MCU+LCD1602+HR-04 display screen shows the working principle of ultrasonic ranging

1. Basic working principle
(1) Use IO port TRIG to trigger ranging and give a high-level signal of at least 10us.
(2) The module automatically sends 8 40khz square waves and automatically detects whether there is a signal return.
(3) If there is a signal return, a high level is output through the IO port ECHO. The duration of the high level is the time from the ultrasonic wave to the return. The test distance = (high level time * sound speed (340M/s) / 2 (the time for the ultrasonic wave to be transmitted and returned, so it must be divided by 2))




2. Module physical picture

3. Driver
There is a link below the article. Since there is no HR04 module in proteus, another microcontroller can be used to simulate the HR-04 module during simulation, and then the microcontroller and the microcontroller communicate. Serial communication cannot be used because the ultrasonic ranging is using a timer for timing, and the baud rate setting uses timer 1. There is no way to use timer 1 to set the baud rate. The process is a bit troublesome, so I didn't build it, but the others are built.
4. Effect diagram
 

The AT89C52 microcontroller source program is as follows:

/*

Experimental description:

         STC89C52 Crystal: 12Mhz Module: HR04 LCD1602

        LCD1602 LCD module-->MCU pins

        Refer to the LCD1602 liquid crystal display experiment wiring (the experimental phenomenon in the corresponding experimental chapter of the development strategy has wiring instructions)

        Ultrasonic module-->MCU pins

        TRIG-->P21

        ECHO-->P20

        LCD1602_RW-->P2^5

        LCD1602_RS-->P2^6

    LCD1602_E-->P2^7

    Because there is no HR04 module in proteus, HR04 is an analog signal, we can use an analog signal to replace HR04, the processing method is the same

Experimental phenomena:

        The distance detected by ultrasonic wave is displayed on LCD1602 in mm.

        Only for communication and learning

*/

#include

#include         

#include "lcd.h"

sbit Trig = P2^1;

sbit Echo = P2^0;

unsigned char PuZh[]=" Pechin Science "; //Display distance

unsigned char code ASCII[15] = {'0','1','2','3','4','5','6','7','8','9','.','-','M'};

static unsigned char DisNum = 0; //display pointer                                 

       unsigned int time=0;

           unsigned long S=0;

           bit flag =0;

           unsigned char disbuff[4] ={ 0,0,0,0,};

/***********************************************************************************

* Function name: main

* Function: Main function

* Input: None

* Output: None

***********************************************************************************/

void Conut(void)

        {

         time=TH0*256+TL0;

         TH0=0;

         TL0=0;

         S=(time*1.7)/100; //The calculated value is CM

         if((S>=700)||flag==1) //Out of measurement range, display "-"

         {         

          flag=0;

          DisplayOneChar(0, 1, ASCII[11]);

          DisplayOneChar(1, 1, ASCII[10]); //Display dot

          DisplayOneChar(2, 1, ASCII[11]);

          DisplayOneChar(3, 1, ASCII[11]);

          DisplayOneChar(4, 1, ASCII[12]); //Display M

         }

         else

         {

          disbuff[0]=S%1000/100;

          disbuff[1]=S%1000%100/10;

          disbuff[2]=S%1000%10%10;

          DisplayOneChar(0, 1, ASCII[disbuff[0]]);

          DisplayOneChar(1, 1, ASCII[10]); //Display dot

          DisplayOneChar(2, 1, ASCII[disbuff[1]]);

          DisplayOneChar(3, 1, ASCII[disbuff[2]]);

          DisplayOneChar(4, 1, ASCII[12]); //Display M

         }

        }

void zd0() interrupt 1 //T0 interrupt is used for counter overflow, exceeding the ranging range

  {

    flag=1; //interrupt overflow flag

  }

void StartModule() //Start module

  {

          Trig=1; //Start the module once

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          _nop_();

          Trig=0;

  }

void delayms(unsigned int ms)

{

        unsigned char i=100,j;

        for(;ms;ms--)

        {

                while(--i)

                {

                        j=10;

                        while(--j);

                }

        }

}

void main(void)

{

         TMOD=0x01; //Set T0 to mode 1, GATE=1;

         TH0=0;

         TL0=0;         

         ET0=1; //Enable T0 interrupt

         EA=1; // Enable general interrupt        

        LcdInit();

        LcdShowStr(0,0,PuZh);

        while(1)

        {

                 StartModule();

             while(!Echo); //Wait when RX is zero

             TR0=1; //Start counting

             while(Echo); //When RX is 1 count and wait

             TR0=0; //Close the count

         Conut(); //Calculation

                 delayms(80);

        }

}