ds18b20.c

用DS18B20和51单片机组合成的温度测量仪器

/*******************************ds18b20***********************/
//本模块对外提供void BeginConver(void)，void ReadTemperature()二个函数
#include <e51.h>
#include <reg51.h>
sbit DQ =P3^7; 
void delay(unsigned int i)
{
 	while(i--);
}
Init_DS18B20(void)
{
	 unsigned char x=0;
	 DQ = 1;    //DQ??
	 delay(8);  //????
	 DQ = 0;    //????DQ??
	 delay(80); //???? ?? 480us
	 DQ = 1;    //????
	 delay(14);
	 x=DQ;      //????? ??x=0?????? x=1??????
	 delay(20);
}
unsigned char ReadOneChar(void)
{
	unsigned char i=0;
	unsigned char dat = 0;
	for (i=8;i>0;i--)
	 {
		  DQ = 0; // ?????
		  dat>>=1;
		  DQ = 1; // ?????
		  if(DQ)
		  dat|=0x80;
		  delay(4);
	 }
 	return(dat);
}
void WriteOneChar(unsigned char dat)
{
 unsigned char i=0;
 for (i=8; i>0; i--)
 {
  DQ = 0;
  DQ = dat&0x01;
  delay(5);
  DQ = 1;
  dat>>=1;
 }
  delay(4);
}

void BeginConver(void)
{
    Init_DS18B20();
	WriteOneChar(0xCC); // ??????????
	WriteOneChar(0x44);
}
unsigned int ReadTemperature(void)
{
	unsigned char a=0;
	unsigned char b=0;
	unsigned int t=0;	
//	Init_DS18B20();
//	WriteOneChar(0xCC); // ??????????
//	WriteOneChar(0x44); // ??????
	Init_DS18B20();
	WriteOneChar(0xCC); //??????????
	WriteOneChar(0xBE); //????????(???9????) ???????
	a=ReadOneChar();
	b=ReadOneChar();
	t=b;
	t<<=8;
	t=t|a;
	t=t*0.625;//????????1?
	return(t);
}