DS18S20 gibt immer nur "2" aus

/*

 * main.c

 *

 *  Created on: 15.07.2010

 *      Author: cesupa

 */

#include <avr/io.h>

#include <util/delay.h>

#include <stdlib.h>

#include "lcd_addonboard.h"

/* Thermometer Connections (At your choice) */

#define PORT PORTD

#define DDR DDRD

#define PIN PIND

#define DQ PD6

/* Utils */

#define INPUT_MODE() DDR&=~(1<<DQ)

#define OUTPUT_MODE() DDR|=(1<<DQ)

#define LOW() PORT&=~(1<<DQ)

#define HIGH() PORT|=(1<<DQ)

uint8_t reset();

uint8_t write_bit(uint8_t bit);

uint8_t read_bit();

uint8_t read_byte();

unsigned char rom_c[8],scratch_pad[9];

void write_byte(uint8_t byte);

int main()

{

  uint8_t z=0;

  char string[20];

  lcd_init();

  if(!reset())

    lcd_str("DS18S20 found");

  else

    lcd_str("FAILURE");

  write_byte(0xcc);

  write_byte(0x44);

  _delay_ms(1000);

  if(!reset())

  {

    write_byte(0xcc);

    write_byte(0xbe);

    for(z=0;z<9;z++)

    {

      scratch_pad[z]=read_byte();

    }

    lcd_str(itoa(scratch_pad[8],string,10));

  }

  else

    lcd_str("FAILURE_2");

  while(1);

  return 0;

}

uint8_t reset()

{

  uint8_t i=0;

  //Pull line low and wait for 480uS

  OUTPUT_MODE();

  LOW();

  _delay_us(480);

  //Release line and wait for 60uS

  INPUT_MODE();

  LOW();

  _delay_us(70);

  //Store line value and wait until the completion of 480uS period

  i=(PIN & (1<<DQ));

  OUTPUT_MODE();

  LOW();

  _delay_us(410);

  //Return the value read from the presence pulse (0=OK, 1=WRONG)

  return i;

}

uint8_t write_bit(uint8_t bit)

{

  //Pull line low for 1uS

  OUTPUT_MODE();

  LOW();

  _delay_us(1);

  //If we want to write 1, release the line (if not will keep low)

  if(bit) INPUT_MODE();

  //Wait for 60uS and release the line

  _delay_us(119);

  INPUT_MODE();

return 0;

}

uint8_t read_bit()

{

  uint8_t bit;

  //Pull line low for 1uS

  OUTPUT_MODE();

  LOW();

  _delay_us(1);

  //Release line and wait for 14uS

  INPUT_MODE();

  _delay_us(14);

  //Read line value

  bit=PIN&(1<<DQ);

  //Wait for 45uS to end and return read value

  _delay_us(105);

  return bit;

}

unsigned char read_byte()

{

  uint8_t i=0;

  unsigned char n=0;

  for(i=0;i<8;i++)

  {

    if(read_bit()) n|=0x01 << 1;

  }

    return n;

}

void write_byte(uint8_t byte)

{

  uint8_t i=8;

  while(i--){

  //Write actual bit and shift one position right to make  the next bit ready

  write_bit(byte&1);

  byte>>=1;

  }

}