P3 Speller with ModularEEG

[UCTEEGLab]

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

[gschalk]

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

[UCTEEGLab]

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