ds1820_temp.c

This code it to make a temperature sensor using 8051 microcontroller. It s an Embedded System projec

//---------------------------------------
// Interfacing DS1820 and LCD
// To AT89S51
// KEIL C51 v7.5
// www.HBeonLabs.com
//---------------------------------------
#include<reg51.h>

sbit RS=P3^7;   	//lcd instruction/data
sbit EN=P3^6;   	// lcd enable
sbit DQ=P3^5;		// connect with DS1820 Data pin

sbit fan=P3^0;
sbit heater=P3^1;

void DelayMs(unsigned int count); 
void ReadTemp(unsigned char * buff);
void ConvertAndDisplay(unsigned char value1,value2);
void display(unsigned char s,t,u,v);
void lcdData(unsigned char l);
void lcdcmd(unsigned char k);
void lcdinit(void);
void lcdhdr(void);

unsigned char MyTemp[9]; 

//---------------------------------------
// Main program
//---------------------------------------
void main(void)
{
    unsigned char tp,tpd;
	lcdinit(); 		// Initialize lcd
	lcdhdr();		// call lcd header
	fan=0;
	heater=0;
		
	while(1)
	{
		ReadTemp(&MyTemp[0]);    
		tp  = MyTemp[0] >> 1;	
		tpd = ((MyTemp[0])& 0x01) ? 5:0;	
  		ConvertAndDisplay(tp,tpd);
		
		if(MyTemp[0]>0x46)
		{
		fan=1;
		heater=0;
		}
		else if(MyTemp[0]<0x3C)
		{
		fan=0;
		heater=1;
	    }
		else
		{
		fan=0;
		heater=0;
		}	
	}
}

//---------------------------------------
// Lcd initialization subroutine
//---------------------------------------
void lcdinit(void)
{
lcdcmd(0x38);
DelayMs(20);
lcdcmd(0x0E);
DelayMs(20);
lcdcmd(0x01);
DelayMs(20);
lcdcmd(0x06);
DelayMs(20);
lcdcmd(0x80);
DelayMs(20);
}

//---------------------------------------
// Lcd header
//---------------------------------------
void lcdhdr(void)
{
unsigned char i=0,w[]="TEMP=      CENT";
while(w[i]!='\0')
{
lcdData(w[i]);
i++;
DelayMs(50);
}
}

//---------------------------------------
// Lcd display
//---------------------------------------
void display(unsigned char s,t,u,v)
{
s=s+0x30;			//convert each digit to equivalent ASCII value
t=t+0x30;
u=u+0x30;

v=v+0x30;
			
lcdcmd(0x85);		//Move the cursor to position 5 on LCD
DelayMs(50);

lcdData(u);			//Display the digits one by one on LCD
DelayMs(50);
lcdData(t);
DelayMs(50);
lcdData(s);
DelayMs(50);
lcdData('.');		//Display decimal point on LCD
DelayMs(50);
lcdData(v);
DelayMs(50);
}

//---------------------------------------
// Lcd data display
//---------------------------------------
void lcdData(unsigned char l)
{
P2=l;
RS=1;
EN=1;
DelayMs(1);
EN=0;
return;
}

//---------------------------------------
// Lcd command
//---------------------------------------
void lcdcmd(unsigned char k)
{
P2=k;
RS=0;
EN=1;
DelayMs(1);
EN=0;
return;
}

//---------------------------------------
// Conver and Display the data on LCD
//---------------------------------------
void ConvertAndDisplay(unsigned char value1, value2)
{
unsigned int i,a=0;
unsigned char d1,d2,d3,d4;
for(i=0;i<value1;i++)
a=a+1;

d1=a%10;		//digits before desible point
a=a/10;
d2=a%10;
a=a/10;
d3=a%10;

d4=value2;

display(d1,d2,d3,d4);
}
			   

//---------------------------------------
// Delay mS function
//---------------------------------------
void DelayMs(unsigned int count) 
{  // mSec Delay 11.0592 Mhz 
    unsigned int i;		      // Keil v7.5a 
    while(count) {
        i = 115; 
		while(i>0) i--;
        count--;
    }
}


//----------------------------------------
// DELAY at 11.0592MHz crystal.
// Calling the routine takes about 22us, and then
// each count takes another 17us.
// test with KEIL C51 V7.5
//----------------------------------------
void DelayUs(int us)
{
	int i;
	for (i=0; i<us; i++);
}

//----------------------------------------
// Reset DS1820
//----------------------------------------
bit ResetDS1820(void)
{
	bit presence;
	DQ=0; 			//pull DQ line low
	DelayUs(29); 		// leave it low for about 490us
	DQ=1; 			// allow line to return high
	DelayUs(3); 		// wait for presence 55 uS
	presence = DQ; 		// get presence signal
	DelayUs(25); 		// wait for end of timeslot 316 uS 
	return(presence); 	// presence signal returned
} 				// 0=presence, 1 = no part

//-----------------------------------------
// Read one bit from DS1820
//-----------------------------------------
bit ReadBit(void)
{
	unsigned char i=0;
	DQ=0;			// pull DQ low to start timeslot
	DQ=1;
	for (i=0; i<3; i++); 	// delay 17 us from start of timeslot
	return(DQ); 		// return value of DQ line
}

//-----------------------------------------
// Write one bit to DS1820
//-----------------------------------------
void WriteBit(bit Dbit)
{
	unsigned char i=0;	
    DQ=0;	
	DQ=Dbit ? 1:0;
	DelayUs(5); 		// delay about 39 uS
	DQ=1;
}

//-----------------------------------------
// Read 1 byte from DS1820
//-----------------------------------------
unsigned char ReadByte(void)
{
	unsigned char i;
	unsigned char Din = 0;
	for (i=0;i<8;i++)
	{
		Din|=ReadBit()? 0x01<<i:Din;
		DelayUs(6); 
	}
	return(Din);
}

//-----------------------------------------
// Write 1 byte
//-----------------------------------------
void WriteByte(unsigned char Dout)
{
	unsigned char i;
	for (i=0; i<8; i++) 			// writes byte, one bit at a time
	{	    
		WriteBit((bit)(Dout & 0x1)); 	// write bit in temp into
		Dout = Dout >> 1;
	}
	DelayUs(5);
}

//-----------------------------------------
// Read temperature
//-----------------------------------------
void ReadTemp(unsigned char * buff)
{
	unsigned char n;
	
	EA=0;			// disable all interrupt
	ResetDS1820();
    WriteByte(0xcc);  		// skip ROM
    WriteByte(0x44);  		// perform temperature conversion
    while (ReadByte()==0xff); 	// wait for conversion complete	
    ResetDS1820();
    WriteByte(0xcc);  		// skip ROM
    WriteByte(0xbe);  		// read the result
    
    for (n=0; n<9; n++)     	// read 9 bytes but, use only one byte
    {
       buff[n]=ReadByte(); 	// read DS1820
    }
	EA=1;

}