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Thread: MediaLab Eyetracker Slide Numbering

  1. #1
    Join Date
    Nov 2007

    MediaLab Eyetracker Slide Numbering

    We are running an ASL eyetracker with Medialab presenting still slides. We can get MediaLab to signal slide changes however we cannot get corresponding slide name/number in our Eyetracker data file. Can Medialab signal to eyetracker the slide number/name from which the information is being sent?

  2. #2
    Join Date
    Nov 2005

    How many digital inputs does your eyetracker system have?

    If you have several, you could number your images and then convert that number to binary and send it out the door using the MediaLab computer's parallel port.

    IE, Show image #6, then have MediaLab briefly activate these I/O lines:


    The eyetracker system would show a '6' as being received and could store that information somewhere in the data file.

    If you have 'X' digital inputs, you can encode 2^X discrete values.

    2 inputs gives you 4 values, 4 inputs gives you 16. 8 inputs gives you 256.

    Does that make any sense?
    Last edited by JEC; 11-13-2007 at 04:05 PM.

  3. #3
    Join Date
    Nov 2007

    Sort of? Could you clarify a few more things

    The eyetracker I believe has 128. But exactly where in the medialab editor sheet would I place the binary number corresponding to the specific slide? Also, as I am not well versed in binary code, what is the best way to figure out the code for each number. At this juncture there will be 96 slides (or images) to present within medialab.

    Thanks again for the help,


  4. #4
    Join Date
    Nov 2005

    Can you send me a link for documentation re: your eye tracker? Specifically, I'd like to see how it handles digital input.

    Converting to binary is easy. If you're on a Windows machine, find the calculator. It's usually in the start menu, then under accessories.

    When the program comes up, just type your decimal number in to the main window. Then, in the top left corner check 'Bin' instead of 'Dec.' The calculator will make the conversion for you.

    You may need to prepend some zeroes to the answer you receive.


    Decimal 32 is

    100000 binary

    You need it to be 8 digits long. So...


    Make sense?

    I would probably put this 'nametag' immediately following the trigger output you have in your MediaLab experiment, but before the stimulus is presented.

    As far as placement goes...

    My syntax is wrong, but the gist of it is:

    --- Trigger EyeTracker
    --- Send binary nametag
    --- Display photo / video clip / etc

    --- Repeat as required.
    Last edited by JEC; 11-14-2007 at 04:10 PM.

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