USB6501 trigger problem

[billbudd]

Hi Coen,

We have just started using the National Instruments digital IO card (USB6501) to send trigger codes to Biosemi using Presentation. Have been through the faq section of this website and think our cabling and pin outs are good as well as the NI card configuration but are having problems with the trigger codes.

Essentially they look OK in the top row (1-8bits) of trigger section of the Biosemi acquisition window (ie a code 1 displays as a 1 and code 3 as a 3 etc). Although immediately under each code there always appears a zero (within the 1- 8 bit row) and not sure that occurred previously when using a parallel port?

The problem is that what ever codes are stored in the BDF file using the NI card they do not convert properly when using software such as SPM / fieldtrip. A code of 1 is now read as 128, 2 as 64 and 3 as 192.

Problem likely our NI card setup or maybe cabling but would appreciate any advice you might have to help us diagnose it.

Cheers
-Bill

[Coen]

Your results suggest that Fieldtrip has a bug that swaps the trigger bytes (LSB becomes MSB, etc., see http://www.binaryhexconverter.com/binar ... -converter)

General hints:

- Check the 16 trigger bits in "analog" trigger display mode (colored bars)
- Check the BDF file with our simple BDF file reader: http://www.biosemi.com/download/ToolsFo ... er-808.zip

Best regards, Coen (BioSemi)

[billbudd]

Many Thanks for the advice Coen.

Have been looking at this further and seems like the problem is with Presentation setting all the pins high on the USB6501 port we are using with Presentation. We can fix it by manually setting them low in the NI software but is reset when ever Presentation is restarted.

We are still investigating a better solution as maybe the way in which we have configured the USB6501 card. Appreciate any advice if you have noticed anything similar when using the USB6501 with Presentation

Cheers
-Bill