Linking Ping Sensor to Coridium ARMite controller.
Hello, hopefully somebody can point to what is going wrong here.· I am a member of a robot team at a technical school.· We are attempting to link a Ping ultrasonic sensor to a Coridium ARMite controller.·We are able to send the pulse and ping the sensor, but we are getting a very inconsistent return.· From the code below we are printing the time of the return pulse in microseconds.· The·return is almost always 5 or 6 us.··Occasionally we get a much higher return, but·it is not related to the distance we are pointing at.· We have moved the ping sensor around attempting to eliminate problems and we feel·we have eliminated any bad echoes or feedback.· It seems the problem is in the code.· Thank you for looking at this and providing whatever help you can.·
#include<pulse.bas>
'' Conversion constants for room temperature measurements.
CmConstant = 2260
InConstant = 890
cmDistance = 0
inDistance = 0
time = 0
DO
PULSOUT(0,5)
time = PULSIN(0,1)
cmDistance = cmConstant * time
inDistance = inConstant * time
' print cmDistance; " cm"
' print inDistance; " in"
print time; " us"
' wait(100)
LOOP
Post Edited (SSCT) : 3/31/2009 5:08:06 PM GMT
#include<pulse.bas>
'' Conversion constants for room temperature measurements.
CmConstant = 2260
InConstant = 890
cmDistance = 0
inDistance = 0
time = 0
DO
PULSOUT(0,5)
time = PULSIN(0,1)
cmDistance = cmConstant * time
inDistance = inConstant * time
' print cmDistance; " cm"
' print inDistance; " in"
print time; " us"
' wait(100)
LOOP
Post Edited (SSCT) : 3/31/2009 5:08:06 PM GMT
Comments
You could also use a built-in timer.
code was
timer = 0
while timer < 650· 'we went from 40us to 2000us with no change in results
loop
After the loop ended, the pulsin was activated.
We still had the same output from the sensor in a 5-7 us range
A 5us or so return pulse doesn't make sense. Read the PING documentation. The minimum width of the echo pulse is 115us.
There's something else going on and it either has to do with the hardware setup or the programming system you're using and
there's no way for me to guess further with the amount of information you've provided.
I did find the ARMlite on SparkFun's website. It's not a 5V logic device. The spec says that the I/O pins are 5V tolerant and that
output voltages are approximately 2.9V. Now the Propeller is also a 3.3V device and it does work with the PING. I've had no
problems with the Propeller and the PING. On the other hand, it is "out of spec" and, if the ARMlite's voltage regulator is a little
low or if there's more voltage drop in the ARMlite's output circuitry than the Propeller's, you're in trouble. You may need some
buffering between the ARMlite and the PING. Philips (NXP) has some application notes on simple bidirectional buffering for use
with I2C busses running at different voltages. There's a Propeller thread on this and related subjects:
http://forums.parallax.com/showthread.php?p=585920.
Post Edited (Mike Green) : 4/3/2009 6:45:01 PM GMT
We have talked to Parallax tech support on the phone. They have said that our program should cause the sensor to function normally and there should not be any problems. The Coridium people have been absolutely no help. Parallax also says their sensors rarely go bad and they don't think we have a problem on that end. To be on the safe side, we ordered a new one just to be sure (we are currently using two that were left from last year's robot).
If you can think of any other information you need from our end, we would be happy to provide whatever we can. Thank you.
http://www.coridiumcorp.com/Products.php
We are using the board all the way on the left, maybe those specs will tell you what you need to know.
I've made several suggestions and observations along the way. You really need to work with them. If you have an oscilloscope or logic analyzer, you need to use them to find out what's going on.