DS18B20 and PIC16F690

#include <htc.h>			//include hitech C header file

#define	_XTAL_FREQ			8000000

// This configuration bits are for PIC16F690 using internal crystal
__CONFIG(FOSC_INTRCIO &		// Clock pins are I/O
		 WDTE_OFF &			// Disable Watchdog Timer.
		 PWRTE_ON &			// Enable Power Up Timer.
		 BOREN_OFF);		// Disable Brown Out Reset.

#define SCS_BIT				0x01
#define INT_OSC_8MHZ 		(0b01110000 | SCS_BIT)
#define INT_OSC_4MHZ 		(0b01100000 | SCS_BIT)
#define INT_OSC_2MHZ 		(0b01010000 | SCS_BIT)
#define INT_OSC_1MHZ 		(0b01000000 | SCS_BIT)
#define INT_OSC_500KHZ 		(0b00110000 | SCS_BIT)
#define INT_OSC_250KHZ 		(0b00100000 | SCS_BIT)
#define INT_OSC_125KHZ 		(0b00010000 | SCS_BIT)
#define INT_OSC_31KHZ 		(0b00000000 | SCS_BIT)

#define Skip_ROM 			0xCC
#define Convert_T 			0x44
#define Read_scratchpad 	0xBE

#define Port_18B20 			RB4
#define Tx_18B20 			TRISB4 = 0
#define Rx_18B20 			TRISB4 = 1

#define WAIT1				1000
#define WAIT2				500

#define DS18B20_CONV_TIME	750
#define DS18B20_RESET_PULSE 480
#define DS18B20_WAIT_TIME 	60
#define DS18B20_PULLUP_TIME 2

#define ONEWIRE_PRESENT 	0
#define ONEWIRE_ABSENT 		1

void init();
void delay_ms(unsigned int ui_value);
void beep(unsigned char uc_count);
unsigned char reset();
void write(char WRT);
unsigned char read();
void nibble(unsigned byte);

/*******************************************************************************
* MAIN FUNCTION                                                                *
*******************************************************************************/
int main(void)
{
	unsigned temp, val;
	unsigned short tempL, tempH, fraction;
	unsigned int i = 0;	// declare a variable to store   

	init();

	while(1) 	// create an infinite loop
	{		
		if (reset() == ONEWIRE_PRESENT)
		{
			write(Skip_ROM);
			write(Convert_T);		
			delay_ms(DS18B20_CONV_TIME);
			
			reset();
			write(Skip_ROM);		
			write(Read_scratchpad);	
			
			tempL = read();			//read low temp value
			tempH = read();			//read high temp value
			
			//put both value in one variable
			nibble(tempH);
			delay_ms(WAIT1);
			nibble(0);
			delay_ms(WAIT2);
			
			temp = tempH >> 4;
			nibble(temp);
			delay_ms(WAIT1);
			nibble(0);
			delay_ms(WAIT2);

			nibble(tempL);
			delay_ms(WAIT1);
			nibble(0);
			delay_ms(WAIT2);

			temp = tempL >> 4;
			nibble(temp);
			delay_ms(WAIT1);
			nibble(0);
			delay_ms(WAIT2);
		} else {
			break;
		}
	}

	// Solid LED pattern to indicate we're somewhere we shouldn't be.
	RC0 = 1;
	RC1 = 0;
	RC2 = 1;
	RC3 = 0;

	while (1) continue;
}

void init()
{
	ANSEL = 0;		//Initialize A/D ports off 
	ANSELH = 0;		//Initialize A/D ports off 
	CM1CON0 = 0;	//Initialize comp 1 off 
	CM2CON0 = 0;	//Initialize comp 2 off 
	PORTA = 0x00;	// Clears PORTA
	PORTB = 0x00;	// Clears PORTB
	PORTC = 0x00;	// Clears PORTC
	TRISA = 0x00;	// Sets PORTA to all output
	TRISB = 0x00;	// Sets PORTB to all output
	TRISC = 0x00;	// sets PORTC to all output. 

	// We want 8MHz
	OSCCON = INT_OSC_8MHZ;

	// Wait for clock to stabilise.
	delay_ms(10);
}

void nibble(unsigned byte)
{
	PORTC = (unsigned)(byte & 0x0f);
	return;
}

void delay_ms(unsigned int ui_value)
{
	while (ui_value-- != 0) {
		__delay_ms(1);					// macro from HI-TECH compiler which will generate 1ms delay base on value of _XTAL_FREQ in system.h
	}	
}

unsigned char reset()
{
	Tx_18B20;							// Tris = 0 (output)
	Port_18B20 = 0;						// set pin# to low (0)
	__delay_us(DS18B20_RESET_PULSE);	// 1 wire require time delay
	Rx_18B20;							// Tris = 1 (input)
	__delay_us(DS18B20_WAIT_TIME);		// 1 wire require time delay

	if (Port_18B20 == 0) 				// if there is a presence pluse
	{ 
		__delay_us(DS18B20_RESET_PULSE);// Reset and return
		return ONEWIRE_PRESENT;			// return 0 ( 1-wire is presence)
	}

	__delay_us(DS18B20_RESET_PULSE);	// Reset and return
	return ONEWIRE_ABSENT;				// return 1 ( 1-wire is NOT presence)
}

void write(char WRT)
{
	char i,Cmd;
	Cmd = WRT;
	Rx_18B20; // set pin# to input (1)
	for(i = 0; i < 8; i++)
	{
		if((Cmd & (1<<i))!= 0) 
		{
			// write 1
			Tx_18B20; // set pin# to output (0)
			Port_18B20 = 0; // set pin# to low (0)
			__delay_us(DS18B20_PULLUP_TIME); // 1 wire require time delay
			Rx_18B20; // set pin# to input (release the bus)
			__delay_us(DS18B20_WAIT_TIME); // 1 wire require time delay
		} else  {
			//write 0
			Tx_18B20; // set pin# to output (0)
			Port_18B20 = 0; // set pin# to low (0)
			__delay_us(DS18B20_WAIT_TIME); // 1 wire require time delay
			Rx_18B20; // set pin# to input (release the bus)
		}
	}
}

unsigned char read()
{
	char i,result = 0;
	Rx_18B20; // TRIS is input(1)
	for(i = 0; i < 8; i++)
	{
		Tx_18B20; // TRIS is output(0)
		Port_18B20 = 0; // genarate low pluse for 2us
		__delay_us(DS18B20_PULLUP_TIME);
		Rx_18B20; // TRIS is input(1) release the bus
		if(Port_18B20 != 0) { 
			result |= 1<<i;
		}
		__delay_us(DS18B20_WAIT_TIME); // wait for recovery time
	}
	return result;
}

#define    _XTAL_FREQ            8000000