ds1302 avr library

main.c

#include "uart.h"
#include "rtc.c"
// Baud rate setting 
#define BAUD 9600 

void main(void)	{
	// Serial channel (9600, N,8,1)	
        uart_init((UART_BAUD_SELECT((BAUD),F_OSC))); 

        sei(); // interrupt enable 
	unsigned char sec, temp;
	sec = 0;
	struct rtc_time ds1302;
	struct rtc_time *rtc;
	rtc = &ds1302;

	ds1302_init();
	ds1302_update(rtc);   // update all fields in the struct
	ds1302_set_time(rtc, SEC, 31);	//set the seconds to 31
	
	while (1)   // read seconds and send it via uart continuously
	{
		ds1302_update_time(rtc, SEC);	//read the seconds
                uart_putc(rtc->second); // send byte to serial line , you may not send it via uart, 
                uart_puts_P( "\r"); // LF	// I just want to mention how to use the data with this
		_delay_ms(100);
	}
}

rtc.c

// rtc.c
// author COSAR DINDAR
// Date: November,23th 2012

#include <avr/interrupt.h>
#include <avr/io.h>
#include <stdio.h>
#include <stdbool.h>
#include <util/delay.h>
#include "rtc.h"

void ds1302_update_time(struct rtc_time * time, unsigned char field)	// read time, field can be SEC, MIN, HOUR...
{
	unsigned char temp;
	ds1302_comms(time, field, 0, READ);
}

void ds1302_set_time(struct rtc_time * time, unsigned char field, unsigned char w_byte)	// set time, field can be SEC, MIN, HOUR...
{																						// w_byte can be the value you want to set
	unsigned char temp;
	ds1302_comms(time, field, w_byte, WRITE);
}

void ds1302_comms(struct rtc_time * time, unsigned char field, unsigned char write_byte, unsigned char rw)
{
	unsigned char temp;

	if(rw == READ)
	{
		if(field == SEC)
		{
			temp = ds1302_read_byte(sec_r);
			time->second = ((temp & 0x0F) + ((temp & 0x70)>>4)*10);
		}
		else if(field == MIN)
		{
			temp = ds1302_read_byte(min_r);		
			time->minute = ((temp & 0x0F) + ((temp & 0x70)>>4)*10);
		}
		else if(field == HOUR)
		{
			temp = ds1302_read_byte(hour_r);
			
			if(temp & 0x80 == 1)		// 12 format 
			{
				if(temp & 0x20 == 1)	// PM
					time->hour_format = PM;
				else					// AM
					time->hour_format = AM;
					
				time->hour = ((temp & 0x0F) + ((temp & 0x10)>>4)*10);
			}
			else						// 24 format
			{
				time->hour_format = H24;
				time->hour = ((temp & 0x0F) + ((temp & 0x30)>>4)*10);
			}		
		}
		else if(field == DAY)
		{
			temp = ds1302_read_byte(day_r);
			time->day = (temp & 0x07);
		}
		else if(field == DATE)
		{
			temp = ds1302_read_byte(date_r);
			time->date = ((temp & 0x0F) + ((temp & 0x30)>>4)*10);
		}
		else if(field == MONTH)
		{
			temp = ds1302_read_byte(month_r);
			time->month = ((temp & 0x0F) + ((temp & 0x10)>>4)*10);
		}
		else if(field == YEAR)
		{
			temp = ds1302_read_byte(year_r);
			time->year = ((temp & 0x0F) + ((temp & 0xF0)>>4)*10);
		}
	}
	else if(rw == WRITE)
	{
		if(field == SEC)
		{
			ds1302_write_byte(sec_w, (((write_byte/10)<<4) & 0x70 | (write_byte%10)));			
		}
		else if(field == MIN)
		{
			ds1302_write_byte(min_w, (((write_byte/10)<<4) & 0x70  | (write_byte%10)));			
		}
		else if(field == HOUR)
		{
			if(time->hour_format == AM)
				ds1302_write_byte(hour_w, (((write_byte/10)<<4) & 0x10  | (write_byte%10)) | 0x80);			
			else if(time->hour_format == PM)
				ds1302_write_byte(hour_w, (((write_byte/10)<<4) & 0x10  | (write_byte%10)) | 0xA0);
			else if(time->hour_format == H24)
				ds1302_write_byte(hour_w, ((((write_byte/10)<<4) & 0x30) | (write_byte % 10)));
		}
		else if(field == DAY)
		{
			ds1302_write_byte(day_w, write_byte & 0x03);
		}
		else if(field == DATE)
		{
			ds1302_write_byte(date_w, (((write_byte/10)<<4) & 0x30  | (write_byte%10)));			
		}
		else if(field == MONTH)
		{
			ds1302_write_byte(month_w, (((write_byte/10)<<4) & 0x10 | (write_byte%10)));			
		}
		else if(field == YEAR)
		{
			ds1302_write_byte(year_w, (((write_byte/10)<<4) & 0xF0 | (write_byte%10)));			
		}		
	}
}

void ds1302_update(struct rtc_time * time) 
{
	ds1302_update_time(time, SEC);
	ds1302_update_time(time, MIN);
	ds1302_update_time(time, HOUR);
	ds1302_update_time(time, DAY);
	ds1302_update_time(time, DATE);
	ds1302_update_time(time, MONTH);
	ds1302_update_time(time, YEAR);	
}

void ds1302_init(void) // sets all pins as output and low 
{
	ds1302_PORT |= (1<<rst) | (1<<clk) | (1<<io);
	clk_0(); // sclk -> 0 
	rst_0(); // rst -> 0 
	io_0(); // io -> 0 
}

void ds1302_reset(void)	 //sets the pins to begin the ds1302 communication 
{ 
	clk_0(); // sclk -> 0 
	rst_0(); // rst -> 0 
	rst_1(); // rst -> 1 
	_delay_us(4);
} 

unsigned char ds1302_read_byte(unsigned char w_byte)	//read the byte with register w_byte 
{ 
	unsigned char temp;
	ds1302_reset();
	write(w_byte);
	temp = read();
	rst_0(); // finish transmittion 
	clk_0();
	return temp;
} 

void ds1302_write_byte(unsigned char w_byte, unsigned char w_2_byte)	//write the byte with register w_byte 
{
	ds1302_reset();
	write(w_byte);
	write(w_2_byte);
	rst_0(); // finish transmittion
	clk_0();
}

void write(unsigned char W_Byte)	//writes the W_Byte to the DS1302 
{
	unsigned char i;

	ds1302_DDR |= (1<<io); // io as output -> 1 

	for(i = 0; i < 8; ++i)
	{
		io_0();

		if(W_Byte & 0x01)
		{
			io_1();
		}
		clk_0();
		_delay_us(2);
		clk_1();
		_delay_us(2);
		W_Byte >>=1;
	}
}

unsigned char read()	 //reads the ds1302 reply 
{
	unsigned char i, R_Byte, TmpByte;

	R_Byte = 0x00;

	ds1302_DDR &= ~(1<<io); // io as input -> 0 

	for(i = 0; i < 8; ++i) //get byte 
	{
		clk_1();
		_delay_us(2);
		clk_0();
		_delay_us(2);
		TmpByte = 0;
		if(bit_is_set(ds1302_PIN,io))
			TmpByte = 1;
		TmpByte <<= 7;
		R_Byte >>= 1;
		R_Byte |= TmpByte;
	}
	return R_Byte;
}

rtc.h

// rtc.c
// author COSAR DINDAR
// Date: November,23th 2012


#ifndef _RTC_H_ 
#define _RTC_H_ 

// ds1302 connection 
#define ds1302_PORT PORTD
#define ds1302_DDR DDRD
#define ds1302_PIN PIND
#define rst 4
#define clk 6
#define io 7

#define rst_1() ds1302_PORT |= (1<<rst); 
#define rst_0() ds1302_PORT &= ~ (1<<rst); 
#define clk_1() ds1302_PORT |= (1<<clk); 
#define clk_0() ds1302_PORT &= ~ (1<<clk); 
#define io_1() 	ds1302_PORT |= (1<<io); 
#define io_0() 	ds1302_PORT &= ~ (1<<io); 

#define AM		10
#define PM		11
#define H24		12

#define READ	15
#define WRITE	16

#define mon 	1
#define tue 	2
#define wed 	3
#define thu 	4
#define fri 	5
#define sat 	6
#define sun 	7

#define sec_w 	0x80
#define sec_r 	0x81
#define min_w 	0x82
#define min_r 	0x83
#define hour_w 	0x84
#define hour_r 	0x85
#define date_w 	0x86
#define date_r 	0x87
#define month_w 0x88
#define month_r 0x89
#define day_w 	0x8a
#define day_r 	0x8b
#define year_w 	0x8c
#define year_r 	0x8d

#define SEC 20
#define MIN 21
#define HOUR 22
#define DAY 22
#define DATE 23
#define MONTH 24
#define YEAR 25

#define w_protect 0x8e

struct rtc_time{
   char second; 
   char minute; 
   char hour; 
   char day;
   char date;
   char month; 
   char year;
   char hour_format;
   };

void ds1302_update_time(struct rtc_time *, unsigned char);
void ds1302_set_time(struct rtc_time * time, unsigned char field, unsigned char w_byte);
void ds1302_comms(struct rtc_time *, unsigned char, unsigned char, unsigned char);
void ds1302_update(struct rtc_time *);
void ds1302_init (void); //ds1302 init 
void ds1302_reset(void);	 //ds1302_reset 
unsigned char ds1302_read_byte(unsigned char);
void ds1302_write_byte(unsigned char, unsigned char);
void write(unsigned char);
unsigned char read(void);
void ds1302_write_byte(unsigned char,unsigned char);

#endif 

Can I get the uart.h file please ?

This library have BUG.
between ds1302_reset and read or write must be delay 4uS. Datasheet page 9 AC Electrical charasteristics - RST to CLK setup.
Library works with 3V+ battery. But with low battery voltage it can read bad rtc result.

@bronek999 Thanks for the comment. I will edit it accordingly.

Hi Corsard!
Line #97 of rtc.c shall correctly be
ds1302_write_byte(hour_w, ((((write_byte/10)<<4) & 0x30) | (write_byte % 10)));

& 0x30 instead of & 0x10 is the difference.
Thanks for the lib, anyway! :)

Do you have an avr-libc library for LCD1602 ?

else if(field == YEAR)
{
temp = ds1302_read_byte(year_r);
time->minute = ((temp & 0x0F) + ((temp & 0xF0)>>4)*10);
}

should by time->year =..

rgds

else if(field == YEAR) { temp = ds1302_read_byte(year_r); time->minute = ((temp & 0x0F) + ((temp & 0xF0)>>4)*10); }

should by time->year =..

rgds

Thanks @roman65536 updated based on your comment.