DYNAMIC DIFFERENTIAL ALGORITHM FOR SIDE TOUCH SIGNALS

• US 20170285857A1
• Filed: 03/30/2016
• Published: 10/05/2017
• Est. Priority Date: 03/30/2016
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: KUAN, Chia-Yun, MANI, Sanjay
• Granted Patent: US 10,466,839 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G06F 3/0488 using a touch-screen or digitiser, e.g. input of commands through traced gestures

Abstract

Input devices described herein include sensing regions that permit the device to identify a location of input objects along a side of the device. To perform gesture detection, an input device selects baseline signals which are subtracted from capacitive sensing signals captured using the sensor electrodes in the sensing region. Doing so results in delta signals that represent the difference between the capacitive sensing signals and the baseline signals. In one embodiment, the baseline signals are selected from capacitive sensing signals received during previous capacitive frames. In one example, the input device uses the capacitive sensing signals received during the Nth previous capacitive frame as the baseline signals. Alternatively, the input device may determine which frame has capacitive sensing signals that vary the most from the current sensing signals and use that frame as the baseline.

Claims

1. An input device, comprising:

a plurality of sensor electrodes in a sensing region of the input device,

a processing system coupled to the plurality of sensor electrodes, the processing system configured to;

receive a plurality of capacitive sensing signals generated using the plurality of sensor electrodes, the plurality of capacitive sensing signals representing a location of an input object along a single axis;

select capacitive sensing signals from a previous capacitive frame stored in a frame buffer to use as a baseline, wherein the frame buffer stores capacitive sensing signals received during a plurality of previous capacitive frames;

generate delta measurements by calculating a difference between the plurality of capacitive sensing signals and the baseline;

identify the location of the input object along the single axis based on the delta measurements;

remove capacitive sensing signals corresponding to one of the plurality of previous capacitive frames stored the longest in the frame buffer; and

add a new entry to the frame buffer based on the plurality of capacitive sensing signals.

2. The input device of claim 1, wherein the processing system is configured to:

before adding the new entry to the frame buffer, temporally filter the plurality of capacitive sensing signals using raw capacitive sensing signals from at least one of the plurality of previous capacitive frames; and

store the temporally filtered capacitive sensing signals in the new entry.

3. The input device of claim 1, wherein selecting the baseline comprises:

using a fixed interval to select the capacitive sensing signals from the previous capacitive frame in the frame buffer.

4. The input device of claim 1, wherein selecting the baseline comprises:

comparing the plurality of capacitive signals to capacitive sensing signals for each of the plurality of previous capacitive frames stored in the frame buffer to determine a respective difference value for each of the plurality of previous capacitive frames;

comparing the difference values for the plurality of previous capacitive frames to identify one of the plurality of previous capacitive frames that has capacitive sensing signals most different from the plurality of capacitive sensing signals; and

selecting the previous capacitive frame with the most different capacitive sensing signals as the baseline.

5. The input device of claim 1, wherein identifying the location of the input object along the single axis based on the delta measurements comprises:

identifying a positive peak in the delta measurements; and

projecting the positive peak onto the single axis to determine the location of the input object on the single axis.

6. The input device of claim 1, wherein the processing system is configured to:

compare the location of the input object to a saved location of a previously identified input object identified from one of the plurality of previous capacitive frames; and

upon determining that the location of the input object is within a predefined distance from the saved location, determining that the input object is the same as the previously identified input object.

7. The input device of claim 6, wherein the processing system is configured to, after determining that the input object is the same as the previously identified input object:

determine whether the location of the input object has moved relative to the saved location to indicate the input object is performing a swiping gesture along the single axis.

8. The input device of claim 6, wherein the processing system is configured to, after determining that the input object is the same as the previously identified input object:

receive new capacitive sensing signals for a subsequent capacitive frame;

evaluate new delta measurements derived from the new capacitive signals to determine if the input object has performed a lift-off event; and

evaluate the lift-off event and a touch-down event to determine if the input object has performed a tapping gesture.

9. The input device of claim 1, wherein a side of the sensing region defines the single axis, wherein the location of the input device corresponds to an estimated physical location of the input device along the side of the sensing region when the input object is not above the sensing region.

10. A processing system, comprising:

a baseline selector configured to;

receive a plurality of capacitive sensing signals generated using a plurality of sensor electrodes, the plurality of capacitive sensing signals representing a location of an input object along a single axis,

select capacitive sensing signals from a previous capacitive frame stored in a frame buffer to use as a baseline, wherein the frame buffer stores capacitive sensing signals received during a plurality of previous capacitive frames, and

generate delta measurements by calculating a difference between the plurality of capacitive sensing signals and the baseline;

a detection module configured to identify the location of the input object along the single axis based on the delta measurements; and

a filter configured to;

remove capacitive sensing signals corresponding to one of the plurality of previous capacitive frames stored the longest in the frame buffer, and

add a new entry to the frame buffer based on the plurality of capacitive sensing signals.

11. The processing system of claim 10, wherein the filter is configured to:

before adding the new entry to the frame buffer, temporally filter the plurality of capacitive sensing signals using raw capacitive sensing signals from at least one of the plurality of previous capacitive frames; and

store the temporally filtered capacitive sensing signals in the new entry.

12. The processing system of claim 10, wherein selecting the baseline comprises:

using a fixed interval to select the capacitive sensing signals from the previous capacitive frame in the frame buffer.

13. The processing system of claim 10, wherein selecting the baseline comprises:

comparing the plurality of capacitive signals to capacitive sensing signals for each of the plurality of previous capacitive frames stored in the frame buffer to determine a respective difference value for each of the plurality of previous capacitive frames;

comparing the difference values for the plurality of previous capacitive frames to identify one of the plurality of previous capacitive frames that has capacitive sensing signals most different from the plurality of capacitive sensing signals; and

selecting the previous capacitive frame with the most different capacitive sensing signals as the baseline.

14. The processing system of claim 10, wherein identifying the location of the input object along the single axis based on the delta measurements comprises:

identifying a positive peak in the delta measurements; and

projecting the positive peak onto the single axis to determine the location of the input object on the single axis.

15. The processing system of claim 10, wherein the detection module is configured to:

compare the location of the input object to a saved location of a previously identified input object identified from one of the plurality of previous capacitive frames; and

upon determining that the location of the input object is within a predefined distance from the saved location, determining that the input object is the same as the previously identified input object.

16. The processing system of claim 15, wherein the detection module is configured to, after determining that the input object is the same as the previously identified input object:

determine whether the location of the input object has moved relative to the saved location to indicate the input object is performing a swiping gesture along the single axis.

17. The processing system of claim 15, wherein the detection module is configured to, after determining that the input object is the same as the previously identified input object:

receive new capacitive sensing signals for a subsequent capacitive frame;

evaluate new delta measurements derived from the new capacitive signals to determine if the input object has performed a lift-off event; and

evaluate the lift-off event and a touch-down event to determine if the input object has performed a tapping gesture.

18. A method, comprising:

receiving a plurality of capacitive sensing signals generated using a plurality of sensor electrodes, the plurality of capacitive sensing signals representing a location of an input object along a single axis;

selecting capacitive sensing signals from a previous capacitive frame stored in a frame buffer to use as a baseline, wherein the frame buffer stores capacitive sensing signals received during a plurality of previous capacitive frames;

generating delta measurements by calculating a difference between the plurality of capacitive sensing signals and the baseline;

identifying the location of the input object along the single axis based on the delta measurements;

removing capacitive sensing signals corresponding to one of the plurality of previous capacitive frames stored the longest in the frame buffer; and

adding a new entry to the frame buffer based on the plurality of capacitive sensing signals.

19. The method of claim 18, further comprising:

temporally filtering the plurality of capacitive sensing signals using raw capacitive sensing signals from at least one of the plurality of previous capacitive frame before adding the new entry to the frame buffer; and

storing the temporally filtered capacitive sensing signals in the new entry.

20. The method of claim 18, wherein selecting the baseline comprises:

comparing the plurality of capacitive signals to capacitive sensing signals for each of the plurality of previous capacitive frames stored in the frame buffer to determine a respective difference value for each of the plurality of previous capacitive frames;

comparing the difference values for the plurality of previous capacitive frames to identify one of the plurality of previous capacitive frames that has capacitive sensing signals most different from the plurality of capacitive sensing signals; and

selecting the previous capacitive frame with the most different capacitive sensing signals as the baseline.