);      
}

void loop()
{
  // here is where you'd put code that needs to be running all the time.

  // check to see if it's time to blink the LED; that is, if the 
  // difference between the current time and last time you blinked 
  // the LED is bigger than the interval at which you want to 
  // blink the LED.
 
  if (millis() > previousMillis + interval) {
    // Aggiorniamo il contatore previousMillis
    previousMillis = millis();   

    // if the LED is off turn it on and vice-versa:
    if (ledState == LOW)
      ledState = HIGH;
    else
      ledState = LOW;
    // e' possibile semplificare questa operazione?
    // Hint: lo stato del LED e' binario: ha solo due stati possibili.

    // set the LED with the ledState of the variable:
    digitalWrite(ledPin, ledState);
  }
}

/* Domande
   1. Aggioungere un LED che brilli ogni 500ms: iniziare pensando
      a quali variabili gestiscono l'attuale LED e a quali si
      dovranno aggiungere.
   2. E' ora agevole cambiare gli intervalli dei due LED? 
      Modificare gli intervalli dei due led (es 500ms - 320ms)
 */