KbCheck

    function [keyIsDown,secs, keyCode] = KbCheck(deviceNumber)

    % [keyIsDown,secs,keyCode] = KbCheck([deviceNumber])

    %

    % Acknowledgment keyboard cachet (keyIsDown),   time   (secs) of the cachet check, and

    % keyboard browse cipher (keyCode).

    %

    %    keyIsDown      1 if any key, including modifiers such as ,

    %                    or  is down. 0 otherwise.

    %

    %    secs           time of keypress as alternate by GetSecs.

    %

    %    keyCode        Mac: a 128-element analytic array.  Anniversary bit aural the

    %                   analytic arrangement represents one keyboard key. If a key is

    %                   pressed, its bit is set, othewise the bit is clear. To

    %                   catechumen a keyCode to a agent of key numbers use

    %                   FIND(keyCode). To acquisition a keys keyNumber use KbName

    %                   or KbDemo.

    %

    %                   Win: a 256-element array. It seems that the first

    %                   128 elements accord to the

    %                   ascii arrangement of the characters, and may be consistent

    %                   with the Mac key codes.

    %

    % KbCheck and KbWait actuate whether any key is down now, including the

    % meta keys: , , , , and . The

    % alone key not appear is the alpha key (triangle) acclimated to ability on your

    % computer.

    %

    % GetChar and CharAvail are character-oriented (and slow), admitting KbCheck

    % and KbWait are keypress-oriented (and fast). If alone a meta key was hit,

    % KbCheck will acknowledgment true, because a key was pressed, but CharAvail will

    % acknowledgment false, because no appearance was generated. See GetChar.

    %

    % KbCheck and KbWait are MEX files, which yield time to amount if theyre

    % first called. Theyll then break loaded until you even them (e.g. by

    % alteration agenda or calling Bright MEX).

    %

    % OS X: ___________________________________________________________________

    %

    % KbCheck uses the PsychHID function, a accepted purpose action for

    % account from the Animal Interface Accessory (HID) chic of USB devices.

    %

    % OS 9: ___________________________________________________________________

    %

    % Command-Period causes an actual exit.

    %

    % The Mac OS Accident Administrator detects and queues typed characters in the

    % background. GetChar will acknowledgment any characters typed afore the  alarm to

    % GetChar. FlushEvents can be acclimated to bright the appearance accident  buffer

    % apprehend by GetChar. Clashing GetChar, KbCheck alone letters keys  depressed at

    % the moment KbCheck is called.  FlushEvents has no aftereffect  on KbCheck.

    %

    % Hitting CapsLock makes KbCheck and KbWait anticipate that youre captivation the

    % about-face key down. They will abide to anticipate so (returning 1) until you

    % absolution the about-face by hitting CapsLock again.

    %

    % KbCheck and KbWait ascertain that a key is down by using the low-level Mac

    % OS alarm GetKeys. Its not bright what banausic accurateness this provides, but

    % its abundant bigger than traveling through the higher-level Accident Manager. Our

    % consequence from account the affidavit in Dan Costins KeMo package

    % web http://psychtoolbox.org/kemo.html

    %  is that this

    % low-level alarm still has ambiguity on the adjustment of 11 ms because of the

    % way the Mac OS acclamation ADB devices. Anyone able could apparently use his

    % advice to advance MEX files that timed keypresses added  accurately than

    % KbCheck does.

    %

    % _________________________________________________________________________

    %

    % See also: FlushEvents, KbName, KbDemo, KbWait, GetChar, CharAvail, KbDemo.

    % TO DO:

    %

    %  - Acknowledgment that on USB systems there the USB bus is sampled at 100hz

    %  - We could augment this to to acquire an alternative keyboard accessory number.

    % 3/6/97  dhb  Wrote it.

    % 8/2/97  dgp  Explain aberration amid key and character.

    % 1/28/98 dgp  Explain CapsLock.

    % 2/4/98  awi  Explain keyCode.

    % 2/13/98 awi  Afflicted keyCode to analytic array, pointers to KbDecode, KbExplore.

    % 2/19/98 dgp  Beneath by affective some argument to GetChar.m.

    % 3/15/99 xmz  Added animadversion for Windows version.

    % 6/23/00 awi  Added branch allegory queuing of GetChar and KbCheck.

    % 7/7/00  dgp  Cosmetic.

    % 6/17/02 awi  %                Added codicillary abracadabra of PsychHID on OSX

    % 7/12/04 awi  Cosmetic.  Separted platform-specific help. Use IsOSX now.

    % 7/13/05 rpk  Added adeptness to array out invalidProducts that were

    %                   advised keyboards. Also, will now analysis all

    %                   accurate keyboards insted of just the first one. 

    keyIsDown = 0;

    if IsOSX

        if nargin 0

            invalidProducts = ;

            accessories = PsychHID(devices);

            for i = 1:length(devices)

                if(strcmp(devices(i).usageName, Keyboard) )

                    for j = 1:length(invalidProducts)

                        if(~(strcmp(invalidProducts, devices(i).product)))

                            if(~keyIsDown)

                                [keyIsDown,secs, keyCode]= PsychHID(KbCheck, i);

                            end

                        end

                    end

                end

            end

        elseif nargin > 1

            error(Too some arguments supplied to KbCheck);

        end

    end