Ultrasonic distance sensor with PIC16F84A

[MrRoboto]

All

I used the code below to light a LED if the distance is less than 12 inches, the code runs , but for only 3 iterations, some time 4 iterations, I cannot seem to find out why, can anyone help.

I am using the parallax ping sonar sensor

Thanks



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code
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SYMBOL Ping = 7


' -----[ Constants ]-------------------------------------------------------

SYMBOL Trigger = 1 ' 10 uS trigger pulse
SYMBOL Scale = 10 ' raw x 10.00 = uS

SYMBOL RawToIn = 889 ' 1 / 73.746 (with **)
SYMBOL RawToCm = 2257 ' 1 / 29.034 (with **)

SYMBOL IsHigh = 1 ' for PULSOUT
SYMBOL IsLow = 0


' -----[ Variables ]-------------------------------------------------------

SYMBOL rawDist = W1 ' raw measurement
SYMBOL inches = W2
SYMBOL cm = W3



' -----[ Initialization ]--------------------------------------------------

Reset:


' -----[ Program Code ]----------------------------------------------------

Main:

GOSUB Get_Sonar ' get sensor value



inches = rawDist ** RawToIn ' convert to inches
'cm = rawDist ** RawToCm ' convert to centimeters

if inches < 12 then pushd




'DEBUG CLS ' report
'DEBUG "Time (uS)..... ", #rawDist, CR
'DEBUG "Inches........ ", #inches, CR
'DEBUG "Centimeters... ", #cm

PAUSE 500
GOTO Main

end




' -----[ Subroutines ]-----------------------------------------------------

' This subroutine triggers the Ping sonar sensor and measures
' the echo pulse. The raw value from the sensor is converted to
' microseconds based on the Stamp module in use. This value is
' divided by two to remove the return trip -- the result value is
' the distance from the sensor to the target in microseconds.

Get_Sonar:
LOW Ping ' make trigger 0-1-0
PULSOUT Ping, Trigger ' activate sensor
PULSIN Ping, IsHigh, rawDist ' measure echo pulse
rawDist = rawDist * Scale ' convert to uS
rawDist = rawDist / 2 ' remove return trip
RETURN


pushd:
high 1 'high RB 1
pause 1000
LOW 1

PAUSE 500

HIGH 1
PAUSE 1000
LOW 1

PAUSE 500
return