/*超聲波測距.
*/

#include <AT89X51.H>
#include <intrins.h>
const char LED[]=		//定義LED數碼管顯示數字.常量（不帶點）
{0x84, 0xF6, 0x4C, 0x64, 0x36, 0x25, 0x05, 0xF4, 0x04, 0x24};
const char LED_P[]=	//定義LED數碼管顯示數字.常量（帶點）
{0x80, 0xF2, 0x48, 0x60, 0x32, 0x21, 0x01, 0xF0, 0x00, 0x20};
char Bai,Shi,Ge;//數碼管顯示位
unsigned long int JuLi;//距離
unsigned char Gao,Di;//存儲計時器高位，低位
void ChuShiHua();//初始化
void FaShe();//發射聲波
void Shou();//接收外部中斷程序
void XianShi();//掃描掃描程序（計時器中斷）
void Deng();//空等待


//主程序------------------------------------------------------
main()
{
	ChuShiHua();
	while (1)
	{
		FaShe();
		Deng();
	}
}
//初始化------------------------------------------------------
void ChuShiHua()
{
	IE = 0x88;		//開T1中斷
	TMOD = 0x01;	//定時器1模式0，定時器0模式1
	PX0 = 1; 	//INT0高優先級
	PT1 = 0;	//T1  低級中斷
	IT0 = 0; 	//INT0電平觸發0
	TR1 = 1; 	//啟動定時器1
}

//空等待------------------------------------------------------
void Deng()
{
	unsigned int i,j;
	for (i = 0; i < 100; i++)
		for (j = 0; j < 100; j++);
}

//發射方波----------------------------------------------------
void FaShe()
{
	unsigned int counter;
	IE = 0;		//關中斷
	TH0 = 0;
	TL0 = 0; //計數器清零
	TR0 = 1; //啟動計算器；
	for (counter = 0;counter < 16; )
	{
P1 = P1 ^ 0x80;
_nop_();_nop_();_nop_();_nop_();_nop_();_nop_();_nop_();_nop_();_nop_();_nop_();_nop_();_nop_();_nop_();_nop_();_nop_();
      counter++;
	}
	P1_7 = 1;
	for (counter = 0;counter < 300; counter++) _nop_();//2.1315
	IE = 0x89;	//開中斷
}

//收，外部中斷程序---------------------------------------------
void Shou() interrupt 0 //外部中斷INT0
{
	IE = 0x00;		//關中斷
	JuLi = 0;
	TR0 = 0;
	Gao = TH0;
	Di = TL0;	
	JuLi = JuLi | Gao;
	JuLi = JuLi << 8;
	JuLi = JuLi | Di;
	JuLi = JuLi - 44;
	JuLi = JuLi * 85;
	JuLi = JuLi/10000;
	Bai = JuLi / 100;
	Shi = (JuLi - (Bai*100))/10;
	Ge = JuLi%10;
	IE = 0x88;	//關int0中斷，開顯示中斷
}

//顯示中斷程序------------------------------------------------
void XianShi() interrupt 3 //定時器中斷1
{
	static char xian_shi_wei = 0; //顯示位
	TH1 = TL1 = 0;	
	if (xian_shi_wei >= 3)
		xian_shi_wei = 0;
	P0 = 0xFF; //全關了
	switch (xian_shi_wei) //開下一個
	{
	case 0:
		P0_2 = 0;
		P2 = LED_P[Bai];
		break;
	case 1:
		P0_1 = 0;
		P2 = LED[Shi];
		break;
	case 2:
		P0_0 = 0;
		P2 = LED[Ge];
		break;
	}
	xian_shi_wei++;
}
//------------------------------------------------------------