--Got IMU timestamp working more efficiently.  After IMU timestamp, could not get Gumstix to pull data from IMU faster than 25 Hz.  Changed the design to have the IMU push data as fast as it computes it, and have the Gumstix loop on a listener.  This got updates at as close to 50 Hz as I think we can get (intervals between IMU data -- measured by IMU clock -- were all either 20 or 21 ms, for a run of ~3000 samples).