ResponsePixx - Control and use the ResponsePixx response button box.

This allows to record button events from the ResponsePixx response box
device. Start and stop of logging of button responses and control of the
button lights (on/off and intensity) can be done immediately or
synchronized to the operation of the Screen(‘Flip’) command, ie.,
synchronized to visual stimulus onset.

By default, ResponsePixx response boxes with 5 buttons are supported.
Specify the ‘nrButtons’ parameter in the ‘Open’ subfunction if you need a
different button count.

The code can scan the first 16 digital input pins of the Datapixx, i.e.,
nrButtons can be up to 16, e.g., to control self-made response boxes. The
last 8 input pins are not useable for timestamped button queries and are
instead used to drive the button illumination of the ResponsePixx

Caution: Avoid intermixing ‘StartNow’/’StopNow’ commands with
‘StartAtFlip’/’StopAtFlip’ commands. While this may work, there is some
potential for using it the wrong way and producing very “funny” bugs.

For reaction time measurements wrt. visual stimuli, see the timestamp
logging functions of the PsychDataPixx driver to get timestamps in
Datapixx clock time. You can also calculate RT’s in GetSecs time wrt. the
host clock by using the usual Screen(‘Flip’) or PsychPortAudio stimulus
onset timestamps, which may be even more convenient. However, if you do
so, make sure that you read and understand the comments about achieving
good precision by correcting for clock drift, both in the help of the
ResponsePixx subfunctions and in the help of PsychDataPixx. Specifically
look at PsychDataPixx(‘GetPreciseTime’) and

Button mapping on the ResponsePixx handheld device

Buttonvector element [1,2,3,4,5] == [Red, Yellow, Green, Blue, White].

Subfunctions and their meaning

ResponsePixx(‘Open’ [, numSamples=1000][, bufferBaseAddress=12e6][, nrButtons=5]);

  • Open ResponsePixx for button response collection. Configures the 24 bit
    digital input port of the DataPixx to receive button responses from a
    ResponsePixx response button box and to drive the button illumination
    lights of that box. Enabled button debouncing on the digital inputs.

Optional argument ‘numSamples’ defines the maximum number of button
transitions to log. Defaults to 1000 if omitted. ‘bufferBasAddress’ if
provided is the memory start address of the logging buffer inside the
Datapixx. Defaults to 12e6 if omitted.

Optional argument ‘nrButtons’ defines the number of buttons to query. Can
be up to 16 buttons for the first 16 TTL inputs of the DataPixx, but
defaults to 5 buttons - the maximum number supported by the current
ResponsePixx devices.

This function doesn’t start logging of responses. Call the ‘StartNow’ or
‘StartAtFlip’ subfunction for start of response collection. Call
‘StopNow’ or ‘StopAtFlip’ to stop response collection.


  • Close ResponsePixx after stopping any running logging operations.
    Disable the button lights and reset the digital input port of the

[startTimeBox, startTimeGetSecs] = ResponsePixx(‘StartNow’ [, clearLog=0][, buttonLightState][, buttonLightIntensity]);

  • Start button response collection immediately (ie., with minimum
    possible delay on your system). Set the optional ‘clearLog’ flag to 1 if
    all currently stored button responses should be discarded prior to
    logging of new responses, e.g., at start of a new trial.

The optional vector ‘buttonLightState’ allows to define the on/off state
of the button illumination, e.g., buttonLightState = [0,1,0,0,1] would
turn on the light inside button 2 and 5 and turn off the lights in
buttons 1, 3 and 4. By default, the state of the button lights is not
changed. The optional value ‘buttonLightIntensity’ in the range 0.0 to
1.0 controls the intensity of the button illumination.

Returns a ‘startTimeBox’ timestamp in Datapixx clock time of when
acquisition actually started. You can also use the 2nd optional return
argument ‘startTimeGetSecs’ to get the same timestamp mapped to
Psychtoolbox GetSecs() time. For a more precise post-hoc mapping to
GetSecs time, you can convert the ‘startTimeBox’ timestamp into
Psychtoolbox GetSecs() time with the proper mapping functions of
PsychDataPixx (see “help PsychDataPixx”).

The function can be called multiple times, while logging is already
started, if you just want to clear the log of stored responses or change
the state of the button lights.

ResponsePixx(‘StartAtFlip’ [, flipCount=next][, clearLog=0][, buttonLightState][, buttonLightIntensity]);

  • Schedule start of response collection synchronized to the visual stimulus
    onset of a future Screen(‘Flip’) or Screen(‘AsyncFlipBegin’) command.

All parameters are identical to the ones for ResponsePixx(‘StartNow’,…),
except for the first optional parameter ‘flipCount’. ‘flipCount’ defines
at which Screen(‘Flip’) acquisition should be started. If omitted or
set to zero or [], acquisition will be started by the next flip command.
Otherwise it will be started by the flip command with the given
‘flipCount’. You can query the current flipCount via PsychDatapixx(‘FlipCount’).

Example: Setting flipCount = PsychDatapixx(‘FlipCount’) + 10; would start
acquisition at the 10’th invocation of a flip command from now.

This function doesn’t return a start timestamp as acquisition will
only happen in the future, so the timestamp is only available in the

[stopTimeBox, stopTimeGetSecs] = ResponsePixx(‘StopNow’ [, clearLog=0][, buttonLightState][, buttonLightIntensity]);

  • Stop button response collection immediately (ie., with minimum
    possible delay on your system). See ‘StartNow’ for meaning of optional

The function can be called multiple times, while logging is already
stopped, if you just want to clear the log of stored responses or change
the state of the button lights.

ResponsePixx(‘StopAtFlip’ [, flipCount=next][, clearLog=0][, buttonLightState][, buttonLightIntensity]);

  • Schedule stop of response collection synchronized to the visual stimulus
    onset of a future Screen(‘Flip’) or Screen(‘AsyncFlipBegin’) command.
    See ‘StartAtFlip’ for meaning of parameters.

[buttonStates, transitionTimesSecs, underflows] = ResponsePixx(‘GetLoggedResponses’ [, numberResponses=current][, blocking=1][, timeout=inf]);

  • Try to fetch logged button responses from a running logging
    operation. Only call this function after logging has been
    started via ResponsePixx(‘StartNow’) or scheduled for start at a
    certain flipCount via ResponsePixx(‘StartAtFlip’) and the flip is
    imminent, i.e., after the flip command for that flip has been called
    already. The function will error-out if you call it too early!

The optional ‘numberResponses’ asks the driver to return exactly
‘numberResponses’ button transitions. By default it will return whatever
is available at time of call. If ‘numberResponses’ is specified, but the
requested amount is not yet available, the optional ‘blocking’ flag will
define behaviour: If set to 1 (default), the driver will wait until the
specified amount becomes available. If set to 0, the driver will return
with empty [] return arguments so you can retry later. If ‘blocking’ is
set, then the driver will wait for at most ‘timeout’ seconds for a
response, then return anyway. By default the timeout is infinite.

‘buttonStates’ is a n-by-5 matrix: The n’th row encodes the button state
after the n’th transition of button state. Each column encodes up/down
state of a button, ie., the j’th column encodes state of the j’th button.
0 = Button released, 1 = Button pressed. A button press followed by a
release would create two rows of button transition, one for the
buttonState after pressing a button, a second one for the state after
releasing the button. The ResponsePixx uses a debouncing algorithm to
filter out multiple transitions within a 30 msecs time window.

‘transitionTimesSecs’ is the vector of timestamps in Datapixx clock time
of when the corresponding button state has changed. The i’th element
corresponds to the time when the i’th element in the ‘buttonStates’
vector was logged due to a change in button state at that time. See
“help PsychDataPixx” on how to map these box timestamps to GetSecs()
timestamps if you wish.

‘underflows’ is the number of times the logging buffer underflowed. This
indicated lost or corrupted button events. It should only happen if your
subject pressed more buttons within two calls to ‘GetLoggedResponses’
than the event buffer can hold. The size of the buffer can be selected at
‘Open’ time with the ‘numSamples’ parameter, but it defaults to a
generous 1000 button events.

[buttonStates, boxTimeSecs, getsecsTimeSecs] = ResponsePixx(‘GetButtons’);

  • Perform immediate query of response box button states. Return current
    state in ‘buttonStates’ and corresponding box time and GetSecs time
    timestamps of time of query in ‘boxTimeSecs’ and ‘getsecsTimeSecs’.
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