简单介绍下DS18B20,它是独特的单线接口，仅需一个端口进行通讯9~12位的分辨率可调（RS）测温范围为-55°C~+125°C;测量范围在-10°C ~+85°C精度为±0.5°C 可设置报警温度存储于EEPROM，掉电保护数据不丢适用电压3~5.5V

下面介绍我封装好的函数,已经测试可以使用，需要注意的是PORTReadBits，需要根据实际端口相应地移位

DS18B20.H:

#ifndef _DS18B20_H_

#define _DS18B20_H_

#include

#define DQ_PORT               IOPORT_D//设置DQ引脚

#define DQ_PIN                         BIT_14

#define SET_OP_1WIRE     PORTSetBits(DQ_PORT, DQ_PIN)

#define CLR_OP_1WIRE     PORTClearBits(DQ_PORT, DQ_PIN)

#define SET_DIR_1WIRE    PORTSetPinsDigitalOut(DQ_PORT, DQ_PIN)

#define CLR_DIR_1WIRE   PORTSetPinsDigitalIn(DQ_PORT, DQ_PIN)

#define CHECK_IP_1WIRE  PORTReadBits(DQ_PORT, DQ_PIN)>>14

extern void delay_us(unsigned int num);

extern void delay_ms(unsigned int num);

float gettemp(void);    //读取温度值

#endif

DS18B20.C

#include "ds18b20.h"

void init_1820() 

{ 

    SET_DIR_1WIRE; //设置PC2 为输出

    SET_OP_1WIRE;  

    CLR_OP_1WIRE; 

    delay_us(480);    //480us以上 

    SET_OP_1WIRE; 

    CLR_DIR_1WIRE; 

    delay_us(20);     //15~60us 

    while(CHECK_IP_1WIRE); 

    SET_DIR_1WIRE; 

    SET_OP_1WIRE; 

    delay_us(140);   //60~240us 

}

void write_1820(unsigned char x) 

{    

     unsigned char m; 

    for(m=0;m<8;m++) 

    { 

       CLR_OP_1WIRE; 

       if(x&(1<

       SET_OP_1WIRE; 

       else 

       {CLR_OP_1WIRE;} 

       delay_us(40);   //15~60us 

       SET_OP_1WIRE; 

    } 

     SET_OP_1WIRE; 

} 

unsigned char read_1820() 

{     

    unsigned char temp,k,n; 

    temp=0; 

    for(n=0;n<8;n++) 

       { 

      CLR_OP_1WIRE; 

      SET_OP_1WIRE; 

      CLR_DIR_1WIRE; 

      k=(CHECK_IP_1WIRE);    //读数据,从低位开始 

      if(k) 

      temp|=(1<

      else 

      temp&=~(1<

      delay_us(50); //60~120us     

      SET_DIR_1WIRE; 

   } 

   return (temp); 

}  

float gettemp()    //读取温度值

{ 

     unsigned char temh,teml; 

     unsigned int temp;

     float value;

     init_1820();        //复位18b20 

     write_1820(0xcc);   // 发出转换命令 

     write_1820(0x44);

 //  delay_nms(800);     //不延时也好使，不知道怎么回事！

     init_1820(); 

     write_1820(0xcc);  //发出读命令 

     write_1820(0xbe); 

     teml=read_1820();  //读数据 

     temh=read_1820(); 

     temp=temh;

       temp<<=8;

       temp|=teml;

       value=temp*0.0625;

       return value;

}