PXIe-6535 sometimes incorrectly reads IO line

[CurtisHx]

I have a problem where a PXIe-6535 (2, actually) will incorrectly read a line.  This might happen a few 10s of times over millions of samples, but it still happens and is causing incorrect results.  I compared what the card was reporting with what the scope showed, and 6535 was clearly wrong.

It always happens when the line is high, and it will read a few 10s of samples as being low.  Due to the nature of the waveform that I'm tracking, the line is being manually sampled in a loop.  The samples come in fast enough to catch the high time.  However, sometimes, it reads low when it should read high.

[FinchTrain]

Hi,

Can you provide more information regarding the exact rates you are reading at as well as more details regarding the waveform you are reading? It could be that you are approaching a speed threshold which is why this is occuring inconsistently. Any further detailed information will be great.

Regards,

Finch Train

[CurtisHx]

Hi Finch,

I forgot to link to the original thread where I was trying to pattern match with tne PXIe-6535 and hitting problems with missing samples.  Hopefully, this will shed some light.

http://forums.ni.com/t5/Multifunction-DAQ/PXIe-6535-Pattern-Matching/td-p/3319577

[FinchTrain]

Hi,

It certainly does help clarify. For the sake of testing, are you by chance able to generate a consistent pulse of 4ms every second (as opposed to a random interval between 5-30ms)? If you have already done so, do it always miss this or does it still log some of the time?

Regards,

Finch Train