Touch Sensor With Measurement to Noise Synchronization

• US 20130106436A1
• Filed: 10/31/2011
• Published: 05/02/2013
• Est. Priority Date: 10/31/2011
• Status: Abandoned Application

• Current Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Brunet, Samuel, Collins, Richard Paul
• Application Number:
  US13/285,739
• Publication Number:
  US 20130106436A1
• Time in Patent Office: Days
• US Class Current: 324/613
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• 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

Abstract

In one embodiment, a method includes sensing by a touch sensor a periodic noise signal caused by an external power source removably coupled to the touch sensor. A measurement signal that is synchronized to the periodic noise signal may be generated and transmitted to a location of the touch sensor. The method may further include detecting whether a touch has occurred at or near the location of the touch sensor based on a response of the location of the touch sensor to the measurement signal.

Claims

1. A method comprising:

sensing by a touch sensor a periodic noise signal caused by an external power source removably coupled to the touch sensor;

generating a measurement signal that is synchronized to the periodic noise signal;

transmitting the measurement signal to a location of the touch sensor; and

detecting whether a touch has occurred at or near the location of the touch sensor based on a response of the location of the touch sensor to the measurement signal.

2. The method of claim 1, wherein:

the method further comprises generating a synchronization signal comprising a plurality of synchronization events that occur at a frequency that is substantially the same or related to the frequency of the noise signal; and

the measurement signal comprises a plurality of measurement events, each measurement event generated in response to a distinct synchronization event of the plurality of synchronization events.

3. The method of claim 2, wherein each synchronization event is an electrical pulse generated by a comparator coupled to the periodic noise signal and a programmable voltage source.

4. The method of claim 3, further comprising adjusting a voltage level of the programmable voltage source if an output of the comparator is not synchronized to the periodic noise signal.

5. The method of claim 2, further comprising adjusting a programmable delay between the synchronization signal and the measurement signal to substantially align the beginning of each measurement event with a particular portion of a generally repeating pattern of the periodic noise signal.

6. The method of claim 1, wherein the measurement signal comprises a plurality of electrical pulses.

7. The method of claim 1, wherein the periodic noise signal is a common mode noise signal coupled to the touch sensor during a touch of the touch sensor by an object.

8. An apparatus comprising:

a touch sensor operable to sense a periodic noise signal caused by an external power source removably coupled to the touch sensor; and

one or more computer-readable non-transitory storage media coupled to the touch sensor and embodying logic that is configured when executed to;

generate a measurement signal that is synchronized to the periodic noise signal;

transmit the measurement signal to a location of the touch sensor; and

detect whether a touch has occurred at or near the location of the touch sensor based on a response of the location of the touch sensor to the measurement signal.

9. The apparatus of claim 8, further comprising:

a synchronization signal generator operable to generate a synchronization signal comprising a plurality of synchronization events that occur at a frequency that is substantially the same or related to the frequency of the noise signal; and

wherein;

the measurement signal comprises a plurality of measurement events, each measurement event generated in response to a distinct synchronization event of the plurality of synchronization events.

10. The apparatus of claim 9, wherein each synchronization event is an electrical pulse generated by a comparator coupled to the periodic noise signal and a programmable voltage source.

11. The apparatus of claim 10, wherein the synchronization signal generator is further operable to adjust a voltage level of the programmable voltage source if an output of the comparator is not synchronized to the periodic noise signal.

12. The apparatus of claim 9, wherein the logic is further operable to adjust a programmable delay between the synchronization signal and the measurement signal to substantially align the beginning of each measurement event with a particular portion of a generally repeating pattern of the periodic noise signal.

13. The apparatus of claim 8, wherein the measurement signal comprises a plurality of electrical pulses.

14. The apparatus of claim 8, wherein the periodic noise signal is a common mode noise signal coupled to the touch sensor during a touch of the touch sensor by an object.

15. An apparatus, comprising:

a capacitive touch sensor; and

a control unit coupled to the capacitive touch sensor, the control unit operable to;

sense a periodic noise signal caused by an external power source removably coupled to the capacitive touch sensor;

generate a measurement signal that is synchronized to the periodic noise signal;

transmit the measurement signal to a location of the capacitive touch sensor; and

detect whether a touch has occurred at or near the location of the capacitive touch sensor based on a response of the location of the capacitive touch sensor to the measurement signal.

16. The apparatus of claim 15, wherein:

the control unit is further operable to generate a synchronization signal comprising a plurality of synchronization events that occur at a frequency that is substantially the same or related to the frequency of the noise signal; and

the measurement signal comprises a plurality of measurement events, each measurement event generated in response to a distinct synchronization event of the plurality of synchronization events.

17. The apparatus of claim 16, wherein each synchronization event is an electrical pulse generated by a comparator coupled to the periodic noise signal and a programmable voltage source.

18. The apparatus of claim 17, the control unit is further operable to adjust a voltage level of the programmable voltage source if an output of the comparator is not synchronized to the periodic noise signal.

19. The apparatus of claim 16, the control unit is further operable to adjust a programmable delay between the synchronization signal and the measurement signal to substantially align the beginning of each measurement event with a particular portion of a generally repeating pattern of the periodic noise signal.

20. The apparatus of claim 15, wherein the measurement signal comprises a plurality of electrical pulses.