Send EEG triggers from OpenSesame via parallel port

For my all EEG paradigms I need to send marks (triggers) via parallel port to EEG to make a stamp when stimuli occurred and which one was that.

In my lab we use Biosemi ActiveTwo 64 active electrode system which can work only with 0-255 range of values. It means you can tag only 255 event types in your recording.

Cookbook

Ingredients

• OpenSesame installed (tested on version 3.0)
• Download dlportio.dll installer for Win-64bit (whole package contains testing paradigm)
• Know you parallel port address (usually 0x378 or 0xCFF8)

Method

1. Unzip downloaded dplportio driver. Run Install/InstallDriver.exe with admin.
2. Copy dlportio.dll and paste it to the two locations a) root of installed OpenSesame and b) C:\Windows\SysWOW64

That is basically it. Just run OpenSesame and start new experiment. Add some sketchpads as fake stimuli (I named them stimA, stimB etc. to get experiment longer to properly see if triggers are working).

How to send triggers

First you can read a lot about initializing and sending EEG trigger by parallel port in OpenSesame on its website.

Initialize parallel port communication

First thing first. At the begging of your experiment you have to initialize a communication between OpenSesame and parallel port. This is done by initializing inline script which is regular in-line script at the top of your main procedure. Enter this code into preparation tab of in-line script.

try:
    from ctypes import windll
    global io
    io = windll.dlportio # requires dlportio.dll !!!
except:
    print 'The parallel port couldn\'t be opened'

 

This part of code initialize dlportio library which do the whole magic in writing bytes into you parallel port.

Null the port

After initialization I highly recommend to set parallel port value to 0 to prevent anything unwanted to be send (“ghost triggers”) from the whole begging.

All you need to do is enter another in-line script and write 0 to your parallel port like this:

global io
port = 0xCFF8
try:
    io.DlPortWritePortUchar(port, 0)
except:
    print 'Failed to send initial zero trigger!'

Or simply:

global io
io.DlPortWritePortUchar(0xCFF8, 0)

 

Write a byte

I guess need more than nilling the parallel port, so let’s look at how to send an integer value.

The method is basically the same but you have to set pulse duration and then set it back to the zero. This is done very similarly:

global io
trigger = 1
port = 0xCFF8
io.DlPortWritePortUchar(port, trigger)	# Send you trigger (int 1)
self.sleep(50)	# Uses trigger pulse for 50 ms
io.DlPortWritePortUchar(port, 0)	# Get back to zero after 50 ms

That it is. If you want to download my testing paradigm to test if your dlportio.dll was installed correctly or see how writing a byte to parallel port work, there is a link.