DS18B20

#include <reg52.H>
#include <intrins.h>

sbit D18B20=P3^7; bit flag;

unsigned char Temperatured;
unsigned char temp_data[2];
unsigned char temp_dis[6]={0xFF,0xFF,0xFF,0xFF,0xFF};
unsigned char temp_tab[16]={0x00,0x01,0x01,0x02,0x03,0x03,0x04,0x04,0x05,0x06,0x07,0x08,0x09,0x09};

void Disp_temperatuer();void read_bytes (void); void TempDelay (unsigned int us);
void Init18b20 (void);void WriteByte (unsigned char idata wr); unsigned char ReadByte (void);

void Disp_temperatuer()
{
   temp_dis[4]= temp_data[0]&0x0f;
   temp_dis[0]= temp_tab[temp_dis[4]]+0x30;
   temp_dis[3]= (((temp_data[0]&0xf0)>>4)|((temp_data[1]&0x0f)<<4));
   temp_dis[5]= (temp_dis[3]%100);
   temp_dis[2]= (temp_dis[3]%100)/10+0x30;
   temp_dis[1]= temp_dis[3]%10+0x30;
}

void read_bytes (void)
{
  Init18b20();
  WriteByte(0xcc); WriteByte(0x44);

  TempDelay(5000);

  Init18b20();
  WriteByte(0xcc); WriteByte(0xbe);
 
  temp_data[0] = ReadByte(); TempDelay(2);
  temp_data[1] = ReadByte(); TempDelay(2);
}


unsigned char ReadByte (void) //读取单字节

{
 unsigned char idata Ti,u=0;
 for(Ti=0;Ti<8;Ti++)
 {
  D18B20 = 0;
  u >>= 1;
  D18B20 = 1;
  TempDelay(3);
  if(D18B20==1)
  u |= 0x80;
  TempDelay (1);
  _nop_();
  D18B20 = 1;
 }
 return(u);
}

void WriteByte (unsigned char idata wr) //单字节写入

{
 unsigned char idata i;
 for (i=0;i<8;i++)
 {
  D18B20 = 0;
  _nop_();
  D18B20=wr&0x01;
  TempDelay(3); //delay 45 uS //5

  _nop_();
  _nop_();
  D18B20=1;
  wr >>= 1;
  _nop_();
 }
}

void Init18b20 (void)
{
 D18B20=1;
 _nop_();
 D18B20=0;
 TempDelay(100); //delay 530 uS//80

 _nop_();
 D18B20=1;
 TempDelay(13); //delay 100 uS//14

 _nop_();
 _nop_();
 _nop_();
 
 if(D18B20==0)
  flag = 1; //detect 1820 success!

 else
  flag = 0; //detect 1820 fail!

 TempDelay(10); //20

 _nop_();
 _nop_();
 D18B20 = 1;
}

void TempDelay (unsigned int us)
{
 while(us--);
}