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Examples > Digital I/O

Loop

We also call this example "Knight Rider" in memory to a TV-series from the 80's where the famous David Hasselhoff had an AI machine driving his Pontiac. The car had been augmented with plenty of LEDs in all possible sizes performing flashy effects.

Thus we decided that in order to learn more about sequential programming and good programming techniques for the I/O board, it would be interesting to use the Knight Rider as a metaphor.

This example makes use of 6 LEDs connected to the pins 2 - 7 on the board using 220 Ohm resistors. The first code example will make the LEDs blink in a sequence, one by one using only digitalWrite(pinNum,HIGH/LOW) and delay(time). The second example shows how to use a for(;;) construction to perform the very same thing, but in fewer lines. The third and last example concentrates in the visual effect of turning the LEDs on/off in a more softer way.

Circuit

Code

int timer = 100;                   // The higher the number, the slower the timing.
int pins[] = { 2, 3, 4, 5, 6, 7 }; // an array of pin numbers
int num_pins = 6;                  // the number of pins (i.e. the length of the array)

void setup()
{
  int i;

  for (i = 0; i < num_pins; i++)   // the array elements are numbered from 0 to num_pins - 1
    pinMode(pins[i], OUTPUT);      // set each pin as an output
}

void loop()
{
  int i;

  for (i = 0; i < num_pins; i++) { // loop through each pin...
    digitalWrite(pins[i], HIGH);   // turning it on,
    delay(timer);                  // pausing,
    digitalWrite(pins[i], LOW);    // and turning it off.
  }
  for (i = num_pins - 1; i >= 0; i--) { 
    digitalWrite(pins[i], HIGH);
    delay(timer);
    digitalWrite(pins[i], LOW);
  }
}