Interfacing PIC16F877A with DHT11 sensor and ST7735R SPI color 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 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.