Lesson nr.14-DS18B20 using 1-Wire Protocol & 7seg

Hardware setup:
In this Lesson, we will make a digital temperature meter using DS18B20. The connection between temperature sensor and microcontroller will be done through a single wire. This is advantage of the temperature sensor model. The temperature value will be displayed on 4 digits-with 7 segment, in multiplexed mod of course.
PORTB will be used for character (RB0=a, RB1=b...RB6=g, RB7=dp) and for digits RA0 = digit1...RA3 = digit4. Data wire from DS18B20 is conected to RA4.
Pull-up resistor (with a value of 4.7 k), is required to perform communication between the sensor and microcontroller.











Circuit Diagram:
For those who want to build it on their own breadboard or other platform, here is the electronic scheme built in Eagle Cad, free version:

Software:
Here is the C program written for MikroC PRO for PIC 2010 (version v4.15).

/*
'*******************************************************************************
'  Lesson nr.14:
'          Digital thermometer with DS18B20 and 7- Segments.
'  Done by:
'          Aureliu Raducu Macovei, 2010.
'  Description:
'          In this experiment we will work with one-wire communication.
'          The thermal sensor used is "DS18B20" and measured value is displayed 
'          on the 7-segment digits. PORTB will be used for character
'          (RB0=a,RB1=b...RB6=g,RB7=dp)and for digits RA0=digit1...RA3=digit4.
'          Data wire from DS18B20 is conected to RA4.
'  Test configuration:
'    MCU:                        PIC16F628A
'    Test.Board:                 WB-106 Breadboard 2420 dots
'    SW:                         MikroC PRO for PIC 2010 (version v4.15)
'  Configuration Word
'    Oscillator:                 INTOSC:I/O on RA.6, I/O on RA.7
'    Watchdog Timer:             OFF
'    Power up Timer:             Disabled
'    Master Clear Enable:        Enabled
'    Browun Out Detect:          Enabled
'    Low Voltage Program:        Disabled
'    Data EE Read Protect:       Disabled
'    Code Protect:               OFF
'*******************************************************************************
*/
unsigned short i, DD0=0x40, DD1=0x40,DD2=0x40, DD3 =0x61, N_Flag;
unsigned temp_value=0;                         // Variable to store temperature register value
unsigned short mask(unsigned short num)        // Mask for 7 segment common cathode;
{
 switch (num)
 {
  case 0 : return 0x3F;           // 0;
  case 1 : return 0x06;           // 1;
  case 2 : return 0x5B;           // 2;
  case 3 : return 0x4F;           // 3;
  case 4 : return 0x66;           // 4;
  case 5 : return 0x6D;           // 5;
  case 6 : return 0x7D;           // 6;
  case 7 : return 0x07;           // 7;
  case 8 : return 0x7F;           // 8;
  case 9 : return 0x6F;           // 9;
  case 10 : return 0x40;          // Symbol '-'
  case 11 : return 0x61;          // Symbol C
  case 12 : return 0x00;          // Blank
  } //case end
}

void display_temp(short DD0, short DD1, short DD2, short DD3)
{
 for (i = 0; i<=4; i++)
 {
  PORTB = DD3;
  RA0_bit = 1;                    // Select C Digit;
  RA1_bit = 0;
  RA2_bit = 0;
  RA3_bit = 0;
  delay_ms(2);
  PORTB = DD0;
  RA0_bit = 0;
  RA1_bit = 1;                    // Select Ones Digit;
  RA2_bit = 0;
  RA3_bit = 0;
  delay_ms(2);
  PORTB = DD1;
  RA0_bit = 0;
  RA1_bit = 0;
  RA2_bit = 1;                    // Select Tens Digit;
  RA3_bit = 0;
  delay_ms(2);
  PORTB = DD2;
  RA0_bit = 0;
  RA1_bit = 0;
  RA2_bit = 0 ;
  RA3_bit = 1;                    // Select +/- Digit;
  delay_ms(2);
  }return;
}

void DS18B20()                              //Perform temperature reading
{
 Display_temp(DD0, DD1, DD2, DD3);
 Ow_Reset(&PORTA, 4);                       // Onewire reset signal
 Ow_Write(&PORTA, 4, 0xCC);                 // Issue command SKIP_ROM
 Ow_Write(&PORTA, 4, 0x44);                 // Issue command CONVERT_T
 Display_temp(DD0, DD1, DD2, DD3);
 Ow_Reset(&PORTA, 4);
 Ow_Write(&PORTA, 4, 0xCC);                 // Issue command SKIP_ROM
 Ow_Write(&PORTA, 4, 0xBE);                 // Issue command READ_SCRATCHPAD
 Display_temp(DD0, DD1, DD2, DD3);
 // Next Read Temperature
 temp_value =  Ow_Read(&PORTA, 4);          // Read Byte 0 from Scratchpad
 temp_value = (Ow_Read(&PORTA, 4) << 8) + temp_value;       // Then read Byte 1 from
                                                            // Scratchpad and shift
                                                            // 8 bit left and add the Byte 0
 if (temp_value & 0x8000) {
                           temp_value = ~temp_value + 1;
                           N_Flag = 1;      // Temp is -ive
                           }
 if (temp_value & 0x0001) temp_value += 1;  // 0.5 round to 1
 temp_value = temp_value >> 4 ;      //<<<  // 1 for DS1820 and
                                            // 4 for DS18B20;
 }

void main()
{
 CMCON  |= 7;                               // Disable Comparators
 TRISB = 0;                                 // Set PORTB direction to be output
 PORTB = 0;                                 // Turn OFF LEDs on PORTB
 PORTA = 0;
 TRISA0_bit = 0;                            // RA.0 to RA3 Output
 TRISA1_bit = 0;
 TRISA2_bit = 0;
 TRISA3_bit = 0;
 
 do {                                        //--- main loop
     N_Flag = 0;                             // Reset Temp Flag
     DS18B20();
     DD0 = temp_value%10;                    // Extract Ones Digit
     DD0 = mask(DD0);
     DD1 = (temp_value/10)%10;               // Extract Tens Digit
     DD1 = mask(DD1);
     DD2 =  temp_value/100;                  // Extract Hundred digit
     if (N_Flag == 1) DD2=0x0A;              // DD2 10 ??
     else if (DD2 == 0) DD2 = 0x0D;          // DD2 13 ??
     DD2 = mask(DD2);
     display_temp(DD0, DD1, DD2, DD3);       // Infinite loop;
     } while (1);
 }