#define IRQ0 __vector_1
#define IRQ1 __vector_2
#define SIGNAL __attribute__ ((signal))

unsigned char *led;
unsigned char *leddir;

unsigned char check_buttons();
void print_led(unsigned char value);
void enable_interrupt();
void leds_on(void);
void leds_off(void);
void IRQ0(void) SIGNAL;
void IRQ1(void) SIGNAL;

int main(void) {
  led = (unsigned char*) 0x38;
  leddir = (unsigned char*) 0x37;
  *leddir = 0xff;

//  led_off();
  enable_interrupt();
  
  while(1) {
  }

  return 0;
}

void IRQ0(void) {
//  print_led(~check_buttons());
  leds_on();
}

void IRQ1(void) {
//  print_led(~check_buttons());
  leds_off();
}

/* verifica qual botão está pressionado. */
unsigned char check_buttons() {
  unsigned char *botoes;
  botoes = (unsigned char*) 0x30;
  return *botoes;
}

/* acende os leds de acordo com o parâmetro "value". */
void print_led(unsigned char value) {
  *led = value;
}

/* acende todos os leds. */
void leds_on(void) {
  *led = 0xff;
}

/* apaga todos os leds. */
void leds_off(void) {
  *led = 0x0;
}

/* ativa o uso de interrupções. */
void enable_interrupt(void) {
  unsigned char *sreg;
  sreg = (unsigned char*) 0x5F;
  *sreg |= 0x80;

  unsigned char *gimsk;
  gimsk = (unsigned char*) 0x5B;
  *gimsk |= 0xC0;

  unsigned char *mcucr;
  mcucr = (unsigned char*) 0x55;
  *mcucr |= 0x0C;
}