PIC18F4550 DS1307 I2C RTC LCD Interfacing

PIC18F4550 has a master synchronous serial ports (MSSP) module inside. This module consist of two sub-communication modules - I2C and SPI. An I2C is communication protocol for short range, low data rate requires only two pins - Serial Data(SDA) and Serial Clock(SCL). However, the SPI communication port doesn't lists here.

x2

x1.5

x1

x0.5

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DS1307 is a real time clock keeper with I2C communication interface. This device keep the time running by an external crystal clock of 32.768 kHz. Even the supply voltage is off, a coin back up battery keep the data RAM synchronizes for future use. Since an I2C is use for communication, there are two communication pins - SDA and SCL. These two pins are open drain, require an individual external pull up resistor. The resistor ranges from 4.7 kOhm to 10 kOhm resistance.

For more technical details about DS1307, please see this post on another blog I wrote.

In this programming example, PIC18F4550 uses its I2C master to write and read timing data from DS1307 I2C slave device. Those data will display on a character display.

Circuit Simulation

PICC Source Code

	#include<18f4550.h>
	/*Use high speed clock no PLL prescaler
	no system clock post scaler */
	#fuses HS,PLL1,CPUDIV1
	#use delay(clock=20M)
	#use i2c(MASTER,SDA=PIN_B0,SCL=PIN_B1,fast=10000)
	#define LCD_ENABLE_PIN PIN_D2
	#define LCD_RS_PIN PIN_D0
	#define LCD_RW_PIN PIN_D1
	#define LCD_DATA4 PIN_D4
	#define LCD_DATA5 PIN_D5
	#define LCD_DATA6 PIN_D6
	#define LCD_DATA7 PIN_D7
	#include<lcd.c>
	void rtcControl(char address,char control){
	i2c_start();
	i2c_write(0xD0);
	i2c_write(address);
	i2c_write(control);
	i2c_stop();
	}
	char rtcGet(char address){
	char dataRam;
	i2c_start();
	i2c_write(0xD0);
	i2c_write(address);
	i2c_stop();
	i2c_start();
	i2c_write(0xD1);
	dataRam=i2c_read(FALSE);
	i2c_stop();
	return dataRam;
	}
	char myDay[3];
	void dayOfWeek(char _day){
	switch(_day){
	case 1: myDay="Sun"; break;
	case 2: myDay="Mon"; break;
	case 3: myDay="Tue"; break;
	case 4: myDay="Wed"; break;
	case 5: myDay="Thu"; break;
	case 6: myDay="Fri"; break;
	case 7: myDay="Sat"; break;
	}
	}
	void main(){
	char s,m,h;
	char _day,_date,_month,_years;
	lcd_init();
	/*Enable 1 second output pin*/
	rtcControl(0x07,0x10);
	while(1){
	s=rtcGet(0x00);
	m=rtcGet(0x01);
	h=rtcGet(0x02);
	_day=rtcGet(0x03);
	_date=rtcGet(0x04);
	_month=rtcGet(0x05);
	_years=rtcGet(0x06);
	/*get day of week in string format*/
	dayOfWeek(_day);
	lcd_gotoxy(1,1);
	printf(LCD_PUTC,"%x:%x:%x %s",h,m,s,myDay);
	lcd_gotoxy(1,2);
	printf(LCD_PUTC,"%x/%x/20%x",_month,_date,_years);
	delay_ms(500);
	}
	}

view raw ds1307Lcd.c hosted with ❤ by GitHub

Schematic Diagram

Schematic Diagram

Click here to download the zip file of this example.