Acquista | Scarica | Come iniziare | Guide | Riferimento | Hardware | FAQ | Dizionario

Learning   Examples | Foundations | Hacking | Links

Examples > Digital I/O

Blink Without Delay

Sometimes you need to blink an LED (or some other time sensitive function) at the same time as something else (like watching for a button press). That means you can't use delay(), or you'd stop everything else the program while the LED blinked. Here's some code that demonstrates how to blink the LED without using delay(). It keeps track of the last time it turned the LED on or off. Then, each time through loop() it checks if a sufficient interval has passed - if it has, it turns the LED off if it was on and vice-versa.

Code

 
int ledPin = 13;                // LED connected to digital pin 13
int value = LOW;                // previous value of the LED
long previousMillis = 0;        // will store last time LED was updated
long interval = 1000;           // interval at which to blink (milliseconds)

void setup()
{
  pinMode(ledPin, OUTPUT);      // sets the digital pin as 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, is the difference
  // between the current time and last time we blinked the LED bigger than
  // the interval at which we want to blink the LED.
  if (millis() - previousMillis > interval) {
    previousMillis = millis();   // remember the last time we blinked the LED

    // if the LED is off turn it on and vice-versa.
    if (value == LOW)
      value = HIGH;
    else
      value = LOW;

    digitalWrite(ledPin, value);
  }
}