This topic shows how to build a real time clock with relative humidity and temperature sensing using PIC16F877A microcontroller, DS1307 RTC and DHT11 (RHT01) sensor where all data are displayed on 20x4 LCD display. The 20x4 LCD has 20 columns and 4 rows which is good enough for this project. The compiler used to program the microcontroller is CCS PIC C PCWHD.
To see how to interface PIC16F877A with DS1307 take a look at the following topic:
Real time clock using PIC16F877A microcontroller and DS1307 serial RTC
And to see how to interface PIC18F4550 with DHT22 (AM2302) take a look at this topic:
Interfacing DHT11 relative humidity and temperature sensor with PIC16F877A microcontroller
The DS1307 RTC is an 8-pin integrated circuit uses I2C communication protocol to communicate with master device which is in our case the PIC16F877A microcontroller. This small chip can count seconds, minutes, hours, day, date, month and year with leap-year up to year 2100.
The DHT11 (RHT01) sensor comes in a single row 4-pin package and operates from 3.3 to 5.5V power supply. It can measure temperature from 0-50 °C with an accuracy of ±2°C and relative humidity ranging from 20-90% with an accuracy of ±5%. The sensor provides fully calibrated digital outputs for the two measurements. It has got its own proprietary 1-wire protocol, and therefore, the communication between the sensor and a microcontroller is not possible through a direct interface with any of its peripherals. The protocol must be implemented in the firmware of the MCU with precise timing required by the sensor.
Component list:
- PIC16F877A microcontroller
- DS1307 RTC
- DHT11 (RHT01) Sensor
- 2004 LCD
- 3V Coin cell battery
- 8MHz and 32.768KHz crystal oscillators
- 2 x 22pF capacitors
- 3 x 10K resistors
- 4.7K resistor
- 10K Potentiometer
- 2 Buttons
- +5V Power Supply
- Protoboard
- Jumper Wires
CCS C code:
The project C code is just a combination of the C codes of the two previous projects.
The reading of relative humidity and temperature data is done every 1 second.
// PIC16F877A + 2004 LCD + DS1307 RTC + DHT11 Sensor 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 <16F877A.h> #fuses HS,NOWDT,NOPROTECT,NOLVP #use delay(clock = 8000000) #include <lcd.c> #use fast_io(B) #use I2C(master, I2C1, FAST=100000) #define DHT11_PIN PIN_B2 // Connection pin between DHT11 and mcu short button_state, Time_out; char time[] = "TIME: : : "; char calendar[] = " / /20 "; unsigned int8 second, second10, minute, minute10, hour, hour10, date, date10, month, month10, year, year10, day, i, j ; char message1[] = "Temperature: 00.0 C "; char message2[] = "Humidity : 00.0 % "; unsigned int8 T_byte1, T_byte2, RH_byte1, RH_byte2, CheckSum, time_read ; 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[16] = second + 48; time[15] = second10 + 48; time[13] = minute + 48; time[12] = minute10 + 48; time[10] = hour + 48; time[9] = hour10 + 48; calendar[9] = year + 48; calendar[8] = year10 + 48; calendar[4] = month + 48; calendar[3] = month10 + 48; calendar[1] = date + 48; calendar[0] = 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 switch(day){ case 1: lcd_putc("DATE:Sun"); break; case 2: lcd_putc("DATE:Mon"); break; case 3: lcd_putc("DATE:Tue"); break; case 4: lcd_putc("DATE:Wed"); break; case 5: lcd_putc("DATE:Thu"); break; case 6: lcd_putc("DATE:Fri"); break; case 7: lcd_putc("DATE:Sat"); break;} lcd_gotoxy(10, 2); // Go to column 9 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 ds1307_read(){ 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 } int8 edit(int8 parameter, int8 xx, int8 yy){ while(TRUE){ if(input(PIN_B0)) button_state = 0; while(!input(PIN_B1)){ parameter++; if(i == 1 && parameter > 23) parameter = 0; if(i == 2 && parameter > 59) parameter = 0; if(i == 3 && parameter > 31) parameter = 1; if(i == 4 && parameter > 12) parameter = 1; if(i == 5 && parameter > 99) parameter = 0; lcd_gotoxy(xx, yy); printf(lcd_putc,"%02u", parameter); delay_ms(200);} lcd_gotoxy(xx, yy); lcd_putc(" "); j = 0; while((input(PIN_B0) || button_state) && input(PIN_B1) && j < 5){ j++; delay_ms(50);} lcd_gotoxy(xx, yy); printf(lcd_putc,"%02u", parameter); j = 0; while((input(PIN_B0) || button_state) && input(PIN_B1) && j < 5){ j++; delay_ms(50);} if(!input(PIN_B0) && !button_state){ button_state = 1; return parameter;} } } void start_signal(){ output_drive(DHT11_PIN); // Configure connection pin as output output_low(DHT11_PIN); // Connection pin output low delay_ms(25); output_high(DHT11_PIN); // Connection pin output high delay_us(30); output_float(DHT11_PIN); // Configure connection pin as input } short check_response(){ delay_us(40); if(!input(DHT11_PIN)){ // Read and test if connection pin is low delay_us(80); if(input(DHT11_PIN)){ // Read and test if connection pin is high delay_us(50); return 1; } } } unsigned int8 Read_Data(){ unsigned int8 i, k, _data = 0; // k is used to count 1 bit reading duration if(Time_out) break; for(i = 0; i < 8; i++){ k = 0; while(!input(DHT11_PIN)){ // Wait until pin goes high k++; if (k > 100) {Time_out = 1; break;} delay_us(1);} delay_us(30); if(!input(DHT11_PIN)) bit_clear(_data, (7 - i)); // Clear bit (7 - i) else{ bit_set(_data, (7 - i)); // Set bit (7 - i) while(input(DHT11_PIN)){ // Wait until pin goes low k++; if (k > 100) {Time_out = 1; break;} delay_us(1);} } } return _data; } void main(){ port_b_pullups(TRUE); // Enable PORTB pull-ups output_b(0); set_tris_b(3); // Configure RB0 & RB1 as inputs lcd_init(); // Initialize LCD module lcd_putc('\f'); // LCD clear while(TRUE){ Time_out = 0; if(input(PIN_B0)) button_state = 0; if(!input(PIN_B0) && (!button_state)){ button_state = 1; // 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 i=1; hour = edit(hour, 10, 1); i=2; minute = edit(minute, 13, 1); while(TRUE){ if(input(PIN_B0)) button_state = 0; while(!input(PIN_B1)){ day++; if(day > 7) day = 1; lcd_gotoxy(6, 2); // Go to column 6 row 2 switch(day){ case 1: lcd_putc("Sun"); break; case 2: lcd_putc("Mon"); break; case 3: lcd_putc("Tue"); break; case 4: lcd_putc("Wed"); break; case 5: lcd_putc("Thu"); break; case 6: lcd_putc("Fri"); break; case 7: lcd_putc("Sat"); break;} delay_ms(200); } lcd_gotoxy(6, 2); lcd_putc(" "); j = 0; while((input(PIN_B0)||button_state) && input(PIN_B1) && j < 5){ j++; delay_ms(50);} lcd_gotoxy(6, 2); switch(day){ case 1: lcd_putc("Sun"); break; case 2: lcd_putc("Mon"); break; case 3: lcd_putc("Tue"); break; case 4: lcd_putc("Wed"); break; case 5: lcd_putc("Thu"); break; case 6: lcd_putc("Fri"); break; case 7: lcd_putc("Sat"); break;} if(!input(PIN_B0) && (!button_state)){ button_state = 1; break;} j = 0; while((input(PIN_B0)||button_state) && input(PIN_B1) && j < 5){ j++; delay_ms(50);} } i=3; date = edit(date, 10, 2); i=4; month = edit(month, 13, 2); i=5; year = edit(year, 18, 2); // 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(3, day); ds1307_write(4, date); ds1307_write(5, month); ds1307_write(6, year); ds1307_write(0, 0); } ds1307_read(); // Read data from DS1307 RTCC ds1307_display(); // Diaplay time and calendar if(((second10 * 10+second)>time_read)||((second10 * 10+second)==0 && time_read)){ time_read = second10 * 10 + second; Start_signal(); if(check_response()){ // If there is response from sensor RH_byte1 = Read_Data(); // read RH byte1 RH_byte2 = Read_Data(); // read RH byte2 T_byte1 = Read_Data(); // read T byte1 T_byte2 = Read_Data(); // read T byte2 Checksum = Read_Data(); // read checksum if(Time_out){ // If reading takes long time lcd_gotoxy(21, 1); // Go to column 1 row 3 lcd_putc(" Time Out! "); lcd_gotoxy(21, 2); // Go to column 1 row 4 lcd_putc(" "); // Clear 4th row } else{ if(CheckSum == ((RH_Byte1 + RH_Byte2 + T_Byte1 + T_Byte2) & 0xFF)){ message1[13] = T_Byte1 / 10 + 48; message1[14] = T_Byte1 % 10 + 48; message1[16] = T_Byte2 / 10 + 48; message2[13] = RH_Byte1 / 10 + 48; message2[14] = RH_Byte1 % 10 + 48; message2[16] = RH_Byte2 / 10 + 48; message1[17] = 223; // Degree symbol lcd_gotoxy(21, 1); // Go to column 1 row 3 printf(lcd_putc, message1); // Display message1 lcd_gotoxy(21, 2); // Go to column 1 row 4 printf(lcd_putc, message2); // Display message2 } else{ lcd_gotoxy(21, 1); // Go to column 1 row 3 lcd_putc(" Checksum Error! "); lcd_gotoxy(21, 2); // Go to column 1 row 4 lcd_putc(" "); // Clear 4th row } } } else { lcd_gotoxy(21, 1); // Go to column 1 row 3 lcd_putc(" No response "); lcd_gotoxy(21, 2); // Go to column 1 row 4 lcd_putc(" from the sensor "); } } delay_ms(50); } }Project Video:
