Trigger Problem

[JaanaVanOverwalle]

Hi everyone,

In the lab, we are currently working with the BioSemi system.
Everything was fine until someone accidentally plugged out the cables connecting the stimulus computer to BioSemi.
After plugging all the cables back in, we are seeing extra trigger numbers during recording:

in the top row: we see our actual trigger numbers but with each a zero beneath them.
in the bottom row: the trigger numbers for the response box press are normally 0 & 1 but now are 2 & 3. Sometimes we also see a bunch of 2s here.

Additionally (maybe due to the extra numbers displayed during recording) when we try to analyze the EEG data, our actual trigger numbers are not saved in the bdf file but for every trigger number the number + 512 is saved. Sometimes this is also a mixture of the actual number and the number + 512. We also experienced for some participants that 1 trigger is missing or a trigger has occurred twice while this should only be once.

Can this be due to a bad connection of the cables to the stimulus computer?
Should I reinstall all the software again?

Thanks in advance!

Jaana

[Coen]

Trigger line 10 (pin 10) is unconnected and therefore always High (internal pull-up). Check with "analog" trigger display (colored bars).

OR

If you use response switches (with CFG set to "1", see viewtopic.php?f=7&t=977&p=2985) then your switch number 2 may be disconnected or malfunctioning (leaving line 10 always High)

Best regards, Coen (BioSemi)

[JaanaVanOverwalle]

Hi Coen,

Thanks for the response!

a. When I look in the analog display: I just see two lines: an orange on top and a red in the middle.
The orange line disappears after I run a trial, the red line stays.
I do not see any bars.

b. In this case, should we maybe buy a new response button?

Kind regards,

Jaana

[Coen]

Check that lines 9 (lower brown) and 10 (lower red) are gray when nothing is connected to the trigger port (all other lines should be colored).

Check the operation of the switches (a brown or red dot/line should appear on respectively line 9 and 10 when the switch is pressed.

Best regards, Coen (BioSemi)

[JaanaVanOverwalle]

What do you mean when nothing is connected to the trigger port?
I think indeed that normally there are multiple colored lines when no triggers are send and now this is not the case (sometimes nothing, sometimes a red line and sometimes a red and orange line).
But what can I do about this?
Also in case that a pin or line is always left high. What can we do about this?

Kind regards,

Jaana

[Coen]

I don't see how "nothing connected to the trigger port" can mean anything else than the situation where no connector is inserted in the 37-pole trigger port.

Each line can be pulled Low by connecting the respective pin (1-16) to pin 37. However, with the CFG set to "1", lines 9 and 10 will only react on the response buttons (and not on the trigger port inputs).

Best regards, Coen (BioSemi)