const uint8_t PIN_DS   = 2;
const uint8_t PIN_SHCP = 4;
const uint8_t PIN_STCP = 3;

void send(uint16_t data) {
  digitalWrite(PIN_STCP, LOW);
  shiftOut(PIN_DS, PIN_SHCP, LSBFIRST, (data >> 8) & 0xFF);  // górny chip
  shiftOut(PIN_DS, PIN_SHCP, LSBFIRST, data & 0xFF);          // dolny chip
  digitalWrite(PIN_STCP, HIGH);
  digitalWrite(PIN_STCP, LOW);
}

void setup() {
  pinMode(PIN_DS,   OUTPUT);
  pinMode(PIN_SHCP, OUTPUT);
  pinMode(PIN_STCP, OUTPUT);
  // Test: zapal wszystkie 16 LEDów
  send(0xFFFF);
  delay(1000);
  // Test: zapal co drugi
  send(0xAAAA);
  delay(1000);

  send(0x5555);
  delay(1000);
}

void loop() {
  // Knight Rider na 16 LEDach
  for (int i = 0; i < 16; i++) {
    send((uint16_t)1 << i);
    delay(60);
  }
  for (int i = 14; i > 0; i--) {
    send((uint16_t)1 << i);
    delay(60);
  }
}