#include <avr/interrupt.h>  
#include <avr/io.h>  

// DONG_PULSE_LEN if the time the relay is energized in milliseconds
// DELAY_BETW_DONGS if pause between dongs in milliseconds
#define DONG_PULSE_LEN 120
#define DELAY_BETW_DONGS 1500

#define INIT_TIMER_COUNT 6  
#define RESET_TIMER2 TCNT2 = INIT_TIMER_COUNT  

#define CONTROL_PORT PORTB
#define SWITCH_PORT  PINB
#define CONTROL_DDR  DDRB

#define RELAY PB0
#define HR_SET PB2
#define MIN_SET PB3
#define SR_DIN PB4
#define SR_CLK PB5

int int_counter = 0;  
volatile int second = 45;  
volatile int minute = 59;  
volatile int hour = 10;  
volatile int digit = 0;
volatile int rintocchi = 0;

volatile int min_pb_was_pressed = 0;
volatile int hour_pb_was_pressed = 0;

int oldSecond = 0;  
long oldmillis = 0;  

// Aruino runs at 16 Mhz, so we have 1000 Overflows per second...  
// 1/ ((16000000 / 64) / 256) = 1 / 1000  
ISR(TIMER2_OVF_vect) {  
  RESET_TIMER2;  
  int_counter += 1;  
  if (int_counter == 1000) {  
    int_counter = 0;  
    do_clock();
  }
  //        do_alarm();
  do_switch();
  do_display();
};

void do_clock(){
  second++;
  if(second > 59){
    second = 0;
    minute++;
    if(minute == 30) rintocchi = -1; // half hour
    if(minute > 59){
      minute = 0;
      hour++;
      if(hour > 23){
        hour = 0;
      }
      rintocchi = hour;
      if (rintocchi == 0) rintocchi = 12;
      if (rintocchi > 12) rintocchi -= 12;
    }
  }
}

void do_switch(){
  if(bit_is_clear(SWITCH_PORT, HR_SET)){
    if(hour_pb_was_pressed == 0){
      hour_pb_was_pressed = 1;
      hour++;
      if(hour > 23) hour = 0;
    }  
  } 
  else hour_pb_was_pressed = 0;
  if(bit_is_clear(SWITCH_PORT, MIN_SET)){
    if(min_pb_was_pressed == 0){
      min_pb_was_pressed = 1;
      minute++;
      second = 0;
      if(minute > 59) minute = 0;
    }  
  } 
  else min_pb_was_pressed = 0;
}

void do_display(){
  switch(digit){
  case 0:
    digit_wr (((hour / 10) == 0 ? 10 : hour / 10), 0, digit);
    break;
  case 1:
    digit_wr (hour % 10, int_counter < 500 ? 1:0, digit);
    break;
  case 2:
    digit_wr (minute / 10, 0, digit);
    break;
  case 3:
    digit_wr (minute % 10, 0, digit);
    break;
  }
  digit++;
  digit &= 0x03;
}

void setup() {
  //	Serial.begin(9600);  
  //	Serial.println("Initializing timerinterrupt");  
  //Timer2 Settings: Timer Prescaler /64,   
  TCCR2B |= (1<<CS22);      
  TCCR2B &= ~((1<<CS21) | (1<<CS20));       
  // Use normal mode  
  TCCR2A &= ~((1<<WGM21) | (1<<WGM20));    
  // Use internal clock - external clock not used in Arduino  
  ASSR |= (0<<AS2);  
  //Timer2 Overflow Interrupt Enable  
  TIMSK2 |= (1<<TOIE2) | (0<<OCIE2A);    
  RESET_TIMER2;
  CONTROL_DDR = _BV(SR_CLK) | _BV(SR_DIN); // these are outputs
  CONTROL_PORT = _BV(HR_SET) | _BV(MIN_SET); // pull ups
  sei();
}  

void loop() {
  while((rintocchi > 0) && (rintocchi <13)){ // strike hours
    CONTROL_PORT |= _BV(RELAY);  // close relay: dong!
    delay(DONG_PULSE_LEN);
    CONTROL_PORT &= ~_BV(RELAY); // release relay.
    delay(DELAY_BETW_DONGS);
    rintocchi--;
  }
  if (rintocchi == -1){  // strike half hour
    rintocchi = 0;
    CONTROL_PORT |= _BV(RELAY);  // close relay: dong!
    delay(DONG_PULSE_LEN);
    CONTROL_PORT &= ~_BV(RELAY); // release relay.
  }
}

void wr_one(){ // write a bit 1 to the shift register but no transfer yet
  CONTROL_PORT |= _BV(SR_DIN);
  CONTROL_PORT |= _BV(SR_CLK);
  CONTROL_PORT &= ~_BV(SR_DIN);
  CONTROL_PORT &= ~_BV(SR_CLK);  // Din == 0 => no transfer (BU2090)
}

void wr_zero(){ // write a bit 0 to the shift register but no transfer yet
  CONTROL_PORT &= ~_BV(SR_DIN);
  CONTROL_PORT |= _BV(SR_CLK);
  CONTROL_PORT &= ~_BV(SR_CLK);  // Din == 0 => no transfer (BU2090)
}

void wr_one_tr(){ // write a bit 1 to the shift register and transfer
  CONTROL_PORT |= _BV(SR_DIN);
  CONTROL_PORT |= _BV(SR_CLK);
  CONTROL_PORT &= ~_BV(SR_CLK);  // Din == 1 => transfer (BU2090)
}

void wr_zero_tr(){ // write a bit 0 to the shift register and transfer
  CONTROL_PORT &= ~_BV(SR_DIN);
  CONTROL_PORT |= _BV(SR_CLK);
  CONTROL_PORT |= _BV(SR_DIN);
  CONTROL_PORT &= ~_BV(SR_CLK);  // Din == 1 => transfer (BU2090)
}

void digit_wr (int val, int dot, int digit){
  switch (digit){
  case 0:  // decine ore
    wr_zero();
    wr_one();
    wr_one();
    wr_one();
    break;
  case 1:  // unita' ore
    wr_one();
    wr_zero();
    wr_one();
    wr_one();
    break;
  case 2:  // decine min
    wr_one();
    wr_one();
    wr_zero();
    wr_one();
    break;
  case 3:  // decine ore
    wr_one();
    wr_one();
    wr_one();
    wr_zero();
    break;
  default:
    break;
  }
  if(dot) wr_zero();
  else wr_one();
  switch(val){
    case(0):
    wr_one();
    wr_zero();
    wr_zero();
    wr_zero();
    wr_zero();
    wr_zero();
    wr_zero_tr();
    break;
    case(1):
    wr_one();
    wr_one();
    wr_one();
    wr_one();
    wr_zero();
    wr_zero();
    wr_one_tr();
    break;
    case(2):
    wr_zero();
    wr_one();
    wr_zero();
    wr_zero();
    wr_one();
    wr_zero();
    wr_zero_tr();
    break;
    case(3):
    wr_zero();
    wr_one();
    wr_one();
    wr_zero();
    wr_zero();
    wr_zero();
    wr_zero_tr();
    break;
    case(4):
    wr_zero();
    wr_zero();
    wr_one();
    wr_one();
    wr_zero();
    wr_zero();
    wr_one_tr();
    break;
    case(5):
    wr_zero();
    wr_zero();
    wr_one();
    wr_zero();
    wr_zero();
    wr_one();
    wr_zero_tr();
    break;
    case(6):
    wr_zero();
    wr_zero();
    wr_zero();
    wr_zero();
    wr_zero();
    wr_one();
    wr_one_tr();
    break;
    case(7):
    wr_one();
    wr_one();
    wr_one();
    wr_one();
    wr_zero();
    wr_zero();
    wr_zero_tr();
    break;
    case(8):
    wr_zero();
    wr_zero();
    wr_zero();
    wr_zero();
    wr_zero();
    wr_zero();
    wr_zero_tr();
    break;
    case(9):
    wr_zero();
    wr_zero();
    wr_one();
    wr_one();
    wr_zero();
    wr_zero();
    wr_zero_tr();
    break;
  default:  // blank
    wr_one();
    wr_one();
    wr_one();
    wr_one();
    wr_one();
    wr_one();
    wr_one_tr();
    break;
  }
}