////////////////////////////////////////////////////////////////////////////////
/// 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                                 ///
///                                                                          ///
////////////////////////////////////////////////////////////////////////////////
////        (C) Copyright 1996,2003 Custom Computer Services                ////
//// This source code may only be used by licensed users of the CCS C       ////
//// compiler.  This source code may only be distributed to other           ////
//// licensed users of the CCS C compiler.  No other use, reproduction      ////
//// or distribution is permitted without written permission.               ////
//// Derivative programs created using this software in object code         ////
//// form are not restricted in any way.                                    ////
////////////////////////////////////////////////////////////////////////////////

#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(true)
{
// 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));
} 
