Signal Processing

• US 20100097133A1
• Filed: 10/21/2008
• Published: 04/22/2010
• 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
• Granted Patent: US 8,056,044 B2
• Time in Patent Office: Days
• US Class Current: 327/551
• 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. An iterative method for generating a series of output signal values from a series of input signal values, wherein iterations of the method comprise the steps of:

(a) obtaining a current input signal value for the current iteration;

(b) comparing the current input signal value with an output signal value determined in a previous iteration;

(c) 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;

(d) determining a slew value based on the counter value; and

(e) adding 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 determination in step (d) is based on the size of a difference between the counter value and a pre-defined base value.

3. The method of claim 2, wherein the determination in step (d) is made such that slew values of greater magnitude are determined for iterations in which the counter value is further from the base value than for iterations in which the counter value is nearer to the base value.

4. The method of claim 1, wherein the relationship between counter values and magnitudes of the slew values used in step (d) for determining the slew value is a non-linear relationship.

5. The method of claim 1, wherein the slew value is determined from the counter value in step (d) 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 step of updating the counter value in step (c) is performed differently depending on whether or not the counter value is beyond the threshold counter value.

8. The method of claim 6, wherein the step of updating the counter value in step (c) comprises comparing the counter value with the pre-defined threshold counter value, and either incrementing, decrementing, or resetting the counter value to a base value depending on both the result of the comparison of the counter value with the pre-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 determining whether both the counter value is beyond the threshold value and the step of updating the counter value in step (c) brought the counter value closer to the threshold value, and if so, setting the current output signal to the previous output signal.

10. The method of claim 1, further comprising determining whether the current input signal is within a range bound by the previous output signal and the current output signal, and if so, setting the current output signal to the current input signal.

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

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

13. The method of claim 12, wherein the notional previous output signal for the first iteration is a 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 is independent of the magnitude of the difference between the current input signal and the previous output signal.

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, wherein the iterations further comprise the step of providing the output signal on an output signal line.

18. An apparatus for generating a series of output signal values from a series of input signal values, the apparatus comprising a processing component and a storage component comprising registers for storing a counter value and a previous output signal value, and wherein the processing component is operable to iteratively perform the steps of

(a) obtaining a current input signal value for the current iteration;

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

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

(d) determining a slew value based on the counter value; and

(e) adding the slew value to the previously determined output signal value to generate a current output signal value.