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So last night I wired up the cabin temperature pots in my 737 overhead to my PoKeys 57E card.  They're working, but very jittery in Prosim, with regular spikes of the virtual knobs. 

What is interesting is loading up the PoKeys software and analyzing the analog ports without the knobs attached the values are still jittery.  Makes me think something is up with the power delivery.  But I just replaced my cheap-o power supply with a much better one and still the same thing.

Anyone run into this and have a solution?  Low pass filter somewhere?

Attached is a crude diagram of how they're wired.

In the Pokeys software there is a slider for the Analog filter value, slide this to the right to slow it down/smooth it out.

Also just double checking the power to the Pokeys, in your diagram it looks like you are feeding the pots and the Pokeys card with the same 3.3v power supply?
The Pokeys E cards need 5v, then you must connect the pots to the on-board 3.3v terminal, not an external source.

Thanks Mick.  Found that analog filter and that seems to have eliminated the spikes, and reduced the jitters significantly at about the half setting.

Sorry, the power in my diagram is a little off.  I'm feeding the pots with 3.3v off the main power supply, and feeding the PoKeys with 5v off the main power supply.  I'll try pulling the 3.3v off the PoKeys instead.  Easy fix and may help things further.

UPDATE:  Connected the 3.3v off the PoKeys and same jitters.  The filter solution is good enough.  At least the real knobs aren't jittery.  THAT would drive me nuttier than I already am, lol.

Line noise, perhaps? Ground loop? Is everything grounded properly?

I've recently completed a CNC build, so during the controller build, "grounding" came up a lot. Can you run a small capacitor, to minimize noise, like in page 99 in the Pokeys manual?