c51: DS1820

//Resolution 12 bits

#include
#include

#define uchar unsigned char
#define uint unsigned int

uchar digit[10]="0123456789";

//Delay 1 millisecond program
void delayms();

//Delay s milliseconds program 
void delaynms(uint);

//Initialize LCD
void InitLCD();

//Write LCD instruction
void WriteInstruction(uchar);

//Write LCD data
void WriteData(uchar);

//Write address
void WriteAdd(uchar);

//Read LCD status
uchar BusyTest();

//LCD busy query
sbit LCDbusy=P1^7;

//LCD operation bit setting
sbit RS=P2^2;
sbit RW=P2^1;
sbit E=P2^0;
sbit BF=P1^7;

//----- DS1820 declare variable function
sbit DQ=P3^0;
sbit led=P3^1; //Signal indication

uchar TL,TH; //Read DS1820 temperature data high and low bits

//Initialize DS1820
bit InitDS1820();

//Read one byte from DS1820
uchar ReadOneChar();

//Write one byte to DS1820
WriteOneChar(uchar);

//Read temperature
void readtemp();

////Display temperature
void dispay();

uchar flag=0;

//main program
void main() 
{

 
 uchar i;

  
 uchar code str[]="thermometer is:";

 //Initialize LCD
 InitLCD();
 //Write address
 WriteAdd(0x01);
 //Write data
 i=0; 
 while(str[i]!='\0')
 {
  WriteData(str[i]);

  i++;
 }

 //Write address

 while(1)
 {
  readtemp();

  //If it is a negative temperature, display a minus signif
  (flag)
  {
   WriteAdd(0x44);
   WriteData('-');
  }
  else
  {
   WriteAdd(0x44);
   WriteData(' ');
  }

   
  
  WriteAdd(0x45);

  dispay();

  delaynms(1000);
 }
}

//Initialize DS1820
bit InitDS1820()
{
 uchar t;
 bit flag;  
 DQ = 1;          
 _nop_();
  
 DQ = 0; 
          
 //Maintain 600us  
 for(t=0;t<200;t++);

 //Release bus
    DQ = 1; 
 
 //Wait 15~30us, DS1820 outputs response signal,
 //Here delay 45us          
    for(t=0;t<15;t++);  
 
 //Sampling response signal
 flag=DQ; 

 //The response signal is maintained for 60~240us
 // Here the delay is 300us, 
 for(t=0;t<100;t++);  
      
    return (flag); //Return the detection success flag
}

//Read a character from DS1820
uchar ReadOneChar()
{
 uchar i,t;
 uchar dat;
 for(i=0;i<8;i++)
 {
  dat>>=1;
 
  DQ=1; //c51 driver
  _nop_();
  
  DQ=0; //c51 driver

  _nop_(); //Delay 1 us to release the bus

  DQ=1; //c51 releases bus
  
  //DS1820 prepares data
  _nop_();
  _nop_();
  _nop_();
  _nop_();
  _nop_();

  //samplingif
  (DQ==1) //c51 samplingdat
   |=0x80; 
  else
   dat|=0x00;

  //It takes 60us to complete a read cycle, and the delay here is 60us.
  //One cycle is about 3us
  for(t=0;t<20;t++);
 }
 return dat;

}

//Write one byte to DS1820
WriteOneChar(uchar dat)
{
 uchar i,t;

 for(i=0;i<8;i++)
 {
  DQ=1; //c51 driver_nop_
  ();
  DQ=0; //c51 releases the bus

  //Starting from the low bit, the i-th bit of data is transmitted to the bus
  DQ=dat&0x01;  
  
  //DS1820 samples 15~60us after DQ=0.
  //So the delay is 60us,
  for(t=0;t<20;t++);

  //Prepare the next data
  dat>>=1;
 }
}

//Read temperature
void readtemp()
{

 InitDS1820();
 
 //Ignore DS1820 address
 WriteOneChar(0xcc); 

 //Start temperature conversion, time 750ms
 WriteOneChar(0x44); 

 //Delay 1000ms,
 delaynms(1000);

 InitDS1820();
 //Ignore DS1820 address
 WriteOneChar(0xcc); 
 //Read temperature
 WriteOneChar(0xbe); 

 TL=ReadOneChar();
 TH=ReadOneChar(); 
}

//Display temperature
void dispay()
{
 uchar b,s,g; //Represents hundreds, tens and ones
 uchar d1,d2; //1st and 2nd decimal places
 unsigned int ti,td;

 if(TH<0xfc)
 {
  //positive temperature
  flag=0;
  ti=TH*16+TL/16; //integer part
  td=TL%16; //decimal part
 
 //

 }
 else
 {
  //Negative temperature,
  flag=1;
  ti=TH*256+TL;
  ti=~ti+1;
  ti=ti/16;
  td=(~TL+1)%16;
 }
          
 g=ti%10 ;
 s=(ti%100)/10;
 b=ti/100;

 d1=td*10/16; // 1st decimal
 d2=td*100/16%10; // 2nd decimal

 //
 WriteData(digit[b]);

 WriteData(digit[s]);

 WriteData(digit[g]);

 WriteData('.'); 

 WriteData(digit[d1]);
 WriteData(digit[d2]);
}

//Initialize LCD
void InitLCD()
{
 delaynms(15); 
 WriteInstruction(0x38); //Display mode setting
 delaynms(5);
 WriteInstruction(0x38);
 delaynms(5);
 WriteInstruction(0x38);

 delaynms(5);
 WriteInstruction(0x0d); //Display mode setting: on display, no cursor, blinking cursor

 delaynms(5);
 WriteInstruction(0x06); //Display mode setting: cursor moves right, text does not move.

 delaynms(5);

 
}

//Write LCD instruction
void WriteInstruction(uchar instruction)
{
 //LCD is busy, waiting.
 while(BusyTest()==1);

 //Write instruction
 RS=0;
 RW=0;
 E=0;

 _nop_();
 _nop_();
 _nop_();

 //Instruction
 P1=instruction;

 _nop_();
 _nop_();
 _nop_();

 E=1;

 _nop_();
 _nop_();
 _nop_();

 E=0;
}

//Write LCD data
void WriteData(uchar d)
{
  //LCD is busy, waiting.
 while(BusyTest()==1);

 //Write data
 RS=1;
 RW=0;
 E=0;

 _nop_();
 _nop_();
 _nop_();

 //Instruction
 P1=d;

 _nop_();
 _nop_();
 _nop_();

 E=1;

 _nop_();
 _nop_();
 _nop_();

 E=0;

}

//Write address, belongs to write instruction
void WriteAdd(uchar ad)
{
 uchar addr=ad+0x80;
 WriteInstruction(addr);
 
}

//Read LCD status
uchar BusyTest()
{
 bit result;

 //Read LCD status
 RS=0;
 RW=1;
 E=1;

 _nop_();
 _nop_();
 _nop_();

 //Command
 result=BF;

 _nop_();
 _nop_();
 _nop_();

 E=0;

 return result;

}

void delaynms(uint s)
{
 uint tem;
 for(tem=0;tem  {
  delayms();
 }

}

//Delay 1ms
void delayms()
{
 uchar i;
 for(i=0;i<250;i++);
 for(i=0;i<80;i++);
}