Real time clock with relative humidity and temperature sensing
This topic shows how to build a real time clock with relative humidity and temperature sensing using PIC18F4550 microcontroller, DS1307 RTC and DHT22 sensor where all data are displayed on 20×4 LCD display. The 20×4 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 PIC18F4550 with DS1307 take a look at the following topic:
Real time clock with PIC18F4550 and DS1307 RTC – CCS C
And to see how to interface PIC18F4550 with DHT22 (AM2302) take a look at this topic:
Interfacing PIC18F4550 with DHT22 sensor – CCS C compiler
Required components:
- PIC18F4550 microcontroller
- DS1307 RTC
- DHT22 (AM2302 – RHT03) sensor
- 20×4 LCD display
- 3V Coin cell battery
- 32.768KHz crystal oscillator
- 2 x 10K resistors
- 4.7K resistor
- 10K Potentiometer
- 2 Buttons
- +5V Power Supply
- Protoboard
- Jumper Wires
AM2302 or RHT03 sensors can be used instead of the DHT22 sensor.
Project circuit:
In this project PIC18F4550 microcontroller internal oscillator is used (8MHz) and MCLR pin function is disabled.
CCS C code:
The C code below was tested with CCS C compiler version 5.051.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 | // PIC18F4550 with DS1307 and DHT22 (AM2302-RHT03) CCS C code //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 #use delay(clock = 8000000) #include <lcd.c> #use fast_io(B) #use I2C(master, I2C1, FAST=100000) #define DHT22_PIN PIN_B4 // Connection pin between DHT22 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 ; unsigned int16 Temp, RH; 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 10 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_B2)) button_state = 0; while(!input(PIN_B3)){ 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_B2) || button_state) && input(PIN_B3) && j < 5){ j++; delay_ms(50);} lcd_gotoxy(xx, yy); printf(lcd_putc,"%02u", parameter); j = 0; while((input(PIN_B2) || button_state) && input(PIN_B3) && j < 5){ j++; delay_ms(50);} if(!input(PIN_B2) && !button_state){ button_state = 1; return parameter;} } } void start_signal(){ output_drive(DHT22_PIN); // Configure connection pin as output output_low(DHT22_PIN); // Connection pin output low delay_ms(25); output_high(DHT22_PIN); // Connection pin output high delay_us(30); output_float(DHT22_PIN); // Configure connection pin as input } short check_response(){ delay_us(40); if(!input(DHT22_PIN)){ // Read and test if connection pin is low delay_us(80); if(input(DHT22_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(DHT22_PIN)){ // Wait until pin goes high k++; if (k > 100) {Time_out = 1; break;} delay_us(1);} delay_us(30); if(!input(DHT22_PIN)) bit_clear(_data, (7 - i)); // Clear bit (7 - i) else{ bit_set(_data, (7 - i)); // Set bit (7 - i) while(input(DHT22_PIN)){ // Wait until pin goes low k++; if (k > 100) {Time_out = 1; break;} delay_us(1);} } } return _data; } void main(){ setup_oscillator(OSC_8MHZ); // Set internal oscillator to 8MHz setup_adc_ports(NO_ANALOGS); // Configure all AN pins as digital port_b_pullups(TRUE); // Enable PORTB pull-ups output_b(0); set_tris_b(0x0F); // Configure RB0,RB1,RB2 & RB3 as inputs lcd_init(); // Initialize LCD module lcd_putc('\f'); // LCD clear while(TRUE){ Time_out = 0; if(input(PIN_B2)) button_state = 0; if(!input(PIN_B2) && (!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_B2)) button_state = 0; while(!input(PIN_B3)){ 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_B2)||button_state) && input(PIN_B3) && 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_B2) && (!button_state)){ button_state = 1; break;} j = 0; while((input(PIN_B2)||button_state) && input(PIN_B3) && 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)){ RH = RH_byte1; RH = (RH << 8) | RH_byte2; Temp = T_byte1; Temp = (Temp << 8) | T_byte2; if(Temp > 0X8000){ message1[12] = '-'; Temp = Temp & 0X7FFF; } else message1[12] = ' '; message1[13] = (Temp / 100) % 10 + 48; message1[14] = (Temp / 10) % 10 + 48; message1[16] = Temp % 10 + 48; message2[13] = (RH / 100) % 10 + 48; message2[14] = (RH / 10) % 10 + 48; message2[16] = RH % 10 + 48; message1[17] = 223; // Degree symbol lcd_gotoxy(21, 1); // Go to column 1 row 1 printf(lcd_putc, message1); // Display message1 lcd_gotoxy(21, 2); // Go to column 1 row 2 printf(lcd_putc, message2); // Display message2 } else{ lcd_gotoxy(21, 1); // Go to column 1 row 3 lcd_putc(" Checksum Error! "); lcd_gotoxy(21, 1); // Go to column 1 row 4 lcd_putc(" "); // Clear 4th row } } } else { lcd_gotoxy(21, 1); // Go to column 3 row 3 lcd_putc(" No response "); lcd_gotoxy(21, 2); // Go to column 1 row 4 lcd_putc(" from the sensor "); } } delay_ms(50); } } |
Interfacing PIC18F4550 with DS1307 and DHT22 Project Video:
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I was gratified to see this program and I wanted to say thank-you! I am not a programmer but it is a hobby for now. I love microelectronics and programming though, and I am hoping to learn new stuff all the time.