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Intuous Pro L, wintab api, incorrect timstamp data

Posted: Fri 16. Feb 2018, 16:34
by amatic
I've been using the Intuous Pro S, and the wintab API (windows 10) for recording human movement in lab experiments. The timestamps seem to be accurate and closely following system time on the Pro S model.
Recently we acquired the L model (Intuous Pro L Paper Edition) for its larger size. Now the timestamps are not accurate. In fact, sometimes the timestamps are showing previous time, and the periods between timestamps go negative! We are using the PK_TIME field of the data packet.

Interestingly the S model is capable of 200Hz in the "Recognition mode", while the L model only does ~170Hz, and there is no setting for "Recognition mode". Could the L model also do 200Hz. Though, the sampling frequency is a side point. The timestamp accuracy is more important.

Is this a driver issue? Hardware changes?

Re: Intuous Pro L, wintab api, incorrect timstamp data

Posted: Tue 20. Feb 2018, 09:07
by amatic
To ilustrate what is happening:

These are differences between timestamps. They are usually 5 or 6 milliseconds, but once in a while, they will go negative. This seems to happen when the pen is lifted a bit from the tablet, and then returned to the surface. As if there is a time compensating mechanism, that attempts to restore correct time.

During one minute: