ds18b20.c

18b20_C51 驱动程序

/*
* -= N U A A =-
* 030210634 H Y X QQ:32242111
* DS18b20.C
* 温度采集系统DS18b20驱动程序
* 版本:1.3
* 2005.7.29-8.4
*/

//ATTENTION:端口必须匹配,51单片机端口别忘接上拉电阻(4.7k)至VCC!否则只能读出数据1; 
//一线一器件程序:

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

#define DATAS P0

sbit PORT_DATA= P2^3;

unsigned char c[2];		//接收码;	
float temperature=0;	//实际温度绝对值,用于其他控制判断;
unsigned char f;		//温符:“0”为正温，“1”为负温;
unsigned char s[16];	//用于显示的字符串,可直接输出;


void delayms(unsigned int count);  //延时1ms;
void restoration(void);		//复位命令;
void judge(void);	//器件判断;		ATTENTION:(器件不存在将会陷入死循环)
bit read_bit(void); //读取一位 1bit;
unsigned char read_byte(void);	//读取一个字节 8bit;
void write_byte(unsigned char dat); //写一个字节 8bit;
void convention(void);	//启动温度转换;
void read_temperature(void);	//温度读取;
void FloatToStr(unsigned char *s,int nMaxLen);//数据存入*s字符串中!供显示使用!	this function made by XLQ! thank him!


/////////////////////////////////////////////////////////////////////////////////////////////

/*
main()
{
	while(1)
	{
		convention();
		delayms(100);
		read_temperature();
		FloatToStr(s,10);		
		//此时温度以存入temperature,以供控制;
		//显示数据存入s字符串中,可直接显示;
	}
}
*/


/////////////////////////////////////////////////////////////////////////////////////////////
void delayms(unsigned int count)	//delay 1ms;
{
	unsigned int i;
	while (count)	
	{
		i = 115;
		while (i>0) i--;
		count--;
    }
}

void restoration(void)	//restoration the DS18b20;
{	
	unsigned int i;
	PORT_DATA= 0;
	i = 100;
	while (i>0) i--;// 900 uS(11.0592Mhz)
	PORT_DATA= 1;
	i = 4;
	while (i>0) i--;
}

void judge(void)	//judge the DS18B20 is entity ?
{
	unsigned char i;
	while (PORT_DATA);	//wait the pulse;
	while (~PORT_DATA);
	i = 4; while (i>0) i--;
}

bit read_bit(void)	//read a bit of the data;
{
	unsigned int i;
	bit dat;
	PORT_DATA= 0;
	_nop_();
	PORT_DATA= 1;
	_nop_();
	_nop_();
	dat = PORT_DATA;
	for(i=8;i>0;i--);
	return (dat);
}

unsigned char read_byte(void)	//read a byte of the data; 
{
	unsigned char i,j,dat;
	dat = 0;
	for (i=1;i<=8;i++)
	{
		dat>>=1;
		j = read_bit();
		if (j)  dat=( dat | 0x80 );
	}
	return (dat);
}

void write_byte(unsigned char dat)	//write a byte to the DS18b20;
{
	unsigned int i;
	unsigned char j;
	bit testb;
	for (j=1;j<=8;j++)
	{
		testb = dat & 0x01;
		dat = dat >> 1;	
		if (testb)
		{
			PORT_DATA= 0;
			_nop_();
			_nop_();
			PORT_DATA= 1;
			for(i=8;i<0;i--);
		}
		else
		{
			PORT_DATA= 0;
			for(i=8;i<0;i--);
			PORT_DATA= 1;
			_nop_();
			_nop_();
		}
	}
}

void convention(void)   //startup temperature-convention;
{
	restoration();
	judge();
	delayms(1);
	write_byte(0xcc);		//the code of jump sequence CCH;
	write_byte(0x44); 	//the code of convention 44H;
}

void read_temperature(void)	//read the temperature;
{                   						
	restoration();				
	//judge();			
	delayms(1);					
	write_byte(0xcc);	
	write_byte(0xbe);
	c[0] = read_byte();		//read the low temperature-data;		
	c[1] = read_byte();  	//read the high temperature-data;
	f=0;
	if( c[1] & 0x80 )
	{
		f=1;
		c[1]=!c[1];
		c[0]=!c[0];
		if( c[0]==0xff )
		{
			c[0]=0x00;
			c[1]+=1;
		}
		else c[0]+=1;
	}
}			

void FloatToStr(unsigned char *s,int nMaxLen) //计算器式数字显示;数据存入s字符串中!
{
	float n;
	int i;
	int nCount=0;
	unsigned char sTmp[9];
	int nLeft;
	float nRight;
	n=c[0]+c[1]*256;
	n=n*0.0625;
	temperature=n;		// 存入实际温度;
	nLeft = (int) n; //整数部分
	nRight = n-nLeft; //小数部分
	while (nLeft > 0) //将整数部分转化为字符串
	{  
		sTmp[nCount] = nLeft%10 + '0';
		nLeft = (int)nLeft/10;
		nCount++;
		if (nCount >= nMaxLen) 
		{
			break;
		}
	}
	for (i=0; i < nCount; i++)  //必须倒序才是从高位到低位的
	{
		s[i] = sTmp[nCount-i-1];
	}
	if (nCount >= nMaxLen || nRight < 1E-6) //如果整数部分已经超过最大长度，或小数部分为零则退出
	{
		s[nCount] = '\0';
		return;
	}
	if (nCount == 0)   //如果整数部分为零，则应赋值0
	{
		s[nCount] = '0';
		nCount++;
	}
	s[nCount] = '.';
	nCount++;
	if (nCount >= nMaxLen) 
	{
		s[nCount] = '\0';
		return;
	}
	while (nRight < 1 && nRight > 1E-6) 
	{
		s[nCount] = (int)(nRight * 10) + '0';
		nCount ++;
		nRight = (nRight*10)- (int)(nRight * 10);
		if (nCount >= nMaxLen)
		{
			break;
		}
	}
	s[nCount] = '\0';
}