reading ultrasonic receve

[majorkuso]

the sensor works, but the led turns off and on rapidly instead of staying on what could be the problem

[LinkMTech]

Hmmmmm.... try putting the trig = 0 before the main loop:

    trig = 0            ' start output in LOW state

main:
GOSUB distance    
    SELECT CASE dist
        CASE 0          ' PULSIN timed out and returns zero, turns LED OFF
            LOW led 
        CASE IS < 8     ' dist <8 inches but not zero, turns ON LED
            HIGH led 
        CASE ELSE       ' dist >8 inches turns LED OFF
            LOW led
    END SELECT
GOTO main    

distance:
    PULSOUT trig,1      ' each count = 10us
    PULSIN sens,1,dist  ' will time out in 655ms if nothing received
    dist= dist/15 'convert to inches
    PAUSE 100
RETURN

END

[majorkuso]

I put the low trig before the main but it still blinks I wonder if the sensor is sending stray numbers when it starts the distance routine, is there a way I can sim the pic in multisim 11? I may try programming another pic and make sure it is not an internal error

[LinkMTech]

You may right about the stray or false triggering as mentioned in the data sheet.
Now try putting a little delay after the PULSOUT to give the device time to complete the transmit function before listening for an echo.

distance:
    PULSOUT trig,1      ' each count = 10us
    PAUSEUS 120      ' Wait for transmit pulse to complete
    PULSIN sens,1,dist  ' will time out in 655ms if nothing received
    dist= dist/15 'convert to inches
    PAUSE 100
RETURN

END