interfacing ultrasonic sensors

Rahul Kumar Vashistha · Mar 5, 2015

guys please help me out!
i am trying to interface two ultrasonic sensors(HC-SR04) with pic16f877a and accordingly have written the code as shown below:-

Code C - [expand]
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#define _XTAL_FREQ 8000000
 
#define RS RD2
#define EN RD3
#define D4 RD4
#define D5 RD5
#define D6 RD6
#define D7 RD7
 
#include <xc.h>
#include <pic16f877a.h>
void Lcd_Port(char a);
void Lcd_Cmd(char a);
void Lcd_Set_Cursor(char a, char b);
Lcd_Clear();
void Lcd_Init();
void Lcd_Write_String(char *a);
void Lcd_Shift_Right();
void Lcd_Shift_Left();
void Lcd_Write_Char(char a);
void sendo();
 
// BEGIN CONFIG
#pragma config FOSC = HS // Oscillator Selection bits (HS oscillator)
#pragma config WDTE = OFF // Watchdog Timer Enable bit (WDT enabled)
#pragma config PWRTE = OFF // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = ON // Brown-out Reset Enable bit (BOR enabled)
#pragma config LVP = OFF // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3 is digital I/O, HV on MCLR must be used for programming)
#pragma config CPD = OFF // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)
#pragma config WRT = OFF // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)
#pragma config CP = OFF // Flash Program Memory Code Protection bit (Code protection off)
//END CONFIG
 
int a;
 
void interrupt echo()
{
  if(RBIF == 1)                 //Makes sure that it is PORTB On-Change Interrupt
  {
    RBIE = 0;                   //Disable On-Change Interrupt
    if(RB4==1 && RB5==1)   
{
      TMR1ON = 1;
      if((RB4==0)|| (RB5==0))
     TMR1ON=0;  
     a = (TMR1L | (TMR1H<<8))/58.82;
      a=a+1;
    if(a>=2 && a<=400)          
    {
      Lcd_Clear();
        Lcd_Set_Cursor(1,1);
      Lcd_Write_String("Speedbreaker");
      Lcd_Set_Cursor(2,1);
      Lcd_Write_String("Distance = ");
      
      Lcd_Set_Cursor(2,14);
      Lcd_Write_Char(a%10 + 48);
 
      a = a/10;
      Lcd_Set_Cursor(2,13);
      Lcd_Write_Char(a%10 + 48);
 
      a = a/10;
      Lcd_Set_Cursor(2,12);
      Lcd_Write_Char(a%10 + 48);
 
      Lcd_Set_Cursor(2,15);
      Lcd_Write_String("cm");
    }
    else
    {
      Lcd_Clear();
      Lcd_Set_Cursor(1,1);
      Lcd_Write_String(" of Range");
    }
    __delay_ms(400);        
        //sendo();
 }                          
    if(RB4 == 1 || RB5==1)                  
    {
      TMR1ON = 1;                    
     }
   if(RB4==0 || RB5==0)              
    {
      TMR1ON = 0;                    //Stop Timer
      a = (TMR1L | (TMR1H<<8))/58.82;  //Calculate Distance
    }
  }
  RBIF = 0;                     //Clear PORTB On-Change Interrupt flag
  RBIE = 1;                     //Enable PORTB On-Change Interrupt
}
 
 
void main()
{
  TRISB = 0b00110000;   //RB4 as Input PIN (ECHO)
  TRISD = 0x00; // LCD Pins as Output
  GIE = 1;                      //Global Interrupt Enable
  RBIF = 0;                     //Clear PORTB On-Change Interrupt Flag
  RBIE = 1;                     //Enable PORTB On-Change Interrupt
 
  Lcd_Init();
 
  Lcd_Set_Cursor(1,1);
  Lcd_Write_String("yo");
  Lcd_Set_Cursor(2,1);
  Lcd_Write_String("mAn");
 
  __delay_ms(3000);
  Lcd_Clear();
 
  T1CON = 0x10;                 //Initialize Timer Module
 
  while(1)
  {
    TMR1H = 0;                  //Sets the Initial Value of Timer
    TMR1L = 0;                  //Sets the Initial Value of Timer
 
    RB0 = 1;               //TRIGGER HIGH
    __delay_us(10);               //10uS Delay
    RB0 = 0;               //TRIGGER LOW
 
    __delay_ms(100); //Waiting for ECHO
    a = a + 1; //Error Correction Constant
 
    if(a>=2 && a<=400)          //Check whether the result is valid or not
    {
      Lcd_Clear();
      Lcd_Set_Cursor(1,1);
      Lcd_Write_String("Distance = ");
      
      Lcd_Set_Cursor(1,14);
      Lcd_Write_Char(a%10 + 48);
 
      a = a/10;
      Lcd_Set_Cursor(1,13);
      Lcd_Write_Char(a%10 + 48);
 
      a = a/10;
      Lcd_Set_Cursor(1,12);
      Lcd_Write_Char(a%10 + 48);
 
      Lcd_Set_Cursor(1,15);
      Lcd_Write_String("cm");
    }
    else
    {
      Lcd_Clear();
      Lcd_Set_Cursor(1,1);
      Lcd_Write_String("Out of Range");
    }
    __delay_ms(400);
  }
}
//LCD Functions
 
 
void Lcd_Port(char a)
{
    if(a & 1)
        D4 = 1;
    else
        D4 = 0;
 
    if(a & 2)
        D5 = 1;
    else
        D5 = 0;
 
    if(a & 4)
        D6 = 1;
    else
        D6 = 0;
 
    if(a & 8)
        D7 = 1;
    else
        D7 = 0;
}
void Lcd_Cmd(char a)
{
    RS = 0;             // => RS = 0
    Lcd_Port(a);
    EN  = 1;             // => E = 1
        __delay_ms(4);
        EN  = 0;             // => E = 0
}
 
Lcd_Clear()
{
    Lcd_Cmd(0);
    Lcd_Cmd(1);
}
 
void Lcd_Set_Cursor(char a, char b)
{
    char temp,z,y;
    if(a == 1)
    {
      temp = 0x80 + b - 1;
        z = temp>>4; //10000000,z=00001000 
        y = temp & 0x0F; //10000000 & 00001111 = 0
        Lcd_Cmd(z);//
        Lcd_Cmd(y);
    }
    else if(a == 2)
    {
        temp = 0xC0 + b - 1; //11000000
        z = temp>>4;//00001100
        y = temp & 0x0F;//0000
        Lcd_Cmd(z);//0X0C
        Lcd_Cmd(y);//0x00
    }
}
 
void Lcd_Init()
{
  Lcd_Port(0x00);
   __delay_ms(20);
  Lcd_Cmd(0x03);
    __delay_ms(5);
  Lcd_Cmd(0x03);
    __delay_ms(11);
  Lcd_Cmd(0x03);
 
  Lcd_Cmd(0x02);
  Lcd_Cmd(0x02);
  Lcd_Cmd(0x08);
  Lcd_Cmd(0x00);
  Lcd_Cmd(0x0C);
  Lcd_Cmd(0x00);
  Lcd_Cmd(0x06);
}
 
void Lcd_Write_Char(char a)
{
   char temp,y;
   temp = a&0x0F;
   y = a&0xF0;
   RS = 1;             // => RS = 1
   Lcd_Port(y>>4);             
   EN = 1;
   __delay_us(40);
   EN = 0;
   Lcd_Port(temp);
   EN = 1;
   __delay_us(40);
   EN = 0;
}
 
void Lcd_Write_String(char *a)
{
    int i;
    for(i=0;a[i]!='\0';i++)
       Lcd_Write_Char(a[i]);
}
 
void Lcd_Shift_Right()
{
    Lcd_Cmd(0x01);
    Lcd_Cmd(0x0C);
}
 
void Lcd_Shift_Left()
{
    Lcd_Cmd(0x01);
    Lcd_Cmd(0x08);
}
 
 
/*void sendo()
{
    if(RB4!=1)
    {
     TMR1ON=0;  
     a = (TMR1L | (TMR1H<<8))/58.82;
    }
    if(a>=2 && a<=400)         
    {
      Lcd_Clear();
        Lcd_Set_Cursor(1,1);
      Lcd_Write_String("Speedbreaker");
      Lcd_Set_Cursor(2,1);
      Lcd_Write_String("Distance = ");
      
      Lcd_Set_Cursor(2,14);
      Lcd_Write_Char(a%10 + 48);
 
      a = a/10;
      Lcd_Set_Cursor(2,13);
      Lcd_Write_Char(a%10 + 48);
 
      a = a/10;
      Lcd_Set_Cursor(2,12);
      Lcd_Write_Char(a%10 + 48);
 
      Lcd_Set_Cursor(2,15);
      Lcd_Write_String("cm");
    }
    else
    {
      Lcd_Clear();
      Lcd_Set_Cursor(1,1);
      Lcd_Write_String(" of Range");
    }
    __delay_ms(400);
 }

tried simulating in proteus but i am getting undesired o/p.
please help..

milan.rajik · Mar 5, 2015

Try using INTx pin and just toggle the INTEDGx when echo is received. Also use a timer interrupt that is when low to high edge is detected, start timer and when high to low edge is detected, stop the timer. additionally use a counter and increment if timer overflows. Use overflow value and timer value and do the maths to get the distance in cm.

Rahul Kumar Vashistha · Mar 7, 2015

i did the same..have a look at the code..help me with the function of interrupt that would get called whenever an interrupt will be generated by the timer after overflow.

- - - Updated - - -

Actually my aim is to receive the echo signal simultaneously from both the echo pin of sensors and print the result as speed breaker is detected.. if i am receiving signal at echo pins at different times i must get the distance of the smaller obstacle present in front of the ultrasonic sensor..

milan.rajik · Mar 7, 2015

Is your circuit like this ?

Rahul Kumar Vashistha · Mar 7, 2015

Yesss.. Absolutely identical
Now please please please can you give me the c code for that interfacing..
Or any other kind help related to this project would also be appreciated.. :-D

milan.rajik · Mar 7, 2015

So, you want to trigger both sensors at the same time and measure distances. Do you want to use one timer for both sensors or can you use two timers ?

Rahul Kumar Vashistha · Mar 8, 2015

Yup.. . That's what I want and I am using pic16877a it has only one 16bit timer(timer1)..That's why I have to use only one timer i. email timer 1 of pic16877a..

milan.rajik · Mar 9, 2015

PIC16F877A also has Timer0 and I guess it also has Timer3.

Rahul Kumar Vashistha · Mar 10, 2015

i know..but 16bit is required..help me with the code..i am runnning out of time..

milan.rajik · Mar 10, 2015

I need some time to write the code. You have to save the timer values into two different variables one for sensor 1 and one for sensor 2 and then do the calculation. I will find a way to do it.

Rahul Kumar Vashistha · Mar 10, 2015

okay...thanks a lot..please post the code here when you are done..

milan.rajik · Mar 12, 2015

Try the attached .hex file in Proteus and also hardware. I have used PIC18F45K22 and 20 MHz external crystal. I have used one timer (Timer1) interrupt and RBIF. See attached image for circuit. Proteus 8.1 SP1 format file attached. I have not tested in hardware.

- - - Updated - - -

One HC-SR04 version .hex file and Proteus simulation. Test in hardware and reply. It uses PIC18F45K22 at 20 MHz external crystal. RB0 is ECHO and RB1 is TRIGGER.

milan.rajik · Mar 13, 2015

Please keep the two sensors in opposite direction and test the readings. I am not sure but I think that if two sensors are kept close to each other then USonic burst of one will affect the other sensor.

milan.rajik · Mar 13, 2015

PIC12F1840 + HC-SR04 .hex file and Proteus file attached.

interfacing ultrasonic sensors

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