Wednesday, September 7, 2016

PIC18F4550 + 20x4 LCD + DS1307 RTC + DHT22 Relative Humidity and Temperature Sensor


Real time clock with relative humidity and temperature sensing
PIC18F4550 + DS1307 RTC + DHT22 sensor hardware circuit 
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 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 PIC18F4550 with DS1307 take a look at the following topic:
Real time clock with PIC18F4550 and DS1307 RTC
And to see how to interface PIC18F4550 with DHT22 (AM2302) take a look at this topic:
Interfacing PIC18F4550 with DHT22(AM2302-RHT03) digital humidity and temperature sensor
Required components:
  • PIC18F4550 microcontroller
  •  DS1307 RTC
  • DHT22 (AM2302 - RHT03) sensor
  • 20x4 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:
PIC18F4550 + 20x4 LCD + DS1307 RTC + DHT22 (AM2302-RHT03)
In this project PIC18F4550 microcontroller internal oscillator is used (8MHz) and MCLR pin function is disabled.
CCS C code:
// PIC18F4550 with DS1307 and DHT22 (AM2302-RHT03) 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
#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: