Interfacing PIC18F4550 with DS1307 RTC
Real time clock using PIC16F877A microcontroller and DS1307 serial RTC
Now let's see how to interface DS1307 with PIC18F4550 microcontroller with full adjustment of time and date.
The microcontroller PIC18F4550 has one I2C module (SDA: RB0, SCL: RB1) which we are going to use for interfacing with DS1307 RTC.
The DS1307 is an 8-pin integrated circuit uses I2C communication protocol to communicate with master device which is in our case the PIC18F4550 microcontroller. This small chip can count seconds, minutes, hours, day, date, month and year with leap-year up to year 2100.
The DS1307 receives and transfers data (clock data and calendar data) as BCD format, so after receiving data we have to convert these data into decimal data, and before writing data to the DS1307 we have to convert this data from decimal to BCD format. For example we have the BCD number 33, converting this number into decimal gives 21.
The following image shows the DS1307 pin configurations:
The DS1307 uses an external 32.768KHz crystal and there is no need to add any resistors or capacitors with it.
More informations are in the DS1307 RTC datasheet.
Interfacing PIC18F4550 with DS1307 RTC:
The following image shows the interfacing circuit schematic diagram.
In this project PIC18F4550 microcontroller internal oscillator is used (8MHz) and MCLR pin function is disabled.
Interfacing PIC18F4550 with DS1307 RTC CCS C code:
The following C code is the full code of this project.
PIC18F4550 hardware I2C module is used at 100KHz.
// Real time clock using PIC18F4550 and DS1307 CCS C code // http://ccspicc.blogspot.com/ // electronnote@gmail.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 #include <18F4550.h> #fuses NOMCLR, INTRC_IO, NOWDT,NOPROTECT,NOLVP #use delay(clock = 8000000) #include <lcd.c> #use fast_io(B) #use I2C(master, I2C1, FAST = 100000) char time[] = "TIME: : : "; char calendar[] = "DATE: / /20 "; unsigned int8 second, second10, minute, minute10, hour, hour10, date, date10, month, month10, year, year10, day; void ds1307_display(){ second10 = (second & 0x70) >> 4; second = second & 0x0F; minute10 = (minute & 0x70) >> 4; minute = minute & 0x0F; hour10 = (hour & 0x30) >> 4; hour = hour & 0x0F; date10 = (date & 0x30) >> 4; date = date & 0x0F; month10 = (month & 0x10) >> 4; month = month & 0x0F; year10 = (year & 0xF0) >> 4; year = year & 0x0F; time[12] = second + 48; time[11] = second10 + 48; time[9] = minute + 48; time[8] = minute10 + 48; time[6] = hour + 48; time[5] = hour10 + 48; calendar[14] = year + 48; calendar[13] = year10 + 48; calendar[9] = month + 48; calendar[8] = month10 + 48; calendar[6] = date + 48; calendar[5] = date10 + 48; lcd_gotoxy(1, 1); // Go to column 1 row 1 printf(lcd_putc, time); // Display time lcd_gotoxy(1, 2); // Go to column 1 row 2 printf(lcd_putc, calendar); // Display calendar } void ds1307_write(unsigned int8 address, data_){ i2c_start(); // Start I2C i2c_write(0xD0); // DS1307 address i2c_write(address); // Send register address i2c_write(data_); // Write data to the selected register i2c_stop(); // Stop I2C } void main(){ setup_oscillator(OSC_8MHZ); // Set internal oscillator to 8MHz setup_adc_ports(NO_ANALOGS); // Configure AN pins as digital port_b_pullups(TRUE); output_b(0); set_tris_b(0x0F); lcd_init(); // Initialize LCD module lcd_putc('\f'); // LCD clear while(TRUE){ if(input(PIN_B2) == 0){ // Convert BCD to decimal minute = minute + minute10 * 10; hour = hour + hour10 * 10; date = date + date10 * 10; month = month + month10 * 10; year = year + year10 * 10; // End conversion lcd_putc('\f'); // LCD clear lcd_gotoxy(5, 1); // Go to column 5 row 1 lcd_putc("Minutes:"); delay_ms(200); while(TRUE){ if(input(PIN_B3) == 0) minute++; if(minute > 59) minute = 0; lcd_gotoxy(8, 2); // Go to column 8 row 2 printf(lcd_putc,"%02u", minute); if(input(PIN_B2) == 0) break; delay_ms(200); } lcd_putc('\f'); // LCD clear lcd_gotoxy(6, 1); // Go to column 6 row 1 lcd_putc("Hour:"); delay_ms(200); while(TRUE){ if(input(PIN_B3) == 0) hour++; if(hour > 23) hour = 0; lcd_gotoxy(8, 2); // Go to column 8 row 2 printf(lcd_putc,"%02u", hour); if(input(PIN_B2) == 0) break; delay_ms(200); } lcd_putc('\f'); // LCD clear lcd_gotoxy(6, 1); // Go to column 6 row 1 lcd_putc("Date:"); delay_ms(200); while(TRUE){ if(input(PIN_B3) == 0) date++; if(date > 31) date = 1; lcd_gotoxy(8, 2); // Go to column 8 row 2 printf(lcd_putc,"%02u", date); if(input(PIN_B2) == 0) break; delay_ms(200); } lcd_putc('\f'); // LCD clear lcd_gotoxy(6, 1); // Go to column 6 row 1 lcd_putc("Month:"); delay_ms(200); while(TRUE){ if(input(PIN_B3) == 0) month++; if(month > 12) month = 1; lcd_gotoxy(8, 2); // Go to column 8 row 2 printf(lcd_putc,"%02u", month); if(input(PIN_B2) == 0) break; delay_ms(200); } lcd_putc('\f'); // LCD clear lcd_gotoxy(6, 1); // Go to column 6 row 1 lcd_putc("Year:"); lcd_gotoxy(7, 2); // Go to column 7 row 1 lcd_putc("20"); delay_ms(200); while(TRUE){ if(input(PIN_B3) == 0) year++; if(year > 99) year = 0; lcd_gotoxy(9, 2); // Go to column 9 row 2 printf(lcd_putc,"%02u", year); if(input(PIN_B2) == 0){ // Convert decimal to BCD minute = ((minute/10) << 4) + (minute % 10); hour = ((hour/10) << 4) + (hour % 10); date = ((date/10) << 4) + (date % 10); month = ((month/10) << 4) + (month % 10); year = ((year/10) << 4) + (year % 10); // End conversion ds1307_write(1, minute); ds1307_write(2, hour); ds1307_write(4, date); ds1307_write(5, month); ds1307_write(6, year); ds1307_write(0, 0); //Reset seconds and start oscillator delay_ms(200); break; } delay_ms(200); } } i2c_start(); // Start I2C i2c_write(0xD0); // DS1307 address i2c_write(0); // Send register address i2c_start(); // Restart I2C i2c_write(0xD1); // Initialize data read second =i2c_read(1); // Read seconds from register 0 minute =i2c_read(1); // Read minuts from register 1 hour = i2c_read(1); // Read hour from register 2 day = i2c_read(1); // Read day from register 3 date = i2c_read(1); // Read date from register 4 month = i2c_read(1); // Read month from register 5 year = i2c_read(0); // Read year from register 6 i2c_stop(); // Stop I2C ds1307_display(); // Diaplay results delay_ms(50); } }
Interfacing PIC18F4550 with DS1307 RTC video:
The following video shows a hardware circuit of this project with some details about the circuit.