Narrow-Band Touch Detection

• US 20130106759A1
• Filed: 10/27/2011
• Published: 05/02/2013
• Est. Priority Date: 10/27/2011
• Status: Abandoned Application

• Current Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Fredriksen, Einar, Bakken, Vemund Kval
• Application Number:
  US13/283,131
• Publication Number:
  US 20130106759A1
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• 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: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 2217/960705 Safety of capacitive touch and proximity switches, e.g. increasing reliability, fail-safe

Abstract

In one embodiment, a method includes generating a first drive signal for transmission to one or more drive lines of a capacitive touch sensor. The first drive signal comprising a function pattern with a first predetermined frequency. The method also includes receiving a sense signal from one or more sense lines of the touch sensor. The sense signal results at least in part from charge transfer driven by the first drive signal. The method also includes, by a bandpass filter with a first center frequency substantially synchronized to the first predetermined frequency, filtering out components of the sense signal outside a range of the first center frequency; and communicating from the bandpass filter to a processor a passband signal that comprises components of the sense signal within the range of the first center frequency.

Claims

1. A method comprising:

generating a first drive signal for transmission to one or more drive lines of a capacitive touch sensor, the first drive signal comprising a function pattern with a first predetermined frequency;

receiving a sense signal from one or more sense lines of the touch sensor, the sense signal resulting at least in part from charge transfer driven by the first drive signal;

by a bandpass filter with a first center frequency substantially synchronized to the first predetermined frequency, filtering out components of the sense signal outside a range of the first center frequency; and

communicating from the bandpass filter to a processor a passband signal that comprises components of the sense signal within the range of the first center frequency.

2. The method of claim 1, wherein the first predetermined frequency is programmable and the first center frequency is adjustable.

3. The method of claim 1, further comprising sampling an amplitude of the passband signal to determine a quality of the bandpass signal.

4. The method of claim 3, further comprising quantifying the amplitude of the passband signal into a digital representation for the sampling.

5. The method of claim 1, wherein the bandpass filter is implemented using a mixer.

6. The method of claim 1, further comprising:

receiving another sense signal resulting at least in part from charge transfer driven by a second drive signal from a stylus, the second drive signal comprising a function pattern with a second predetermined frequency; and

by the bandpass filter with a second center frequency substantially synchronized to the second predetermined frequency, filtering out components of the other sense signal outside a range of the second center frequency.

7. The method of claim 6, further comprising decoupling components of the sense signal within the range of the first center frequency from components of the other sense signal within the range of the second center frequency.

8. One or more computer-readable non-transitory storage media embodying logic that is configured when executed to:

generate a first drive signal for transmission to one or more drive lines of a capacitive touch sensor, the drive signal comprising a function pattern with a first predetermined frequency;

receive a sense signal from one or more sense lines of the touch sensor, the sense signal resulting at least in part from charge transfer driven by the first drive signal;

by a bandpass filter with a first center frequency substantially synchronized to the first predetermined frequency, filter out components of the sense signal outside a range of the first center frequency; and

communicate from the bandpass filter to a processor a passband signal that comprises components of the sense signal within the range of the first center frequency.

9. The media of claim 8, wherein the first predetermined frequency is programmable and the first center frequency is adjustable.

10. The media of claim 8, wherein the logic is further configured to sample an amplitude of the passband signal to determine a quality of the bandpass signal.

11. The media of claim 10, wherein the logic is further configured to quantify the amplitude of the passband signal into a digital representation for the sampling.

12. The media of claim 8, wherein the bandpass filter is implemented using a mixer.

13. The media of claim 8, wherein the logic is further configured to:

receive another sense signal resulting at least in part from charge transfer driven by a second drive signal from a stylus, the second drive signal comprising a function pattern with a second predetermined frequency; and

by the bandpass filter with a second center frequency substantially synchronized to the second predetermined frequency, filter out components of the other sense signal outside a range of the second center frequency.

14. The media of claim 13, wherein the logic is further configured to decouple components of the sense signal within the range of the first center frequency from components of the other sense signal within the range of the second center frequency.

15. A device comprising:

a capacitive touch sensor; and

one or more computer-readable non-transitory storage media embodying logic that is configured when executed to;

generate a first drive signal for transmission to one or more drive lines of a capacitive touch sensor, the drive signal comprising a function pattern with a first predetermined frequency;

receive a sense signal from one or more sense lines of the touch sensor, the sense signal resulting at least in part from charge transfer driven by the first drive signal;

by a bandpass filter with a first center frequency substantially synchronized to the first predetermined frequency, filter out components of the sense signal outside a range of the first center frequency; and

communicate from the bandpass filter to a processor a passband signal that comprises components of the sense signal within the range of the first center frequency.

16. The device of claim 15, wherein the first predetermined frequency is programmable and the first center frequency is adjustable.

17. The device of claim 15, wherein the logic is further configured to sample an amplitude of the passband signal to determine a quality of the bandpass signal.

18. The device of claim 17, wherein the logic is further configured to quantify the amplitude of the passband signal into a digital representation for the sampling.

19. The device of claim 15, wherein the logic is further configured to:

receive another sense signal resulting at least in part from charge transfer driven by a second drive signal from a stylus, the second drive signal comprising a function pattern with a second predetermined frequency; and

by the bandpass filter with a second center frequency substantially synchronized to the second predetermined frequency, filter out components of the other sense signal outside a range of the second center frequency.

20. The device of claim 19, wherein the logic is further configured to decouple components of the sense signal within the range of the first center frequency from components of the other sense signal within the range of the second center frequency.