Triggers for Biosemi EEG

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Triggers for Biosemi EEG

Postby englishmatt » Tue Jan 15, 2013 3:29 pm

I'm trying to send triggers to a Biosemi EEG acquisition system. The system requires a DB-37 input to the trigger box. Does anyone know how if can get Psykinematix (on a Mac, of course) to output to a DB37 port? Or will we need to purchase a new trigger box that accepts USB inputs?

Thanks,

-- Matt
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Re: Triggers for Biosemi EEG

Postby psykinematix » Wed Jan 16, 2013 12:25 am

Dear Matt,

If you are referring to the ActiveTwo USB receiver as your trigger box with the DB-37 connector, then the Biosemi website (http://www.biosemi.com/faq/trigger_signals.htm) seems to indicate that the trigger signals are TTL levels. So in theory, you could simply use a serial port (through a USB-to-serial adapter) to send TTL triggers from Psykinematix (note however that you would be limited to only 2 TTL lines through pin 4, aka DTR, and pin 7, aka RTS, of a DB9 serial port). For more details about sending TTLs from Psykinematix using a serial port, see the "Serial devices/Remote PC" section in the documentation:

http://www.psykinematix.com/documentati ... es.html#io

Hope this helps!

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Re: Triggers for Biosemi EEG

Postby englishmatt » Wed Jan 16, 2013 2:33 pm

Thanks. So I'll need a USB-toDB9 adapter, connected to a DB9-to-DB37 adapter, which will then interface with the trigger box? Makes me a little worried about timing, but could be worth a try.

Another option is to use the Cedrus StimTracker. Is that device compatible with Psykinematix?

-- Matt
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Re: Triggers for Biosemi EEG

Postby psykinematix » Wed Jan 16, 2013 3:16 pm

Dear Matt,

Yes you will need a USB-toDB9 adapter (one with a PL-2303 chip from Prolific would work fine). However a simple DB9-to-DB37 adapter is unlikely to work as they use different interfaces (parallel for your DB-37 box and serial for DB9): instead you will have to get 2 independent connectors (DB37 male and DB9 female with pins access for customization) and connect the pins 4 and 7 of the DB9 female to some pins of the DB37 male corresponding to trigger inputs of the ActiveTwo USB receiver (pin 1 to pin 16). Of course you will have to connect their respective ground pins too. You should probably ask an electronic technician in your lab/department if you need help to create this custom DB9-to-DB37 adapter.

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Re: Triggers for Biosemi EEG

Postby psykinematix » Wed Jan 16, 2013 3:39 pm

Not sure about timing but serial communication has typically a delay less than 1 ms.

We were not aware of the Cedrus StimTracker: it seems to use a serial communication through USB and appears to be compatible with Macs (http://www.cedrus.com/support/stimtracker/). So Psykinematix could support it if this works similarly to the way Psykinematix communicates with Cedrus RB Series Response Pads and Lumina Controller. However Psykinematix will have to be modified to do so and this would require a support package.

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