Advanced frequency calibration

• US 20080158179A1
• Filed: 01/03/2007
• Published: 07/03/2008
• Est. Priority Date: 01/03/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Wilson, Thomas James
• Granted Patent: US 8,085,247 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/04184 Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally
• 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

Abstract

An oscillating signal of relatively precise frequency is generated by tuning an oscillator using an external stable oscillating source as a reference. Calibration logic is included to compare a signal from the local oscillator to the reference signal and vary the local signal to a desired frequency. In one embodiment, a binary search algorithm is used to tune the local oscillator. The local oscillating signal can be sent to one or more circuits including at least one sensor of a touch sensitive panel for detecting touch events.

Claims

1. A method for tuning an oscillator of an event-sensitive device, comprising:

tuning an oscillator to a desired frequency using a binary search algorithm;

outputting a local oscillator signal from the local oscillator; and

applying the local oscillator signal to at least one sensor node of an event-sensitive panel.

3. The method of claim 1, further comprising activating calibration logic circuitry.

4. The method of claim 3, wherein the activating step comprises activating a reference signal.

5. The method of claim 1, further comprising counting the number of cycles in the oscillating signal, the counting comprising starting a counter upon occurrence of a first event of a reference signal and stopping the counter upon occurrence of a second event of the reference signal.

6. The method of claim 5, wherein the first event is a first rising edge of the reference signal and the second event is a second rising edge of the reference signal.

7. The method of claim 5, wherein the counting step further comprises storing the number of cycles counted in a memory unit.

8. The method of claim 7, further comprising comparing the number of cycles counted with a predetermined desired number of cycles.

9. The method of claim 8, further comprising tuning the local oscillator to a lower frequency when the number of cycles counted is greater than the predetermined desired number of cycles.

2. The method of claim 2, wherein the tuning step further comprises changing a binary tuning value.

10. A method for tuning the frequency of an oscillating signal comprising:

determining a desired clock count corresponding to a desired frequency of a local oscillator;

outputting a local oscillator signal having a first frequency;

counting an actual clock count corresponding to the first frequency of the local oscillator signal;

comparing the actual clock count with the desired clock count;

changing a tune bit value based on a binary search algorithm; and

modifying the frequency of the local oscillator signal to a second frequency based upon the tune bit value.

11. The method of claim 10, wherein the actual clock count is a total number of cycles of a local signal generated from the local oscillator counted during one cycle of a reference clock signal.

12. The method of claim 10, wherein the changing step further comprises lowering the tune bit value when the actual clock count is greater than the desired clock count.

13. The method of claim 10, wherein the changing step further comprises increasing the tune bit value when the actual clock count is lower than the desired clock count.

14. A multi-event sensor device comprising:

a local oscillator circuit configured to generate an oscillating signal having a frequency at least partially based on an incoming control signal;

a reference signal generator configured to generate a reference signal;

calibration logic circuitry configured to compare the frequency of the oscillating signal with the frequency of the reference signal and configured to use a binary search algorithm to tune the local oscillator to a desired frequency.

15. The multi-event sensor device of claim 14, wherein the local oscillator is a voltage controlled oscillator.

16. The multi-event sensor device of claim 14, further comprising a touch sensitive panel comprising:

a plurality of event-sensing nodes configured to receive the oscillating signal and provide one or more panel output signals; and

event sensor circuitry configured to process the panel output signal to determine whether an event has occurred.

17. The multi-event sensor device of claim 16, wherein the event-sensing nodes include at least two electrodes and output results from capacitances formed as a result of the interaction among the at least two electrodes.

18. The multi-event sensor device of claim 14, wherein the local oscillator circuit comprises a current controlled oscillator.

19. The multi-event sensor device of claim 14, wherein the calibration logic circuitry comprises a counter that starts counting the number of cycles in the oscillating signal upon an occurrence of first event triggered by a reference signal and stops counting the number of cycles in the oscillating signal upon an occurrence of a second event triggered by the reference signal.

20. A circuit for generating an oscillating signal comprising:

oscillator generation means for generating an oscillating signal;

calibration means for calibrating the oscillator generation means to a desired frequency; and

event sensitive means for sensing a plurality events occurring simultaneously or nearly simultaneously on an event-sensing panel.

21. The circuit of claim 20, wherein the calibration means uses a binary search algorithm to calibrate the oscillator generation means.

22. An electronic device comprising:

an event sensitive panel configured to receive an oscillating signal and generate an output signal based on the received oscillating signal;

an oscillating circuit configured to generate the oscillating signal; and

a calibration controller configured to modify the frequency of the oscillating signal by controlling the oscillating circuit,

wherein the controller is further configured to use a binary search algorithm to modify the oscillation circuit so that the oscillating signal is at or near a desired frequency.

23. The electronic device of claim 22, wherein the output signal is also based on whether an event is occurring at the event sensitive panel.

24. The electronic device of claim 22, wherein the electronic device further comprises a reference signal generator configured to generate a reference signal and provide the reference signal to the calibration controller, wherein the calibration controller is configured to count a number of cycles occurring in the oscillating signal during a reference signal cycle.

25. The electronic device of claim 24, wherein the reference signal generator is a crystal oscillator.

26. The electronic device of claim 25, wherein the calibration controller is configured to generate a control signal comprising a digital tune value.

27. The electronic device of claim 24, wherein the electronic device is a computing system.

28. The electronic device of claim 24, wherein the electronic device is a mobile telephone.

29. The electronic device of claim 24, wherein the electronic device is a digital audio player.

30. A mobile telephone comprising:

an event sensitive panel configured to receive an oscillating signal and generate an output signal based on the received oscillating signal;

an oscillating circuit configured to generate the oscillating signal; and

a calibration controller configured to control the frequency of the oscillating signal by controlling the oscillating circuit,

wherein the calibration controller is further configured to use a binary search algorithm to tune the oscillation circuit so that the oscillating signal is at or near a desired frequency.

31. A portable audio player comprising:

an event sensitive panel configured to receive an oscillating signal and generate an output signal based on the received oscillating signal;

an oscillating circuit configured to generate the oscillating signal; and

a calibration controller configured to control the frequency of the oscillating signal by controlling the oscillating circuit,

wherein the calibration controller is further configured to use a binary search algorithm to tune the oscillation circuit so that the oscillating signal is at or near a desired frequency.