function serialData = PR650serialread
% serialData = PR650serialread
%
% Reads data off the serial port until there is nothing left.  Returns an
% empty matrix if there is nothing to read.

global g_serialPort;

data = IOPort('Read', g_serialPort);
serialData = char(data);

% If data exists keep reading off the port until there's nothing left.
if ~isempty(serialData)
  tmpData = 1;
  while ~isempty(tmpData)
    WaitSecs(0.050);
    tmpData = IOPort('Read', g_serialPort);
    serialData = [serialData, char(tmpData)]; %#ok<AGROW>
  end
end