可以测当前距离，当超过阈值距离时，蜂蜜器报警，并且实时显示温度数据，51单片机超声波测距C语言程序

制作出来的实物图如下：

源代码资料下载 ： www.dzkfw.com.cn/Soft/mcu/92.html

 
51单片机超声波测距C语言程序部分代码如下:

#include
#include 
#define uchar unsigned char
#define uint unsigned int
int num=0;
unsigned char table[]={"0123456789"};//显示的数值
//   1602的引脚定义
sbit RW=P2^5; 
sbit RS=P2^6;  
sbit E=P2^7;   
//报警引脚定义
sbit feng=P2^4;
sbit led=P1^2;
sbit key1=P1^0;
sbit key2=P1^1;
int numm=0,nnum=0;
void delayms(unsigned int ms)
{
        unsigned char i=100,j;
        for(;ms;ms--)
        {
                while(--i)
                {
                        j=10;
                        while(--j);
                }
        }
}
bit flag;           //温度变量
uint temp;
sbit ds=P1^3;  //温度引脚
//超声波位定义
sbit Trig = P2^1;
sbit Echo = P2^0;
uint time=0;
unsigned long S=0;
bit flagg=0;
void delay2(uchar p)
        {
          uchar l,k;
           for(l=p;l>0;l--)
              for(k=110;k>0;k--);
        }
void delay(uchar z)
{
    while(z--);
}
//温度初始化函数                        
void ds_reste()          
{
        ds=1;
        delay(5);
        ds=0;
        delay(80);
        ds=1;
        delay(14);
        if(ds==0)                 //判断ds总线被拉低
        flag=1;
        else 
        flag=0;
        delay(20);
}
//读一位字节
bit ds_read_byte()        
{
         bit dat;
         ds=0;                
         _nop_();
         _nop_();
         ds=1;
         _nop_();
         dat=ds;         
         delay(10);
         return dat;
}
//读一位字节
uchar ds_read()        
{
        uchar i,j,k;
      for(i=0;i<8;i++)
        {
        j=ds_read_byte();
        k=(j<<7)|(k>>1);
        }
         return k;
}
//写入数据
void ds_write(uchar dat)
{
         uchar i;
         for(i=0;i<8;i++)
    {
         ds=0;
         _nop_();
         ds=dat&0x01;
         delay(6);
         ds=1;
         dat=dat>>1;
        }
         delay(6);
}
//读取温度
uint read_temp()          
{
        uchar a,b;
        ds_reste();
        ds_write(0xcc);
        ds_write(0xbe);
        a=ds_read();
        b=ds_read(); 
        temp=b;
        temp=temp<<8;
        temp=temp|a;
        temp=temp*0.0625*10+0.5;                 
        return temp;
} 
//写入命令1602
void write_com(uchar com)           
{
        RS=0;
        RW=0;
        E=0;
        P0=com;           
        delay2(5);
        E=1;
        delay2(5);
        E=0;
}
//写入数据 1602
void write_data(uchar date)        
{
        RS=1;
        RW=0;
        E=0;
        P0=date;                
        delay2(5);
        E=1;
        delay2(5);
        E=0;
}
//1602初始化显示
void init()                                 
{
    RS=0;
        write_com(0x38);
         write_com(0x0c);
         write_com(0x06);
        write_com(0x01);
        write_com(0x80);
}
//温度在1602上显示出来
void display(uint tempp)           
{  
         write_com(0x80+0x0b);                         
         write_data(table[tempp/100]);         
         delay2(0);
         write_com(0x80+0x0c);
         write_data(table[tempp%100/10]);           
         delay2(0);        
            write_com(0x80+0x0d);
         write_data('.');                           
         delay2(0);
            write_com(0x80+0x0e);
         write_data(table[tempp%100%10]);
         delay2(0);                                                         
         write_com(0x80+0x0f);
         write_data('C');                                    
         delay2(0);
         write_com(0x80+0x09);
         write_data('T');                                    
         delay2(0);
         write_com(0x80+0x0a);
         write_data(':');                                  
         delay2(0);
}