SMSLib is the software library used by SeisMac and SeisMaCalibrate to access the Sudden Motion Sensors in recent Macintosh laptops. Written in Objective-C, it provides easy and stable access, abstracting hardware differences across eleven different models of laptop. For better accuracy, you can use SeisMaCalibrate to calibrate your laptop's Sudden Motion Sensors. SMSLib is open source, released under the University of Illinois/NCSA Open Source License.

I've just been notified of the first non-Suitable Systems application using SMSLib! Mirailabs' Chroma Player now uses SMSLib to do playback stabilization. Wiggle your laptop and the window wiggles in the other direction! Very cool.

The package also inclues smsutil, a stand-alone command-line tool that prints a series of acceleration samples. You can control how many samples are to be fetched, how quickly they are to be fetched, and which axes should be displayed. You can collect up to 500 three-axis accelerations a second (measured on a MacBook Pro). For example, if you open the Terminal, change to the directory containing smsutil, and type

./smsutil -i0.01 -c1000 -atxyz -s09 >capture.txt

then smsutil will start sampling every 10ms, running for 1000 samples (10 seconds), writing one line per sample into the file capture.txt, with each line including the time in milliseconds since smsutil started, and the calibrated x, y and z axis values, all separated by tabs.

You can download version 1.8 of SMSLib here (Mac OS X 10.3.9 or later). All source code is included.