This post shows how to build a simple real time clock/calendar using PIC18F46K22 microcontroller and DS1307 RTC chip where time and date are displayed on 20×4 LCD screen and they could be set using two push buttons connected to the PIC18F46K22 microcontroller.
The compiler used in this project is CCS PIC C.

Hardware Required:

PIC18F46K22 microcontroller —-> datasheet
20×4 LCD screen
DS1307 RTC —-> datasheet
32.768 kHz crystal oscillator
2 x 10k ohm resistor
330 ohm resistor
2 x push button
10k ohm variable resistor or potentiometer
3V coin cell battery
5V power source
Breadboard
Jumper wires

Interfacing PIC18F46K22 with DS1307 and 20×4 LCD circuit:
The following image shows project circuit schematic diagram.

All grounded terminals are connected together.

The two push buttons in the circuit are used to set time and date of the real time clock, button 1 (B1) is connected to RB0 pin (#33) and button 2 (B2) is connected to RB1 pin (#34).

SCL and SDA pins of DS1307 are respectively connected to PIC18F46K22 pins RC3 (#18) and RC4 (#23) which are hardware I2C module pins (MSSP1).

The 20×4 LCD screen is connected to the PIC18F46K22 microcontroller as follows:
RS —> RD0 pin
RW —> RD1 pin
E —> RD2 pin
D4 —> RD3 pin
D5 —> RD4 pin
D6 —> RD5 pin
D7 —> RD6 pin
VSS, D0, D1, D2, D3 and K are connected to circuit GND (ground).
VEE to the variable resistor (or potentiometer) output pin.
VDD to +5V and A to +5V through 330 ohm resistor.

VEE pin is used to control the contrast of the LCD. A (anode) and K (cathode) are the back light LED pins.

In this project the PIC18F46K22 microcontroller runs with its internal oscillator @ 8 MHz, MCLR pin is configured as an input pin.

Interfacing PIC18F46K22 with DS1307 and 20×4 LCD C code:
The following C code is for CCS C compiler, it was tested with version 5.051.

To be able to compile the C code below, a driver (library) for DS1307 RTC is required, its full name (with extension) is DS1307.C, download link is the one below:
DS1307 CCS C driver

After the download, add it to project folder or CCS C drivers folder (for example C:\Program Files (x86)\CCS\Drivers).

For more information about DS1307 driver for CCS C compiler, visit the following post:
DS1307 RTC driver for CCS C compiler

I2C Bus (using I2C1 module) is initialized in the code as shown below at clock frequency of 100kHz:

#use I2C(MASTER, I2C1, SLOW = 100000, STREAM = DS1307_STREAM)

1	#use I2C(MASTER, I2C1, SLOW = 100000, STREAM = DS1307_STREAM)

Functions used in the code:
int1 debounce (): this function is for button B1 debounce, returns 1 if button is debounced.

void dow_print(): displays day of the week (Monday, Tuesday …) on the LCD.

void rtc_print(): displays time, date and day of the week on the LCD. This function calls the previous one for displaying the day of the week.

void wait(): this function is just a delay of 500 ms except that it can be interrupted by the two push buttons (B1 and B2). In this function Timer0 module is used to count the 500 milliseconds, it is used as 16-bit timer with prescaler = 16 (==> 1 tick every 8 microseconds ==> 62500 x 8 = 500000 us = 500 ms).

int8 edit(int8 x_pos, int8 y_pos, int8 parameter): this function is for setting the real time clock, returns the edited parameter.

Rest of code is described through comments.

Full CCS C code:

/*
 * Interfacing PIC18F46K22 microcontroller with DS1307 RTC.
 * C Code for CCS C compiler.
 * This is a free software with NO WARRANTY.
 * http://simple-circuit.com/
 */

// LCD module connections
#define LCD_RS_PIN      PIN_D0
#define LCD_RW_PIN      PIN_D1
#define LCD_ENABLE_PIN  PIN_D2
#define LCD_DATA4       PIN_D3
#define LCD_DATA5       PIN_D4
#define LCD_DATA6       PIN_D5
#define LCD_DATA7       PIN_D6
// end LCD module connections

// button definitions
#define button1      PIN_B0
#define button2      PIN_B1

#include <18F46K22.h>
#fuses  NOMCLR,NOLVP,NOBROWNOUT,PUT,NOXINST
#use delay(internal = 8MHz)
#use I2C(MASTER, I2C1, SLOW = 100000, STREAM = DS1307_STREAM)
#include <lcd.c>     // include LCD driver source file
#include <DS1307.c>  // include DS1307 driver source file

int8 i;
// DS1307 library variable declaration
RTC_Time *mytime;

// function for displaying day of the week
void dow_print()
{
  lcd_gotoxy(6, 2);
  switch(mytime->dow)
  {
    case SUNDAY   :  printf(lcd_putc, " SUNDAY  ");  break;
    case MONDAY   :  printf(lcd_putc, " MONDAY  ");  break;
    case TUESDAY  :  printf(lcd_putc, " TUESDAY ");  break;
    case WEDNESDAY:  printf(lcd_putc, "WEDNESDAY");  break;
    case THURSDAY :  printf(lcd_putc, "THURSDAY ");  break;
    case FRIDAY   :  printf(lcd_putc, " FRIDAY  ");  break;
    default       :  printf(lcd_putc, "SATURDAY ");
  }
}

// function for printing time and date on LCD
void rtc_print()
{
  // print day of the week
  dow_print();
  // print time
  lcd_gotoxy(21, 1);  // move cursor to row 3, column 1
  printf(lcd_putc, "TIME: %02u:%02u:%02u", mytime->hours, mytime->minutes, mytime->seconds);
  // print date
  lcd_gotoxy(21, 2);  // move cursor to row 4, column 1
  printf(lcd_putc, "DATE: %02u-%02u-20%02u", mytime->day, mytime->month, mytime->year);
}

// a small function for button1 (B1) debounce
int1 debounce()
{
  int8 count = 0;
  for(int8 i = 0; i < 5; i++)
  {
    if ( !input(button1) )
      count++;
    delay_ms(10);
  }

  if(count > 2)  return 1;
  else           return 0;
}

void wait()
{
  set_timer0(0);
  while( (get_timer0() < 62500L) && input(button1) && input(button2) ) ;
}

int8 edit(int8 x_pos, int8 y_pos, int8 parameter)
{
  while(debounce());  // call debounce function (wait for B1 to be released)
  lcd_gotoxy(x_pos, y_pos);  // move cursor to row y_pos, column x_pos

  while(TRUE)
  {
    while(!input(button2))
    {
      parameter++;
      if(i == 0 && parameter > 23)   // if hours > 23 ==> hours = 0
        parameter = 0;
      if(i == 1 && parameter > 59)   // if minutes > 59 ==> minutes = 0
        parameter = 0;
      if(i == 2 && parameter > 31)   // if day > 31 ==> day = 1
        parameter = 1;
      if(i == 3 && parameter > 12)   // if month > 12 ==> month = 1
        parameter = 1;
      if(i == 4 && parameter > 99)   // if year > 99 ==> year = 0
        parameter = 0;

      printf(lcd_putc, "%02u\b\b", parameter);
      delay_ms(200);
    }

    lcd_putc("  \b\b");
    wait();
    printf(lcd_putc, "%02u\b\b", parameter);
    wait();

    if(!input(button1)) // if button B1 is pressed
    {
      i++;                // increment 'i' for the next parameter
      return parameter;   // return parameter value and exit
    }
  }
}

// main function
void main()
{
  setup_oscillator(OSC_8MHZ);  // set internal oscillator to 8MHz
  port_b_pullups(3);           // enable RB0 & RB1 internal weak pull-ups

  delay_ms(1000);  // wait a second
  lcd_init();      // initialize LCD module
  lcd_putc("\fPIC18F46K22 + DS1307");

  OSC_Enable();  // enable DS1307 oscillator

  while(TRUE)
  {
    // read current time and date from the RTC chip
    mytime = RTC_Get();
    // print all data
    rtc_print();

    if(!input(button1))   // if button B1 is pressed
    if(debounce())        // call debounce function (make sure if B1 is pressed)
    {
      i = 0;
      while(debounce());  // call debounce function (wait for button B1 to be released)
      setup_timer_0(T0_INTERNAL | T0_DIV_16);  // start Timer0 with internal clock & prescaler=16

      while(TRUE)
      {
        while( !input(button2) )  // if button B2 button is pressed
        {
          mytime->dow++;
          if(mytime->dow > SATURDAY) mytime->dow = SUNDAY;
          dow_print();     // print week day
          delay_ms(500);
        }
        lcd_gotoxy(6, 2);
        lcd_putc("         ");
        wait();           // call wait() function
        dow_print();      // print week day
        wait();           // call wait() function
        if( !input(button1) )  // if button B1 is pressed
          break;
      }

      mytime->hours   = edit(27, 1, mytime->hours);    // edit hours
      mytime->minutes = edit(30, 1, mytime->minutes);  // edit minutes
      mytime->day     = edit(27, 2, mytime->day);      // edit day (day of month)
      mytime->month   = edit(30, 2, mytime->month);    // edit month
      mytime->year    = edit(35, 2, mytime->year);     // edit year
      mytime->seconds = 0;                             // reset seconds

      setup_timer_0(T0_OFF);  // disable Timer0
      while(debounce());      // call debounce function (wait for button B1 to be released)

      // write data to the RTC chip
      RTC_Set(mytime);
    }

    delay_ms(100);  // wait 100 ms
  }

}
// end of code.

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* Interfacing PIC18F46K22 microcontroller with DS1307 RTC.

* C Code for CCS C compiler.

* This is a free software with NO WARRANTY.

* http://simple-circuit.com/

// LCD module connections

#define LCD_RS_PIN PIN_D0

#define LCD_RW_PIN PIN_D1

#define LCD_ENABLE_PIN PIN_D2

#define LCD_DATA4 PIN_D3

#define LCD_DATA5 PIN_D4

#define LCD_DATA6 PIN_D5

#define LCD_DATA7 PIN_D6

// end LCD module connections

// button definitions

#define button1 PIN_B0

#define button2 PIN_B1

#include <18F46K22.h>

#fuses NOMCLR,NOLVP,NOBROWNOUT,PUT,NOXINST

#use delay(internal = 8MHz)

#use I2C(MASTER, I2C1, SLOW = 100000, STREAM = DS1307_STREAM)

#include <lcd.c> // include LCD driver source file

#include <DS1307.c> // include DS1307 driver source file

int8 i;

// DS1307 library variable declaration

RTC_Time *mytime;

// function for displaying day of the week

void dow_print()

{

lcd_gotoxy(6, 2);

switch(mytime->dow)

{

case SUNDAY : printf(lcd_putc, " SUNDAY "); break;

case MONDAY : printf(lcd_putc, " MONDAY "); break;

case TUESDAY : printf(lcd_putc, " TUESDAY "); break;

case WEDNESDAY: printf(lcd_putc, "WEDNESDAY"); break;

case THURSDAY : printf(lcd_putc, "THURSDAY "); break;

case FRIDAY : printf(lcd_putc, " FRIDAY "); break;

default : printf(lcd_putc, "SATURDAY ");

}

// function for printing time and date on LCD

void rtc_print()

{

// print day of the week

dow_print();

// print time

lcd_gotoxy(21, 1); // move cursor to row 3, column 1

printf(lcd_putc, "TIME: %02u:%02u:%02u", mytime->hours, mytime->minutes, mytime->seconds);

// print date

lcd_gotoxy(21, 2); // move cursor to row 4, column 1

printf(lcd_putc, "DATE: %02u-%02u-20%02u", mytime->day, mytime->month, mytime->year);

}

// a small function for button1 (B1) debounce

int1 debounce()

{

int8 count = 0;

for(int8 i = 0; i < 5; i++)

{

if ( !input(button1) )

count++;

delay_ms(10);

}

if(count > 2) return 1;

else return 0;

}

void wait()

{

set_timer0(0);

while( (get_timer0() < 62500L) && input(button1) && input(button2) ) ;

}

int8 edit(int8 x_pos, int8 y_pos, int8 parameter)

{

while(debounce()); // call debounce function (wait for B1 to be released)

lcd_gotoxy(x_pos, y_pos); // move cursor to row y_pos, column x_pos

while(TRUE)

{

while(!input(button2))

{

parameter++;

if(i == 0 && parameter > 23) // if hours > 23 ==> hours = 0

parameter = 0;

if(i == 1 && parameter > 59) // if minutes > 59 ==> minutes = 0

parameter = 0;

if(i == 2 && parameter > 31) // if day > 31 ==> day = 1

parameter = 1;

if(i == 3 && parameter > 12) // if month > 12 ==> month = 1

parameter = 1;

if(i == 4 && parameter > 99) // if year > 99 ==> year = 0

parameter = 0;

printf(lcd_putc, "%02u\b\b", parameter);

delay_ms(200);

}

lcd_putc(" \b\b");

wait();

printf(lcd_putc, "%02u\b\b", parameter);

wait();

if(!input(button1)) // if button B1 is pressed

{

i++; // increment 'i' for the next parameter

return parameter; // return parameter value and exit

}

// main function

void main()

{

setup_oscillator(OSC_8MHZ); // set internal oscillator to 8MHz

port_b_pullups(3); // enable RB0 & RB1 internal weak pull-ups

delay_ms(1000); // wait a second

lcd_init(); // initialize LCD module

lcd_putc("\fPIC18F46K22 + DS1307");

OSC_Enable(); // enable DS1307 oscillator

while(TRUE)

{

// read current time and date from the RTC chip

mytime = RTC_Get();

// print all data

rtc_print();

if(!input(button1)) // if button B1 is pressed

if(debounce()) // call debounce function (make sure if B1 is pressed)

{

i = 0;

while(debounce()); // call debounce function (wait for button B1 to be released)

setup_timer_0(T0_INTERNAL | T0_DIV_16); // start Timer0 with internal clock & prescaler=16

while(TRUE)

{

while( !input(button2) ) // if button B2 button is pressed

{

mytime->dow++;

if(mytime->dow > SATURDAY) mytime->dow = SUNDAY;

dow_print(); // print week day

delay_ms(500);

}

lcd_gotoxy(6, 2);

lcd_putc(" ");

wait(); // call wait() function

dow_print(); // print week day

wait(); // call wait() function

if( !input(button1) ) // if button B1 is pressed

break;

}

mytime->hours = edit(27, 1, mytime->hours); // edit hours

mytime->minutes = edit(30, 1, mytime->minutes); // edit minutes

mytime->day = edit(27, 2, mytime->day); // edit day (day of month)

mytime->month = edit(30, 2, mytime->month); // edit month

mytime->year = edit(35, 2, mytime->year); // edit year

mytime->seconds = 0; // reset seconds

setup_timer_0(T0_OFF); // disable Timer0

while(debounce()); // call debounce function (wait for button B1 to be released)

// write data to the RTC chip

RTC_Set(mytime);

}

delay_ms(100); // wait 100 ms

}

// end of code.

The following video shows Proteus simulation of this project (simulation circuit is not the same as real hardware circuit, project hardware circuit is shown above):

Proteus simulation file download:
PIC18F46K22 + DS1307 RTC + 20×4 LCD