STC89C52RC MCU Ultrasonic Distance Measurement Program

The STC89C52RC single-chip ultrasonic ranging program and electronic production object collected on the Internet are tested using the single-chip minimum system. The ultrasonic part uses the HC-SR04 module, with a measurement range of 4-300cm. The actual measurement can reach up to 5.70m. The following is a physical picture, and the source program is attached at the end of the article.

4-300cm, the longest actual measurement can reach 5.7m

#include 'AT89X51.H' //header file

unsigned char code fseg[]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90};

unsigned char code segbit[]={0x80,0x40,0x20,0x10,0x08,0x04,0x02,0x01};

unsigned char disbuf[8]={0,0,0,0,0,0,0,0};

//------------------------------------------------ --------------------------

// Function prototype definition

#define uchar unsigned char

#define uint unsigned int

void main (void); // Main function

void LED4_Display (void); // LED display

void LED_OUT(uchar X); //LED single byte serial shift function

void delayms(uint); //delay sub-function ms

void jisuan(void);

unsigned char code LED_0F[]; //LED font table

sbit DIO=P1^0; //Serial data input

sbit RCLK=P1^1; //Clock pulse signal——rising edge is valid

sbit SCLK=P1^2; //Input signal————Rising edge is valid

sbit echo=P3^2; //echo

sbit trig=P3^3; //trig

//------------------------------------------------ --------------------------

// Global variables

uchar LED[8]; //8-bit display buffer for LED

uint temp;                                                                                        

uint temp1;

uint a,b; //define a variable a, b, the latter is used to determine whether the signal is received

//

// Main program

//

void main(void) //main function starts

{    

        uint f;

    echo=0; //Pull down the echo and trig pins first

    trig=0;

        f=500;

    while(f>0); //Start delay to eliminate the fluctuation caused by the first power-on

        {

           LED[3]=16;

      LED[2]=15;

      LED[1]=15;

      LED[0]=16;

         f--;

       }

    EA=1; //Open the general interrupt

    TMOD=0x11; //Set the timer to mode 1

    ET0=1; //Enable timer interrupt This is mainly to prevent the ultrasonic module from not sending a signal

    ET1=1;

    while(1)

    {

        echo=0;//a assignment

        a=0;        

        b=1;

        TH0=0; //Initial value of timer

        TL0=0;

        TH1=(65536-25000)/256; //Timer initial value

        TL1=(65536-25000)%6;

        trig=1; //trig sends high

        LED4_Display (); // Delay 3ms

        LED4_Display();

        LED4_Display();

        LED4_Display();

        LED4_Display();

        LED4_Display();

        LED4_Display();

        trig=0; //trig is sent low

        TR1=1;

        while(echo==0); //Wait for echo to become high level

                if(b==1) determines whether the signal is received

        {

            TR1=0; //Turn off timer 1

            EX0=1; //Open external interrupt

            TR0=1; //Start the timer

            while(a==0); //Note here! a is assigned 0 before. The program stops here and waits for interruption.

//Originally I added a screen scanning program here, but I found a major BUG so I deleted it  

        }

        else

        {

            LED[3]=16;

            LED[2]=15;

            LED[1]=15;

            LED[0]=16;

        LED4_Display();

        LED4_Display();

        LED4_Display();

        LED4_Display();

        LED4_Display();

        LED4_Display();

        }

    }

}

void waibu() interrupt 0 //External interrupt service subroutine

{

    temp=TH0; //Get the value of the timer

    temp1=TL0;                                                                                    

    EX0=0; //Disable external interrupt

    TR0=0; //Turn off the timer

    jisuan(); //Run calculation subroutine

    a=1; //a is assigned a value of 1. The program returns to while(a) because the value of a has become 1, and the program starts from the beginning.

}

void time1() interrupt 1 //Timer interrupt service subroutine

{

    TH0=0; //Reload initial value

    TL0=0;

}

void time2() interrupt 3

{

    TR1=0;

    TH0=(65536-25000)/256; //Timer initial value

    TL0=(65536-25000)%6;

    b=0;

    echo=1;

}

void jisuan(void) //Calculation subroutine

{

    uint c,d; //define a variable c, d to determine the distance

    c=0; //assign value 0

    d=0; //Reassign value to b

    LED4_Display (); //Scan the digital tube

    temp=(temp<<8)+temp1; //TH0 TL0 merge

    temp=temp/5; //I didn't calculate it exactly, so I just divided it by 5 to get an approximate value

    if(temp>40) //Judge whether the distance is too close

        {

            c=1;

        }

        LED4_Display (); //Scan the digital tube

    if(temp<40)

        {

         c=0;

        }

        LED4_Display();

        if(temp<3000) //Judge whether the distance is too far

        {

            d=1;

        }

        LED4_Display();

    if(temp>3000)

        {

         d=0;

        }

    c=c&d; //AND operation

    if(c==1) //Judge whether the distance is normal

        {

            LED[3]=temp/1000; //Separate display of values

            LED[2]=temp00/100;

            LED[1]=(temp000/10)+20; //Why do we need to add 20? Because this is the unit digit and needs to display a decimal point  

            LED[0]=temp000;

        }

    if(c==0) //Judge whether the distance is normal

        {

            LED[3]=16;

            LED[2]=14;

            LED[1]=14;

            LED[0]=16;

        }

}

void delayms(uint xms) //delay sub-function ms

    {

        uint i,j;

        for(i=xms;i>0;i--)

            for(j=110;j>0;j--);

    }

    //The following program is the hc595 module display program

    //The program of each module can be transplanted to the routine of the data

    //

void LED4_Display (void) //Screen scanning sub-function   

{

    unsigned char code *led_table; // table pointer

    uchar i;

    // Display the first

    led_table = LED_0F + LED[0];

    i = *led_table;

    LED_OUT(i);            

    LED_OUT(0x01);        

    RCLK = 0;

    RCLK = 1;

    //Display the second digit

    led_table = LED_0F + LED[1];

    i = *led_table;

    LED_OUT(i);        

    LED_OUT(0x02);        

    RCLK = 0;

    RCLK = 1;

    //Display the 3rd digit

    led_table = LED_0F + LED[2];

    i = *led_table;

    LED_OUT(i);            

    LED_OUT(0x04);    

    RCLK = 0;

    RCLK = 1;

    //Display the 4th digit

    led_table = LED_0F + LED[3];

    i = *led_table;

    LED_OUT(i);            

    LED_OUT(0x08);        

    RCLK = 0;

    RCLK = 1;

}

void LED_OUT(uchar X)

{

    uchar i;

    for(i=8;i>=1;i--)

    {

        if (X&0x80) DIO=1; else DIO=0;

        X<<=1;

        SCLK = 0;

        SCLK = 1;

    }

}

//The following is the display array

unsigned char code LED_0F[] = 

{// 0 1 2 3 4 5 6 7 8 9 A b C d E F - .

   0xc0,0xF9,0xA4,0xB0,0x99,0x92,0x82,0xF8,0x80,0x90,0x8C,0xBF,0xC6,0xA1,0x86,0x8e,0xbf,0x7f,0x00,0x00,

// 20 21 22 23 24 25 26 27 28 29 30

    0x40,0x79,0x24,0x30,0x19,0x12,0x12,0x78,0x00,0x10,0xbf,

};