TRACKPixx Demo 8 -- Running a simple saccade to target task with analog output of eye position
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.. Note::
    This demo requires TRACKPixx Revision 18 or later. You can check for recent firmware updates at vpixx.com/whatsnew

This demo is a version of the eight-trial saccade to target experiment with analog output of left and right x, y eye positions. We use the analog Loopback feature on the DATAPixx3 to read this analog signal on the analog to digital converter. At the end of the demo, we plot this recorded analog output in MATLAB.

On each trial, a fixation cross appears in the center of the screen. At the same time an eye-tracking schedule is started, and we check the ``IsSubjectFixating`` flags and ``GetEyePosition`` to determine when the participant is fixating centrally. After central fixation, a target appears in one of four locations on the screen. Participants must saccade to fixate on the target as quickly as possible. As soon as this target fixation is detected, a 500 ms, full-screen visual mask is displayed and the next trial begins. 

At the beginning of the demo there is an optional calibration step. This step calls ``TPxTrackpixx3CalibrationTesting``, which implements a standard MATLAB TRACKPixx3 calibration script. The tracker must be calibrated for every new participant. We also recommend calibrating after a participant moves away from the chinrest.


.. literalinclude:: ../DatapixxToolbox/DatapixxDemos/TPxSaccadeToTargetAnalog.m
   :language: matlab
   :linenos: