Keyboard with plural key switch matrices to detect ghosting

• US 8,159,372 B2
• Filed: 10/16/2007
• Issued: 04/17/2012
• Est. Priority Date: 10/16/2007
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Sherman, Nathan C
• Primary Examiner(s): Bugg, George
• Assistant Examiner(s): Balseca, Franklin
• Application Number:
  US11/872,729
• Publication Number:
  US 20090096640A1
• Time in Patent Office: 1,645 Days
• Field of Search: 341 20- 35, 200/520, 200/600, 345/168, 345/173, 307/116, 400472-496, 340/2.27, 340 141- 1469, 710/67, 710/73
• US Class Current: 341/24
• CPC Class Codes: H03M 11/003 Phantom keys detection and prevention

Abstract

Keyboard apparatus and methods for processing keyboard depressions are disclosed. One disclosed keyboard apparatus includes a keyboard having a plurality of keys configured to be depressed in a concurrent depression state, and a plurality of key switch matrices. Each key switch of the plurality of key switch matrices may be configured to be actuated by a corresponding key of the keyboard. The keyboard apparatus may further include a keyboard controller configured to determine whether a sensed key depression in the concurrent depression state is a ghost key depression, based on sensed key switch states of respective key switches in each of the plurality of key switch matrices which correspond to the sensed key depression.

Claims

1. A keyboard apparatus, comprising:

a keyboard including a plurality of keys configured to be depressed in a concurrent depression state;

a plurality of electronic key switch matrices, each key switch matrix comprising a plurality of key switches and each key switch of the plurality of key switch matrices being configured to be actuated by a corresponding key of the keyboard, one or more keys on the keyboard configured to actuate a key switch in each of the plurality of key switch matrices; and

a keyboard controller electronically coupled to the plurality of key switch matrices, the keyboard controller configured to determine whether a sensed key depression in the concurrent depression state is a ghost key depression, based on concurrently sensed key switch states of respective key switches in each of the plurality of key switch matrices which correspond to the sensed key depression.

2. The keyboard apparatus of claim 1,

wherein the keyboard controller includes a key switch state sensing unit configured to utilize a first key switch matrix of the plurality of key switch matrices to sense the concurrent depression state for the plurality of keys of the keyboard.

3. The keyboard apparatus of claim 1, wherein the keyboard controller includes an anti-ghosting logic unit configured to determine whether a potential ghost key combination exists for the concurrent depression state for the plurality of keys of the keyboard.

4. The keyboard apparatus of claim 1, wherein the keyboard controller further includes a ghost key detector configured to utilize a second key switch matrix to determine whether any of the keys that is sensed by the first key switch matrix to be in the concurrent depression state is a ghost key depression or an actual key depression.

5. The keyboard apparatus of claim 1, wherein the plurality of key switch matrices are sufficiently orthogonal to enable the keyboard controller to eliminate ghosting for all 3-key depression combinations of the keyboard.

6. The keyboard apparatus of claim 1, wherein the plurality of key switch matrices are sufficiently orthogonal to enable the keyboard controller to eliminate ghosting for all 4-key depression combinations of the keyboard.

7. The keyboard apparatus of claim 1, wherein the plurality of key switch matrices are sufficiently orthogonal to enable the keyboard controller to eliminate ghosting for all 5-key depression combinations of the keyboard.

8. The keyboard apparatus of claim 1, wherein the plurality of key switch matrices includes a first key switch matrix and a second key switch matrix, and the first key switch matrix and the second key switch matrix are sufficiently orthogonal to enable the keyboard controller to eliminate ghosting for all 3-key depression combinations of the keyboard.

9. The keyboard apparatus of claim 1, wherein the plurality of key switch matrices includes a first key switch matrix and a second key switch matrix, and the first key switch matrix and the second key switch matrix are sufficiently orthogonal to enable the keyboard controller to eliminate ghosting for all 4-key depression combinations of the keyboard.

10. The keyboard apparatus of claim 1, wherein the keyboard controller further includes a key depression processor configured to suppress a reporting of the sensed key depression if the key depression processor determines the sensed key depression is a ghost key depression.

11. The keyboard apparatus of claim 1, wherein each of the plurality of key switch matrices includes a circuit grid, the circuit grid includes a plurality of drive lines intersecting a plurality of sense lines, the circuit grid further includes a plurality of key switches disposed at intersections of the plurality of drive lines and the plurality of sense lines, each of the plurality of key switches configured to be actuated by a corresponding key of the keyboard when the corresponding key of the keyboard is depressed, and a key switch state of each of the key switch matrices is sensed by sequentially selecting and inputting a signal to an arbitrary one of the plurality of the drive lines, and by reading the plurality of sense lines.

12. The keyboard apparatus of claim 11, wherein the keyboard controller includes a plurality of drive line pins and a plurality of sense line pins, each of the plurality of drive line pins is coupled to a corresponding drive line in each of the plurality of key switch matrices, and each of the plurality of sense line pins is coupled to a corresponding sense line in each of the plurality of key switch matrices.

13. The keyboard apparatus of claim 1, wherein each two key switch matrices of the plurality of key switch matrices are electronically isolated by one or more diodes.

14. A method of processing key depressions of a keyboard, comprising:

sensing a concurrent depression state for a plurality of keys using a first key switch matrix, each of the plurality of keys being associated with a respective key switch of the first key switch matrix, the first key switch matrix being electronic and including a plurality of key switches; and

detecting that a key of the plurality of keys in the concurrent depression state is in a ghost key depression state by concurrently querying a key switch state of a key switch in a second key switch matrix associated with the detected key, the second key switch matrix being electronic.

15. The method of claim 14, further comprising:

determining whether a ghost key depression combination exists for the sensed concurrent depression state prior to detecting that a key of the plurality of keys in the concurrent depression state is in a ghost key depression state by querying a key switch state of the key in a second key switch matrix.

16. The method of claim 14, further comprising:

determining that the sensed depression is not a ghost key depression if either a ghost key depression combination is determined to not exist for the sensed concurrent key depression state sensed utilizing the first key switch matrix, or if the ghost key depression combination is determined to exist but a sensed key depression is validated to be an actual key depression utilizing the second key switch matrix.

17. The method of claim 14, further comprising reporting an output indicating a sensed key depression is an actual key depression if the sensed key depression is determined to be an actual key depression, and suppressing reporting of the output indicating the sensed key depression is an actual key depression if the sensed key depression is determined to be a ghost key depression.

18. The method of claim 14, wherein the first key switch matrix and the second key switch matrix are sufficiently orthogonal to eliminate ghosting for all 3-key depression combinations of the keyboard.

19. The method of claim 14, wherein the first key switch matrix and the second key switch matrix are sufficiently orthogonal to eliminate ghosting for all 4-key depression combinations of the keyboard.

20. The method of claim 14, wherein the first key switch matrix and the second key switch matrix are sufficiently orthogonal to eliminate ghosting for all 5-key depression combinations of the keyboard.