interfacing ultrasonic sensors

[Rahul Kumar Vashistha]

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:-

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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);
 }

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

 

[milan.rajik]

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]

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]

Is your circuit like this ?

 

[Rahul Kumar Vashistha]

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]

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]

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]

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

 

[Rahul Kumar Vashistha]

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

 

[milan.rajik]

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]

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

 

[milan.rajik]

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]

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]

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