Temperature Sensor project with LM35DZ & PIC16F877A

// ***************************************************************************
//  File Name    : pictemp.c
//  Version      : 1.0
//  Description  : PIC Thermometer
//  Target       : Microchip PIC16F877a Microcontroller
//  Last Updated : 28 March 2010
// ***************************************************************************

#include <pic.h>

__CONFIG(XT & WDTDIS & PWRTDIS & UNPROTECT & BORDIS & \
  LVPDIS & DEBUGEN);

#define FOSC 20000000L

const char SSEG[] = {
  
  0b11000000,  // 0, LED Segment: A,B,C,D,E,F
  0b11111001,  // 1, LED Segment: B,C
  0b10100100,  // 2, LED Segment: A,B,D,E,G
  0b10110000,  // 3, LED Segment: A,B,C,D,G
  0b10011001,  // 4, LED Segment: B,C,F,G
  0b10010010,  // 5, LED Segment: A,C,D,F,G
  0b10000010,  // 6, LED Segment: A,C,D,E,F,G
  0b11111000,  // 7, LED Segment: A,B,C
  0b10000000,  // 8, LED Segment: A,B,C,D,E,F,G
  0b10010000,  // 9, LED Segment: A,B,C,D,F,G
  0b11000110,  // C, LED Segment: A,D,E,F

};

unsigned char DispDigit[4];
unsigned char DigitCount;

static void interrupt isr(void)
{
  if(TMR0IF) {			       // TIMER0 Interrupt Flag
    /* Pull Low the Segment */
    PORTB = DispDigit[DigitCount];
    /* Activate the Digit and Advanced to next Digit */
    PORTD = ~(1 << DigitCount++);     

    /* Reset the Digit Count */
    if (DigitCount > 3)
      DigitCount=0;

    TMR0 = 156;            	   
    TMR0IF = 0;			     
  }
}


// Delay Function

#define _delay_us(x) { unsigned char us; \
	  	       us = (x)/(30000000/FOSC)|1; \
		       while(--us != 0) continue; }


void _delay_ms(unsigned int ms)
{
  unsigned char i;
  do {
    i = 4;
    do {
      _delay_us(164);
    } while(--i);
  } while(--ms);
}


/* Seven Segment Put Number: Implementing floating value from 0 to 99.9 */

void SSEG_putnum(float number)
{
   unsigned char iDigit,iDigit1,iDecimal;
   if (number > 99.9) return;
   
   /* Global interrupt disable */
   GIE = 0;		                   

   iDigit=(int)number;  
   //float temp=number-iDigit;                       // Convert float to Integer
   //float temp2=temp*10;
   //iDecimal=(int)temp2;                            
   iDecimal=(int)(number - iDigit) * 10;       // Get The Decimal Digit
   DispDigit[1]=SSEG[iDecimal];                 // First Decimal Digit
   if (iDigit >= 10) {
     iDigit1=iDigit / 10;
     DispDigit[3]=SSEG[iDigit1];                  // Second Digit
     iDigit=iDigit - (iDigit1 * 10);
   } else { 
     DispDigit[3]=SSEG[0];                           // Zero Sign Second Digit
   }
   DispDigit[2]=SSEG[iDigit] & 0x7F;           // First Digit with Decimal Point
   
   /* Global interrupt enable */
   GIE = 1;
}


void main(void)
{
  unsigned int iValue,iCTemp;
  float CentTemp;


  TRISA = 0xFF;        // Input for RA0 to RA7
  TRISB = 0x00;        // Output for RB0 to RB7
  TRISD = 0x00;        // Output for RC0 to RC7
 
  /* Initial Output Port */
  
  PORTB=0xFF;
  PORTD=0xFF;
  

  /* Init TIMER0: Period: 1/(Fosc/32) x Prescale x TMR0
     0.0016 ms x 64 * 100 = 10.24 ms */
  
  OPTION = 0b00000101;    // 1:64 Prescale
  TMR0=156;                          // Interupt every 10.24 ms
  TMR0IE = 1;	          // Enable interrupt on TMR0 overflow
  GIE = 1;	                           // Global interrupt enable
  
  
  /* Initial variables used */
  
  DigitCount=0;
  DispDigit[0]=SSEG[10];     // Centigrade Sign
  DispDigit[1]=SSEG[0];      // Zero Digit
  DispDigit[2]=SSEG[0];      // Zero Digit
  DispDigit[3]=SSEG[0];      // Zero Digit
  for(;;) {
  
  /* Get First Sample */
  
  ADCON0=0b10000001;       
  ADCON1=0b10001101;           // Right Justified,Vref: VCFG1 and VCFG0(1 VoltReference)
  GODONE=1;	                   // initiate conversion on the channel 0
  while(GODONE) continue;         // Wait conversion done
  iValue=ADRESL;                        // Get the 8 bit LSB result
  iValue += (ADRESH << 8);       // Get the 2 bit MSB result
  iCTemp = iValue;
  _delay_ms(50);
    
  /* Get Second Sample */
   
  GODONE=1;	                 // initiate conversion on the channel 0
  while(GODONE) continue;      // Wait conversion done
  iValue=ADRESL;                     // Get the 8 bit LSB result
  iValue += (ADRESH << 8);     // Get the 2 bit MSB result
  iCTemp += iValue;
  _delay_ms(50);
    
  /* Get Third Sample */
   
  GODONE=1;             	  // initiate conversion on the channel 0
  while(GODONE) continue;         // Wait conversion done
  iValue=ADRESL;                        // Get the 8 bit LSB result
  iValue += (ADRESH << 8);       // Get the 2 bit MSB result
  iCTemp += iValue;

  /* Calculate the Average Centigrade Value */
  /* (ADC Value/5.12) / Vref, LM35DZ Out=10mV/C, Vref = 2 Volt */
  
  CentTemp=(iCTemp/3.0)/ 5.12;
   


  /* Now Display The Result */
    SSEG_putnum(CentTemp);
    _delay_ms(200);
  }
}
/* EOF: pictemp.c */