bci2000.org BBS

Hi

I am trying to use the P3 Speller but with a ModularEEG board. I have created a new batch file to run ModularEEG.exe with the speller and I can get the application to run, but I get the following warnings:
2011-07-14T16:31:15 - Warning: P3SpellerTask::Preflight: Due to a sample block duration of 31.25ms, the actual value of StimulusDuration for stimulus 1 will be 31.25ms rather than 40ms.
2011-07-14T16:31:15 - Warning: P3SpellerTask::Preflight: Due to a sample block duration of 31.25ms, the actual value of ISIMinDuration for stimulus 1 will be 62.5ms rather than 80ms.
2011-07-14T16:31:15 - Warning: P3SpellerTask::Preflight: Due to a sample block duration of 31.25ms, the actual value of ISIMaxDuration for stimulus 1 will be 62.5ms rather than 80ms.

I am using a sample block size of 8, which is the same as is used with the Signal Generator and also a sampling rate of 256Hz, so I am not sure why these warnings show up. I have also tried changing the sample block size but still get warnings.
The P3 speller also does not display correctly, although with the Signal Generator it is fine.

I know this may be more due to using ModularEEG than BCI2000 but I just wanted to post the question here in case someone else has managed to solve a similar problem.

Thanks

Leandra

Hi,

If the P3Speller does not show up properly, simply load the P3Speller_SignalGenerator parameter file as a basis, and modify it for your use.

The warnings say exactly what the problem is. You specify 40ms in the StimulusDuration and other parameters, which the system cannot produce given a 256 Hz 8 SampleBlockSize configuration (i.e., 31.25 ms temporal resolution). Actually, with the P3Speller_SignalGenerator parameter file, you should not get this problem in the first place, but in case you encounter it again, simply change the 40ms to 31.25ms.

Gerv

Hi

Thanks for the reply. I actually hadn't realised you could specify the StimulusDuration because that was on another tab of the parameters - so I thought it only had to do with the SampleBlockSize.
I reverted to an older set of parameters and it's working fine now, so obviously the StimulusDuration got changed at some point, although I can't remember doing that.

Thanks for the help

Leandra