Sending/Receiving triggers through parallel port interface

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Parallel Port

The Stim computer and the Data Acquisition computer are connected via a parallel port. This is how the triggers are sent from the stim computer to the STI channels. You can use any experimental program - Eprime, Psychopy in order to send triggers to the MEG system. The codes are completely your choice. In MEG, one would want to tag every event in the data for further analyses. So you can specify the event codes in the script you are using to tag the event stim.

Sending Triggers

You can bring your own laptop or use the stim computer we have setup in the MEG lab. In order to send triggers to the MEG acq Trigger system, you will need a parallel port available in your device. The parallel port will connect your laptop to the BNC trigger box that sends the triggers to the MEG_ACQ computer.

The MEG acquisition software accepts stimulus codes as binary triggers. The system supports a 8 bit code, which means you can send pulses between 0 and 255. While your scripts are coded with event numbers (0 to 255), you will actually be seeing binary trigger combinations light up on the BNC trigger box (STI 102) that is located on the stim computer table.

Reading Button Responses VIA Parallel Port

You can use the fibre optic response pads to record your responses in the MEG data acquisition computer along with your raw signal data. If you would like to design a task that is adaptive to the participant's response or if you would simply like to have the responses recorded both in the MEG raw signal and in the stim computer side, you will need to have the participant responses fed into the stim computer via the parallel port.

TO DO: Connect your response cables to any of the BNC "IN" pins 12 to 16 in the trigger box STI101, and have it mirrored to STI102 so it can be read through the interfaced parallel port.

REASON: The cable from the 37 pin output on the trigger box is connected to the 25 pin input to the computer. Basically, only 5 of the output channels (12-16) are being fed to the computer. These channels appear on pins 11-15 on the 25 pin end of the cable, which are the status channels, not the data channels. So in order to read the responses on the stim computer end, one must connect the response cables to channels in the 12-16 range of the trigger box.

1) To write to the trigger box, use address 0x378.
2) To read from the box, use address 0x379.
3) The button box and any TTL input should be plugged into lines 12-16 on the trigger box.