PIC16F877 MCU DS18B20 digital tube thermometer simulation program can display negative temperature

The circuit diagram is as follows:

//************************************************************

// Function implemented: Digital tube displays real-time temperature, supports negative temperature

// Chip PIC16F877

// XT:4MHZ

//************************************************************

#include //Includes the predefined internal resources of the MCU

#define LVP 0x3f39

// Crystal: XT; Code: No code protection; Power-on delay timer off;

//Low voltage reset disabled; watchdog disabled; low voltage programming disabled

__CONFIG (XT & UNPROTECT & PWRTDIS & BORDIS & WDTDIS & LVP);

#define uch unsigned char //Give unsigned char an alias name of uch

#define DQ RA2 //Define 18B20 data port 

#define DQ_DIR TRISA2 //Define 18B20D port direction register 

#define DQ_HIGH() DQ_DIR =1 //Set the data port to input

#define DQ_LOW() DQ_DIR = 0; DQ = 0 //Set the data port to output

const unsigned char ledcode[12]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F,0x00,0x40};

//Common cathode digital tube 0123456789 segment code without decimal point, positive and negative sign bit

const unsigned char ledcode1[12]={0xBF,0x86,0xDB,0xCF,0xE6,0xED,0xFD,0x87,0xFF,0xEF,0x00,0x40};   

//Common cathode digital tube with decimal point 0123456789 segment code, positive and negative sign bit 

void init_port(void);

void delay(char x,char y); 

void delay_1ms(void);

void delay_ms(unsigned int time);

void interrupt dealtime();

void tmint(void);

void timetoseg(uch fh_temp,uch bai_temp,uch shi_temp,uch ge_temp,uch sf_temp,uch bf_temp,uch qf_temp,uch wf_temp);

void binary_temp(uch TL , signed char TH);

void reset(void);

void write_byte(uch val);

uch read_byte(void);

void get_temp(void);

unsigned char display_data[8];

unsigned char intcount=0; 

uch TLV=0 ; //The collected temperature is 8 bits high

uch THV=0; //The collected temperature is 8 bits lower

union temp //define a union

{

int T;        

uch TV[2];        

}temp;

signed char TZ=0; //The integer part of the converted temperature value, with a sign bit

uch TX=0; //The decimal part of the converted temperature value

unsigned int wd; //BCD code format of the converted temperature value

unsigned char fh; //sign bit

unsigned char bai; // integer hundreds place

unsigned char shi; // tens digit

unsigned char ge; // integer digit

unsigned char shifen; //tenths place

unsigned char baifen; //percentile

unsigned char qianfen; //thousandths

unsigned char wanfen; //ten thousandth place

//************************************************************

// Main program

//************************************************************

void main(void)

{

init_port();

tmint();

while(1)

  {         

   get_temp();

   timetoseg(fh,bai,shi,ge,shifen,baifen,qianfen,wanfen);  

  }

}

//************************************************************

//Port initialization

// PORTD is used as digital tube segment driver (high effective)

//PORTE is used as digital tube bit selection driver (low effective)

//************************************************************

void init_port(void)

{

  RBPU=0;

// PORTB = 0xFF;

  TRISB=0xFF; 

  PORTD=0x00; //

  TRISC=0x00; //Port C controls the LED indicator, set to output

  TRISD=0; //Port D is used as a digital tube segment and is set to output

  ADCON1=0x07; // Make port A and port E all digital I/O ports

  TRISE=0x00; //Port E is used as the digital tube position selection control pin, set to output   

  PORTE=0x00; 

}

//************************************************************

// Delay procedure

//************************************************************

void delay(char x,char y) 

{

  char z;

  do{

      z=y;

      do{;}while(--z);

     }while(--x);

}

//The instruction time is: 7+(3*(Y-1)+7)*(X-1). If we add the 7 instructions for calling the function, setting the page, and passing parameters, the instruction time is: 7+(3*(Y-1)+7)*(X-1).

//Then it is: 14+(3*(Y-1)+7)*(X-1).

//************************************************************

// Delay procedure

//************************************************************

void delay_1ms(void)

{

  unsigned int n;

  for(n=0;n<50;n++)

   {

    NOP();

   }

}

//************************************************************

void delay_ms(unsigned int time)

{

  for(;time>0;time--)

   {

    delay_1ms();

   }

}

//-----------------------------------------------

//Reset DS18B20 function

void reset(void)

{

  uch presence=1;

  while(presence)

  { 

    DQ_LOW(); //Host pulls to low level

    delay(2,90); //delay>480503us

    DQ_HIGH(); //Release the bus and wait for the resistor to pull the bus high and keep it for 15~60us

    delay(2,8); //delay>60us

    if(DQ==1) presence=1; //No response signal received, continue to reset

    else presence=0; //Receive response signal

    delay(2,70); //delay>240us

   }

  }

//-----------------------------------------------

//Write 18b20 write byte function

void write_byte(uch val)

{

uch i;

uch temp;

for(i=8;i>0;i--)

{

   temp=val&0x01; //lowest bit shifted out

   DQ_LOW(); 

   NOP();

   NOP();

   NOP();

   NOP();

   NOP(); //Pull from high level to low level to generate write time gap

   if(temp==1) DQ_HIGH(); //If write 1, pull the level high

   delay(2,7); //delay 63us

   DQ_HIGH(); 

   NOP();

   NOP();

   val=val>>1; //Move right one bit

  }

}

//------------------------------------------------

//18b20 read byte function

uch read_byte(void)

{

uch i;

uch value=0; //Read the temperature

static bit j;

for(i=8;i>0;i--)

{

   value>>=1; 

   DQ_LOW(); //Each read time slot is initiated by the host, pulling the bus low for at least 1μs.

   NOP();

   NOP();

   NOP();

   NOP();

   NOP();

   NOP(); //6us

   DQ_HIGH(); //Release the bus within 15μs after the start of the read time slot, pull it to a high level, and prepare to sample the bus.

   NOP(); 

   NOP();

   NOP();  

   NOP(); 

   NOP(); //5us

   j=DQ; //sampling bus

   if(j) value|=0x80; //Put the sampled data into value

   delay(2,7); //All read time slots are at least 60μs, here about 63us

  }

  return(value);

}

//-------------------------------------------------

//Start the temperature conversion function

void get_temp()

{ 

int i;

DQ_HIGH();

reset(); //Reset and wait for slave response 

write_byte(0XCC); //Ignore ROM match 

write_byte(0X44); //Send temperature conversion command  

for(i=10;i>0;i--)

    {    

        delay(201,132);                       

    }    

reset(); //Reset again and wait for the slave to respond 

write_byte(0XCC); //Ignore ROM match 

write_byte(0XBE); //Send the temperature read command 

TLV=read_byte(); //Read the lower 8 bits of temperature 

THV=read_byte(); //Read the high 8 bits of temperature 

DQ_HIGH(); //Release the bus 

TZ=(TLV>>4)|(THV<<4); //Temperature integer part

TX=TLV<<4; //Temperature decimal part, note that the last four digits of TX are invalid

binary_temp(TX, TZ ); //Convert the corresponding temperature binary value into a decimal number

}

//Convert the binary values ​​of the corresponding temperature integer and decimal parts into decimal numbers

void binary_temp(char TL , signed char TH)

{

  if(TH>=0) //If it is positive temperature

  {

    fh=0x0A; //positive number sign bit

    bai=TH/100; //hundreds digit of integer

    shi=(TH%100)/10; //Tens digit //Tens digit

    ge=(TH%100)%10; //unit digit //unit digit of integer part

    wd=0;  

    if (TL & 0x80) wd=wd+5000;

    if (TL & 0x40) wd=wd+2500;

    if (TL & 0x20) wd=wd+1250;

    if (TL & 0x10) wd=wd+625; //The above 4 instructions convert the decimal part into BCD code             

    shifen=wd/1000; //tenth place                    

    baifen=(wd%1000)/100; //percentile

    qianfen=(wd%100)/10; //thousandths

    wanfen=wd%10; //ten thousandth place

    NOP();

   }

else //Otherwise, it is a negative temperature, requiring complement

{

  temp.TV[0]=TL;temp.TV[1]=TH;

  temp.T=(~temp.T)+0x0010; //complement code, add 1       

  TL=temp.TV[0];

  TH=temp.TV[1];

    fh=0x0B; //Negative sign bit

    bai=TH/100; //hundreds digit of integer

    shi=(TH%100)/10; //Tens digit //Tens digit

    ge=(TH%100)%10; //unit digit //unit digit of integer part

    wd=0;  

    if (TL & 0x80) wd=wd+5000;

    if (TL & 0x40) wd=wd+2500;

    if (TL & 0x20) wd=wd+1250;

    if (TL & 0x10) wd=wd+625; //The above 4 instructions convert the decimal part into BCD code             

    shifen=wd/1000; //tenth place                    

    baifen=(wd%1000)/100; //percentile

    qianfen=(wd%100)/10; //thousandths

    wanfen=wd%10; //ten thousandth place

    NOP();

}                

}

// Convert each temperature value into segment code

//************************************************************

void timetoseg(uch fh_temp,uch bai_temp,uch shi_temp,uch ge_temp,uch sf_temp,uch bf_temp,uch qf_temp,uch wf_temp)

{

   display_data[0] = ledcode[wf_temp];

   display_data[1] = ledcode[qf_temp];

   display_data[2] = ledcode[bf_temp];

   display_data[3] = ledcode[sf_temp];

   display_data[4] = ledcode1[ge_temp];

   display_data[5] = ledcode[shi_temp];

   display_data[6] = ledcode[bai_temp];

   display_data[7] = ledcode[fh_temp];

}

//************************************************************

// Timer interrupt initialization (OPTION_REG)

//************************************************************

void tmint(void)

{

  T0CS=0; //Clock source is internal instruction cycle                   

  PSA=0; //The divider is assigned to TMR0 

//  

  PS2=0; //The division ratio of TMR0 is 1:16          

  PS1=1;

  PS0=1;

//

  GIE=1; //Enable general interrupt 

  T0IE=1; //Enable timer 0 overflow interrupt

  T0IF=0; // Clear timer 0 interrupt flag

  TMR0=0X06; //Preset initial value T=(256-6)x16=4000uS

}

//************************************************************

void interrupt dealtime() //Interrupt entry, this interrupt completes the dynamic scanning of the digital tube

{ //Each interruption lasts for 4 milliseconds

    T0IF=0;

    TMR0=0X06;

    PORTD = 0x00; //Turn off the display first

   if(intcount==0)

     {

      PORTD = display_data[0];

      PORTE=0x00;

      intcount+=1;

     }

   else if(intcount==1)

     {

      PORTD = display_data[1];

      PORTE=0x01;

      intcount+=1;

     }

   else if(intcount==2)

     {

      PORTD = display_data[2];

      PORTE=0x02;

      intcount+=1;