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Parallel Port Sending Extra Random Triggers?

The triggers in my EEG experiment are working beautifully. I have a unique trigger number to mark the beginning and end of each type of stimulus (video). An example of one successful iteration from BrainVision post-collection is pasted below:

However, the port sometimes randomly sends extra triggers with no apparent pattern, and I cannot figure out a way to stop it. The correct trigger is also sent, but an extra trigger is sent at the same exact time. An example of a bad iteration is shown below:

My setup in Psychopy during which the problem occurs is below:

I want to clarify that the extra trigger is not a “delayed” trigger from a previous trial, but an additional trigger. Although I troubleshot the non-slip timing (e.g., changing the movie to a fixed duration), the fact that the underlying code resets the routine timer after each trial led me away from nailing the timer as the problem. Perhaps I am wrong? I’ve searched these threads, and I have not found a similar problem with extra triggers. Could someone please assist me?

Thanks so much,

For further clarification, Epoch_1 sends “S 3,” and Epoch_2 sends “S 6.” There is a subsequent response routine that sends “S 7” to mark the end of Epoch_2. (Epoch_1 = S 3 - S 6; Epoch_2 = S6 - S7)

That’s weird - how does the BrainVision system read out parallel port pins? Is it only looking for particular data pins or is it reading a decimal value off the entire set of data pins? Are you masking the parallel port input signal to BrainVision to code the beginning/end markers? I’ve never encountered this issue before but I have experienced parallel port pins being randomly high/low. One sanity check could be to swap the parallel port cable and make sure it’s not the cable itself causing your issue.