Device with proximity detection capability

• US 8,115,499 B2
• Filed: 05/22/2009
• Issued: 02/14/2012
• Est. Priority Date: 05/22/2009
• Status: Expired due to Fees

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Osoinach, Bryce T., Ko, Tak Kwan Vincent
• Primary Examiner(s): NGUYEN, HOAI AN D
• Application Number:
  US12/470,729
• Publication Number:
  US 20100295559A1
• Time in Patent Office: 998 Days
• Field of Search: 324/713, 324/691, 324/649, 324/600, 324/522, 324/663, 324/662, 324/661, 324/658, 324/671, 324/686, 324/635, 324/644, 324/699, 324/716, 324/688, 340/686.6, 340/686.1, 340/539.23, 340/545.1, 340/2, 340/4, 340/541, 340/6, 345/173, 345/174
• US Class Current: 324/686
• CPC Class Codes: G06F 1/3231 Monitoring the presence, absence or movement of users
• CPC Class Codes: G06F 1/3287 by switching off individual functional units in the computer system
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 2217/960765 Details of shielding arrangements
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

The electrical equivalent of a relatively large area proximity detection capability is provided in a space limited electronic device (20, 30) with many individual input electrodes (24, 34, 44) by dynamically coupling parallel groups of the individual electrodes (24, 34, 44) and applying a proximity and/or contact test thereto. The parallel grouped electrodes act like a single large electrode and permit proximity detection at greater distances and with greater sensitivity. A multiplexer (74) automatically couples individual input electrodes (23, 24, 44) and then parallel grouped electrodes to the proximity (or contact) sensor(s) (46, 66), so that they are scanned and sensed individually and collectively in a time less than human reaction time, whereby the proximity sense function appears as if provided by a separate large area electrode. Proximity spatial detection accuracy is increased by using some of the electrodes (24, 34, 44) as driven shields to remove positional ambiguity.

Claims

1. A method for providing proximity detection in an electronic device having multiple individual input electrodes, comprising:

sensing and reporting the state of the individual input electrodes;

modifying the state of the device according to the state of the individual input electrodes;

coupling some or all of the multiple individual input electrodes together in parallel;

sensing and reporting the state of the coupled input electrodes;

modifying the state of the device according to the state of the coupled input electrodes; and

de-coupling the coupled input electrodes.

2. The method of claim 1, wherein the sensing, reporting and modifying steps for the individual input electrodes, comprise:

choosing an individual input electrode to be sensed;

sensing the state of the chosen input electrode by measuring a signal affected by the approach or contact of an input element to the chosen input electrode;

testing whether the measured signal passes a predetermined threshold; and

if YES, changing the state of the device; and

if NO, choosing another individual input electrode and repeating the sensing and threshold testing steps until all input electrodes of interest have been chosen, sensed and threshold tested.

3. The method of claim 1, wherein when the sensing, reporting and modifying steps for the individual input electrodes indicate that an input element is in the vicinity of more than one input electrode, the method further comprising:

first choosing one of the more than one input electrodes as the first chosen input electrode to be sensed and coupling others of the more than one input electrodes to a driven shield signal derived from the first chosen input electrode;

first sensing and reporting the state of the first chosen input electrode;

second choosing another of the more than one input electrodes as a second chosen input electrode to be sensed and coupling others of the more than one input electrodes to a driven shield signal derived from the second chosen input electrode;

second sensing and reporting the state of the second chosen input electrode;

repeating the first and second choosing, sensing and reporting steps until all of the more than one input electrodes have been chosen, sensed and reported while the others of the more than one input electrodes have been coupled to a driven shield signal derived therefrom; and

comparing the reported results to determine which of the more than one input electrodes is closest to the input element.

4. The method of claim 1, wherein the step of sensing the state of the individual input electrode comprises, driving the individual input electrode with a constant current and measuring the voltage appearing across the individual input electrode as a result of the constant current drive.

5. The method of claim 4, wherein the constant current drive is a constant current pulse of first predetermined duration.

6. The method of claim 5, wherein the step of measuring the voltage occurs at a second predetermined time after the constant current drive starts.

7. The method of claim 1, wherein the step of reporting the state of the individual input electrodes and modifying the state of the device comprise, storing a first sensed state of the individual input electrode in a memory and then comparing the stored first sensed state with a second sensed state determined later in time so as to detect changes between the first and second sensed states and modifying the state of the device based at least in part on such changes.

8. The method of claim 1, wherein the step of sensing and reporting the state of the coupled input electrodes comprises, driving the coupled input electrodes with a constant current and measuring the voltage appearing across the coupled input electrodes as a result of the constant current drive.

9. The method of claim 8, wherein the constant current drive is a constant current pulse of first predetermined duration.

10. The method of claim 9, wherein the step of measuring the voltage occurs at a second predetermined time after the constant current drive starts.

11. An apparatus for detecting proximity of an input element, comprising:

multiple individual input electrodes;

an individual electrode drive and sense element having a drive-sense terminal adapted to be coupled to the individual input electrodes and having an output terminal for reporting on the states of the individual input electrode coupled to its drive-sense terminal;

a proximity drive and sense element having a drive-sense terminal adapted to be coupled to parallel groups of the individual input electrodes and having an output terminal reporting on the states of the parallel coupled groups of individual input electrodes coupled to its drive-sense terminal; and

a multiplexer for sequentially coupling;

(i) the individual input electrodes to the drive-sense terminal of the individual electrode drive and sense element, and (ii) the parallel coupled groups of individual input electrodes to the drive-sense terminal of the proximity drive and sense element.

12. The apparatus of claim 11, further comprising:

a first filter for receiving from the output terminal of the individual electrode drive and sense element first signals related to the states of the individual input electrodes; and

a second filter for receiving from the output terminal of the proximity drive and sense element second signals related to the states of the parallel coupled individual input electrodes.

13. The apparatus of claim 12, further comprising:

a memory having an input coupled to an output of the first and second filters for temporarily storing signals determined by the states of the individual and parallel coupled individual input electrodes.

14. The apparatus of claim 13, further comprising:

a comparator receiving an input from the memory and an input from the first and second filters for comparing the state of various individual input electrodes singly or in groups with previous values of the states of the same or other of the various individual input electrodes or groups of electrodes.

15. A method for providing proximity detection in an electronic device having multiple individual input electrodes, comprising:

sensing and storing a proximity or contact state of the individual input electrodes;

comparing current values of the proximity or contact state of the individual input electrodes with one or more stored values of the proximity or contact state of the same or different individual input electrodes;

sensing and storing a proximity or contact state of one or more groups of the individual input electrodes;

comparing current values of the proximity or contact state of the one or more groups of the individual input electrodes with one or more stored values of the proximity or contact state of the same or different groups of the individual input electrodes; and

modifying the state of the device according to the results of one or both comparing steps.

16. The method of claim 15, wherein the sensing and storing steps for the proximity or contact state of the individual input electrodes are performed sequentially in any order.

17. The method of claim 16, wherein the sensing and storing steps for the proximity or contact state of the one or more groups of input electrodes are performed during or after the sensing and storing steps for the proximity or contact state of the individual input electrodes.

18. The method of claim 17 wherein a time period used for the sensing, comparing and modifying steps for all input electrodes is less than human reaction time for approaching or contacting an input electrode.

19. The method of claim 17, wherein a time period for the sensing, comparing and modifying steps for an individual input electrode is less than or equal to about 64 microseconds.

20. The method of claim 15, wherein the step of modifying the state of the device comprises lighting some of the input electrodes.

21. An electronic apparatus, comprising:

a plurality of individual input electrodes; and

a touch and proximity detection system coupled to the plurality of individual input electrodes, wherein in a first mode of operation, the detection system provides an indication of whether or not an input element has touched or is in proximity to a single one of the individual input electrodes, and in a second mode of operation provides an indication of whether or not the input element is in proximity to a parallel-coupled group of multiple ones of the individual input electrodes.