Interfacing DS1307 to PIC Microcontroller with C code and Circuit Diagram

Interfacing DS1307 to PIC Microcontroller with C code and Circuit Diagram

This tutorial explains how to interface the DS1307 Real Time Clock (RTC) with a PIC16F877 microcontroller. The project is compiled using the CCS compiler and simulated in Proteus.

The DS1307 communicates with the PIC microcontroller through the I2C protocol, which is a two-wire, serial, synchronous, bi-directional communication method. Data is transferred via the SDA (Serial Data) and SCL (Serial Clock) pins. Pull-up resistors are required on these lines, and their values determine the communication speed. The master device controls the clock, and no data transfer occurs without it.

In this design, the PIC acts as the master, transmitting and receiving time data from the DS1307. The RTC values are read and displayed on an LCD.

Embedded C Program for DS-1307 I2C Communication

Embedded C Program for DS-1307 I2C Communication
#include <16F877.h>
#include
#use delay(clock=4000000)

#define RTC_SDA PIN_C4
#define RTC_SCL PIN_C3
#use i2c(master, sda=RTC_SDA, scl=RTC_SCL)

void rtc_get_time();
int convert(int k);

int sec, min, hr, k[20], z, k1[20];
int day1, date, month, year;

void main() {
SETUP_ADC(ADC_OFF);
lcd_init();
while(1) {
rtc_get_time();
lcd_cmd(0x80);
sprintf(k, “%02d:%02d:%02d”, hr, min, sec);
lcd_array(k);
lcd_cmd(0xc0);
sprintf(k1, “%02d:%02d:%02d”, date, month, year);
lcd_array(k1);
lcd_cmd(0xc9);
switch(day1) {
case 1: lcd_str(“Sunday”); break;
case 2: lcd_str(“Monday”); break;
case 3: lcd_str(“Tuesday”); break;
case 4: lcd_str(“Wednesday”); break;
case 5: lcd_str(“Thursday”); break;
case 6: lcd_str(“Friday”); break;
case 7: lcd_str(“Saturday”); break;
}
}
}

void rtc_get_time() {
i2c_start();
i2c_write(0xD0);
i2c_write(0x00);
i2c_start();
i2c_write(0xD1);
sec = i2c_read();
min = i2c_read();
hr = i2c_read();
day1 = i2c_read();
date = i2c_read();
month = i2c_read();
year = i2c_read(0);
i2c_stop();

sec = convert(sec);
min = convert(min);
hr = convert(hr);
day1 = convert(day1);
date = convert(date);
month = convert(month);
year = convert(year);

z = ‘a’;
if(hr > 12) {
hr = hr – 12;
z = ‘p’;
}
}

int convert(int k) {
int a0, a1, a;
a0 = (k & 0x0F);
a1 = k >> 4;
a = (a1 * 10) + a0;
return a;
}

Above shows  a simple program to read the Time value from DS-1307 IC. RTC Ds-1307 consumes very low power(500nA), so it can be backup by a battery for power failure issues.   For DS1307, the device address is D0. The data, for example seconds value, located in the zeroth register is taken and converted from BCD to integer, before displaying it on the LCD. We can also write the Time value to Ds1307 registers one by one.

For more detail: Interfacing DS1307 to PIC Microcontroller with C code and Circuit Diagram