/* Blink without Delay 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 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; // the number of the LED pin // 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. 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. unsigned long currentMillis = millis(); if(currentMillis - previousMillis > interval) { // save the last time you blinked the LED previousMillis = currentMillis; // if the LED is off turn it on and vice-versa: if (ledState == LOW) ledState = HIGH; else ledState = LOW; // set the LED with the ledState of the variable: digitalWrite(ledPin, ledState); } }