DS18B20_单总线协议

#ifndef _ONEWIRE_H
#define _ONEWIRE_H

#include "STC15F2K60S2.H"
#include <intrins.h>

#define OW_SKIP_ROM 0xcc
#define DS18B20_CONVERT 0x44
#define DS18B20_READ 0xbe

//IC引脚定义
 sbit DQ = P1^4;

//函数声明
extern void Delay_OneWire(unsigned int t);
extern void Write_DS18B20(unsigned char dat);
extern bit Init_DS18B20(void);
extern unsigned char Read_DS18B20(void);
extern void Delay1ms();
extern unsigned char read_temp();

#endif

.C文件

#include "onewire.h"


//单总线延时函数
void Delay_OneWire(unsigned int t)
{
  while(t--);
}


void Delay1ms()		//@11.0592MHz
{
	unsigned char i, j;

	_nop_();
	_nop_();
	_nop_();
	i = 11;
	j = 190;
	do
	{
		while (--j);
	} while (--i);
}


//DS18B20芯片初始化
bit Init_DS18B20(void)
{
	bit initflag = 0;
	DQ = 1;
	Delay_OneWire(12);
	DQ = 0;
	Delay_OneWire(80); 
	DQ = 1;
	Delay_OneWire(10); 
	initflag = DQ;    
	Delay_OneWire(5);
  
	return initflag;
}

//通过单总线向DS18B20写一个字节
void Write_DS18B20(unsigned char dat)
{
	unsigned char i;
	for(i=0;i<8;i++)
	{
		DQ = 0;
		DQ = dat&0x01;
		Delay_OneWire(5);
		DQ = 1;
		dat >>= 1;
	}
	Delay_OneWire(5);
}

//从DS18B20读取一个字节
unsigned char Read_DS18B20(void)
{
	unsigned char i;
	unsigned char dat;
  
	for(i=0;i<8;i++)
	{
		DQ = 0;
		dat >>= 1;
		DQ = 1;
		if(DQ)
		{
			dat |= 0x80;
		}	    
		Delay_OneWire(5);
	}
	return dat;
}

unsigned char read_temp()
{
	unsigned char temp, high, low;
	
	Init_DS18B20();
	Write_DS18B20(0xcc);
	Write_DS18B20(0x44);
	Delay1ms();
	
	Init_DS18B20();
	Write_DS18B20(0xcc);
	Write_DS18B20(0xbe);
	
	low=Read_DS18B20();
	high=Read_DS18B20();
	
	temp=(high<<4)|(low>>4);
	
	return temp;
}