#include<c8051f020.h>
#include < intrins.h >
#include <absacc.h>
#include <stdio.h> 

#define SYSCLK       22118400          // SYSCLK frequency in Hz


sbit DataPortDS1820=P0^4;

void SYSCLK_Init (void);
void PORT_Init (void);


void SYSCLK_Init (void)
{
   	int i;                              // delay counter
   	OSCXCN = 0x67;                      // start external oscillator with
                                       // 18.432MHz crystal
   	for (i=0; i < 256; i++) ;           // Wait for osc. to start up
   	while (!(OSCXCN & 0x80)) ;          // Wait for crystal osc. to settle
   	OSCICN = 0x88;                      // select external oscillator as SYSCLK
}                                      // source and enable missing clock    
void PORT_Init (void)
{ 
 	XBR2=0x40;                     // Enable crossbar and weak pull-ups 
	P0MDOUT |=0xf0;
	P1MDOUT |=0xff;
	P2MDOUT |=0x0f;                        //P2低位弱上拉
//	P3MDOUT |=0xff;
}
void Delay1us(unsigned char us)
{
	while (us)
	{
	  _nop_(); _nop_(); _nop_(); _nop_(); _nop_();
	  --us;
	}
}
void Delay15us(void)  
{
	Delay1us(15);
}


void Delay10us(void)
{	
	Delay1us(10);
}

bit RstDS1820(void)  //返回0-有设备连接1-无设备连接
{
unsigned char i;
bit RstFlag;
	RstFlag=1;	
	DataPortDS1820=0;
	for (i=0;i<100/*40*/;i++)	//480us
		Delay15us(); 
	DataPortDS1820=1;
	for (i=0;i<4;i++)	//15us-60us
	{
		Delay15us();
	}
	for (i=0;i<16;i++)	//60us-240us
	{
		Delay15us();
		if (DataPortDS1820==0) RstFlag=0;
	}
	for (i=0;i<16;i++)	//240us
	{
		Delay15us();
	}
	return RstFlag;	
}

void WriteDS1820(unsigned char ch)
{
unsigned char i;
	DataPortDS1820=1;
	Delay1us(1);
	for (i=0;i<8;i++)
	{
		EA=0;
		DataPortDS1820=0;
		Delay15us();
		DataPortDS1820=ch&0x1;
		EA=1;
		Delay15us();Delay15us();Delay15us();
		DataPortDS1820=1;
		ch=ch>>1;
		Delay1us(1);
	}	
}

unsigned char ReadDS1820(void)
{
unsigned char i,ch;
	ch=0;
	DataPortDS1820=1;
	Delay1us(1);
	for (i=0;i<8;i++)
	{
		EA=0;
		DataPortDS1820=0;
		Delay10us();
		DataPortDS1820=1;
		Delay1us(2);
		ch=ch>>1;
		if (DataPortDS1820==1)
		{
			ch=ch+0x80;
		}
		EA=1;
		Delay15us();Delay15us();Delay15us();
	}	
	return ch;
}
void SkipROMCode(void)
{
	RstDS1820();
	WriteDS1820(0xcc); 
}
void StartADC(void)
{

	RstDS1820();		//复位
	WriteDS1820(0xcc);  //广播
	WriteDS1820(0x44); 	//启动AD转换 12bit700ms
}

unsigned int GetTempValue(void)
{
unsigned char i,j;
unsigned int T;
	SkipROMCode();
	WriteDS1820(0xBE); 
	i=ReadDS1820();
	j=ReadDS1820();
	StartADC();
	T=i+j*256;
	if (T==0xffff) return 0xffff;
	if (T>0x8000) 
	{
		T=-T;
		return (0x8000+T*5/8);
	}
	else
		return (T*5/8);
}
void main(void)
{
	unsigned int w;
	WDTCN = 0xde;
	WDTCN = 0xad;
    SYSCLK_Init();
	PORT_Init();
//	w= GetTempValue();
	while(1)
	{
		Delay1us(100);
		w= GetTempValue();
	}
}