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ADC output oscillates

Posted: Fri Feb 27, 2009 3:08 pm

I wonder whether anyone can help me fix the following behavior I see with the 8/8/8 interface kit under both windows and LINUX with the 2.1 library.

When making measurements I get the correct value followed immediately by a bogus lower value. For example a temperature sensor would return 19 immediately followed by 15. The first value is correct, the second is bogus. I tried different temp sensors, different ports and did even raw ADC conversions. It's always the same, there is a correct measurement followed by a lower bogus value.

I don't know much about electronics and was thinking that maybe the supply volatge breaks in under a measurement but even with a USB hub I see this behavior.

Since the 2 values are so far apart I cannot put a simple threshold in place.

Maybe someone knows what is going on.
Thank you.

P.S. Does the phidget run a firmware btw?

Posted: Fri Feb 27, 2009 4:21 pm
by fitchett
When/where did you buy it?

Can you tell us the firmware device version? It's exposed through the API.


Posted: Sun Mar 01, 2009 3:55 pm
The firmware version is 824. The serial number is 37784. Is there an upgrade available?

I bought it from Trossen Robotics some time ago (1 year). I had done one experiment before where I didn't mind the oscillation and then did some Arduino stuff. Now however do I need accuracy in the sensor output for some precision measurements.

Still hoping I can upgrade the firmware to fix it...

Posted: Mon Mar 02, 2009 11:37 am
by fitchett
This is our bad. We ran the SPI clock a bit fast on that firmware version.
Email, and we'll send you a new one.