volatile char *TWC_R = (char*)0xBC;
volatile char *TWS_R = (char*)0xB9;
volatile char *TWD_R = (char*)0xBB;
volatile char *TWB_R = (char*)0xB8;
unsigned char status,sec,minutes,hours,day,date,month,year;
char days [7][20]= {"Sun","Mon","Tue","Wed","Thu","Fri","Sat"};

void setup() {
  Serial.begin(115200);
  init_timer();
  init_port();
}

void init_timer(){
  volatile char *TCCR1_A = 0x80;
  volatile char *TCCR1_B = 0x81;
  volatile short *TCNT_1 = 0x84;
  volatile short *OCR1_A = 0x88;
  volatile char *TIMSK_1 = 0x6F;

  *TCCR1_A = 0;
  *TCCR1_B = 0x0C;
  *TCNT_1  = 0;
   
  *OCR1_A  = 60000;
  *TIMSK_1 = 0x02;
}

ISR (TIMER1_COMPA_vect){
  repeat();
}

void repeat(){
    init_lcd();
    i2c_init();
    i2c_start();
    delay1();
    // status = *TWS_R & 0xF8;
    // Serial.println(status,HEX);

    i2c_write(0xD0);//slave address of RTC 
    delay1();
    // status = *TWS_R & 0xF8;
    // Serial.println(status,HEX);
    i2c_write(0x00);
    delay1();
    // status = *TWS_R & 0xF8;
    // Serial.println(status,HEX);

    // i2c_init();
    get_date_time();
    show_date_time();
}

void init_port(){
  char *ddr1 = (char*)0x30;
  *ddr1 = 0x03;

  char *ddr2 = (char*)0x107;
  *ddr2 = 0xFF;
}

void init_lcd(){
  data_lcd(0x38);
  enable();
  data_lcd(0x84);
  enable();
  data_lcd(0x0F);
  enable();
}

void lcd_write(char data){
  data_lcd(data);
  register_enable();
}

void register_enable(){
  control_lcd(0x02);
  delay1();
  control_lcd(0x03);
  delay1();
}

void enable(){
  control_lcd(0x01);
  delay1();
  control_lcd(0x00);
  delay1();
}

void control_lcd(char data){
  char *out = (char*)0x31;
  *out = data;
}

void data_lcd(char data){
  char *out = (char*)0x108;
  *out = data;
}

void second_line(){
  data_lcd(0x38);
  enable();
  data_lcd(0xC0);
  enable();
}

void show_date_time(){
  // Serial.print("TIME -  ");
  // Serial.print(hours,HEX);
  // Serial.print(":");
  // Serial.print(minutes,HEX);
  // Serial.print(":");
  // Serial.println(sec,HEX);
  // Serial.print("Date -  ");
  // Serial.print(date,HEX);
  // Serial.print("/");
  // Serial.print(month,HEX);
  // Serial.print("/20");
  // Serial.print(year,HEX);
  // Serial.print(" (");
  // Serial.print(days[day-1]);
  // Serial.print(")");
  char hours1 = (hours>>4)&0x0F;
  char hours2 = (hours)&0x0F;
  lcd_write(hours1+'0');
  lcd_write(hours2+'0');
  lcd_write(':');

  char minutes1 = (minutes>>4)&0x0F;
  char minutes2 = (minutes)&0x0F;
  lcd_write(minutes1+'0');
  lcd_write(minutes2+'0');
  lcd_write(':');

  char sec1 = (sec>>4)&0x0F;
  char sec2 = (sec)&0x0F;
  lcd_write(sec1+'0');
  lcd_write(sec2+'0');

  second_line();

  char date1 = (date>>4)&0x0F;
  char date2 = (date)&0x0F;
  lcd_write(date1+'0');
  lcd_write(date2+'0');
  lcd_write('/');

  char month1 = (month>>4)&0x0F;
  char month2 = (month)&0x0F;
  lcd_write(month1+'0');
  lcd_write(month2+'0');
  lcd_write('/');

  char year1 = (year>>4)&0x0F;
  char year2 = (year)&0x0F;
  lcd_write('2');
  lcd_write('0');
  lcd_write(year1+'0');
  lcd_write(year2+'0');
  
  lcd_write(' ');
  lcd_write('(');
  for(char i=0;i<3;i++){
    lcd_write(days[day-1][i]);
  }
  lcd_write(')');
}

void get_date_time(){
  i2c_start();
  delay1();
  // status = *TWS_R & 0xF8;
  // Serial.println(status,HEX);

  i2c_write(0xD1);
  delay1();
  // status = *TWS_R & 0xF8;
  // Serial.println(status,HEX);

  set_ack();
  delay1();
  // status = *TWS_R & 0xF8;
  // Serial.println(status,HEX);

  set_ack();
  sec = *TWD_R;
  delay1();
  // status = *TWS_R & 0xF8;
  // Serial.println(status,HEX);

  set_ack();
  minutes = *TWD_R;
  delay1();
  // status = *TWS_R & 0xF8;
  // Serial.println(status,HEX);

  set_ack();
  hours = *TWD_R;
  delay1();
  // status = *TWS_R & 0xF8;
  // Serial.println(status,HEX);

  set_ack();
  day = *TWD_R;
  delay1();
  // status = *TWS_R & 0xF8;
  // Serial.println(status,HEX);

  set_ack();
  date = *TWD_R;
  delay1();
  // status = *TWS_R & 0xF8;
  // Serial.println(status,HEX);

  set_ack();
  month = *TWD_R;
  delay1();
  // status = *TWS_R & 0xF8;
  // Serial.println(status,HEX);
  
  
  not_ack();
  year = *TWD_R;
  status = *TWS_R & 0xF8;
  // Serial.println(status,HEX);

  i2c_stop();
  status = *TWS_R & 0xF8;
  // Serial.println(status,HEX);

}

void i2c_init(){
  *TWB_R = 0x48;
  *TWS_R = 0x00;
  *TWC_R = 0x04; //TWI enable
}

void i2c_start(){
  *TWC_R = 0b10100100;
  while((*TWC_R>>7)&0x01 != 0);
}

void i2c_stop(){
  *TWC_R = 0b10010100;
  // while((*TWC_R>>7)&0x01 != 0);
}

void i2c_write(unsigned data){
  *TWD_R = data;
  *TWC_R = 0b10000100;
  while((*TWC_R>>7)&0x01==0);
}

void set_ack(){
  *TWC_R = 0b11000100;
  while((*TWC_R>>7)&0x01==0);
}

void not_ack(){
 *TWC_R = 0b10000100;
  while((*TWC_R>>7)&0x01==0);
}

void delay1(){
  volatile long i;
  for(i=0;i<50;i++);
}

// void delay2(){
//   volatile long i;
//   for(i=0;i<500000;i++);
// }


void loop() {
}