What command to accept/reject trial with left button press for eye tracker

Hello,

We are doing a project involving eye tracking and EEG measurements, with a PING being sent to the EEG when we accept/reject a trial. Most of the code is specified for a space bar and not a button press, but we need to indicate if we accepted or rejected a trial on the eye tracker which requires a left button press. What command can we use for this?

See below for an example of the code. We believe the command we need would be added before the fprintf(s2,'12') line:

if target_type==1;

fprintf(s2, '00'); %reset USB BBT module code line

Anti_only;

fprintf(s2, '0B'); %BBT ping for fixation cross baseline

disp('EEG baseline recording press enter to continue')

pause;

anti_Fix_left_far;

fprintf(s2, '03'); %ping code for anti_left_far

WaitSecs(rand()*(max_wait_time - min_wait_time) + min_wait_time); %%%%this needs to be randomized between 900 and 1,000 ms for fixation extinguish

Anti_only;

fprintf(s2, '01'); %%%%ping for target extinction

WaitSecs(0.9)

if strcmp(button, 'Yes')

fprintf(s2,'12'); %%% PING EEG computer to denote a "GOOD trial". %%%ADDED BY Michelle ON DEC 3, 2021

elseif strcmp(button, 'No')

fprintf(s2,'13'); %%% PING EEG computer to denote a "BAD TRIAL". %%%ADDED BY Michelle ON DEC 3, 2021

gap=2;

task=2;

eccentricity=2;

space=2;

fprintf(s2, '00');%%%%ping for clearing BBT module

disp('GUI should go up')

end

end

Answer 1

[Alagu Sankar Esakkiappan]

I see that you are trying to detect a keystroke from keyboard to perform further actions in your MATLAB code. This may easily be achieved using waitforbuttonpress to wait for a keystroke and then obtaining keystroke input from current figure using get function.

You may refer to the following code snippet for reference:

k = waitforbuttonpress; % Waits in this line till a Keystroke is detected
value = double(get(gcf,'CurrentCharacter')); % Stores the ASCII value for detected Keystroke
close(gcf); % Closes the Figure opened for detecting Keystroke
target = 28; % ASCII value for "Left Button" press
if ( value == target ) % Check if "Left Button" is pressed
    disp('Left Button pressed');
else
	disp('Left Button not pressed');
end

[Priyanka Persaud]

Thank you Alagu :)