74HC595 test code.ino

int latchPin = 12;
int clockPin = 11;
int dataPin = 13;
byte leds = 0;
int currentLED = 0;

void setup() {
  pinMode(latchPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  pinMode(clockPin, OUTPUT);

  leds = 0;
}

void loop() {
  leds = 0;

  if (currentLED == 7) {
    currentLED = 0;
  }
  else {
    currentLED++;
  }

  bitSet(leds, currentLED);

  digitalWrite(latchPin, LOW);
  shiftOut(dataPin, clockPin, LSBFIRST, leds);
  digitalWrite(latchPin, HIGH);

  delay(250);
}