PIC18F4550 ds18B20 16x2 LCD Example

The ds18B20 is a digital one-wire temperature sensor. It can converts between -55 and +125 Degree Celsius. It has three pins, GND, Data and GND. Its open-drain data pin need an additional pullup resistor with a resistance between 4.4 kOhm and 10kOhm.

This popular digital thermometer is widely used among electronics hobbyist due to its low cost, simple communication and rich of libraries (especially Arduino). The MCU just use its digital I/O pin to communicate with this sensor.

Some C compilers for PIC micro-controller like MikroC and CCS PICC have their libraries to interface with this device. However I prefer CCS PICC here due to its simplicity. 

Program Simulation 1

Program Simulation 2

In this example the PIC18F4550 read the temperature data from ds18B20 via RB4 pin. The temperature data will display on the on-board 16x2 character LCD. The PIC18F4550 clock at its maximum frequency of 48MHz.

1. #include <18F4550.h>
2. #DEVICE ADC = 10
3. #fuses HSPLL,NOWDT,NOPROTECT,NOLVP,NODEBUG,USBDIV,PLL5,CPUDIV1,VREGEN
4. #use delay(clock=48000000)
5. #use rs232(baud=9600,xmit=PIN_C6,rcv=PIN_C7)
7. #define PIN_DS18B20_DATA PIN_B4
8. #include <ds18b20.c>
10. #define LCD_ENABLE_PIN PIN_D3
11. #define LCD_RS_PIN PIN_D2
13. #define LCD_DATA4 PIN_D4
14. #define LCD_DATA5 PIN_D5
15. #define LCD_DATA6 PIN_D6
16. #define LCD_DATA7 PIN_D7
18. #include "lcd.c"
19. #define lcd_clear() lcd_putc('\f')
21. void main(){
22. signed int16 val;
23. printf("\n\rPIC18F4550 DIY USB Prototype Board.");
24. printf("\n\rWednesday 03 September 2025");
25. printf("\n\rds18B20 one-wire Temperature Sensor Example\n\r");
26. printf("\r\n\r\ds18b20.c - ds18B20 example starting\r\n\r\n");
27. ds18b20_init();
28. lcd_init();
29. lcd_clear();
30. printf(LCD_PUTC,"PIC18F4550 LCD\nds18b20 Example");
31. delay_ms(5000);
32. lcd_clear();
34. while(1){
35. ds18b20_read(&val);
36. printf("temperature = %ldC\r\n", val/(signed int16)16);
37. lcd_gotoxy(1,1);
38. printf(LCD_PUTC, "Temperature:\n%ld%cC",val/(signed int16)16,223);
39. delay_ms(2000);
40. }
41. }

Click here to download this example.

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