interfacing DS1307 (RTC) with AVR By Elecdude

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                  FUNCTIONS IN DS1307.H
```````````````````````
    DSinit();        To initialise DS1307 RTC chip

DSWriteTime(h, m, s); To write time hr, min, sec to RTC

    DSReadTime(&h, &m, &s); To read time hr, min, sec from RTC

    DSWriteDate(d, m, y); To write date to RTC

    DSReadDate(&d, &m, &y); To read date from RTC
 
    DSReadDay(&dy);     To read day from RTC

    DSWriteDay(dy); To write day to RTC
***********************************************************/

#ifndef _ds1307_H
#define _ds1307_H
#include "I2C.h"


//declare variables for hour, minutes, seconds, day, date, month & year.
unsigned char h=0,m=0,s=0; //comment these lines if defined in Main.c
unsigned char dy=0,dd=0,mm=0,yy=0; //comment these lines if defined in Main.c

/*_________________________________________________________________________
                   DECLARATION FOR DS1307                   */
#define DS_R 0xD1   //7 bit SLA + 1(read bit)
#define DS_W 0xD0 //7 bit SLA + 0(write bit)

//DS1307 RTC Registers addresses....
#define secr   0x00
#define minr   0x01
#define hrr 0x02
#define dayr   0x03
#define dater 0x04
#define monr   0x05
#define yrr 0x06
#define conr 0x07
/*_________________________________________________________________________*/
// DSWrite(addr1,data1);
// To write 'data1' in the 'addr1' location
unsigned char DSWrite(unsigned char addr,uint8_t data)
{
//_delay_us(500);
  I2CStart();

  if(! (I2CWriteSLA(DS_W)) )//Select device
return FALSE;

  if(! (I2CWriteByte(addr)) )//select destn. register
return FALSE;

  if(! (I2CWriteByte(data)) )//write data
return FALSE;
  I2CStop();
  return TRUE;
}

// DSRead(addr1,&data1);
// To data 'data1' from the 'addr1' location
unsigned char DSRead(unsigned char addr,unsigned char *data)
{
  I2CStart();
  if(! (I2CWriteSLA(DS_W)) )//select device
return FALSE;
  if(! (I2CWriteByte(addr)) )//select register
return FALSE;

//_______________Send Repeat start for read_____________
  I2CStart();

  if(! (I2CWriteSLA(DS_R)) )// select device in MASTER READ mode
return FALSE;
  if(! (I2CReadByte(data)) )//read data form device
return FALSE;

  I2CStop();
  return TRUE;
}
/*_________________________________________________________________________*/
// DSinit();
        // To initialise DS1307 RTC chip
void DSinit()
{
unsigned char x;
DSRead(secr,&x);
x&=(~(1<<CH)); //Clear CH Bit
DSWrite(secr,x);

x=0x10;
DSWrite(conr,x);//enable out @ 1Hz
}

// DSWriteTime(h, m, s)
// To write time hr, min, sec to RTC
DSWriteTime(unsigned char h, uns
igned char m, unsigned char s)
{
DSWrite(secr,s);
DSWrite(minr,m);
DSWrite(hrr,h);
}

// DSReadTime(&h, &m, &s)
// To read time hr, min, sec from RTC
DSReadTime(unsigned char *h, unsigned char *m, unsigned char *s)
{
DSRead(secr,&s);
DSRead(minr,&m);
DSRead(hrr,&h);
}

// DSWriteDate(d, m, y)
// To write date to RTC
DSWriteDate(unsigned char dd, unsigned char mm, unsigned char yy)
{
DSWrite(dater,dd);
DSWrite(monr,mm);
DSWrite(yrr,yy);
}
// DSReadDate(&d, &m, &y)
// To read date from RTC
DSReadDate(unsigned char *h, unsigned char *m, unsigned char *s)
{
DSRead(dater,&dd);
DSRead(monr,&mm);
DSRead(yrr,&yy);
}

// DSReadDay(&dy)
// To read day from RTC
DSReadDay(unsigned char *dy)
{
DSRead(dayr,&dy);
}
// DSWriteDay(dy)
// To write day to RTC
DSWriteDay(unsigned char dy)
{
DSWrite(dayr,dy);
}

#endif

DS1307.H 

Please follow this link for I2C header File 

http://www.elecdude.com/2015/01/i2c-header-file-for-avr-by-elecdude.html

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