Smoke detector sensor interface with pic16f877a

// 'C' source line config statements

// CONFIG

#pragma config FOSC = HS    // Oscillator Selection bits (HS oscillator)

#pragma config WDTE = OFF    // Watchdog Timer Enable bit (WDT disabled)

#pragma config PWRTE = OFF   // Power-up Timer Enable bit (PWRT disabled)

#pragma config BOREN = ON    // Brown-out Reset Enable bit (BOR enabled)

#pragma config LVP = OFF    // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3 is digital I/O, HV on MCLR must be used for programming)

#pragma config CPD = OFF    // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)

#pragma config WRT = OFF    // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)

#pragma config CP = OFF     // Flash Program Memory Code Protection bit (Code protection off)

// #pragma config statements should precede project file includes.

// Use project enums instead of #define for ON and OFF.

#include <xc.h>

#define _XTAL_FREQ 20000000

int analogRead(int a);

void adcconfig();

int main()

{

 int result;//digital conversion values

 TRISD=0X00;//

 adcconfig();

 result=analogRead(0);

   if(result<120)

   {

     PORTD=0X00;

   }

   else

   {

     PORTD=0Xff;

   }

  }

void adcconfig()

{

  ADCON0=0X00;

  ADCON1=0X80;

}

int analogRead(int a)

{

  ADCON0=((1<<0)|(a<<3));

  __delay_ms(3);

  GO=1;

  while(GO_DONE==1);

  return((ADRESH<<8)|ADRESL);

}