How do I get MATLAB to output a digital marker via the parallel port to Biopac's Acqknowledge software?

I'm basically using MATLAB in place of E-Prime/Superlab/DirectRT etc. In order to mark Acqknowledge (Biopac) with a digital marker (and trigger acquisition), I require the STP100C - This module would accept a digital marker via the parallel port. Therefore, I need to program MATLAB to output a digital marker via the parallel port of the computer, I'm sure there must be some command for that.

I am trying to collect Event Related Potentials and I have 2 targets/stimuli (T1 & T2). These are letters that are part of a rapid serial visual presentation. After each string is presented, the participant has to reply yes/ no to whether T1 or T2 was presented. As far as physiology is concerned I am measuring the onset of the P300.

Answer 1

[PT]

Take a look at "digitalio" in the Data Acquisition Toolbox. Here's a short example code:

% Initialize 2 lines (2nd line reserved for future use)
ppobjects.dio = digitalio('parallel', 'LPT1');
ppobjects.lines = addline(ppobjects.dio,1:2,'out');

% Set line 1 to high
linenum = 1;
value = 1;
putvalue(ppobjects.lines(linenum),value);

% Set line 1 to low
linenum = 1;
value = 0;
putvalue(ppobjects.lines(linenum),value);

[sonia]

Thanks, I am trying to understand the above. Could you clarify? I'm a novice programmer.For example where would these lines go in my script? and is it the same for every single trigger?

[PT]

The initialization code should be placed near the beginning.

When you need to send a brief pulse of digital-high, do a

   putvalue(ppobjects.lines(1),1);
   pause(0.050);
   putvalue(ppobjects.lines(1),0);

This will generate a 0.050 seconds long digital-high pulse.

[sonia]

Just to clarify I am using a 25-pin parallel port cable, from the stimulus (MATLAB) computer to the physiological recording (Biopac) computer.

I have the data acq. toolbox. What I need is a digital pulse to be sent to the recording computer every time the number 4/7 or the letter X is shown. Also it should be on a separate chennel and not directly on top of the EEG wave form.

It should look something like this: http://www.biopac.com/e-prime-professional-isolated-digital-interface

[PT]

In that case, wire line 1 and gnd of parallel port to the signal and return on your device's digital input. From Wikipedia, it should be pin 2 or 3 for + and any of the gnd pins for -.

Answer 2

[steamrice]

I am haveing a similar software and hardware design problem using biopac and stp100C. Could someone help?