accurate_timing.m

% Clear the workspace and the screen
sca;
close all;
clear all;

% Here we call some default settings for setting up Psychtoolbox
PsychDefaultSetup(2);

% Get the screen numbers. This gives us a number for each of the screens
% attached to our computer.
screens = Screen('Screens');

% To draw we select the maximum of these numbers. So in a situation where we
% have two screens attached to our monitor we will draw to the external
% screen. 
screenNumber = max(screens);

% Define black and white (white will be 1 and black 0). This is because
% in general luminace values are defined between 0 and 1 with 255 steps in
% between. All values in Psychtoolbox are defined between 0 and 1
white = WhiteIndex(screenNumber);
black = BlackIndex(screenNumber);

% Do a simply calculation to calculate the luminance value for grey. This
% will be half the luminace values for white
grey = white / 2;

% Open an on screen window using PsychImaging and color it grey.
[window, windowRect] = PsychImaging('OpenWindow', screenNumber, grey);

% Measure the vertical refresh rate of the monitor
ifi = Screen('GetFlipInterval', window)

% Retreive the maximum priority number
topPriorityLevel = MaxPriority(window)

% Length of time and number of frames we will use for each drawing test
numSecs = 1;
numFrames = round(numSecs / ifi)

% Numer of frames to wait when specifying good timing. Note: the use of
% wait frames is to show a generalisable coding. For example, by using
% waitframes = 2 one would flip on every other frame. See the PTB
% documentation for details. In what follows we flip every frame.
waitframes = 1;

KbStrokeWait;
sca; 

%% 

WaitSecs(1);
for i=1:100000;
    [keyIsDown(i), secs(i), keyCode] = KbCheck;
end;

plot(secs-(secs(1)),keyIsDown)