Low pin count solution using capacitance sensing matrix for keyboard architecture

• US 20070273560A1
• Filed: 05/25/2006
• Published: 11/29/2007
• Est. Priority Date: 05/25/2006
• Status: Active Grant

• Current Assignee: Wistron Corporation
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: XiaoPing, Jiang, Hua, Liu
• Granted Patent: US 8,059,015 B2
• Time in Patent Office: Days
• US Class Current: 341/33
• CPC Class Codes: G06F 2203/04111 Cross over in capacitive digitiser, i.e. details of structures for connecting electrodes of the sensing pattern where the connections cross each other, e.g. bridge structures comprising an insulating layer, or vias through substrate
• CPC Class Codes: G06F 3/0202 Constructional details or processes of manufacture of the input device
• CPC Class Codes: G06F 3/0383 Signal control means within the pointing device
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• 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 3/04886 by partitioning the display area of the touch-screen or the surface of the digitising tablet into independently controllable areas, e.g. virtual keyboards or menus
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 2017/9602 characterised by the type or shape of the sensing electrodes
• CPC Class Codes: H03K 2217/960755 Constructional details of capacitive touch and proximity switches

Abstract

An apparatus and method for selecting a keyboard key based on a position of a presence of a conductive object on a sensing device and a pre-defined area of the keyboard key. The apparatus may include a sensing device and a processing device. The sensing device may include a plurality of sensor elements to detect a presence of a conductive object on the sensing device. Multiple keyboard keys are assigned to pre-defined areas of the sensing device. The processing device is coupled to the sensing device using capacitance sensing pins, and may be operable to determine a position of the presence of the conductive object, and to select a keyboard key based on the position of the conductive object and the pre-defined areas of the sensing device.

Claims

1. A method, comprising:

assigning a plurality of keyboard keys into pre-defined areas of a sensing device having a plurality of sensor elements and a plurality of capacitance sensing pins to couple the sensing device to a processing device;

detecting a presence of a conductive object on the sensing device;

determining a position of the presence of the conductive object on the sensing device; and

selecting a keyboard key of the plurality of keyboard keys based on the position of the presence of the conductive object and the pre-defined areas of the sensing device.

2. The method of claim 1, wherein selecting the keyboard key comprises comparing the position of the conductive object with the pre-defined areas.

3. The method of claim 1, further comprising outputting keyboard data corresponding to the selected key from the processing device to a component external to the processing device.

4. The method of claim 1, wherein determining the position of the conductive object comprises:

measuring a capacitance of each row of sensor elements of a capacitance sensor matrix of the sensing device;

determining a first dimension position based on the measured capacitance of the rows of sensor elements;

measuring a capacitance of each column of sensor elements of the capacitance sensor matrix; and

determining a second dimension position based on the measured capacitance of the columns of sensor elements, wherein determining the position of the detected presence is determined using the first and second dimension positions.

5. The method of claim 3, wherein assigning the plurality of keyboard keys into pre-defined areas comprises defining a data structure comprising positional data of the pre-defined areas of the plurality of keyboard keys, wherein selecting the keyboard key comprises comparing the position of the conductive object with the positional data of the pre-defined areas of the data structure to determine a pressed key of the plurality of keyboard keys, and wherein outputting the keyboard data comprises outputting keyboard data that corresponds to the pressed key.

6. An apparatus, comprising:

a sensing device comprising a plurality of sensor elements to detect a presence of a conductive object on the sensing device, wherein a plurality of keyboard keys are assigned to pre-defined areas of the sensing device; and

a processing device coupled to the sensing device using capacitance sensing pins, wherein the processing device is operable to determine a position of the presence of the conductive object on the sensing device, and to select a keyboard key of the plurality of keyboard keys based on the position of the presence of the conductive object and the pre-defined areas of the sensing device.

7. The apparatus of claim 6, wherein the plurality of keyboard keys are a personal computer (PC) keyboard, and wherein the processing device is coupled to the sensing device using less than 21 capacitance sensing pins.

8. The apparatus of claim 6, wherein the plurality of keyboard keys comprises approximately 48 keyboard keys, and wherein the processing device is coupled to the sensing device using 4 capacitance sensing pins.

9. The apparatus of claim 6, wherein the plurality of keyboard keys comprises approximately 101 keyboard keys, and wherein the processing device is coupled to the sensing device using less than 12 capacitance sensing pins.

10. The apparatus of claim 6, wherein the plurality of keyboard keys comprises approximately 107 keyboard keys, and wherein the processing device is coupled to the sensing device using less than 21 capacitance sensing pins.

11. The apparatus of claim 6, wherein the plurality of keyboard keys comprises approximately 107 keyboard keys, and wherein the processing device is coupled to the sensing device using less than 12 capacitance sensing pins.

12. The apparatus of claim 6, wherein a total surface area of the assigned keyboard keys is less than approximately 10 centimeters (cm) by 10 cm.

13. The apparatus of claim 6, wherein a total surface area of the assigned keyboard keys is approximately 3 centimeters (cm) by 3 cm.

14. The apparatus of claim 6, wherein the sensing device comprises a capacitance sensor matrix comprising the plurality of sensor elements configured in rows and columns to detect the presence of the conductive object on the sensing device, and wherein the plurality of keyboard keys are assigned to the pre-defined areas of the capacitance sensor matrix.

15. The apparatus of claim 14, wherein the processing device comprises one or more capacitance sensors coupled to the capacitance sensor matrix, wherein the one or more capacitance sensors are operable to measure a capacitance of each row of sensor elements of the capacitance sensor matrix, and to measure a capacitance of each column of sensor elements of the capacitance sensor matrix, and wherein the processing device is operable to determine the position of the presence of the keyboard key using the measured capacitance of the rows and columns of sensor elements of the capacitance sensor matrix.

16. The apparatus of claim 15, wherein the one or more capacitance sensors are relaxation oscillators, wherein each relaxation oscillator comprises:

a current source to provide a charge current to the plurality of sensor elements;

a selection circuit coupled to the plurality of sensor elements and the current source, wherein the selection circuit is operable to sequentially select a sensor element of the plurality of sensor elements to provide the charge current and to measure the capacitance of each sensor element of the sensing device;

a comparator coupled to the current source and the selection circuit, wherein the comparator is operable to compare a voltage on the selected sensor element and a threshold voltage; and

a reset switch coupled to the comparator, current source, and selection circuit, wherein the reset switch is operable to reset the charge current on the selected sensor element, wherein the one or more capacitance sensors further comprise a digital counter coupled to the relaxation oscillator, wherein the digital counter is operable to count at least one of a frequency of an oscillator output or a period of the oscillator received from the relaxation oscillator.

17. The apparatus of claim 6, further comprising a component external to the processing device, wherein the processing device is operable to send keyboard data to the component that corresponds to the selected keyboard key.

18. The apparatus of claim 17, wherein the component external to the processing device is at least one of a processor, a driver of a processor, or an embedded controller.

19. The apparatus of claim 17, wherein the keyboard data comprises is at least one of a keyboard data signal, or a keyboard data command.

20. The apparatus of claim 6, wherein the sensing device is mounted on a mobile handset.

21. The apparatus of claim 6, wherein the processing device is coupled to an additional user input device, and wherein the additional input device is at least one of a cursor positioning device, a touch-sensor pad, a touch-sensor slider, a touch-sensor button, mouse, or a touch-screen display.

22. An apparatus, comprising:

a sensing device comprising a plurality of sensor elements to detect a presence of a conductive object on the sensing device, wherein a plurality of keyboard keys are assigned to pre-defined areas of the sensing device;

means for determining a position of the presence of the conductive object on the sensing device; and

means for selecting a keyboard key of the plurality of keyboard keys based on the position of the presence of the conductive object and the pre-defined areas of the sensing device.

23. The apparatus of claim 22, further comprising means for assigning the plurality of keyboard keys into the pre-defined areas of the sensing device.

24. The apparatus of claim 22, further comprising means for reducing a number of capacitance sensing pins used to connect the sensing device to the means for determining the position of the conductive object.

25. The apparatus of claim 22, further comprising means for reducing a total surface area of the sensing device while maintaining a number of keyboard keys on a device.

26. The apparatus of claim 22, further comprising means for outputting keyboard data based on the position of the presence of the keyboard key.