Ultrasonic Range Measurement problem

Hello
I am using PIC16F887A with 8Mhz Crystal to do range measurement the transducers are standard 40Khz Tx and RX module , The problem is 37 always appear on the LCD screen , The code goes here , Its compiled with

mikroc_pro_pic_2011_v460

Downloaded from
https://www.mikroe.com/eng/downloads/get/29/mikroc_pro_pic_2011_v460_setup.zip

The output is from Pin B3 and input on B0



//////////////////////////////////////////////////////////////////////////////////////////////
sbit LCD_RS at RE2_bit;

sbit LCD_EN at RC2_bit;

sbit LCD_D4 at RD4_bit;

sbit LCD_D5 at RD5_bit;

sbit LCD_D6 at RD6_bit;

sbit LCD_D7 at RD7_bit;



sbit LCD_RS_Direction at TRISE2_bit;

sbit LCD_EN_Direction at TRISC2_bit;

sbit LCD_D4_Direction at TRISD4_bit;

sbit LCD_D5_Direction at TRISD5_bit;

sbit LCD_D6_Direction at TRISD6_bit;

sbit LCD_D7_Direction at TRISD7_bit;

extern sfr sbit Abit;

sbit Abit at PORTB.B3;







unsigned int T1_O = 0; // timer1 overflow updated in interrupt routine.

unsigned short gCapInt = 0; // captured something in interrupt routine.

unsigned short gfCapOn = 1; // control capture only capture 1st value.



unsigned int t_capL = 0; // timer 1 low.

unsigned int t_capH = 0; // timer 1 high.

unsigned int t_capO = 0; // timer 1 overflow.



unsigned int gCapVal = 0; // captured this.



//////////////////////////////////////////////////////////////////////

void init(void) {



// OSCCON = 0x60; // b6..4 = 110 = 4MHz



// set CCP to capture mode every rising edge.

CCP1CON = 0x05;



// ANSEL = 0; // all ADC pins to digital I/O



// Timer 1 on

T1CON = (1<<TMR1ON);

}



//////////////////////////////////////////////////////////////////////

void init_ports(void) {



PORTA = 0;

TRISA = 0; // 0=o/p - sets analogue pins to digital output.



PORTB = 0;

TRISB = 0x01; // 0=o/p Receive on RB0.



// PORTD = 0;

// TRISD = 0;



}



//////////////////////////////////////////////////////////////////////

void enable_interrupts(void) {



// Timer 1

PIR1 &= ~(1<<TMR1IF); // Zero T1 overflow register value.



// Capture

PIR1 &= ~(1<<CCP1IF); // Zero Capture flag



// Interrupt enable.

PIE1 = (1<<CCP1IE);



// Global interrupt enable.

INTCON = (1<<GIE) | (1<<PEIE); // enable global & peripheral

}



//////////////////////////////////////////////////////////////////////

void disable_interrupts(void) {

INTCON &= ~(1<<GIE); // disable global & peripheral

}



void seg_display_int(int val) {

char op[7];



IntToStr(val,op);



// 6 digits op by above.



// e.g. for num 1234

// pos 5 4 3 2 1 0

// num x x 1 2 3 4 \0

// index from left ! 0 1 2 3 4 5



// Display the lower 4 digits.

Lcd_Out(2, 1, op) ;

Lcd_Out(2, 1, op) ;



/* PORTA=int2seg(op[2]-'0');

setBit(PORTB,5);

delay_ms(4);

resBit(PORTB,5);



Lcd_Config(&PORTA,1,2,0,3,5,4,6);





PORTA=int2seg(op[3]-'0');

setBit(PORTB,2);

delay_ms(4);

resBit(PORTB,2);



PORTA=int2seg(op[4]-'0');

setBit(PORTB,6);

delay_ms(4);

resBit(PORTB,6);



PORTA=int2seg(op[5]-'0');

setBit(PORTB,7);

delay_ms(4);

resBit(PORTB,7);



PORTB &= ~0xe4; // turn off all resBit should do this

PORTB=0; */



// PORTA=0x00;

}

//////////////////////////////////////////////////////////////////////

// generate 4 pulses of ultrasonic @ 32kHz (8 periods of 32kHz).

// Use the simulator to set correct period.

// single ended drive

void gen_ultra(void) {



Abit = 1; // setBit(PORTB,3);

// original 12 usc and 11 usec

delay_us(12);

Abit = 0; // resBit(PORTB,3);



delay_us(11);



Abit =1; // setBit(PORTB,3);



delay_us(12);

Abit = 0; //resBit(PORTB,3);

delay_us(11);



Abit = 1;// setBit(PORTB,3);

delay_us(12);

Abit = 0; //resBit(PORTB,3);

delay_us(11);



Abit= 1;//setBit(PORTB,3);

delay_us(12);

Abit = 0;//resBit(PORTB,3);

delay_us(11);



}





void main() {

int j = -4220,val;

char txt[7];

unsigned int i,s1,s2,tH,tL,tO;

char op[12];

unsigned long calc=0;

// IntToStr(j,txt);

// Lcd_Init();

init_ports();

init();

Lcd_Init();

//Lcd_Config(&PORTD,1,2,0,3,5,4,6);

Lcd_Cmd(_LCD_CLEAR); // Clear display

Lcd_Cmd(_LCD_CURSOR_OFF); // Turn cursor off

//Lcd_Out(1,1,"Initializing");

//Delay_ms(2000);



Lcd_Out(1, 1, "UltraSonicRanger") ;

Lcd_Out(2, 5, "cm") ;



gCapInt=0; // Reset capture indicator.



while(1) {



gfCapOn = 1; // allow one capture value



tO = T1_O; // Get the current timer value.

tH = TMR1H;

tL = TMR1L;



t_capL = 0; t_capH = 0; t_capO = 0; // initialise capture



gen_ultra();



enable_interrupts();

seg_display_int(val);

disable_interrupts(); // had 20 ish ms of time so stop



if (! gCapInt) { // no echo from soft output ? try loud



enable_interrupts();

seg_display_int(val);

seg_display_int(val);

disable_interrupts(); // had 20 ish ms of time so stop

}



// Did we get any echo from soft or loud ?

if (gCapInt) { // captured anything ?

gCapInt=0; // reset for next time




s1=(t_capH-tH);

s2=(t_capL-tL);



calc = ((s1)<<8)+s2;

calc *= 34;

calc /= 2000; // output in cm

val = (int)calc;

}

} // while(1)

}



////////////////////////////////////////////////////////////////////////

void interrupt(void) {



// Free run Timer 1 get the overflow to extend counter here.

if (PIR1 & (1<<TMR1IF) ) { // T1 overflowed ?

PIR1 &= ~(1<<TMR1IF); // clear timer1 overflow bit.

T1_O++;

}



// Capture

if (PIR1 & (1<<CCP1IF)) {

PIR1 &= ~(1<<CCP1IF); // Zero Capture flag.



if (gfCapOn) { // allow only 1 capture



gfCapOn = 0;



t_capL = CCPR1L;

t_capH = CCPR1H;

t_capO = T1_O;



gCapInt = 1; // signal that a capture occured.

}

}



// Interrupts are only enabled at a specific point from program.

// They are not re-enabled here



// Note GIE set by RETFIE instruction

}






///////////////////////////////////////////////////////////////////////////////////////////////////

regards
Moin Karlskrona SE