Stupid PowerBook Tricks: Sudden Motion Sensor Software

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Date: Monday, April 11th, 2005, 23:13
Category: Software

PowerBook Sudden Motion SensorApple added a feature called Sudden Motion Sensor (SMS) to the PowerBook line in early 2005. The sensor attempts to prevent data loss by parking the heads of an active disk drive after detecting a “sudden motion”, which could be due to strong vibrations or a fall. The SMS is also called the Mobile Motion Module, The Mac OS X kernel refers to it as “AMS,” for Apple Motion Sensor, so we’ll adopt the term “AMS” to refer to both the hardware and its software abstraction. Read More…


PowerBook Sudden Motion SensorApple added a feature called Sudden Motion Sensor (SMS) to the PowerBook line in early 2005. The sensor attempts to prevent data loss by parking the heads of an active disk drive after detecting a “sudden motion”, which could be due to strong vibrations or a fall. The SMS is also called the Mobile Motion Module, The Mac OS X kernel refers to it as “AMS,” for Apple Motion Sensor, so we’ll adopt the term “AMS” to refer to both the hardware and its software abstraction.
Amit Singh has figured out how to gather data generated by those sensors. He’s even built a couple of little apps that make use of the sensors.
AMSVisualizer is a graphical application that displays a 3D picture of a PowerBook. The picture’s orientation is a real-time approximation of the PowerBook’s physical orientation. Thus, the on-screen picture moves with the movement of the AMS-equipped PowerBook.
Stable Window creates a window displaying a bicycle wheel. The window is “stable” in the sense that if you rotate the PowerBook left or right, the window compensates by rotating itself by an equal amount in the opposite direction in an attempt to remain in its original orientation with respect to the ground. The bicycle wheel rotates too ? independently of the window.
With Perturbed Desktop the orientation of on-screen windows is set to be a strangely complicated function of several things: the physical orientation of the PowerBook, the amount of resources consumed by the application, and how much the user is using the application. Based on these factors, a given window’s orientation keeps changing. Regardless of orientation, however, you can still interact with all windows.

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