Hello everyone, Ive written a code to make a flickering square with a specific frequency but the problem is I can just get the frequencies that are dividable to my screen frame rate. I can use the floor for the division but in that case I wont have an exact frequency of 40 for example since 144/40 is not an integer. (duty cycle is 50%)
Here`s my code:
clear all
clc
%tic
Screen(‘Preference’, ‘SkipSyncTests’, 1);
screenNum=0;
flipSpd=0;
[wPtr,rect]=Screen(‘OpenWindow’,screenNum); % wPtr - designate the window, rect - screen size
monitorFlipInterval=Screen(‘GetFlipInterval’, wPtr); % Refresh time [s]
frame_rate = (1/monitorFlipInterval); % Frame rate [Hz]
%%%%%%%%%%%%%%%% Setteing Frequencies of the Square %%%%%%%%%%%%%%%%%%%%%
% change "fi"s to change the freq of stimulus
f1 = 2;
p1 = floor(frame_rate/(f1));
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
color_white = [255 255 255]; % Defining white color
color_black = [0 0 0]; % Defining black color
CenX = rect(3)/2; % Center of width screen
CenY = rect(4)/2; % Center of height screen
% Squares coordinates and length
Dis = 2CenX;
SqS = 2CenY;
X1=CenX;
Y1=CenY;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Position of the square %%%%%%%%%%%%%%%%%%%%%
pos1=[CenX-Dis CenY-SqS CenX+Dis CenY+SqS]; % up left
% pos2=[CenX-X2 CenY-Y2-SqS CenX-X2+Dis CenY-Y2]; % bottom left
% pos3=[CenX-X3-Dis CenY-Y3 CenX-X3 CenY-Y3+SqS]; % up right
% pos4=[CenX-X4-Dis CenY-Y4-SqS CenX-X4 CenY-Y4]; % up bottem
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
black=BlackIndex(wPtr); % Find the color lookup table values (black)
white=WhiteIndex(wPtr); % Find the color lookup table values (white)
%% -----------------------------------------------------------------------
Screen(‘FillRect’,wPtr,black); % Fills a rectangle the size of the screen to be black
Screen(wPtr, ‘Flip’); % Flip the screen from offscreen to onscreen
HideCursor;
Screen(‘FillRect’,wPtr,black); % Blacks the screen
vbl=Screen(wPtr, ‘Flip’); % Collect the time for the first flip with vbl
turn1 = 1;
flag = 0;
tic
for i=1:600 % “time of run”
% Generate the flickering squares
if i <= (turn1)p10.5
Screen(‘FillRect’,wPtr,color_black, pos1);
elseif i <= (turn1+1)p10.5 && i > (turn1)p10.5
Screen(‘FillRect’,wPtr,color_white, pos1);
if i == (turn1+1)p10.5
turn1 = turn1 + 2;
flag = 1;
end
end
Screen(wPtr, ‘Flip’);
end
Screen(‘FillRect’,wPtr,black); % Blacks the screen
vbl=Screen(wPtr, ‘Flip’, vbl+(flipSpd*monitorFlipInterval));
Screen(‘CloseAll’);
Anyone has any idea how to fix this or give a suggestion to make flickering squares with exact frequency?
Many thanks