武林教你學PIC32（十八）單總線DS18B20溫度傳感器

簡單介紹下DS18B20,它是獨特的單線接口，僅需一個端口進行通訊9~12位的分辨率可調(diào)（RS）測溫范圍為-55°C~+125°C;測量范圍在-10°C ~+85°C精度為±0.5°C可設(shè)置報警溫度存儲于EEPROM，掉電保護數(shù)據(jù)不丟適用電壓3~5.5V

下面介紹我封裝好的函數(shù),已經(jīng)測試可以使用，需要注意的是PORTReadBits，需要根據(jù)實際端口相應(yīng)地移位

DS18B20.H:

#ifndef _DS18B20_H_

#define _DS18B20_H_

#include

#define DQ_PORTIOPORT_D//設(shè)置DQ引腳

#define DQ_PINBIT_14

#define SET_OP_1WIREPORTSetBits(DQ_PORT, DQ_PIN)

#define CLR_OP_1WIREPORTClearBits(DQ_PORT, DQ_PIN)

#define SET_DIR_1WIREPORTSetPinsDigitalOut(DQ_PORT, DQ_PIN)

#define CLR_DIR_1WIREPORTSetPinsDigitalIn(DQ_PORT, DQ_PIN)

#define CHECK_IP_1WIREPORTReadBits(DQ_PORT, DQ_PIN)>>14

extern void delay_us(unsigned int num);

extern void delay_ms(unsigned int num);

float gettemp(void);//讀取溫度值

#endif

DS18B20.C

#include "ds18b20.h"

void init_1820()

{

SET_DIR_1WIRE; //設(shè)置PC2為輸出

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);//讀數(shù)據(jù),從低位開始

if(k)

temp|=(1<

else

temp&=~(1<

delay_us(50); //60~120us

SET_DIR_1WIRE;

}

return (temp);

}

float gettemp()//讀取溫度值

{

unsigned char temh,teml;

unsigned int temp;

float value;

init_1820();//復位18b20

write_1820(0xcc);//發(fā)出轉(zhuǎn)換命令

write_1820(0x44);

//delay_nms(800);//不延時也好使，不知道怎么回事！

init_1820();

write_1820(0xcc);//發(fā)出讀命令

write_1820(0xbe);

teml=read_1820();//讀數(shù)據(jù)

temh=read_1820();

temp=temh;

temp<<=8;

temp|=teml;

value=temp*0.0625;

return value;

}