Mouse lags for >5 seconds when waveforms update on screen

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ajohns
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Mouse lags for >5 seconds when waveforms update on screen

Post by ajohns » Mon Sep 24, 2012 9:03 pm

Hi,

A very specific problem - the mouse lags for about 5 seconds whenever equipment is plugged in and turned on (128 channels), and I've opened the ActiView software to the tab that just shows the continuous raw EEG. The delay is regardless of whether I'm saving the data, and there is no lag when I switch over to the offsets tab, so I'm thinking the problem is centered around having to continuously update the visual display.

The acquisition computer is a Dell OptiPlex GX 280 with Windows XP. It used to work perfectly with the recording equipment, no problems. But our lab got moved around, and all equipment was unplugged for more than a year. When we tried to plug everything back together, the computer no longer recognized the USB connection, so we downloaded the most recent driver and BioSemi software (as of 7/2011). Ever since then, we've had the mouse delay.

I'm wondering if the newer software is just too much for the GX 280, and I have access to an Optiplex 330 if that could help fix things.

Thank you!

Coen
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Re: Mouse lags for >5 seconds when waveforms update on scree

Post by Coen » Wed Sep 26, 2012 2:48 pm

The mouse lag problem was not reported earlier, even though several customers still (successfully) use quite slow PCs for acquisition.

It is unlikely that the driver upgrade is the cause. The driver is just running in the background (transferring data from the USB port to the ringbuffer), and does not really interact with ActiView (besides providing buffer pointer values). So, the driver does not "know" which ActiView tab is selected. The driver load on the processor is quite constant, and we have not seen much differences between the old and new drivers.

We have not seen processor load differences either when comparing ActiView 6.05 (with LabVIEW RTE 8.2) versus ActiView 7.03 (with LabVIEW RTE 8.6.1).

It is correct that ActiView puts a higher load on the processor when displaying scrolling signals (selecting the Offset or About tabs reduces load). However, mouse and keyboard commands have priority over LabVIEW processes. A slow processor can certainly affect the performance of ActiView (depending on the selected tab page), but we have not seen much influence on mouse pointer behavior in these cases.

In general, processor speed problems can be detected by watching the behavior of the ringbuffer clock indicator in the lower right corner of the ActiVIEW screen. The red pointer indicates where new data coming from the USB port is being written into the ringbuffer, while the green pointer indicates where data is read out of the ringbuffer by ActiView for further processing. On a fast PC, the green pointer will have now problem staying close to the red pointer. Only on some occasions (for example: dragging another window over the ActiView display) the green pointer will fall a bit behind momentarily, but it will have no trouble to quickly catch up. In addition, scrolling in the monolopar display will be smooth (in many small steps) most of the time. When there are processor speed problems however, then you will continuously see the green pointer lagging behind the red pointer, sometimes even to the point where the green pointer gets a full revolution behind the red one (and acquisition will stop because unread data is being overwritten with newer data). In addition, scrolling will be in large steps (with a size of even up to a second). Please let me know if you see these effects.

Best regards, Coen (BioSemi)

ajohns
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Joined: Mon Sep 24, 2012 8:40 pm

Re: Mouse lags for >5 seconds when waveforms update on scree

Post by ajohns » Thu Sep 27, 2012 5:45 pm

Hi Coen,

Thank you for the quick reply! Today I ran two participants and didn't observe any differences between the green and red pointers - in fact, they were almost always completely overlapping. Does this mean at least that I can be confident that the mouse lag is not affecting any of the recorded data in terms of timing? Also, are there other things that you think could be causing this problem?

Thanks-
Alexis

Coen
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Re: Mouse lags for >5 seconds when waveforms update on scree

Post by Coen » Thu Sep 27, 2012 6:21 pm

The overlapping pointers indicate that you processor is fast enough, there does not seem to be a general processor speed problem

As long as ActiView is running, you can trust that the timing of the data is perfect, even if the green pointer is lagging behind as on a slower PC. The mouse lag cannot in any way affect the recorded data. In case of a speed problem worse enough to affect the data (e.g. buffer overflow), ActiView will stop with an error popup.

It seems that on your particular PC, Windows does not give the mouse a higher priority then LabVIEW (as in the normal case). When LabVIEW takes up all processor time (by calculating the smooth scrolling graphs), the mouse action has difficulties to come in between. We have never seen this before, we are puzzled at the moment, sorry.

Are you running the ActiView.exe under the LabVIEW run-time-engine, or the ActiView.vi under a full LabVIEW programming installation (which version of LabVIEW) ?

Best regards, Coen (BioSemi)

ajohns
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Joined: Mon Sep 24, 2012 8:40 pm

Re: Mouse lags for >5 seconds when waveforms update on scree

Post by ajohns » Thu Sep 27, 2012 8:02 pm

I apologize - I'm not sure if I quite understand the question/where to get the answer, but I'm opening ActiView605-Lores.exe if that helps?

Coen
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Re: Mouse lags for >5 seconds when waveforms update on scree

Post by Coen » Mon Oct 01, 2012 11:27 am

That answers my question (you use the 8.2 version RTE, so the problem cannot be caused be a recent LabVIEW version).

The only thing you could try is whether changing to ActiView 7.02 (http://www.biosemi.com/download/LatestA ... -LoRes.zip) in combination with RTE 8.6.1 (http://ftp.ni.com/support/softlib/labvi ... 861STD.exe) makes a difference.

Best regards, Coen (BioSemi)

ajohns
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Joined: Mon Sep 24, 2012 8:40 pm

Re: Mouse lags for >5 seconds when waveforms update on scree

Post by ajohns » Mon Oct 15, 2012 4:38 pm

Hi Coen,

We went ahead and replaced the acquisition computer (hence my other recent post about the USB2 driver install), and that solved the mouse lagging problem.

Thank you for your help!
Alexis

Coen
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Re: Mouse lags for >5 seconds when waveforms update on scree

Post by Coen » Mon Oct 15, 2012 4:53 pm

Thanks for the feedback, although remains a mystery what exactly caused the mouse lag (definitely not just a problem of slow processor speed).

By the way, how did you eventually solve the USB installation problem (please post in your thread about the driver) ?

Best regards, Coen (BioSemi)

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