/* Simple Cylon / knight rider kitt
  Cylon Eye sweep using 8 LEDs
  http://www.hobbytronics.co.uk/arduino-tutorial4-cylon
 */

unsigned char upDown=1;	// start off going UP	
unsigned char cylon=0;  // determines which LED is on 0 to 7

void setup() {                
  // initialize the digital pins as outputs.
  DDRD = B11111111;  // sets Arduino port D pins 0 to 7 as outputs	   
}

void loop() {
  if(upDown==1){
    cylon++;
    if(cylon>=7) upDown=0;      // Reached max LED, next time we need to go down
  }
  else {
    cylon--;
    if(cylon==0) upDown=1;      // Reached min LED, next time we need to go up
  }
  PORTD = 1 << cylon;
  delay(100);              // wait for 0.1 second
}