Programming Example of 51 Single Chip Microcomputer Digital Clock Thermometer

#include "reg51.h"

char disp[11]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f,0x40};
char disp_dot[11]={0xbf,0x86,0xdb,0xcf,0xe6,0xed,0xfd,0x87,0xff,0xef,0xc0};

sbit DQ = P1^3; //define communication port

//晶振12MHz
void delay_18B20(unsigned int i)
{
while(i--);
}

//Init function
Init_DS18B20(void)
{
unsigned char x=0;
DQ = 1; //DQ reset
delay_18B20(8); //Slight delay
DQ = 0; //MCU pulls DQ low
delay_18B20(80); //Precise delay greater than 480us
DQ = 1; //Pull the bus high
delay_18B20(14);
x=DQ; //After a slight delay, if x=0, initialization is successful, if x=1, initialization fails
delay_18B20(20);
}

//Read a
byteReadOneChar(void)
{
unsigned char i=0;
unsigned char dat = 0;
for (i=8;i>0;i--)
{
DQ = 0; //Give pulse signaldat
>>=1;
DQ = 1; //Give pulse signalif
(DQ)
dat|=0x80;
delay_18B20(4);
}
return(dat);
}

//Write one byte
WriteOneChar(unsigned char dat)
{
unsigned char i=0;
for (i=8; i>0; i--)
{
DQ = 0;
DQ = dat&0x01;
delay_18B20(5);
DQ = 1;
dat>>=1;
}
}

//Read temperatureReadTemperature
(void)
{
unsigned char a=0;
unsigned char b=0;
unsigned int t=0;

Init_DS18B20();
WriteOneChar(0xCC); // Skip reading serial number and column
numberWriteOneChar(0x44); // Start temperature conversion
delay_18B20(100);
Init_DS18B20();
WriteOneChar(0xCC); // Skip reading serial number and column numberWriteOneChar
(0xBE); //Read temperature registers, etc. (9 registers can be read in total) The first two are temperaturea
=ReadOneChar();
b=ReadOneChar();

//Sensor return value divided by 16 to get the actual temperature value
//In order to get 2 decimal places, multiply by 100 first, then divide by 16, considering the length of integer data,
//After processing, multiply by 25 first, then divide by 4, and divide by 4 is implemented by right shift

t = (b*256+a)*25;
return( t >> 2 );
}

main()
{
unsigned int tmp;
unsigned char counter;
while(1)
{
//The temperature measurement frequency does not need to be too high. Too high a frequency will affect the digital display.
//So use a counter to control it
if(counter-- == 0)
{
tmp = ReadTemperature();
counter = 20;
}

P2 = 0xff;
P0 = disp[tmp%10];
P2 = 0xfb;
delay_18B20(1000);
P2 = 0xff;
P0 = disp[tmp/10%10];
P2 = 0xf7;
delay_18B20(1000);
P2 = 0xff;
P0 = disp_dot[tmp/100%10];
P2 = 0xef;
delay_18B20(1000);
P2 = 0xff;
P0 = disp[tmp/1000%10];
P2 = 0xdf;
delay_18B20(1000);
}
}