Interfacing DS18B20 Sensor with PIC MCU

In this blog there are many examples shows how to interface some sensors with different types of microcontrollers and in this topic I’m going to show how to connect the popular and low cose temperature sensor DS18B20 with PIC16F887 microcontroller. The compiler used in this example is mikroC PRO for PIC.

The DS18B20 sensor is a 3-pin electronic component (like a simple transistor) from Analog Devices (formerly Maxim Integrated) which uses 1-wire protocol to communicate with master device (microprocessor, microcontroller….).
The DS18B20 sensor provides 9-bit to 12-bit Celsius temperature measurement resolution (programmable resolution).

Components Required:

PIC16F887 microcontroller —> datasheet
DS18B20 temperature sensor — datasheet
16×2 LCD screen
4.7k ohm resistor
10k ohm variable resistor or potentiometer
Power source with 5 VDC
Breadboard & jumper wires
PIC Microcontroller programmer (PICkit 2, PICkit 3…)

Interfacing DS18B20 sensor with PIC microcontroller circuit:
Example circuit schematic diagram is shown below.

(All grounded terminals are connected together)

The DS18B20 sensor has 3 pins (from left to right): GND, data and VCC (+5V). The data pin is connected to PIC16F887 pin RB1.

The LCD screen is used to display the temperature value read by the DS18B20 sensor. It’s connected to PORTD pins with:
RS —> RD0
E —> RD1
D4 —> RD2
D5 —> RD3
D6 —> RD4
D7 —> RD5

In this example the PIC16F887 microcontroller runs with its internal oscillator (@ 8MHz) and MCLR pin is configured as a digital input pin (configured in the software).

Interfacing DS18B20 sensor with PIC microcontroller mikroC code:
The C code below is for mikroC PRO for PIC compiler, the configuration words are:
CONFIG1 : 0x2CD4
CONFIG2 : 0x0700

The mikroC compiler has a built-in one-wire protocol library which makes the interfacing more easier.

The default resolution of DS18B20 is 12-bit which means the step of the temperature is 0.0625°C. The datasheet of the device contains more details about that. Rest of code is described through comments.

/* Interfacing DS18B20 temperature sensor with PIC16F887
   mikroC PRO for PIC code
   Internal oscillator used @ 8MHz
   Configuration words: CONFIG1 = 0x2CD4
                        CONFIG2 = 0x0700
*/

// LCD module connections
sbit LCD_RS at RD0_bit;
sbit LCD_EN at RD1_bit;
sbit LCD_D4 at RD2_bit;
sbit LCD_D5 at RD3_bit;
sbit LCD_D6 at RD4_bit;
sbit LCD_D7 at RD5_bit;
sbit LCD_RS_Direction at TRISD0_bit;
sbit LCD_EN_Direction at TRISD1_bit;
sbit LCD_D4_Direction at TRISD2_bit;
sbit LCD_D5_Direction at TRISD3_bit;
sbit LCD_D6_Direction at TRISD4_bit;
sbit LCD_D7_Direction at TRISD5_bit;
// End LCD module connections

int raw_temp;
char *temp = "000.0000 C";

void main() {
  OSCCON =  0X70;                  // Set internal oscillator to 8MHz
  ANSELH = 0;                      // Configure all PORTB pins as digital
  Lcd_Init();                      // Initialize LCD module
  Lcd_Cmd(_LCD_CURSOR_OFF);        // cursor off
  Lcd_Cmd(_LCD_CLEAR);             // clear LCD
  lcd_out(1, 3, "Temperature:");

  while(1) {

    Ow_Reset(&PORTB, 1);                         // Onewire reset signal
    Ow_Write(&PORTB, 1, 0xCC);                   // Issue command SKIP_ROM
    Ow_Write(&PORTB, 1, 0x44);                   // Issue command CONVERT_T
    
    while(Ow_Read(&PORTB, 1) == 0) ;
    Ow_Reset(&PORTB, 1);                         // Onewire reset signal
    Ow_Write(&PORTB, 1, 0xCC);                   // Issue command SKIP_ROM
    Ow_Write(&PORTB, 1, 0xBE);                   // Issue command READ_SCRATCHPAD
    
    raw_temp  = Ow_Read(&PORTB, 1);              // Read temperature LSB byte
    raw_temp |= (Ow_Read(&PORTB, 1) << 8);       // Read temperature MSB byte
    
    if(raw_temp & 0x8000) {                       // If the temperature is negative
      temp[0] = '-';                              // Put minus sign (-)
      raw_temp = ~raw_temp + 1;                   // Change temperature value to positive form
    }
    else {
      if((raw_temp >> 4) >= 100)                  // If the temperatue >= 100 °C
        temp[0] = '1';                            // Put 1 of hundreds
      else                                        // otherwise
        temp[0] = ' ';                            // put space ' '
    }

    // Put the first two digits ( for tens and ones)
    temp[1] = ( (raw_temp >> 4) / 10 ) % 10 + 48;      // Put tens digit
    temp[2] =   (raw_temp >> 4)        % 10  + 48;     // Put ones digit

    // Put the 4 fraction digits (digits after the point)
    // Why 625: because we're working with 12-bit resolution
    temp[4] = ( (raw_temp & 0x0F) * 625) / 1000 + 48;          // Put thousands digit
    temp[5] = (((raw_temp & 0x0F) * 625) / 100 ) % 10 + 48;    // Put hundreds digit
    temp[6] = (((raw_temp & 0x0F) * 625) / 10 )  % 10 + 48;    // Put tens digit
    temp[7] = ( (raw_temp & 0x0F) * 625) % 10 + 48;            // Put ones digit

    temp[8] = 223;                                // Put degree symbol ( ° )
    lcd_out(2, 4, temp);                          // Display temperature

    delay_ms(1000);                               // Wait 1 second
  }
}
// End of code

/* Interfacing DS18B20 temperature sensor with PIC16F887

mikroC PRO for PIC code

Internal oscillator used @ 8MHz

Configuration words: CONFIG1 = 0x2CD4

CONFIG2 = 0x0700

// LCD module connections

sbit LCD_RS at RD0_bit;

sbit LCD_EN at RD1_bit;

sbit LCD_D4 at RD2_bit;

sbit LCD_D5 at RD3_bit;

sbit LCD_D6 at RD4_bit;

sbit LCD_D7 at RD5_bit;

sbit LCD_RS_Direction at TRISD0_bit;

sbit LCD_EN_Direction at TRISD1_bit;

sbit LCD_D4_Direction at TRISD2_bit;

sbit LCD_D5_Direction at TRISD3_bit;

sbit LCD_D6_Direction at TRISD4_bit;

sbit LCD_D7_Direction at TRISD5_bit;

// End LCD module connections

int raw_temp;

char *temp = "000.0000 C";

void main() {

OSCCON = 0X70; // Set internal oscillator to 8MHz

ANSELH = 0; // Configure all PORTB pins as digital

Lcd_Init(); // Initialize LCD module

Lcd_Cmd(_LCD_CURSOR_OFF); // cursor off

Lcd_Cmd(_LCD_CLEAR); // clear LCD

lcd_out(1, 3, "Temperature:");

while(1) {

Ow_Reset(&PORTB, 1); // Onewire reset signal

Ow_Write(&PORTB, 1, 0xCC); // Issue command SKIP_ROM

Ow_Write(&PORTB, 1, 0x44); // Issue command CONVERT_T

while(Ow_Read(&PORTB, 1) == 0) ;

Ow_Reset(&PORTB, 1); // Onewire reset signal

Ow_Write(&PORTB, 1, 0xCC); // Issue command SKIP_ROM

Ow_Write(&PORTB, 1, 0xBE); // Issue command READ_SCRATCHPAD

raw_temp = Ow_Read(&PORTB, 1); // Read temperature LSB byte

raw_temp |= (Ow_Read(&PORTB, 1) << 8); // Read temperature MSB byte

if(raw_temp & 0x8000) { // If the temperature is negative

temp[0] = '-'; // Put minus sign (-)

raw_temp = ~raw_temp + 1; // Change temperature value to positive form

}

else {

if((raw_temp >> 4) >= 100) // If the temperatue >= 100 °C

temp[0] = '1'; // Put 1 of hundreds

else // otherwise

temp[0] = ' '; // put space ' '

}

// Put the first two digits ( for tens and ones)

temp[1] = ( (raw_temp >> 4) / 10 ) % 10 + 48; // Put tens digit

temp[2] = (raw_temp >> 4) % 10 + 48; // Put ones digit

// Put the 4 fraction digits (digits after the point)

// Why 625: because we're working with 12-bit resolution

temp[4] = ( (raw_temp & 0x0F) * 625) / 1000 + 48; // Put thousands digit

temp[5] = (((raw_temp & 0x0F) * 625) / 100 ) % 10 + 48; // Put hundreds digit

temp[6] = (((raw_temp & 0x0F) * 625) / 10 ) % 10 + 48; // Put tens digit

temp[7] = ( (raw_temp & 0x0F) * 625) % 10 + 48; // Put ones digit

temp[8] = 223; // Put degree symbol ( ° )

lcd_out(2, 4, temp); // Display temperature

delay_ms(1000); // Wait 1 second

}

// End of code

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Interfacing DS18B20 Sensor with PIC MCU – mikroC Projects

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