Temperature compensation method for capacitive sensors

• US 20080047764A1
• Filed: 08/28/2006
• Published: 02/28/2008
• Est. Priority Date: 08/28/2006
• Status: Abandoned Application

• Current Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Hammer, Christopher M., Seguine, Dennis R., Lee, Mark R.
• Application Number:
  US11/512,042
• Publication Number:
  US 20080047764A1
• Time in Patent Office: Days
• US Class Current: 178/18.06
• 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: G08C 21/00 Systems for transmitting the position of an object with respect to a predetermined reference system, e.g. tele-autographic system
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard

Abstract

A method and apparatus for detecting an environmental effect and a presence of a conductive object on a touch-sensing device without using a dedicated environmental effect sensor, and compensating for the environmental effect on the detection of the conductive object. The method may include detecting an environmental effect on a touch-sensing device using a touch sensor, detecting a presence of a conductive object, and compensating for the environmental effect on the detection of the conductive object. The apparatus may include a touch-sensing device having a touch sensor to detect an environmental effect and a processing device to compensate for the environmental effect.

Claims

1. A method, comprising:

detecting an environmental effect on a touch-sensing device using a touch sensor that is unresponsive to a presence of a conductive object during the detecting;

detecting the presence of the conductive object; and

compensating for the environmental effect on the detection of the conductive object.

2. The method of claim 1, wherein the touch-sensing device further comprises a touch-sensing switch coupled to the touch sensor, and wherein the touch-sensing switch is responsive to the presence of the conductive object and the environmental effect.

3. The method of claim 2, wherein the touch sensor comprises a plurality of pins, wherein a first pin of the plurality of pins is uncoupled to the touch-sensing switch, and wherein a second pin of the plurality of pins is coupled to the touch-sensing switch.

4. The method of claim 3, wherein compensating for the environmental effect on the detection of the conductive object comprises:

reading a signal corresponding to the environmental effect from the first pin;

calculating a difference value between the signal and a first baseline value related to the first pin; and

adjusting the first baseline value related to the first pin and a second baseline value related to the second pin if the difference value exceeds a predetermined range for a predetermined amount of time.

5. The method of claim 4, wherein adjusting the first baseline value related to the first pin and the second baseline value related to the second pin if the difference value exceeds the predetermined range for the predetermined amount of time comprises:

determining whether the difference value exceeds the predetermined range for the predetermined amount of time by using an abnormal count variable;

increasing the baseline values by a multiple of the difference value if the difference value exceeds the predetermined range for the predetermined amount of time; and

resetting the abnormal count variable.

6. The method of claim 3, wherein the touch sensor further comprises a capacitive sensor and wherein the touch-sensing switch comprises a capacitive switch.

7. The method of claim 6, wherein the capacitive sensor comprises:

a relaxation oscillator having the plurality of pins; and

a digital counter coupled to the relaxation oscillator.

8. The method of claim 3, wherein the first pin is coupled to a conductive element and wherein the conductive element is unresponsive to the presence of the conductive object.

17. The apparatus of claim 11, wherein the first pin is coupled to a conductive element and wherein the conductive element is unresponsive to the presence of the conductive object.

9. An apparatus, comprising:

a touch-sensing device comprising;

a touch sensor to detect an environmental effect and a presence of a conductive object on the touch-sensing device, wherein the touch sensor is unresponsive to the presence of the conductive object during the detection of the environmental effect; and

a processing device coupled to the touch sensor to compensate for the environmental effect on the detection of the conductive object.

10. The apparatus of claim 9, wherein the touch-sensing device further comprises a touch-sensing switch coupled to the touch sensor, and wherein the touch-sensing switch is responsive to the presence of the conductive object and the environmental effect.

11. The apparatus of claim 10, wherein the touch sensor comprises a plurality of pins, wherein a first pin of the plurality of pins is uncoupled to the touch-sensing switch, and wherein a second pin of the plurality of pins is coupled to the touch-sensing switch.

12. The apparatus of claim 11, wherein the processing device is configured to read a signal corresponding to the environmental effect from the first pin.

13. The apparatus of claim 11, wherein the processing device is configured to calculate a difference value between a signal corresponding to the environmental effect from the first pin and a first baseline value related to the first pin.

14. The apparatus of claim 11, wherein the processing device is configured to adjust a first baseline value related to the first pin and a second baseline value related to the second pin if a difference value between a signal corresponding to the environmental effect from the first pin and the first baseline value exceeds a predetermined range for a predetermined amount of time.

15. The apparatus of claim 11, wherein the touch sensor is a capacitive sensor and the touch-sensing switch is a capacitive switch.

16. The apparatus of claim 15, wherein the capacitive sensor comprises:

a relaxation oscillator having the plurality of pins; and

a digital counter coupled to the relaxation oscillator.

18. An apparatus, comprising:

means for detecting an environmental effect on a touch-sensing device without using a dedicated environmental effect sensor;

means for detecting a presence of a conductive object; and

means for compensating for the environmental effect on the detection of the conductive object.