Untitled

function [ dx, dy, sx, sy ] = RawMouse2(devIndex)
% Parse raw HID datastream from a mouse to implement
% raw mouse movement from HID reports.
%
% This is just an example! The data format is mouse
% dependent, this is for a DELL LaserMouse.
%
% Must be run "sudo" root unless proper udev rules
% are defined to allow non-root raw access to mouse
% on your system.
%
% Will (violently) detach the mouse from the GUI,
% making it unuseable for regular "mousing" until
% mouse is unplugged and replugged.
%
% Should work on Linux and probably OS/X. Will not
% work on Windows, as MS forbids low-level HID access to
% mouse and keyboard.
%
% You should disable mouse queries after use via
% PsychHID('ReceiveReportsStop', devIndex); and/or
% flush the buffer via a PsychHID('GiveMeReports', devIndex);
% This is not shown in this demo...

persistent sx;
persistent sy;

% devIndex must be found out by proper matching against
% output of dev = PsychHID('Devices').
if nargin < 1 || isempty(devIndex)
   devIndex = 1;
end

if isempty(sx)
  sx = 0;
  sy = 0;

  % Process at most 2 msecs per 'ReceiveReports' call, so we
  % don't block script execution for too long.
  options.secs = 0.002;
  PsychHID('ReceiveReports', devIndex, options);
end

dx = 0;
dy = 0;

% Fetch a bunch of HID-Reports from the HID device into
% PsychHID internal buffer:
PsychHID('ReceiveReports', devIndex);

% Retrieve them from PsychHID buffer:
reps = PsychHID('GiveMeReports', devIndex);

% Parse them:
for i=1:numel(reps)
  rep = reps(i).report;
  if ~isempty(rep)
    % DELL Lasermouse encodes x,y motion as two 12 bit numbers,
    % packed into bytes 2, 3 and 4: Decode...

    % Byte2[0:7] = 8 LSB of x, Byte 3[0:3] = 4 MSB of x:
    ix = bitshift(bitand(int32(rep(3)), 1+2+4+8), 8) + int32(rep(2));
    % Byte3[4:7] = 4 LSB of y, Byte 4[0:7] = 8 MSB of x:
    iy = bitand(bitshift(int32(rep(3)), -4), 1+2+4+8) + bitshift(int32(rep(4)), 4);

    % 12th bit (aka Bit 11) encodes sign: 1 (aka dx >= 2048) -> Negative dx:
    dx = double(ix);
    if dx >= 2048
      dx = dx - 4096;
    end

    dy = double(iy);
    if dy >= 2048
      dy = dy - 4096;
    end

    % (dx, dy) is mouse delta. Accumulate for abs position:
    sx = sx + dx;
    sy = sy + dy;
  end
end

return;