Reply by sharkzone1 ●November 10, 20032003-11-10
Hi to all..
I'm having a problem with my srf04 ultrasonic sensor
I'm using basic stamp 2 SX (BSX2) and I found this example on a
website
The problem is the readings that I get are not correct for example if
the distance is 20cm.
The readings that I get from the srf04 are:
21 inc. and 51 cm (Please what is the problem?)
'
`Devantech SRF04 Example

wDist var word

INIT con 0
ECHO con 1 ' CONVERSION FACTORS:
'
' The PULSIN command returns the round-trip echo time in 2us units
' which is equivalent to the one-way trip time in 1us units.
'
' distance = (echo time) / (conversion factor)
'
' use 74 for inches (73.746us per 1 in)
' use 29 for centimeters (29.033us per 1 cm)
'
convfac con 74 ' use inches
'---------
main

gosub sr_sonar
debug dec wDist, cr
pause 200
goto main sr_sonar:

pulsout INIT,5 ' 10us init pulse
pulsin ECHO,1,wDist ' measure echo time
wDist=wDist/convfac ' convert to inches
pause 10
return


Reply by sreenu dindi ●August 16, 20032003-08-16
Hey I had done it. I had implemented a different method . I used the timer1 pulse detector. Using the capture mode is easier.
bye

sreenu_dindi <s...@yahoo.com> wrote:
Hi,
       I am trying to measure the distance using srf04. I am using
ccs compiler. The pic16f877 is unable to recognize the echo..
Though srfo4 is returning an echo, i had verified it with an
OScilloscope. my program ismain() {
      int  echo_time=0;

            lcd_init();
     

 

   do {
        
     

         echo_time=0;
         delay_ms(1000);
        
      output_low(PIN_D2);
         output_high(PIN_D2);
      delay_us(15);
         output_low(PIN_D2);
          delay_us(100);
              
           

          
           
         while(input(pin_d3))
          echo_time++
                

             
       printf(lcd_putc,"\fecho:%04ld\n",echo_time);
               

     

   } while (TRUE);
}
it is not entering the while loop at all. Please reply me as
asap .Thank  you
Sreenu Dindi



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Sreenu Dindi

University of South Carolina

Department of Electrical Engineering

Phno: 803-765-9589


Reply by Ian Bell ●August 14, 20032003-08-14
On Wednesday 13 Aug 2003 11:40 pm, sreenu_dindi wrote:

>
> while(input(pin_d3))
> echo_time++
>

My C is a bit rusty but don't you need a ; after echo_time++ ?

Ian

Reply by sreenu_dindi ●August 13, 20032003-08-13
Hi,
I am trying to measure the distance using srf04. I am using
ccs compiler. The pic16f877 is unable to recognize the echo..
Though srfo4 is returning an echo, i had verified it with an
OScilloscope. my program is main() {
int echo_time=0;

lcd_init();

do {
echo_time=0;
delay_ms(1000);

output_low(PIN_D2);
output_high(PIN_D2);
delay_us(15);
output_low(PIN_D2);
delay_us(100); while(input(pin_d3))
echo_time++
printf(lcd_putc,"\fecho:%04ld\n",echo_time);

} while (TRUE);
}
it is not entering the while loop at all. Please reply me as
asap .Thank you
Sreenu Dindi