Arduino Blink All Pins

BlinkAll.c

/*
  Blink
  Turns on an LED on for one second, then off for one second, repeatedly.
 
  This example code is in the public domain.
 */
 
// Pin 13 has an LED connected on most Arduino boards.
// Pin 11 has the LED on Teensy 2.0
// Pin 6  has the LED on Teensy++ 2.0
// Pin 13 has the LED on Teensy 3.0
// give it a name:


// the setup routine runs once when you press reset:
void setup() {                
  // initialize the digital pin as an output.
  for (int led = 0; led < 20; led++)
  pinMode(led, OUTPUT);     
}

// the loop routine runs over and over again forever:
void loop() {
  for (int led = 0; led < 20; led++){
    digitalWrite(led, HIGH);   // turn the LED on (HIGH is the voltage level)
  }
  delay(1000);               // wait for a second
  for (int led = 0; led < 20; led++){
    digitalWrite(led, LOW); 
  }
  delay(1000);               // wait for a second
}