dsPIC30F2010 and DHT-11 Environmental Sensor Interfacing

The DHT11 temperature and humidity sensor features a temperature and humidity sensor
complex with a calibrated digital signal output. By using the exclusive digital-signal-acquisition
technique and temperature and humidity sensing technology, it ensures high reliability and
excellent long-term stability. This sensor includes a resistive-type humidity measurement
component and an NTC temperature measurement component, and connects to a high performance 8-bit micro-controller, offering excellent quality, fast response, anti-interference
ability and cost-effectiveness.

Its standard TTL bi-directional I/O suitable for dsPIC30F2010 Interfacing and Programming. It needs only three wires, +5VDC, DATA and GND. Its DATA pin requires a weak pull up resistor with a resistance around 4.7k. 

I use my dsPIC30F2010 DIY Prototype Board to test this program. 

DHT11 Humidity & Temperature
Sensor

Parameters

Relative Humidity
Resolution：             16Bit
Repeatability：         ±1%RH
Accuracy：               25℃ ±5%RH
Interchangeability：  Fully interchangeable
Response time：       1/e (63%)25℃ 6s
                                1m/s Air 6s
Hysteresis：             <±0.3%RH
Long-term stability： <±0.5%RH/yr

Temperature
Resolution：             16Bit
Repeatability：         ±1℃
Accuracy：               25℃ ±2℃
Response time：       1/e (63%) 10S

Electrical Characteristics
Power supply：         DC 3.3～ 5.5V
Supply current：       Measure 0.3mA Standby 60μA
Sampling period：     Secondary Greater than 2 seconds 

For more detail about interfacing this sensor with a micro-controller please see this post. 

dsPIC30F2010 CCS PICC Programming

The newer version of CCS PICC (v5.119) has a C driver for the DHT-11 environmental sensor that could be called using a few lines of code. The "dht11.c" C driver locates in the drivers directory in program files. I use pin RB0 of dsPIC30F2010 to interface with this sensor.

The following example shows a simple sensor reading and data displaying over the RS-232.

• board.h 

1. #include <30F2010.h>
2. #device ICSP=1
3. #fuses HS,NODEBUG,NOWDT,PR,CKSFSM
4. #use delay(crystal=20000000)
5. 
   
6. #define LED0 PIN_D0
7. #define LED1 PIN_D1
8. #define SW0 PIN_C13
9. #define SW1 PIN_C14
10. 
    
11. #define DELAY 500
12. 
    
13. #use rs232(UART1, baud=9600, stream=UART_PORT1)

 

•  main.c

1. #include "board.h"
2. 
   
3. #define PIN_DHT11_DATA PIN_B0
4. #include <dht11.c>
5. 
   
6. void main(){
7. unsigned int8 relativeHumidity;
8. unsigned int8 tempC;
9. printf("\n\rdsPIC30F2010 Prototype Board.");
10. printf("\n\rWednesday 25 September 2025");
11. printf("\n\rDHT-11 Humidity Sensor Example\n\r");
12. printf("\r\n\r\dht-11.c - DHT11 example starting\r\n\r\n");
13. dht11_init();
14. delay_ms(1000);
15. while(1){
16. dht11_read(&relativeHumidity, &tempC);
17. printf("HUMIDITY=%03u%%, TEMPERATURE=%02uC\r\n", relativeHumidity, tempC);
18. delay_ms(2000);
19. }
20. }

 

• Memory Use 

•  Serial Input/Output Monitor

 

  Click here to download this example.

I add a 16x4 LCD (TC1604A-04) to display temperature and humidity data. Using a character LCD is very conventional for most small micro-controller programming and interfacing. I copied the "lcd.c" 16x2 LCD C driver to my project folder that I can modify it without changing the original file. I disable the LCD R/W pin (wire to GND) and I upgrade this LCD driver to a 16x4 LCD.

Its "board.h" header file remains the same to above example. 

• main.c

 

1. #include "board.h"
2. 
   
3. #define PIN_DHT11_DATA PIN_B0
4. #include <dht11.c>
5. 
   
7. #define LCD_RS_PIN PIN_E4
8. #define LCD_RW_PIN PIN_E5
9. #define LCD_ENABLE_PIN PIN_E5
11. #define LCD_DATA4 PIN_E0
12. #define LCD_DATA5 PIN_E1
13. #define LCD_DATA6 PIN_E2
14. #define LCD_DATA7 PIN_E3
15. 
    
16. #include "lcd.c"
17. 
    
18. #define lcd_clear() lcd_putc('\f')
19. #define lcd_home() lcd_putc('\a')
20. /*For 16x4 LCD Only*/
21. #define line_1() lcd_send_byte(0,0x80);
22. #define line_2() lcd_send_byte(0,0xC0);
23. #define line_3() lcd_send_byte(0,0x90);
24. #define line_4() lcd_send_byte(0,0xD0);
25. 
    
26. 
    
27. void main(){
28. unsigned int8 relativeHumidity;
29. unsigned int8 tempC;
30. printf("\n\rdsPIC30F2010 Prototype Board.");
31. printf("\n\rFriday 26 September 2025");
32. printf("\n\rDHT-11 Humidity Sensor Example\n\r");
33. printf("\r\n\r\dht-11.c - DHT11 example starting\r\n\r\n");
34. dht11_init();
35. lcd_init();
36. printf(LCD_PUTC,"dsPIC30F2010 LCD");
37. line_2();
38. printf(LCD_PUTC,"DHT-11 Sensor");
39. line_3();
40. printf(LCD_PUTC,"Example Using");
41. line_4();
42. printf(LCD_PUTC,"CCS PICC v5.119");
43. delay_ms(5000);
44. lcd_clear();
45. while(1){
46. dht11_read(&relativeHumidity, &tempC);
47. printf("HUMIDITY=%03u%%, TEMPERATURE=%02uC\r\n", relativeHumidity, tempC);
48. lcd_home();
49. printf(LCD_PUTC," DHT-11 Sensor");
50. line_2();
51. printf(LCD_PUTC," Reading:");
52. line_3();
53. printf(LCD_PUTC,"Humidity: %03u%%",relativeHumidity);
54. line_4();
55. printf(LCD_PUTC,"Temperature:%02u%cC",tempC,0xDF);
56. delay_ms(1000);
57. }
58. }

 The TC1604A-04 works fine even it's too old.

Start-Up Screen

DHT-11 Sensor Reading and Displaying

Click here to download this example.