[Blue Bridge Road -- bug free code] DS18B20 temperature reading code analysis

adopt DS18B20 Measure the outside temperature and display it on the nixie tube , The temperature value should be accurate to the decimal point 2 position

main.c

#include"STC15F2K60S2.h"
#include"onewire.h"
#include"intrins.h"

typedef unsigned char uchar;
typedef unsigned int uint;

uchar dsp_code[]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90};
uchar dsp_Temp[8]={0xff,0xff,0xff,0xff};

uint temp;
uchar count_temp;

void Timer_Init()
{
	AUXR|= 0x80;
	TMOD&= 0xf0;
	TL0=0xcd;
	TH0=0xd4;
	TR0=1;
	ET0=1;
	EA=1;
}

void serviceTimer() interrupt 1
{
	static uchar dsp_com=0;

	P0=0;P2=0xc0;P2=0;

	P0=dsp_Temp[dsp_com];P2=0xe0;P2=0;

	P0=1<<dsp_com;P2=0xc0;P2=0;

	if(++dsp_com==8)dsp_com=0;

	++count_temp;
}

void Initsystem()
{
	P0=0xff;P2=0x80;P2=0;
	P0=0x00;P2=0xa0;P2=0;
}

void main()
{
	char i=0;
	Initsystem();
	for(i=0;i<70;i++)
	{
		temp=read_temp()*100+0.5;
	}
	Timer_Init();
	while(1)
	{
		if(count_temp>759)
		{
			count_temp=0;
			temp=read_temp()*100+0.5;
		}
	dsp_Temp[4]=dsp_code[temp/1000];
	dsp_Temp[5]=dsp_code[temp/100%10]&0x7f;
	dsp_Temp[6]=dsp_code[temp/10%10];
	dsp_Temp[7]=dsp_code[temp%10];
	}
}

onewire.c

/*
   Program description :  Single bus driver 
   Software environment : Keil uVision 4.10 
   Hardware environment : CT107 SCM comprehensive training platform ( External crystal oscillator 12MHz) STC89C52RC Single chip microcomputer 
   Japan      period : 2011-8-9
*/
#include "reg52.h"
#include"onewire.h"
#include"intrins.h"

sbit DQ = P1^4;  // Single bus interface 

// Single bus delay function 
void Delay_OneWire(unsigned int t);  //STC89C52RC

// Through a single bus to DS18B20 Write a byte 
void Write_DS18B20(unsigned char dat)
{
	unsigned char i;
	for(i=0;i<8;i++)
	{
		DQ = 0;
		DQ = dat&0x01;
		Delay_OneWire(5);
		DQ = 1;
		dat >>= 1;
	}
	Delay_OneWire(5);
}

// from DS18B20 Read a byte 
unsigned char Read_DS18B20(void)
{
	unsigned char i;
	unsigned char dat;
  
	for(i=0;i<8;i++)
	{
		DQ = 0;
		dat >>= 1;
		DQ = 1;
		if(DQ)
		{
			dat |= 0x80;
		}	    
		Delay_OneWire(5);
	}
	return dat;
}

//DS18B20 Device initialization 
bit init_ds18b20(void)
{
  	bit initflag = 0;
  	
  	DQ = 1;
  	Delay_OneWire(12);
  	DQ = 0;
  	Delay_OneWire(80);
  	DQ = 1;
  	Delay_OneWire(10); 
    initflag = DQ;     
  	Delay_OneWire(5);
  
  	return initflag;
}

void Delay_Onewire(unsigned int t)
{
	t*=11;
	while(t--);
}

float read_temp()
{
	float temp;
	unsigned char low,high;

	init_ds18b20();
	Write_DS18B20(0xcc);
	Write_DS18B20(0x44);
	Delay_OneWire(200);

	init_ds18b20();
	Write_DS18B20(0xcc);
	Write_DS18B20(0xbe);
	low=Read_DS18B20();
	high=Read_DS18B20();
	temp=(high<<8|low)*0.0625;

	return temp;
}

 onewire.h

#ifndef __ONEWIRE_H
#define __ONEWIRE_H

float read_temp();
bit init_ds18b20(void);
unsigned char Read_DS18B20(void);
void Delay_OneWire(unsigned int t);
void Write_DS18B20(unsigned char dat);
unsigned char rd_temperature(void);  //; ;

#endif