18b20.c

数码管显示温度与时间

#include <at89x52.h>
#include <intrins.h>
#define  uchar    unsigned char
#define  uint     unsigned int
 bit ready;
sbit Q=P2^7;
void delay_t (uint tt)
{
 while (tt--);
}
//复位18B20
void init_18b20 (void)
{
 Q=1;
 _nop_ ();
 Q=0;
 delay_t (160);
 Q=1;
 delay_t (9);
 ready=Q;
 delay_t (100);

}
//写入BYTE到18B20
void w_18b20 (uchar dat)
{
 unsigned char i;
	for(i=8;i;i--)
	{
		Q=0;
		Q=dat&0x01;
		delay_t(5); //延时61us（在I/O线由高电平变为低电平之后DS1820在15us~60us之间对 I/O 线采样）
		Q=1;
		dat>>=1;
	}
}
//读入数据
uchar r_18b20 (void)
{
 unsigned char i,dat=0;
	for(i=8;i;i--)
	{
	Q=0;
	dat>>=1;
	Q=1;
	if(Q)
	dat|=0x80;
	delay_t(5);
  }
  return dat;
}
get_18b20 (void)
{
  uint Low,Hight,a;
  float T;
  init_18b20 ();
  w_18b20 (0xcc);
  w_18b20 (0x44);
  delay_t (120);
  init_18b20 ();
  w_18b20 (0xcc);
  w_18b20 (0xbe);
  Low=r_18b20 ();
  Hight=r_18b20 ();
  a=Hight;
  a=a<<8;
  T=(a|Low)*0.0625*100;			
  return T; 
}