Method and apparatus for motion sensing of a handheld device relative to a stylus

1. A method for determining motion of a handheld device relative to a stylus, the method comprising:

receiving, from the stylus, stylus orientation data comprising data descriptive of an absolute orientation of the stylus;

determining handheld device orientation data, descriptive of an absolute orientation of the handheld device, from signals from sensors of the handheld device;

sensing local motion of the handheld device, the sensing generating local motion data descriptive of handheld device motion in a frame of reference of the handheld device;

calculating a relative orientation between the handheld device and the stylus from the local motion data and the stylus orientation data;

determining motion of the handheld device relative to the stylus from the relative orientation; and

in response to user input, selecting if a software application executed on the handheld device is to be controlled in response to an absolute motion of the handheld device or in response to the determined motion of the handheld device relative to the stylus.

2. The method of claim 1 , where determining the handheld device orientation data comprises determining the handheld device orientation dependent upon signals from one or more of: an accelerometer, a gyroscope and a magnetic field sensor of the handheld device.

3. The method of claim 1 , where determining motion of the handheld device relative to the stylus comprises:

rotating the local motion data dependent upon the relative orientation between the handheld device and the stylus.

4. The method of claim 1 , further comprising:

controlling a software application executed on the handheld device in response to the motion of the handheld device relative to the stylus.

5. The method of claim 1 , further comprising time-aligning the stylus orientation data and the handheld device orientation data.

6. The method of claim 1 , further comprising:

determining orientation of the handheld device relative to the stylus from the stylus orientation data and the handheld device orientation data.

7. A handheld device comprising:

one or more sensors operable to provide sensor signals in response to motion or orientation of the handheld device;

a communication module operable to receive stylus orientation data from a stylus, the stylus orientation data descriptive of an absolute orientation of the stylus; and

a processor coupled to the one or more sensors and the communication module and operable to:

determine handheld device orientation data, descriptive of an absolute orientation of the handheld device, from sensor signals;

determine motion of the handheld device relative to the stylus from the stylus orientation data and the handheld device orientation data; and

in response to user input, select if a software application executed on the handheld device is to be controlled in response to an absolute motion of the handheld device or in response to the determined motion of the handheld device relative to the stylus.

8. The handheld device of claim 7 , where the processor is further operable to:

determine orientation of the handheld device relative to the stylus from the stylus orientation data and the handheld device orientation data; and

execute an application dependent upon the orientation of the handheld device relative to the stylus.

9. The handheld device of claim 7 , where the one or more sensors comprise a tilt sensor, a magnetic field sensor, or a combination thereof.

10. The handheld device of claim 7 , where the one or more sensors comprise an accelerometer, a gyroscope, or a combination thereof.

11. The handheld device of claim 7 , where the processor is further operable to execute an application in response to an orientation of the handheld device relative to the orientation of the stylus.

12. The handheld device of claim 7 , where the processor is further operable to execute an application in response to an orientation of the handheld device relative to an absolute frame of reference.

13. The handheld device of claim 7 , where the processor is further operable to execute an application in response to a motion of the handheld device relative to an absolute frame of reference.

14. The handheld device of claim 7 , further comprising a clock, where the handheld device is operable to time-align the stylus orientation data and the handheld device orientation data in response to a timing signal provided by the clock.

15. The handheld device of claim 7 , where the handheld device comprises a tablet computer.

16. The handheld device of claim 7 , where the handheld device comprises a mobile telephone.

17. A method executed on a handheld device, the method comprising:

determining motion of the handheld device relative to a stylus, dependent upon:

obtaining stylus orientation data descriptive of an orientation of the stylus and received through communication with the stylus;

obtaining orientation data descriptive of an orientation of the handheld device;

sensing local motion of the handheld device, the sensing generating local motion data descriptive of handheld device motion in a frame of reference of the handheld device; and

calculating a relative orientation between the handheld device and the stylus from the local motion data and the stylus orientation data; and

executing an application dependent upon the determined motion of the handheld device relative to the stylus.

18. The method of claim 17 , further comprising executing an application dependent upon one or more of:

an orientation of the handheld device relative to the orientation of the stylus;

an orientation of the handheld device relative to an absolute frame of reference; and

motion of the handheld device relative to the absolute frame of reference.

19. The method of claim 17 , further comprising transmitting to a remote device a description of the motion of the handheld device relative to the stylus.