I am not sure about the details @t3on please correct me if I'm wrong. The first issue is that events are sent as on-to-off changes by our hardware when controlled through psychtoolbox, but the brainvision software assumes off-to-on. So trigger ID 255 would be sent as all-channels-off, which brainvision reads as event 0 (if it is recorded at all which, now that I think it, I'm not sure). Second, whenever channels revert to baseline (all on) that is registered as an event with value 255.

> why not fixing the synthesizing of the stim channel?

@agramfort how do you mean that? In a way that does not require a system specific argument?