Bug 1233 - using pre-trigger halves all timings
Summary: using pre-trigger halves all timings
Status: RESOLVED DUPLICATE of bug 1133
Alias: None
Product: libsigrok
Classification: Unclassified
Component: Driver: fx2lafw (show other bugs)
Version: 0.5.0
Hardware: All All
: Normal normal
Target Milestone: ---
Assignee: Nobody
Depends on:
Reported: 2018-06-14 16:17 CEST by Wilko Lunenburg
Modified: 2018-06-15 11:50 CEST (History)
2 users (show)

1kHz signal without and with pre-trigger set (33.33 KB, image/png)
2018-06-14 16:17 CEST, Wilko Lunenburg

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Description Wilko Lunenburg 2018-06-14 16:17:45 CEST
Created attachment 436 [details]
1kHz signal without and with pre-trigger set

Using Pulseview v0.5.0 on Windows10
with LHT00SU1 logic analyser recognised as CWAV USBee AX

When I put anything other than 0% in the Pre-Trigger capure ratio all timings halve. 

That means that a 1kHz signal is shown as a 2kHz signal. In the attached picture both traces are the same signal.
Comment 1 Soeren Apel 2018-06-14 22:53:33 CEST
I don't have an explanation for this on the PV side, suspecting a driver bug.
Comment 2 Wilko Lunenburg 2018-06-15 09:41:02 CEST
Forgot to tell that the "time-halving" only happens when triggering is active together with the non-zero Pre-Trigger capture ratio. 

Today I checked two other things. First, the effect is also seen on Linux (Linux Mint 18.3 Sylvia) where it happens under the same conditions, triggering active and a non-zero Pre-Trigger capture ratio.

The second thing I tested today is with a (even cheaper) 24MHz_8CH Logic Analyser under Windows 10. (Those tiny things you can get on Ebay for less than 10 euros)

To my surprise it works flawlessly! No "time-halving" under any conditions. 

And also, the triggering makes much more sense with the 24MHz_8CH analyser. 
With the LHT00SU1 the triggering happened more or less at the moment I expected, with the 24MHz_8CH it is spot on.
Comment 3 Soeren Apel 2018-06-15 09:52:00 CEST
Thanks for the follow-up :)

That confirms my suspicion and so I'm re-assigning the bug.
Comment 4 Uwe Hermann 2018-06-15 11:50:42 CEST
Pretty sure this is a duplicate of #1133, marking as such.

*** This bug has been marked as a duplicate of bug 1133 ***