新建 文本文档 (8).txt

是一个基于51单片机的温度监控系统设计的源程序

PIC16F877的用18B20测温的部分程序 
[电子技术资料] [回复] [引用回复] [表格型] [跟帖] [转发到Blog] [关闭] [浏览64次]  

--------------------------------------------------------------------------------
 
用户名: lin_feng  
 要关中断,
在每个字节读写时序发起时的低电平时关中断,时间只有几个US,
不是在整个读写数据期间关中断
以下是一个PIC16F877的用18B20测温的部分程序
#include <pic.h>
#include "temperature.h"
#include "main.h"
bank1 bit RE2Bit;
bank1 bit bStartConversion;
bank1 unsigned int TemperatureMs1000;
bank1 bit bWaitConversion;
bank1 bit bCanRead;
bank1 bit tempBit; 
void InitTemperatureTest()
{
    TRISE2 = 1;
    bStartConversion = 1;
    TemperatureMs1000 = 1000;
    bWaitConversion = 0;
    bCanRead = 0;
// Not set 18B20,12 bit precision
}
bit Reset18B20()
{
    RE2 = 0;
    TRISE2 = 0;
    SetDelayTenUs(55);//3+500 US
    TRISE2 = 1;//Set Input,RES pull High 
    SetDelayTenUs(7);//73 us
    tempBit = RE2;
    SetDelayTenUs(24);//240us
    return tempBit;
}
unsigned char ReadOneChar()
{
    unsigned char i=0;
    unsigned char dat = 0;
    
    for (i=8;i>0;i--)
    {
        GIE = 0;//Close Globle Intterupt
        RE2 = 0;//delay 2us
        TRISE2 = 0;
        dat>>=1;
        asm("NOP");
        TRISE2 = 1;
        
        //delay 4Us
        asm("NOP");
        asm("NOP");
        asm("NOP");
        asm("NOP");
        RE2Bit = RE2;
        GIE = 1;//Open Globle Intterupt
        if(RE2Bit)
        {
            dat |= 0x80;
        }
        SetDelayTenUs(5);//53 us,all > 60Us
    }
    return(dat);
}
void WriteOneChar(unsigned char dat)
{
     unsigned char j;
    for(j=8; j>0; j--)
    {
        GIE = 0;//Close Globle Intterupt
        RE2 = 0;//delay 2us
        TRISE2 = 0;
        asm("NOP");
        asm("NOP");
        RE2 = dat&0x01;
        GIE = 1;//Open Globle Intterupt
        SetDelayTenUs(6);//63us
        TRISE2 = 1;
        dat>>=1;
    }
    SetDelayTenUs(10);//103us
}
bit StartTemperatureTest()
{
    if(!Reset18B20())
    {
        WriteOneChar(0xCC); // ignore ROM Oprator
        WriteOneChar(0x44); // start temperature conversion
        bStartConversion = 0;
        TemperatureMs1000 = 1000;
        bWaitConversion = 1;
        return 1;
    }
    return 0;
}
unsigned char ReadTemperature()
{
    unsigned char a=0;
    unsigned char b=0;
    unsigned char t=0;
    
    if(!Reset18B20())
    {
        WriteOneChar(0xCC); // ignore ROM Oprator
        WriteOneChar(0xBE); //read cmd
        a=ReadOneChar();   //low char
        b=ReadOneChar();   //high char
        a=a>>4;            //低位右移4位，舍弃小数部分
        t=b<<4;            //高位左移4位，舍弃符号位
        t |= a;
        t |= (b & 0x80);
        bCanRead = 0;
        bStartConversion = 1;
    }           
    return(t);
}