Creating a response time game with the RESPONSEPixx

This demo showcases a game we usually run on demo nights at conferences. It tests reaction times using a beep and a RESPONSEPixx. The RESPONSEPixx must be plugged into the digital In of any of our devices.

The game rules are as follows:

If there is a beep and a button lights up, press that button as fast as possible.
If there is no beep, you must not press the button.

The beep is created using a sin wave: audioWave = sin([1:32]/32*2*pi);.

Since we are going to light up buttons on the RESPONSEPixx and it is plugged into digital inputs, we must change some of the pins to be treated as output pins by our device. Datapixx('SetDinDataDirection', hex2dec('1F0000'));, sets up 5 pins to be treated as digital outputs (0x1F 00 00 is 0b0001 1111 0000 0000 0000 0000 0000 0000).

We also enable debouncing on the button box. This makes it so that when you press a button, the vibration caused by the push does not trigger from the button box: Datapixx('EnableDinDebounce');.

To keep track of the button presses we use a logger built in the device. The logger keeps track of which inputs were triggered and a precise time-stamp of when the trigger happened Datapixx('SetDinLog');.

For every button press, you will get 2 data points, one for when the button was pressed and one for when it was released. We usually only care about the first value, but the 2nd can be useful. Data is acquired by first updating the local registers: Datapixx('RegWrRd');, and then receiving the data as follows [data timetags] = Datapixx('ReadDinLog');. The status of the digital in when every value is 0 will be (0x00FFFF), or all 1. When a button press happens, one the of digital ins will become zero. For red, we get 0x00FFFE, for green we get 0x00FFFB. You can always convert to binary in order to double check the values, as it is easier to understand a binary expression.

To compare with a value, we usually use a bit-wise and operator. In MATLAB, since we are handling values as decimals, we can just use the normal ~= and = compare operators.

MATLAB

function DatapixxSimonGame()
% DatapixxSimonGame()
%
% A microsecond-accurate audio-visual reaction time game using RESPONSEPixx.
%
% History:
%
% Oct 1, 2009  paa     Written

AssertOpenGL;   % We use PTB-3

% for igame = 0:1000

% User initiates test from keyboard
fprintf('\n\nDATAPixx response-time game.\n');
fprintf('-Connect RESPONSEPixx button box to \"Digital IN\" db-25.\n');
fprintf('-If a button lights up, and a beep sounds, press the button as fast as possible.\n');
fprintf('-If a button lights up, but no beep sounds, do not press any buttons.\n');
HitKeyToContinue('Hit any key on keyboard to begin...\n');

% Open Datapixx, and stop any schedules which might already be running
Datapixx('Open');
Datapixx('StopAllSchedules');
Datapixx('RegWrRd');    % Synchronize DATAPixx registers to local register cache

% Initialize audio system
Datapixx('InitAudio');
Datapixx('SetAudioVolume', 0.25);  % If using headphones, 0.2 is a bit too loud

% Our audio cues and feedback beeps will all be sinewaves.
% Sample a single sinewave period,
% and download the waveform to the Datapixx's default audio address. 
nSinewaveSamples = 32;
audioWave = sin([1:nSinewaveSamples]/nSinewaveSamples*2*pi);
Datapixx('WriteAudioBuffer', audioWave);

% Configure digital input system for monitoring button box
Datapixx('SetDinDataDirection', hex2dec('1F0000'));     % Drive 5 button lights
Datapixx('EnableDinDebounce');                          % Debounce button presses
Datapixx('SetDinLog');                                  % Log button presses to default address
Datapixx('StartDinLog');                                % Turn on logging
Datapixx('RegWrRd');

% Bit locations of button inputs, and colored LED drivers
doutRed     = hex2dec('00010000');
doutGreen   = hex2dec('00040000');
dinRed      = hex2dec('0000FFFE');
dinGreen    = hex2dec('0000FFFB');

% Generate random list of 4 trial types
nReps = 16;
condList = bitand(randperm(nReps),3);

% Initialize response time statistics
nData = 0;
sumData = 0;

% Assume the best, and away we goooo....
winner = 1;
for iRep = 1:nReps

    % Turn off RESPONSEPixx button lights
    Datapixx('SetDinDataOut', 0);
    Datapixx('RegWrRd');

    % Wait until all buttons are up
    while (bitand(Datapixx('GetDinValues'), hex2dec('FFFF')) ~= hex2dec('FFFF'))
        Datapixx('RegWrRd');
    end

    % Flush any past button presses
    Datapixx('SetDinLog');
    Datapixx('RegWrRd');
    % Wait random 1-2 second trial onset delay, so player can't anticipate.
    % Any button press during this period is considered a wrong answer.
    trialStartTime = Datapixx('GetTime') + 1 + rand();
    while (Datapixx('GetTime') < trialStartTime)
        Datapixx('RegWrRd');
        buttonLogStatus = Datapixx('GetDinStatus');
        if (buttonLogStatus.newLogFrames > 0)
            fprintf('OOPS...You pressed a button before any lights came on!\n');
            winner = 0;
            break;
        end
    end
    if (winner == 0)
        break;
    end

    % Bit 0 of condition specifies whether the red or green button should light up
    if (bitand(condList(iRep), 1))
        Datapixx('SetDinDataOut', doutRed);
        correctResponse = dinRed;
    else
        Datapixx('SetDinDataOut', doutGreen);
        correctResponse = dinGreen;
    end

    % Bit 1 of condition indicates if we should beep.
    % 32-sample sinewave buffer playing at 40 kSPS gives a 1250 Hz tone.
    % Playing for 16000 samples gives a tone duration of 400 milliseconds.
    if (bitand(condList(iRep), 2))
        Datapixx('SetAudioSchedule', 0, 40000, 16000, 0, 16e6, nSinewaveSamples);
        Datapixx('StartAudioSchedule');
    end

    % The following 'RegWrRd' register cache update command will simultaneously:
    %   -Turn on the button light.
    %   -Start audio playback (if enabled above).
    %   -Latch all register values, including DATAPixx time at which the stimulus began.
    % Calling 'RegWrRdVideoSync' instead of 'RegWrRd' would synchronize all 3 with video refresh.
    Datapixx('RegWrRd');
    stimulusStartTime = Datapixx('GetTime');

    % Wait up to 1 second for a keypress
    while (Datapixx('GetTime') < stimulusStartTime + 1)
        Datapixx('RegWrRd');
        buttonLogStatus = Datapixx('GetDinStatus');
        if (buttonLogStatus.newLogFrames > 0)
            break;
        end
    end

    % First we'll handle the case where the audio tone was on.
    % In this case, player was supposed to hit the illuminated button.
    if (bitand(condList(iRep), 2))

        % If they didn't hit any button, it's a wrong answer
        if (buttonLogStatus.newLogFrames == 0)
            fprintf('OOPS...You were supposed to press the illuminated button!\n');
            winner = 0;
            break;
        end

        % Check if they hit the correct key
        [data timetags] = Datapixx('ReadDinLog');
        if (data(1) ~= correctResponse)
            fprintf('OOPS...You pressed the wrong button!\n');
            winner = 0;
            break;
        end

        % Accumulate their response time into the statistics
        reactionTime = timetags(1) - stimulusStartTime;
        fprintf('reactionTime = %f\n', reactionTime);
        if (exist('OCTAVE_VERSION'))
            fflush(stdout);
        end
        sumData = sumData + reactionTime;
        nData = nData + 1;

    % Second we'll handle the case where the audio tone was off.
    % In this case, player was not supposed to hit any button.
    elseif (buttonLogStatus.newLogFrames > 0)
        fprintf('OOPS...There was no beep, so do not press any buttons!\n');
        winner = 0;
        break;
    end
end

% Game is over, so turn off all button lights
Datapixx('SetDinDataOut', 0);
Datapixx('RegWrRd');

% If player made it through all trials without any errors, they win!
% Reward with a pleasant musical chirp, and print their stats.
if (winner)
    fprintf('\nSuccess!\n', sumData / nData * 1000);
    fprintf('Mean reactionTime = %d ms\n', sumData / nData * 1000);
    Datapixx('SetAudioSchedule', 0, 40000, 8000, 0, 16e6, nSinewaveSamples);
    Datapixx('StartAudioSchedule');
    Datapixx('RegWrRd');
    while 1
        Datapixx('RegWrRd');   % Update registers for GetAudioStatus
        status = Datapixx('GetAudioStatus');
        if (~status.scheduleRunning)
            break;
        end
    end
    Datapixx('SetAudioSchedule', 0, 80000, 16000, 0, 16e6, nSinewaveSamples);
    Datapixx('StartAudioSchedule');
    Datapixx('RegWrRd');
    while 1
        Datapixx('RegWrRd');   % Update registers for GetAudioStatus
        status = Datapixx('GetAudioStatus');
        if (~status.scheduleRunning)
            break;
        end
    end

% If player hit a key when they weren't supposed to,
% then taunt them with an unsavoury buzz.
else
    Datapixx('SetAudioSchedule', 0, 10000, 10000, 0, 16e6, nSinewaveSamples);
    Datapixx('StartAudioSchedule');
    Datapixx('RegWrRd');
    while 1
        Datapixx('RegWrRd');   % Update registers for GetAudioStatus
        status = Datapixx('GetAudioStatus');
        if (~status.scheduleRunning)
            break;
        end
    end
end

% Job done
Datapixx('Close');
fprintf('\nGame completed\n\n');

% end