#define DATA_PIN  8  // Pin connected to DS of 74HC595
#define LATCH_PIN 9  // Pin connected to STCP of 74HC595
#define CLOCK_PIN 10 // Pin connected to SHCP of 74HC595

uint16_t bitsToSend = 0x0001;


void setup()
{
  pinMode(DATA_PIN, OUTPUT);
  pinMode(LATCH_PIN, OUTPUT);
  pinMode(CLOCK_PIN, OUTPUT);
}

void loop()
{
  if(bitsToSend == 0)
  {
    bitsToSend = 1;
  }

  digitalWrite(LATCH_PIN, LOW);
  shiftOut16(DATA_PIN, CLOCK_PIN, LSBFIRST, bitsToSend);
  digitalWrite(LATCH_PIN, HIGH);

  bitsToSend <<= 1;
  delay(1000);
}

void shiftOut16(uint8_t dataPin, uint8_t clockPin, uint8_t bitOrder, uint16_t val)
{
  uint8_t i;

  for (i = 0; i < 16; i++)
  {
    if (bitOrder == LSBFIRST)
    {
      digitalWrite(dataPin, val & 1);
      val >>= 1;
    }
    else
    {
      digitalWrite(dataPin, (val & 128) != 0);
      val <<= 1;
    }

    digitalWrite(clockPin, HIGH);
    digitalWrite(clockPin, LOW);
  }
}