Random '20202020...' triggers

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m_c_
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Joined: Fri Oct 26, 2018 11:31 am

Random '20202020...' triggers

Post by m_c_ » Fri Oct 26, 2018 12:03 pm

Hello All,

I am hoping someone can offer some advice regarding an issue that I am experiencing (photos attached).

I am using a 64-channel Biosemi system. The triggers that I am sending via a parallel port -> parallel port trigger cable are appearing no problem. These appear in the upper half of the trigger panel in Actiview, i.e. in 'Trig 1-8'.

However, I am experiencing random "20202020..." triggers that are appearing in the bottom half of the trigger panel in Actiview, i.e. in 'Trig 9-16'. These triggers appear at random time intervals, usually starting as a burst, then appearing every 1-2 seconds, after an undefined amount of time, which appears random, the "2020202020..." persistently pulse at a very rapid rate (~every 0.5 seconds). See attached photos for examples.

This issues started a few months ago, and occurred on rare, but random occasions, but it now occurs in nearly every single recording that we make now. It is worth noting that the issues persists when we detach the parallel port -> parallel port trigger cable, i.e. when there is no trigger input from the presentation PC. I can only assume that this is an issue in the data sync box or the recording PC?

Also, it is worth noting that this isn't simply a case of random triggers. I have noticed that when these random "20202020..." triggers occur, they are somehow manipulating the triggers that are subsequently sent as part of my task. For example, a trigger of 210 might appear as 752. There doesn't appear to be any order or sequence to these manipulations, the output triggers in my data file appear random, but they are always very high numbers, which are way beyond the 255 cap that can be sent via the parallel port trigger cable.

There are no issues with the actual EEG recordings, signals are high quality and stable throughout. It is only an issue with the triggers that I am experiencing.

Has anyone experienced this or a similar issue and found a fix? Any help or advice would be much appreciated.

Regards,
Michael
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Coen
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Re: Random '20202020...' triggers

Post by Coen » Fri Oct 26, 2018 12:59 pm

viewtopic.php?f=7&t=977&p=2985

Best regards, Coen (BioSemi)

Sal_Ar99
Posts: 2
Joined: Fri Aug 09, 2019 1:50 pm

Re: Random '20202020...' triggers

Post by Sal_Ar99 » Fri Aug 09, 2019 1:58 pm

Dear All,

Apologies for bringing up this post on the top again but my issue is very similar.

The difference is that trigger 10 is now always on (out of the blue - see bottom red line here https://photos.app.goo.gl/1VS6xCckZANmWt789) and changing the value of RespSwitch from 1 to 0 (zero) both in the default configuration file and in the 10-20system64+8 file (set up we use) hasn't rectified the issue and we ran out of ideas.

Many thanks in advance for any advice/tips/ideas.

Regards

Coen
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Re: Random '20202020...' triggers

Post by Coen » Fri Aug 09, 2019 2:12 pm

Disconnect the trigger cable from the USB-receiver. All trigger lines should now be high (if 9 and/or 10 are low, then there is still a wrong setting in the CFG). Then short pin 10 to pin 37. This should pull line 10 low (also compare with other lines). If line 10 does not respond, then sent the USB-receiver for repair. If line 10 does respond, then the error is in your trigger cable or your stimulation setup.

Best regards, Coen (BioSemi)

Sal_Ar99
Posts: 2
Joined: Fri Aug 09, 2019 1:50 pm

Re: Random '20202020...' triggers

Post by Sal_Ar99 » Tue Aug 13, 2019 1:02 pm

Hi Coen,

So many thanks for the very swift reply and instructions very much appreciated.

The stimultion PC was not powered on when testing. Below is what happened when we tried different scenarios.
  • Presentation cable not present.
    All triggers are high apart from 9. 10 starts as dashed lines and it clears up i.e. goes low, after 10-15 secs. The rest of the triggers remain high https://photos.app.goo.gl/4jTFoPDA6pAz5wnV8.
  • USB trigger interface cable is plugged in.
    Only 10 is high and after 10-15 secs it goes low.
I am really confused, not sure if it is a hardware problem or a configuration files problem.

Again, many thanks for the support on this, appreciated.

Coen
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Joined: Fri Mar 26, 2004 7:00 pm
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Re: Random '20202020...' triggers

Post by Coen » Tue Aug 13, 2019 1:41 pm

If 9 and 10 are not continuously high with detached cable, then the RespSwitch setting in the used CFG is still on "1", change it to "0".

You state that all other trigger lines are high, but the picture shows line 16 low. Probably a hardware problem, but unrelated to the 9 and 10 behavior. You can ignore this for now.

Best regards, Coen

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