Selective scanning for touch-sensitive display device

1. A method for touch input detection, comprising:

over a series of touch-sensing time frames, interpreting electrical conditions of display electrodes of a touch-sensitive display device to estimate frame-by-frame positions of two or more stylus electrodes of an active stylus relative to the touch-sensitive display device, the two or more stylus electrodes having a known spatial separation relative to one another;

based on the estimated frame-by-frame positions of the stylus electrodes and the known spatial separation of the stylus electrodes, predicting future positions of each of the two or more stylus electrodes during a future touch-sensing time frame;

identifying two or more regions of interest on the touch-sensitive display device, each region of interest including a plurality of display electrodes surrounding the predicted future position of a stylus electrode of the two or more stylus electrodes, the two or more regions of interest having a spatial separation derived from the known spatial separation of the two or more stylus electrodes; and

during the future touch-sensing time frame, selectively scanning display electrodes in the regions of interest.

2. The method of claim 1 , further comprising estimating frame-by-frame positions of an input object other than the active stylus, predicting a future position of the input object during the future touch-sensing time frame, and identifying a region of interest for the input object.

3. The method of claim 2 , where the input object is a passive stylus.

4. The method of claim 2 , where the input object is a human finger.

5. The method of claim 2 , where the input object is an electrostatic dial.

6. The method of claim 1 , where each region of interest is a box centered on the predicted future position of a stylus electrode of the two or more stylus electrodes.

7. The method of claim 1 , where each region of interest is a stripe that includes one or more rows of display electrodes of the touch-sensitive display device.

8. The method of claim 1 , where a size of each region of interest is proportional to an estimated speed of the two or more stylus electrodes.

9. The method of claim 1 , where selectively scanning display electrodes in the regions of interest includes driving the display electrodes with a display excitation signal detectable by the stylus electrodes and receiving a stylus excitation signal applied to the stylus electrodes.

10. The method of claim 9 , where two or more regions of interest are identified for each stylus electrode, including a transmit region of interest including display electrodes that are driven with the display excitation signal, and a receive region of interest including display electrodes that receive the stylus excitation signal.

11. The method of claim 10 , where the transmit and receive regions of interest have different shapes.

12. The method of claim 10 , where selectively scanning display electrodes in the regions of interest further includes exchanging data between the touch-sensitive display device and active stylus, and where the two or more regions of interest identified for each stylus electrode further include a data region of interest including display electrodes driven to exchange data with the active stylus.

13. A touch-sensitive display device, comprising:

a touch-sensitive display including a plurality of display electrodes;

a logic machine; and

a storage machine holding instructions executable by the logic machine to:

over a series of touch-sensing time frames, interpret electrical conditions of display electrodes of a touch-sensitive display device to estimate frame-by-frame positions of two or more stylus electrodes of an active stylus relative to the touch-sensitive display device, the two or more stylus electrodes having a known spatial relation relative to one another;

based on the estimated frame-by-frame positions of the stylus electrodes and the known spatial separation of the stylus electrodes, predict future positions of each of the two or more stylus electrodes during a future touch-sensing time frame;

identify two or more regions of interest on the touch-sensitive display device, each region of interest including a plurality of display electrodes surrounding the predicted future position of a stylus electrode of the two or more stylus electrodes, the two or more regions of interest having a spatial separation derived from the known spatial separation of the two or more stylus electrodes; and

during the future touch-sensing time frame, selectively scan display electrodes in the regions of interest.

14. The touch-sensitive display device of claim 13 , where each region of interest is a box centered on the predicted future position of a stylus electrode of the two or more stylus electrodes.

15. The touch-sensitive display device of claim 13 , where each region of interest is a stripe that includes one or more rows of display electrodes of the touch-sensitive display device.

16. The touch-sensitive display device of claim 13 , where the instructions are further executable to estimate frame-by-frame positions of an input object other than the active stylus, predict a future position of the input object during the future touch-sensing time frame, and identify a region of interest for the input object.

17. The touch-sensitive display device of claim 13 , where a size of each region of interest is proportional to an estimated speed of the two or more stylus electrodes.

18. A method for touch input detection, comprising:

over a series of touch-sensing time frames, interpreting electrical conditions of display electrodes of a touch-sensitive display device to estimate frame-by-frame positions for each of a plurality of stylus electrodes of an active stylus, the plurality of stylus electrodes having a known spatial separation relative to one another;

based on the estimated frame-by-frame positions of the stylus electrodes and the known spatial separation of the stylus electrodes, predicting future positions of each stylus electrode during a future touch-sensing time frame;

identifying a plurality of regions of interest on the touch-sensitive display device, each region of interest including a plurality of display electrodes surrounding the predicted future position of a stylus electrode of the plurality of stylus electrodes, and each region of interest having a size proportional to an estimated speed of its corresponding stylus electrode, the plurality of regions of interest having a spatial separation derived from the known spatial separation of the plurality of stylus electrodes; and

during the future touch-sensing time frame, selectively scanning display electrodes in the regions of interest.