You can include this bit of code in your PsychToolbox script to make sure you have selected the right port of the stimulus PC:
function memento(MEG)
% Very simple script to check whether the correct port is selected
%
% memento must pre preceded by the MEGSynchClass constructor
% e.g.
% MEG = MEGSynchClass;
% memento(MEG)
%
%alessandro.tomassini@mrc-cbu.cam.ac.uk
try
MEG.WaitForButtonPress(0.0001)
strcmp(MEG.LastButtonPress',MEG.LastButtonPress);
catch
h=warndlg('Check if NI CARD is selected!');
uiwait(h);
end
end