#define IRQ0 __vector_1
#define TIM0_OVF __vector_7
#define SIGNAL __attribute__ ((signal))

unsigned char *led;
unsigned char *leddir;
unsigned int counter; //contador de interrupções
unsigned char tipo_interrupcao;
unsigned char value;

void print_led(unsigned char value);
void leds_off(void);
void enable_interrupt(void);
unsigned char check_buttons(void);

void IRQ0(void) SIGNAL;
void TIM0_OVF(void) SIGNAL;

int main(void) {
  led = (unsigned char*) 0x38;
  leddir = (unsigned char*) 0x37;
  *leddir = 0xff;
  tipo_interrupcao = 0x00; // interrupção na descida  
  counter = 0;

  leds_off(); 
  enable_interrupt();

  while(1);
  return 0;
}

void IRQ0(void) {
  unsigned char *timsk;
  timsk = (unsigned char*) 0x59;
  unsigned char *mcucr;
  mcucr = (unsigned char*) 0x55;

  if (tipo_interrupcao == 0x00) { //apertou o botão
    counter = 0;
    *mcucr = 0x03; //altera para interrupção na rampa de descida
    *timsk = 0x02; //ativa o contador
  }
  else { //soltou o botão
    *mcucr = 0x02; //altera para interrupção na rampa de subida
    *timsk = 0x00; //reseta o contador
    leds_off();
    counter = 0;
  }
  tipo_interrupcao = ~tipo_interrupcao;
}

void TIM0_OVF(void) {
  counter++;
   if (counter >= 61) {
     print_led(check_buttons());
   }
}

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

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

/* 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;

  /* ativa interrupções na rampa de descida */
  unsigned char *mcucr;
  mcucr = (unsigned char*) 0x55;
  *mcucr = 0x02;

  /* divisor do contador (ck/1024).  */
  unsigned char *tccr0;
  tccr0 = (unsigned char*) 0x53;
  *tccr0 |= 0x05;
}

unsigned char check_buttons(void){
  unsigned char *botoes;
  botoes = (unsigned char*) 0x30;
  return *botoes;
}