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Thread: Sending responses via TTL (case 5907)

  1. #1
    Join Date
    Sep 2006
    Posts
    14

    Sending responses via TTL (case 5907)

    Hi

    I am using DirectRT to present stimuli in an event-related potential (ERP) experiment. Codes for each stimulus and response have to be sent via TTL to the ERP recording computer so that we can both time-lock ERP responses to stimuli and (importantly) sort ERP responses bsed on whether the subject's response was correct or not. While I've figured out how to send a code via TTL after a response, thus telling the ERP equipment WHEN a response occurred, I can't see any way to send a TTL pulse that codes WHAT key was pressed. It seems that you have to specify the TTL code in advance. Ideally what I would like is something similar to the "feedback" code that you can put in the Stim column to show the last keypress to the subject, but sending that code to the TTL rather than the screen. I tried "ttl:feedback" and "ttl:=" but these didn't work.

    Is it currently possible to do this? Or, could you implement it? It's absolutely essential for using DirectRT in ERP experiments in which we're collecting subject responses.

    thanks
    Aaron
    Last edited by jason_reed; 08-15-2014 at 02:25 PM.

  2. #2
    Join Date
    Nov 2005
    Posts
    3,320
    Hi Aaron,

    See: www.empirisoft.com/support/showthread.php?t=273

    Specifically, look at the release notes for DirectRT v2006.2.18--we added a feature that allows you to echo every response code as a TTL signal--with virtually no delay. It's pretty cool for this type of application. Let me know if it helps!

    -Blair

  3. #3
    Join Date
    Sep 2006
    Posts
    14
    Hi Blair

    Thanks for creating that feature! I downloaded and installed the new version and it works great. In the interim I had figured out another way of doing it, using jumping to different trials depending on which response was made, and sending codes (followed by presenting a "space" character for 0 msec) from the jump trials. But, the TTLecho method is far more flexible and saves one from coding a lot of jump trials if there are many response options.

    It would be great if this could be integrated into the Styles file in a future release, rather than being dependent on an extra file.

    thanks again, DirectRT rocks!

    Aaron

  4. #4

    Change in v2008.1?

    Blair & Aaron
    I am working on programming a task with very similar demand I have created the ttlEcho.txt file and still have had no success in getting a response locked ttl signal. Is there any differences in how v2008.1 handles this situation? I know this thread is old, hopefully this topic is still relevant.

    Evan

  5. #5
    Join Date
    Sep 2006
    Posts
    14
    Hi Evan

    We use 2008 now and as far as I know, sending TTL codes works the same way. However we haven't been using the TTLecho feature so I can't comment on that specifically. Are you able to successfully send TTL codes using the standard approach of including a stim/loc/time triple with your ttl code, port address, and a short value for time (e.g., 10)?

    Aaron

  6. #6
    Hi Aaron,
    The ttl signal feature is working. It is just the ttlEcho feature that is not working. We just need a way to get a ttl signal that generates for responses.

    Thanks for all the help!
    Evan

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