Nebula Pi 开发板评测报告（十）——温度传感器DS18B20功能测试

#ifndef _DS18B20_H
#define _DS18B20_H

#include "reg52.h"
#include "intrins.h"


void delay_10us(unsigned char t);
void DS18B20_Init(void);
void DS18B20_WriteByte(unsigned char dat);
unsigned char DS18B20_ReadByte(void);
unsigned int GetTemperature(void);

#endif

#include "DS18B20.h"

sbit Tem = P3^7;

void delay_10us(unsigned char t)
{
    while(t--)
    {
        _nop_();_nop_();_nop_();_nop_();_nop_();
        _nop_();_nop_();_nop_();_nop_();_nop_();
    }
}

void DS18B20_Init(void)
{
    Tem = 0;                    //拉低P3.7 500us
    delay_10us(50);

    Tem = 1;                    //拉高P3.7 60us
    delay_10us(6);      
    
    while(!Tem);            //等待P3.7引脚返回低电平
    delay_10us(50);     //延时500us
}

void DS18B20_WriteByte(unsigned char dat)       //写数据
{
    unsigned char i;
    bit flag;
    
    for(i=1;i<9;i++)
    {
        flag = dat&0x01;        //0 和 1 的标志位不同
        dat = dat>>1;               //逐位传输
            
        Tem = 0;                        //拉低总线2us
        _nop_();
        _nop_();
        
        Tem = flag;                 //将数据放到总线上
        delay_10us(6);          //延时60us
        
        Tem = 1;                        //拉高总线
    }
}

unsigned char DS18B20_ReadByte(void)        //读数据
{
    unsigned char dat,flag,i;
    
    
    for(i=1;i<9;i++)
    {
        Tem = 0;                //拉低总线2us   
        _nop_();
        _nop_();
        Tem = 1;                //拉高总线2us
        _nop_();
        _nop_();
        
        flag = Tem;         //读取总线的内容
        delay_10us(6);          //延时60us
        
        dat = (dat>>1)|(flag<<7);     //每次读出的数值放到右侧       
    }
    return dat;
}

unsigned int GetTemperature(void)
{
    unsigned char Temp_L,Temp_H;    //定义温度数值的高低八位
    unsigned int Temp;              //定义十六位的温度数值
    
    DS18B20_Init();                         //初始化温度传感器
    DS18B20_WriteByte(0xCC);            //跳过ROM
    DS18B20_WriteByte(0x44);            //启动温度转换
    DS18B20_Init();                         //初始化温度传感器
    DS18B20_WriteByte(0xCC);            //跳过ROM
    DS18B20_WriteByte(0xBE);            //发送读温度指令
    
    Temp_L = DS18B20_ReadByte();    //读温度低八位
    Temp_H = DS18B20_ReadByte();    //读温度高八位

    Temp = ((unsigned int)(Temp_H)<<8)+Temp_L;  //将温度组成十六位的数据
    return Temp;
}

#include "reg52.h"  
#include "DS18B20.h"  
#include "LCD1602.H"  
  
unsigned int time;  
unsigned int Temperature;  
unsigned char t[10];                //温度储存数组  
  
void Timer0_Init(void);  
  
void Timer0_Init(void)  
{  
     TMOD = 0x01;  //工作方式1，16位定时器  
     TH0 = 0x4C;   //定时50ms初值高八位  
     TL0 = 0x00;   //定时50ms初值低八位  
     ET0 = 1;    //开定时器0中断  
     EA = 1;     //开总中断  
     TR0 = 1;    //开启定时器0  
}     
  
  
void main(void)  
{  
    Timer0_Init();      //定时器初始化  
    LCD_Init();             //LCD初始化  
    LCD_WriteString(1,1,"Temperature:");  
    while(1)  
    {  
        if(time == 20)      //1s时间到  
        {  
            time = 0;               //重新计时  
            EA = 0;                 //关总中断，防止与温度采集冲突  
            Temperature = GetTemperature();     //将读取的温度值放入Temperature中  
            t[0] = ( Temperature>>4 )/10+'0';   
            t[1] = ( Temperature>>4 )%10+'0';     //两位数温度的整数部分  
            t[2] = '.';  
            if( (Temperature >>3)%10 )                    //温度左移三位取余后为1  
            {  
                t[3] = '5';  
            }  
            else  
            {  
                t[3] = '0';  
            }  
            t[4] = '\0';  
            LCD_WriteString(2,1,t);  
            EA = 1;       
        }         
    }  
}  
  
void Timer0() interrupt 1 using 1  
{  
     time++;  
     TH0 = 0x4C;   //重装初值，定时50ms初值高八位  
     TL0 = 0x00;   //定时50ms初值低八位  
}