Dual measurement for high sensitivity capacitive sensing applications and related systems, methods and devices
Disclosed embodiments relate, generally, to a dual measurement technique for capacitance sensing, and related systems and methods. In one embodiment, a capacitance sensing method characterized by moisture tolerance is performed and another capacitance sensing method characterized by proximity tolerance is performed. In one embodiment, the method characterized by moisture tolerance is a driven-shield self-capacitance sensing measurement, and the method characterized by proximity tolerance is a grounded-shield self-capacitance sensing measurement.
1. A capacitive sensing circuitry, comprising:
a sensor comprising electrodes and shielding for the electrodes, the sensor configured to generate measurable signals responsive to capacitive changes at or near the sensor; and
a touch controller configured to:
perform a capacitive sensing measurement using the measureable signals, the capacitive sensing measurement comprising:
a driven-shield self-capacitance sensing measurement comprising providing a driven-shield signal to at least part of the shielding of the sensor; and
a grounded-shield self-capacitance sensing measurement comprising providing a ground signal to at least part of the shielding of the sensor and performing a self-capacitance sensing measurement; and
detect a touch responsive to both:
a determination that the driven-shield self-capacitance sensing measurement exceeds a first threshold value; and
a determination that the grounded-shield self-capacitance sensing measurement exceeds a second threshold value, the second threshold value different from the first threshold value.
2. The circuitry of claim 1 , wherein a first shielding of the shielding for the electrodes comprises:
a back conductive material; and
a front conductive material,
wherein the back conductive material and front conductive material extend within parallel planes.
3. The circuitry of claim 2 , wherein the first shielding further comprises conductive materials disposed at lateral sides of the back conductive material and the front conductive material.
4. The circuitry of claim 1 , wherein the shielding is arranged relative to the electrodes to facilitate directionality of electric fields projecting from the electrodes.
5. The circuitry of claim 4 , wherein the shielding is arranged relative to the electrodes such that electric fields projecting from the electrodes extend farther in a first direction than in a second direction that is substantially opposite the first direction.
6. The circuitry of claim 1 , wherein the touch controller is configured to provide a signal indicative of a touch responsive to the driven-shield self-capacitance sensing measurement and the grounded-shield self-capacitive sensing measurement.
7. The circuitry of claim 1 , wherein the touch controller is configured to:
provide the driven-shield signal to a shield line operatively coupled to the at least part of the shielding of the sensor;
provide the driven-shield signal to inactive sense lines of the sensor; and
measure first measureable signals at an active sense line of the sensor.
8. The circuitry of claim 7 , wherein the touch controller is configured, subsequent to measuring the first measurable signals at the active sense line to:
provide a ground signal to the shield line;
provide a ground or supply voltage signal to the inactive sense lines of the sensor; and
measure second measurable signals at the active sense line of the sensor.
9. The circuitry of claim 1 , wherein the touch controller is configured to determine that the driven-shield self-capacitance sensing measurement exceeds the first threshold value independently from the grounded-shield self-capacitance sensing measurement.
10. A touch processor, comprising:
a computer-readable media having computer-readable instructions stored thereon; and
a processing core configured to execute the computer-readable instructions, the computer readable instructions including modules of executable code, the modules of executable code including:
a grounded-shield self-capacitance sensing module configured to perform a self-capacitance sensing measurement after providing a ground signal to a shielding of an electrode of a touch sensor; and
a driven-shield self-capacitance sensing module configured to perform a self-capacitance sensing measurement while providing a driven shield to the shielding of the electrode of the touch sensor;
wherein the processing core is configured to report a touch responsive to both:
a determination, by the grounded-shield self-capacitance sensing module, that the self-capacitance sensing measurement after providing the ground signal to the shielding exceeds a first threshold value; and
a determination, by the driven-shield self-capacitance sensing module, that the self-capacitance sensing measurement while providing the driven shield exceeds a second threshold value, the second threshold value different from the first threshold value.
11. The touch processor of claim 10 , wherein the second threshold value is greater than the first threshold value.
12. The touch processor of claim 10 , wherein the first threshold value is selected to reduce susceptibility to proximity touches and the second threshold value is selected to reduce susceptibility to moisture touches.
13. The touch processor of claim 10 , wherein the driven-shield self-capacitance sensing module is configured to determine that the self-capacitance sensing measurement exceeds the second threshold value independently from the self-capacitance sensing measurement of the grounded-shield self-capacitance sensing module.
14. A dual measurement sensing method, comprising:
performing a driven-shield self-capacitance sensing operation;
determining a first sensing result responsive to determining that a first measurement of the performed driven-shield self-capacitance sensing operation exceeds a first threshold value;
performing a grounded-shield self-capacitance sensing operation;
determining a second sensing result responsive to determining that a second measurement of the performed grounded-shield self-capacitance sensing operation exceeds a second threshold value, the second threshold value different from the first threshold value; and
determining a touch result responsive to both the first measurement exceeding the first threshold value and the second sensing result exceeding the second threshold value.
15. The method of claim 14 , wherein the first threshold value is greater than the second threshold value.
16. The method of claim 15 , wherein determining the first sensing result responsive to determining that a first measurement of the performed driven-shield self-capacitance sensing operation exceeds the first threshold value comprises determining that the first measurement exceeds the first threshold value independently from the second measurement.
17. A capacitive sensing system, comprising:
a sensor comprising electrodes and sense lines;
an acquisition circuitry operatively coupled to the sense lines; and
a touch processor operatively coupled to the acquisition circuitry and the sensor, the touch processor configured to detect a touch event responsive to both a first capacitive sensing measurement exceeding a first threshold value and a second capacitive sensing measurement exceeding a second threshold value, the second threshold value different from the first threshold value, wherein one of the first and second capacitive sensing measurements is characterized by moisture tolerance and the other of the first and second capacitive sensing measurements is characterized by proximity detection tolerance.
18. The system of claim 17 , wherein the one of the first and the second capacitive sensing measurements that is characterized by moisture tolerance is a driven-shield capacitive sensing measurement.
19. The system of claim 17 , wherein the one of the first and the second capacitive sensing measurements that is characterized by proximity tolerance is a grounded-shield capacitive sensing measurement.
20. The system of claim 17 , wherein the sensor further comprises shielding arranged to facilitate directionality of electric fields projecting from the electrodes.