DS18B20 是单线接口数字温度传感器，测量范围是-55℃～+125℃，-10℃～+85℃范围内精
度是±0.5℃，测量分辨率为 9～12 位（复位值为 12 位，最大转换时间为 750ms）。
DS18B20 包括寄生电源电路、64 位 ROM 和单线接口电路、暂存器、EEPROM、8 位 CRC 生
成器和温度传感器等。寄生电源电路可以实现外部电源供电和单线寄生供电，64 位 ROM 中存放
的 48 位序列号用于识别同一单线上连接的多个 DS18B20，以实现多点测温。
64 位 ROM 代码的格式为：
8 位 CRC 校验码 + 48 位序列号 + 8 位系列码（0x28） 其中 8 位 CRC 校验码是 48 位序列号和 8 位系列码的
CRC 校验码。
DS18B20 的暂存器如表
DS18B20 的操作包括下列 3 步：
- 复位
- ROM 命令
- 功能命令
DS18B20 ROM 功能命令如表
国信长天单片机竞赛实训平台的 DS18B20 电路图如图
基于国信长天单片机竞赛实训平台的温度传感器示例程序
#include "reg52.h" //定义51单片机特殊功能寄存器
#include "onewire.h" //单总线函数库
#include "absacc.h"sfr AUXR = 0x8E;unsigned char dspbuf[8] = {
10,10,10,10,10,10,10,10};//显示缓冲区
unsigned char dspcom = 0;
unsigned char intr;
bit temper_flag = 0;//温度读取标志
code unsigned char tab[] = {
0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90,0xff};void display(void);void cls_buzz()
{
P2 = ((P2&0x1f)|0xA0);P0 = 0x00;P2 &= 0x1f;
}
void cls_led()
{
P2 = ((P2&0x1f)|0x80);P0 = 0xFF;P2 &= 0x1f;
}//主函数
void main(void)
{
unsigned char temperature;cls_buzz();cls_led();AUXR |= 0x80;TMOD &= 0xF0;TL0 = 0xCD;TH0 = 0xD4;TF0 = 0;TR0 = 1;ET0 = 1;EA = 1;while(1){
if(temper_flag){
temper_flag = 0;temperature = rd_temperature(); //读温度}//显示数据更新(temperature>=10)?(dspbuf[6] = temperature/10):(dspbuf[6]=10);dspbuf[7] = temperature%10;}
}//定时器中断服务函数
void isr_timer_0(void) interrupt 1 //默认中断优先级 1
{
display();if(++intr == 100) //1ms执行一次{
intr = 0;temper_flag = 1; //100ms温度读取标志位置1}
}//显示函数
void display(void)
{
P2 = ((P2&0x1f)|0xE0);P0 = 0xff;P2 &= 0x1f;P0 = 1<<dspcom;P2 = ((P2&0x1f)|0xC0);P2 &= 0x1f;P0 = tab[dspbuf[dspcom]];P2 = ((P2&0x1f)|0xE0);P2 &= 0x1f;if(++dspcom == 8) {
dspcom = 0;}
}
/*-------------------------------------------------------------------------- ABSACC.HDirect access to 8051, extended 8051 and NXP 8051MX memory areas. Copyright (c) 1988-2010 Keil Elektronik GmbH and ARM Germany GmbH All rights reserved. --------------------------------------------------------------------------*/#ifndef __ABSACC_H__
#define __ABSACC_H__#define CBYTE ((unsigned char volatile code *) 0)
#define DBYTE ((unsigned char volatile data *) 0)
#if !defined (__CX2__)
#define PBYTE ((unsigned char volatile pdata *) 0)
#endif
#define XBYTE ((unsigned char volatile xdata *) 0)#define CWORD ((unsigned int volatile code *) 0)
#define DWORD ((unsigned int volatile data *) 0)
#if !defined (__CX2__)
#define PWORD ((unsigned int volatile pdata *) 0)
#endif
#define XWORD ((unsigned int volatile xdata *) 0)#if defined (__CX51__) || defined (__CX2__)
#define FVAR(object, addr) (*((object volatile far *) (addr)))
#define FARRAY(object, base) ((object volatile far *) (base))
#define FCVAR(object, addr) (*((object const far *) (addr)))
#define FCARRAY(object, base) ((object const far *) (base))
#else
#define FVAR(object, addr) (*((object volatile far *) ((addr)+0x10000L)))
#define FCVAR(object, addr) (*((object const far *) ((addr)+0x810000L)))
#define FARRAY(object, base) ((object volatile far *) ((base)+0x10000L))
#define FCARRAY(object, base) ((object const far *) ((base)+0x810000L))
#endif#if defined (__CX2__)
#define HBYTE ((unsigned char volatile huge *) 0)
#define HWORD ((unsigned int volatile huge *) 0)
#define HVAR(object, addr) (*((object volatile huge *) (addr)))
#define HARRAY(object, base) ((object volatile huge *) (base))
#endif#define CVAR(object, addr) (*((object volatile code *) (addr)))
#define CARRAY(object, base) ((object volatile code *) (base))
#define DVAR(object, addr) (*((object volatile data *) (addr)))
#define DARRAY(object, base) ((object volatile data *) (base))
#define XVAR(object, addr) (*((object volatile xdata *) (addr)))
#define XARRAY(object, base) ((object volatile xdata *) (base))#endif#ifndef _ONEWIRE_H
#define _ONEWIRE_H#define OW_SKIP_ROM 0xcc
#define DS18B20_CONVERT 0x44
#define DS18B20_READ 0xbe//函数声明
unsigned int rd_temperature(void);
float rd_temperature_f(void);
#endif
#include "reg52.h"sbit DQ = P1^4;//单总线延时函数
#ifndef STC12
void Delay_OneWire(unsigned int t) //STC89C52RC
{
while(t--);
}
#else
void Delay_OneWire(unsigned int t) //STC12C5260S2
{
unsigned char i;while(t--) {
for(i=0; i<12; i++);}
}
#endif//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;
}//DS18B20初始化
bit init_ds18b20(void)
{
bit initflag = 0;DQ = 1;Delay_OneWire(12);DQ = 0;Delay_OneWire(80); // 延时大于480usDQ = 1;Delay_OneWire(10); // 14initflag = DQ; // initflag等于1初始化失败Delay_OneWire(5);return initflag;
}//DS18B20温度采集程序：整数
unsigned char rd_temperature(void)
{
unsigned char low,high;char temp;init_ds18b20();Write_DS18B20(0xCC);Write_DS18B20(0x44); //启动温度转换Delay_OneWire(200);init_ds18b20();Write_DS18B20(0xCC);Write_DS18B20(0xBE); //读取寄存器low = Read_DS18B20(); //低字节high = Read_DS18B20(); //高字节temp = high<<4;temp |= (low>>4);return temp;
}