EyeTribe Toolbox for Matlab

version 0.0.3 (03-Jun-2015)

ABOUT

The EyeTribe Toolbox for Matlab is a set of functions that can be used to communicate with eye trackers manufactured by the EyeTribe. The communication process is not direct, but goes via a sub-server that receives input from Matlab (when the functions from this toolbox are called), and then sends commands to the actual EyeTribe server.

This setup is rather odd, but it is the most elegant solution that I could come up with to get around the problem of Matlab not having decent multithreading functionality. This functionality is required for running a heartbeat Thread (which keeps the connection with the EyeTribe alive), and another Thread to monitor samples (and write these to a log file). Similar results might be obtained by using callback functions within Matlab's TCP/IP framework, but that approach causes timing errors that extent into other domains: timing issues when using PsychToolbox's WaitSecs function, and background processes in Matlab screwing up all sorts of other timing sensitive processes.

So, out of lazine... Err... Out of a well-planned timing management effort to avoid time loss by re-inventing the wheel, I simply used PyTribe in a short Python script (see the python_source folder for the source) to compile a Windows executable, which should be run before you run your Matlab script.

The calibration routine is based on the PsychToolbox for Matlab, and requires an active window to be passed to it. This assures that you are free to calibrate the tracker at any given moment in your experiment, without having any external calibration routine battle with your experiment for control of the active display.

If you do not want to calibrate using the PsychToolbox, you can still use the EyeTribe Toolbox for Matlab, by simply NOT calling the eyetribe_calibrate function. Please do note that you should then calibrate the system with your own means, e.g. by using the EyeTribe's own GUI (C:\Program Files (x86)\EyeTribe\Client\EyeTribeWinUI.exe) before starting any software that calls upon the EyeTribe Toolbox for Matlab.

IMPORTANT

A very common assumption among people using the EyeTribe for Matlab Toolbox is that calling the sample function is a requirement. This is not true! After calling eyetribe_start_recording the executable (EyeTribe_Matlab_server.exe) will make sure that data will be written to the log file. Calling eyetribe_stop_recording will halt data logging. The eyetribe_sample and eyetribe_pupil_size functions have nothing to do with data recording!

So why are they there? Well, sometimes you want to use participant's point of regard to change something on-screen or to give feedback. To this end, you can call eyetribe_sample to get the most recent gaze coordinates. These can be used to set the location of a stimulus (e.g. to lock it to gaze position), or to monitor whether a participants is looking at a certain stimulus.

In sum, the eyetribe_sample and eyetribe_pupil_size functions are there to support gaze-contingent displays. They are not related to the recording of data: the executable running in the background will handle this in the background, storing gaze and pupil data in a text file.

DOWNLOAD

1. Go to: https://github.com/esdalmaijer/EyeTribe-Toolbox-for-Matlab

2. Press the Download ZIP button, or click this direct link.

3. Extract the ZIP archive you just downloaded.

4. Copy the folder EyeTribe_for_Matlab to where you want it to be (e.g. in your Documents folder, under MATLAB).

5. In Matlab, go to File -> Set Path -> Add folder and select the folder you copied at step 4.

Alternatively, place the following code at the start of your experiment:

% assuming you placed the EyeTribe_for_Matlab directly under C:
addpath('C:\EyeTribe_for_Matlab')

USAGE ON WINDOWS

1. Start EyeTribe Server C:\Program Files(x86)\EyeTribe\Server\EyeTribe.exe

2. Start EyeTribe_Matlab_server.exe.

3. Run your Matlab script, e.g. the one below:

USAGE ON OS X AND LINUX

Thanks to @shandelman116 for trying this out (see issue #4).

1. Open a Terminal.
2. Use the cd function to go to the python_source folder. An example:

cd /home/python_source

3. Use Python to run the source. Python should be installed on any Linux system, and I think OS X usually comes with it as well. Type the following command in the Terminal:

python EyeTribe_Matlab_server.py

4. Now run your Matlab script (but do it within two minutes of starting the Python script, because it will time out after that).

EXAMPLE SCRIPT

% don't bother with vsync tests for this demo
Screen('Preference', 'SkipSyncTests', 1);

% initialize connection
[success, connection] = eyetribe_init('test');

% open a new window
window = Screen('OpenWindow', 2);

% calibrate the tracker
success = eyetribe_calibrate(connection, window);

% show blank window
Screen('Flip', window);

% start recording
success = eyetribe_start_recording(connection);

% log something
success = eyetribe_log(connection, 'TEST_START');

% get a few samples
% NOTE: this is NOT necessary for data recording and
% collection, but just a demonstration of the sample
% and pupil_size functions!
for i = 1:60
    pause(0.0334)
    [success, x, y] = eyetribe_sample(connection);
    [success, size] = eyetribe_pupil_size(connection);
    disp(['x=' num2str(x) ', y=' num2str(y) ', s=' num2str(size)])
end

% log something
success = eyetribe_log(connection, 'TEST_STOP');

% stop recording
success = eyetribe_stop_recording(connection);

% close connection
success = eyetribe_close(connection);

% close window
Screen('Close', window);