/* Blink without Delay - only led
 
 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.
 
Schema: https://lab.piffa.net/schemi/circuito_led_bb.png
 
 http://www.arduino.cc/en/Tutorial/BlinkWithoutDelay
 */

const int led = 13;      // Primo LED
              
unsigned long previousMillis = 0;        // Ultimo agiornamento
unsigned long interval = 1000;           // Pausa tra i lampeggi

void setup() {
  pinMode(led, OUTPUT);      
}

void loop()
{
  if (millis() - previousMillis >= interval) {
    previousMillis += interval ;

    digitalWrite(led, !digitalRead(led));
  }
}