constexpr uint8_t LED_PIN {4};
constexpr uint32_t INTERVAL {1000};

int main(void)
{
  uint32_t timeStamp;

	init();
  pinMode(LED_PIN, OUTPUT);
  while(1) {
    uint32_t now {millis()};
    if(now - timeStamp >= INTERVAL) {
      timeStamp = now;
      digitalWrite(LED_PIN, !digitalRead(LED_PIN));
    }
  }
	return 0;
}