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Wednesday, November 9, 2016

PIC16F877A With DHT11 sensor and ST7735 SPI TFT

Interfacing PIC16F877A with DHT11 sensor and ST7735R SPI color TFT display
PIC16F877A with DHT11 sensor and ST7735 SPI TFT display 
This post shows how to interface PIC16F877A microcontroller with DHT11 relative humidity and temperature sensor and 1.8" ST7735R SPI TFT display.
DHT11 sensor is a digital device used to sense relative humidity and temperature and convert that data into digital signals. For more details about this type of sensors and how to interface it with PIC16F877A microcontroller see the following two topics:
Interfacing PIC16F877A with DHT11 (RHT01) sensor Proteus simulation
Interfacing DHT11 relative humidity and temperature sensor with PIC16F877A microcontroller
And to see how to interface PIC16F877A with ST7735 SPI TFT display read the following topic:
ST7735 1.8" TFT display with PIC16F877A example
Components List:
  • PIC16F877A Microcontroller
  • ST7735R SPI TFT Display
  • DHT11 (RHT01) Sensor
  • 8MHz Crystal oscillator
  • 2 x 22pF Capacitors
  • 10K Resistor 
  • 4.7K Resistor
  • 5 x 1K Resistors
  • +5V Power Supply Source
  • Breadboard
  • Jumper Wires
PIC16F877A With DHT11 sensor and ST7735 SPI TFT circuit:
PIC16F877A with DHT11 sensor and ST7735 SPI TFT display circuit
PIC16F877A With DHT11 sensor and ST7735 SPI TFT CCS C code:
PIC16F877A hardware SPI module is used in this project..
ST7735 SPI TFT driver is required to compile this code, download link in this topic:
ST7735 SPI TFT Display Driver for CCS PIC C compiler
The code is has been tested with versions 4.068 and 5.051.
/* PIC16F877A with DHT11 sensor and ST7735 1.8" SPI color TFT display example CCS C code
   ST7735 TFT display driver for CCS PIC C compiler is required
   http: //ccspicc.blogspot.com/
   electronnote@gmail.com
*/

// TFT module connections
#define TFT_CS   PIN_D1
#define TFT_DC   PIN_D0
#define TFT_SPI_HARDWARE
// End TFT module connections

#include <16F877A.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP                       
#use delay(clock = 8000000)
#include <ST7735_TFT.c>
#use fast_io(D)
#use fast_io(B)
#define DHT11_PIN PIN_B0                              // DHT11 Data pin is connected to pin RB0

char *text = "DHT11 Sensor with    PIC16F877A and ST7735 TFT";
char temperature[] = "00.0";
char humidity[]    = "00.0%";
short Time_out;
unsigned int8 T_byte1, T_byte2, RH_byte1, RH_byte2, CheckSum, clear = 0 ;
void start_signal(){
  output_drive(DHT11_PIN);                            // Configure DHT11 pin as output
  output_low(DHT11_PIN);                              // DHT11 pin output low
  delay_ms(25);
  output_high(DHT11_PIN);                             // DHT11 pin output high
  delay_us(30);
  output_float(DHT11_PIN);                            // Configure v pin as input
}
short check_response(){
  delay_us(40);
  if(!input(DHT11_PIN)){                              // Read and test if DHT11 pin is low
    delay_us(80);
    if(input(DHT11_PIN)){                             // Read and test if DHT11 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 DHT11 pin get raised
      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 DHT11 pin goes low
        k++;
        if(k > 100){
        Time_out = 1;
        break;
      }
      delay_us(1);}
    }
  }
  return _data;
}
void main(){
  TFT_BlackTab_Initialize();
  fillScreen(ST7735_BLACK);
  drawtext(0, 0, text, ST7735_WHITE, ST7735_BLACK, 1);
  drawFastHLine(0, 35, _width, ST7735_BLUE);
  while(TRUE){
    Time_out = 0;
    Start_signal();
    if(check_response()){                             // If there is a 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
        if(clear != 1){
          clear = 1;
          fillrect(0, 40, _width, 120, ST7735_BLACK);
        }
        strcpy(text, "Time out!");
        drawtext(10, 90, text, ST7735_RED, ST7735_BLACK, 2);
      }
      else{
       if(CheckSum == ((RH_Byte1 + RH_Byte2 + T_Byte1 + T_Byte2) & 0xFF)){
         temperature[0]  = T_Byte1/10  + 48;
         temperature[1]  = T_Byte1%10  + 48;
         temperature[3] = T_Byte2/10  + 48;
         humidity[0]  = RH_Byte1/10 + 48;
         humidity[1]  = RH_Byte1%10 + 48;
         humidity[3] = RH_Byte2/10 + 48;
         if(clear != 2){
          clear = 2;
          fillrect(0, 50, _width, 120, ST7735_BLACK);
          drawFastHLine(0, 96, _width, ST7735_BLUE);
        }
         strcpy(text, "Temperature:");
         drawtext(28, 50, text, ST7735_MAGENTA, ST7735_BLACK, 1);
         drawtext(34, 70, temperature, ST7735_YELLOW, ST7735_BLACK, 2);
         drawCircle(84, 70, 2, ST7735_YELLOW);
         drawchar(90, 70, 'C', ST7735_YELLOW, ST7735_BLACK, 2);
         strcpy(text, "Humidity:");
         drawtext(37, 110, text, ST7735_MAGENTA, ST7735_BLACK, 1);
         drawtext(34, 130, humidity, ST7735_CYAN, ST7735_BLACK, 2);
       }
       else{
         if(clear != 3){
          clear = 3;
          fillrect(0, 40, _width, 120, ST7735_BLACK);
         }
         strcpy(text, "Checksum");
         drawtext(16, 80, text, ST7735_RED, ST7735_BLACK, 2);
         strcpy(text, "Error!");
         drawtext(28, 100, text, ST7735_RED, ST7735_BLACK, 2);
       }
      }
    }
    else {
      if(clear != 4){
        clear = 4;
        fillrect(0, 40, _width, 120, ST7735_BLACK);
      }
      strcpy(text, "No");
      drawtext(52, 60, text, ST7735_RED, ST7735_BLACK, 2);
      strcpy(text, "response");
      drawtext(16, 80, text, ST7735_RED, ST7735_BLACK, 2);
      strcpy(text, "from the");
      drawtext(16, 100, text, ST7735_RED, ST7735_BLACK, 2);
      strcpy(text, "sensor");
      drawtext(28, 120, text, ST7735_RED, ST7735_BLACK, 2);
    }
  delay_ms(1000);
  }
}
PIC16F877A With DHT11 sensor and ST7735 SPI TFT video:
This video shows a simple hardware circuit of this project.