MEGSynch - CBU MRI facility Wiki

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MEGSynch

MEGSynch provides an interface for National Instruments PCI 6503 card used to capture all pulses (scanner synch pulse and button pulses alike) when using MATLAB.

For more information, type in MATLAB 

help MEGSynchClass

N.B.: National Instruments PCI 6503 card does not monitor pulses in the background, so you have to make sure that you wait for any pulse before it comes!

Any problems, report them to Tibor Auer.

Contents

  1. MEGSynch
    1. Obtain MEGSynch
    2. Using MEGSynch
      1. Initialise
      2. Close
      3. Send trigger
      4. Capture button presses

Obtain MEGSynch

  • MEGSynch is available on MEG PC

  • From your desktop PC (Windows), you can also have a copy from \\cbsu\data\Group\Imaging-Local\cbu\matlab

  • You can also download it from here (right-click and "Save As...")

Using MEGSynch

Initialise

  • Default. Use only in MEG lab! 
  • MEG = MEGSynchClass;
  • Default button mapping:

    Button

    Button name in MATLAB

    Channel

    'Left Yellow'

    'LY'

    'S3'

    'Right Blue'

    'RB'

    'S4'

    'Right Yellow'

    'RY'

    'S5'

    'Right Green'

    'RG'

    'S6'

    'Right Red'

    'RR'

    'S7'

  • To change button mapping: 
  • MEG = MEGSynchClass({'B1','S4';'B2','S5'}); % specify button names "B1" and "B2" and maps them to S4 and S5
  • Emulation: 
  • MEG = MEGSynchClass(1);   % full emulation

Close

MEGSynchClass has a destructor, which is automatically triggered if the object is deleted (e.g. clear, returning function). If you use a script, however, it does not perform any auto-clear, so you have to destroy the object manually: 

  • MEG.delete;

Send trigger

  • for v = 0:255  % send triggers 0 to 255 ...
    pause(0.1) % ... in every 100ms
    MEG.SendTrigger(v)
end

Capture button presses

  • SSO.SetButtonReadoutTime(0.5);      % block individual buttons for 0.5s after button press so we will not detect the same button press twice
% SSO.SetButtonBoxReadoutTime(0.5); % block the whole buttonbox for 0.5s after button press 
% SSO.Keys = {'f1','f2','f3','f4'}; % emulation Buttons #1-#4 with F1-F4
n = 0;
% SSO.BBoxTimeout = 1.5;            % Wait for button press for 1.5s
% SSO.BBoxTimeout = -1.5;           % Wait for button press for 1.5s even in case of response
SSO.ResetClock;
while n ~= 10                       % polls 10 button presses
    SSO.WaitForButtonPress;         % Wait for any button to be pressed
    % SSO.WaitForButtonRelease;       % Wait for any button to be released
    % SSO.WaitForButtonPress([],2); % Wait for Button #2
    % SSO.WaitForButtonPress(2);    % Wait for any button for 2s (overrides SSO.BBoxTimeout only for this event)
    % SSO.WaitForButtonPress(-2);   % Wait for any button for 2s even in case of response (overrides SSO.BBoxTimeout only for this event)
    % SSO.WaitForButtonPress(2,2);  % Wait for Button #2 for 2s (overrides SSO.BBoxTimeout only for this event)
    % SSO.WaitForButtonPress(-2,2); % Wait for Button #2 for 2s even in case of response (overrides SSO.BBoxTimeout only for this event)
    n = n + 1;
    fprintf('At %2.3fs, ',SSO.Clock);
    fprintf('Button %d ',SSO.LastButtonPress);
    fprintf('pressed: %2.3fs\n',SSO.TimeOfLastButtonPress);
end