////////////////////////////////////////////////////////////////////////////////
///                               DS1307.C                                   ///
///                     Driver for Real Time Clock                           ///
///                                                                          ///
/// ds1307_init() - Enable oscillator without clearing the seconds register -///
///                 used when PIC loses power and DS1307 run from 3V BAT     ///
///               - Disable squarewave output                                ///
///                                                                          ///
/// ds1307_set_date_time(day,mth,year,dow,hour,min,sec)  Set the date/time   ///
///                                                                          ///
/// ds1307_get_date(day,mth,year,dow)               Get the date             ///
///                                                                          ///
/// ds1307_get_time(hr,min,sec)                     Get the time             ///
///                                                                          ///
////////////////////////////////////////////////////////////////////////////////

#define RTC_SDA  PIN_C4
#define RTC_SCL  PIN_C3

#use i2c(master, sda=RTC_SDA, scl=RTC_SCL)

BYTE bin2bcd(BYTE binary_value);
BYTE bcd2bin(BYTE bcd_value);

void ds1307_init(void)
{
   BYTE seconds = 0;

   i2c_start();
   i2c_write(0xD0);      // WR to RTC
   i2c_write(0x00);      // REG 0
   i2c_start();
   i2c_write(0xD1);      // RD from RTC
   seconds = bcd2bin(i2c_read(0)); // Read current "seconds" in DS1307
   i2c_stop();
   seconds &= 0x7F;

   delay_us(3);

   i2c_start();
   i2c_write(0xD0);      // WR to RTC
   i2c_write(0x00);      // REG 0
   i2c_write(bin2bcd(seconds));     // Start oscillator with current "seconds value
   i2c_start();
   i2c_write(0xD0);      // WR to RTC
   i2c_write(0x07);      // Control Register
   i2c_write(0x80);     // Disable squarewave output pin
   i2c_stop();

}

void ds1307_set_date_time(BYTE day, BYTE mth, BYTE year, BYTE dow, BYTE hr, BYTE min, BYTE sec)
{
  sec &= 0x7F;
  hr &= 0x3F;

  i2c_start();
  i2c_write(0xD0);            // I2C write address
  i2c_write(0x00);            // Start at REG 0 - Seconds
  i2c_write(bin2bcd(sec));      // REG 0
  i2c_write(bin2bcd(min));      // REG 1
  i2c_write(bin2bcd(hr));      // REG 2
  i2c_write(bin2bcd(dow));      // REG 3
  i2c_write(bin2bcd(day));      // REG 4
  i2c_write(bin2bcd(mth));      // REG 5
  i2c_write(bin2bcd(year));      // REG 6
  i2c_write(0x80);            // REG 7 - Disable squarewave output pin
  i2c_stop();
}

void ds1307_get_date(BYTE &day, BYTE &mth, BYTE &year, BYTE &dow)
{
  i2c_start();
  i2c_write(0xD0);
  i2c_write(0x03);            // Start at REG 3 - Day of week
  i2c_start();
  i2c_write(0xD1);
  dow  = bcd2bin(i2c_read() & 0x7f);   // REG 3
  day  = bcd2bin(i2c_read() & 0x3f);   // REG 4
  mth  = bcd2bin(i2c_read() & 0x1f);   // REG 5
  year = bcd2bin(i2c_read(0));            // REG 6
  i2c_stop();
}

void ds1307_get_time(BYTE &hr, BYTE &min, BYTE &sec)
{
  i2c_start();
  i2c_write(0xD0);
  i2c_write(0x00);            // Start at REG 0 - Seconds
  i2c_start();
  i2c_write(0xD1);
  sec = bcd2bin(i2c_read() & 0x7f);
  min = bcd2bin(i2c_read() & 0x7f);
  hr  = bcd2bin(i2c_read(0) & 0x3f);
  i2c_stop();

}

BYTE bin2bcd(BYTE binary_value)
{
  BYTE temp;
  BYTE retval;

  temp = binary_value;
  retval = 0;

  while(1)
  {
    // Get the tens digit by doing multiple subtraction
    // of 10 from the binary value.
    if(temp >= 10)
    {
      temp -= 10;
      retval += 0x10;
    }
    else // Get the ones digit by adding the remainder.
    {
      retval += temp;
      break;
    }
  }

  return(retval);
}


// Input range - 00 to 99.
BYTE bcd2bin(BYTE bcd_value)
{
  BYTE temp;

  temp = bcd_value;
  // Shifting upper digit right by 1 is same as multiplying by 8.
  temp >>= 1;
  // Isolate the bits for the upper digit.
  temp &= 0x78;

  // Now return: (Tens * 8) + (Tens * 2) + Ones

  return(temp + (temp >> 2) + (bcd_value & 0x0f));
}