#define K1 (!(PINB & (1 << PB1)))
#define K2 (!(PINB & (1 << PB2)))
#define K3 (!(PINB & (1 << PB3)))

uint16_t teller = 0;
uint8_t pK1 = 0, pK2 = 0;

uint16_t knipper = 0;

void uart_init() {
  UBRR0L = 103;          // 9600 baud
  UCSR0B = (1 << TXEN0);
}

void uart_send(char c) {
  while (!(UCSR0A & (1 << UDRE0)));
  UDR0 = c;
}

void uart_send_num(uint16_t n) {
  char buf[10];
  itoa(n, buf, 10);

  for (char* p = buf; *p; p++) uart_send(*p);
  uart_send('\n');
}

void setup() {
  DDRD = (1 << PD2);    // knipper LED
  DDRB = 0x00;
  PORTB = 0xFF;
  uart_init();
}

void loop() {

  // --- blink LED onafhankelijk van knoppen ---
  knipper++;
  if (knipper >= 200) {
    PORTD ^= (1 << PD2);
    knipper = 0;
  }

  // --- reset met K3 ---
  if (K3) teller = 0;

  // --- K1 voorrang ---
  if (K1 && !pK1) {
    teller++;
  }
  else if (!K1) {
    if (K2 && !pK2)
      uart_send_num(teller);
  }

  pK1 = K1;
  pK2 = K2;

  delay(10);
}