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(0x CC ); // 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. Divide by 4 with 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);
 }
}