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This example is for Wiring version 1.0 build 0100+. If you have a previous version, use the examples included with your software. If you see any errors or have comments, please let us know.

Blink an LED by BARRAGAN http://barraganstudio.com
turns on and off an LED connected to digital pin 8, with intervals of 1 second (1000 milliseconds) Note in the circuit the LED it has a positive (long leg) and a ground (short leg), if the LED doesn't turn ON, it might be it is inverted.

    int ledPin = 8;  // LED connected to digital pin 8

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

    void loop()
    {
      digitalWrite(ledPin, HIGH);  // set the LED on
      delay(1000);                 // wait for a second
      digitalWrite(ledPin, LOW);   // set the LED off
      delay(1000);                 // wait for a second
    }