Signal processing

• US 8,056,044 B2
• Filed: 10/21/2008
• Issued: 11/08/2011
• Est. Priority Date: 10/21/2008
• Status: Active Grant

• Current Assignee: Neodrón Limited (Atlantic IP Services Limited)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Philipp, Harald, Yilmaz, Esat
• Primary Examiner(s): Lin, Sun
• Application Number:
  US12/254,859
• Publication Number:
  US 20100097133A1
• Time in Patent Office: 1,113 Days
• Field of Search: 716/108, 716/113, 716/115, 716/136, 716/134, 327/551
• US Class Current: 716/136
• CPC Class Codes: G06F 2218/04 Denoising
• 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 3/044 by capacitive means
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• 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
• CPC Class Codes: H03K 5/1252 Suppression or limitation of noise or interference specially adapted for transmission systems H04B15/00, H04L25/08

Abstract

An iterative method for generating a series of output signal values from a series of input signal values is described. Iterations of the method comprise the steps of obtaining a current input signal value for the current iteration, comparing the current input signal value with an output signal value determined in a previous iteration, updating a counter value determined in the previous iteration based on the result of the comparison between the current input signal value and the previous output signal value such that the updated counter value replaces the counter value determined in the previous iteration, determining a slew value based on the counter value; and adding the slew value to the previously determined output signal value to generate a new current output signal value. Thus different slew values may be added to the previous output signal to obtain a new output signal. The counter value is updated so that its value reflects recent trends in the input signals. E.g. if the input signal is on an upward trend, the counter value may achieve a relative high value, for example because it is incremented each time an input signal exceeds a previously determined output signal. The magnitude of the slew values may increase as the counter value increases, thereby allowing the output signals to more rapidly track changes in the input signals.

Claims

1. A method comprising:

obtaining, using one or more microcontrollers, a current input signal value for a current iteration;

comparing, using the one or more microcontrollers, the current input signal value with an output signal value determined in a previous iteration;

updating, using the one or more microcontrollers, a counter value determined in the previous iteration based on a result of the comparison between the current input signal value and the previously determined output signal value;

determining, using the one or more microcontrollers, a slew value based on the updated counter value; and

adding, using the one or more microcontrollers, the slew value to the previously determined output signal value to generate a current output signal value.

2. The method of claim 1, wherein the determining the slew value is performed based on a size of a difference between the updated counter value and a pre-defined base value.

3. The method of claim 2, wherein the determining the slew value is made such that slew values of greater magnitude are determined if the updated counter value is farther away from the pre-defined base value than if the updated counter value is nearer to the pre-defined base value.

4. The method of claim 1, wherein a relationship between counter values and magnitudes of slew values is a non-linear relationship.

5. The method of claim 1, wherein the slew value is determined from the updated counter value by reference to a pre-defined look-up table.

6. The method of claim 1, further comprising defining a threshold counter value.

7. The method of claim 6, wherein the updating the counter value is performed differently depending on whether the counter value is beyond the threshold counter value.

8. The method of claim 6, wherein updating the counter value comprises:

comparing the updated counter value with the defined threshold counter value; and

incrementing, decrementing, or resetting the counter value to a base value depending on both a result of the comparing the counter value with the defined threshold counter value and the result of the comparison of the current input signal value with the output signal value determined in the previous iteration.

9. The method of claim 6, further comprising if the counter value is beyond the defined threshold value and the updating the counter value brought the updated counter value closer to the defined threshold value, then setting the current output signal value to the previously determined output signal value.

10. The method of claim 1, further comprising if the current input signal value is within a range bound by the previously determined output signal value and the current output signal value, then setting the current output signal value to the current input signal value.

11. The method of claim 1, wherein the updated counter value is constrained to values between a predefined maximum counter value and a pre-defined minimum counter value.

12. The method of claim 1, further comprising initializing a counter value and defining a notional previous output signal value for the first iteration.

13. The method of claim 12, wherein the notional previous output signal value for the first iteration is one of the input signal values.

14. The method of claim 1, wherein the slew value is defined to a higher precision than the input signal values.

15. The method of claim 1, wherein the current output signal value is independent of a magnitude of a difference between the current input signal value and the previously determined output signal value.

16. The method of claim 1, wherein the input signal values represent measurements from a sensing element of a capacitive sensor.

17. The method of claim 1, further comprising providing the output signal value on an output signal line.

18. An apparatus comprising:

a storage component comprising registers for storing a counter value and a previous output signal value; and

a processing component operable to iteratively perform operations comprising;

obtaining a current input signal value for a current iteration;

comparing the current input signal value with a previous output signal value retrieved from the storage component;

updating a counter value stored in the storage component based on a result of the comparing between the current input signal value and the previous output signal value;

determining a slew value based on the updated counter value; and

adding the slew value to the previous output signal value to generate a current output signal value.

19. The apparatus of claim 18, wherein the updating the counter value is performed differently depending on whether the counter value is beyond a threshold counter value.

20. One or more non-transitory computer-readable storage media that embody logic that is operable, when executed by a processor, to perform operations comprising:

obtaining a current input signal value for a current iteration;

comparing the current input signal value with a previous output signal value retrieved from a storage component;

updating a counter value stored in the storage component based on a result of the comparing the current input signal value and the previous output signal value;

determining a slew value based on the updated counter value; and

adding the slew value to the previous output signal value to generate a current output signal value.