Methods and apparatus for capacitive sensing
The present disclosure addresses methods and apparatus facilitating capacitive sensing using a conductive surface, and facilitating the sensing of proximity to the conductive surface. The sensed proximity will often be that of a user, but can be another source of a reference voltage potential. In some examples, the described systems are capable of sensing capacitance (including parasitic capacitance) in a circuit that includes the outer conductive surface, and where that outer conductive surface is at a floating electrical potential. In some systems, the systems can be switched between two operating modes, a first mode in which the system will sense proximity to the conductive surface, and a second mode in which the system will use a capacitance measurement to sense contact with the conductive surface.
1. An electronic device comprising:
a plurality of capacitive sensing regions arranged at different locations across the electronic device, the plurality of capacitive sensing regions including a plurality of electrodes separated by a gap from a plurality of conductive element portions held at a first potential;
wherein each of the plurality of capacitive sensing regions is configured to change the gap between the electrode and the conductive element portion when a first object contacts the conductive element portion; and
sensing circuitry coupled to the electrode in each of the plurality of capacitive sensing regions, the sensing circuitry configured to determine a change in capacitance between the electrode and the conductive element portion due to the change in the gap and detect a touch of the first object.
2. The electronic device of claim 1 , wherein the conductive element portions are continuously formed as a surface of the electronic device.
3. The electronic device of claim 1 , further comprising a processor coupled to the sensing circuitry and capable of performing one or more functions upon detection of the touch of the first object.
4. The electronic device of claim 1 , further comprising a processor coupled to the sensing circuitry and capable of determining a first location of the touch of the first object.
5. The electronic device of claim 4 , wherein the sensing circuitry is further configured to detect a touch of a second object, and wherein the processor is further capable of determining a second location of the touch of the second object.
6. The electronic device of claim 1 , wherein the first potential is a ground potential.
7. The electronic device of claim 1 , wherein the plurality of capacitive sensing regions comprise one or more touch-sensitive invisible buttons.
8. The electronic device of claim 1 , wherein two or more of the plurality of electrodes are coupled together.
9. The electronic device of claim 1 , wherein the gap comprises one of air or a dielectric layer.
10. The electronic device of claim 1 , incorporated into a portable computing device.
11. The electronic device of claim 1 , wherein the plurality of conductive element portions form a part of an external surface of the electronic device.
12. A method of capacitive touch sensing at an electronic device, comprising:
forming each of a plurality of capacitive sensing regions by separating an electrode and a conductive element portion by a gap, and holding the conductive element portion at a first potential;
arranging the plurality of capacitive sensing regions at different locations across the electronic device;
changing the gap between the electrode and the conductive element portion of a particular capacitive sensing region when a first object contacts the conductive element portion of the particular capacitive sensing region;
determining a change in capacitance between the electrode and the conductive element portion due to the change in the gap; and
detecting a touch of the first object based on the determined change in capacitance.
13. The method of claim 12 , further comprising continuously forming the conductive element portions as a surface of the electronic device.
14. The method of claim 12 , further comprising performing one or more functions upon detection of the touch of the first object.
15. The method of claim 12 , further comprising determining a first location of the touch of the first object.
16. The method of claim 15 , further comprising detecting a touch of a second object, and determining a second location of the touch of the second object.
17. The method of claim 12 , further comprising holding the conductive element portion at a ground potential.
18. The method of claim 12 , further comprising forming touch-sensitive invisible buttons from the plurality of capacitive sensing regions.
19. The method of claim 12 , further comprising coupling two or more of the plurality of electrodes together.
20. The method of claim 12 , further comprising forming the gap from one of air or a dielectric layer.
21. The method of claim 12 , wherein the conductive element portions form a part of an external surface of the electronic device.
22. An electronic device comprising:
a touch-sensitive surface;
one or more capacitive touch sensing regions cooperatively arranged with the touch-sensitive surface, each capacitive touch sensing region including a first electrode and a second electrode separated by a gap, the second electrode being held at a first potential;
sensing circuitry coupled to the first electrode in each of the one or more capacitive touch sensing regions, the sensing circuitry configured for generating a first signal indicative of a capacitance between the first electrode and the second electrode; and
a processor cooperatively coupled to the sensing circuitry and capable of receiving the first signal and sensing a touch by detecting a change in the first signal caused by a change in a gap between the first electrode and the second electrode, the change in the gap caused by an object in contact with the touch-sensitive surface.
23. The electronic device of claim 22 , wherein the second electrode forms an external surface of the electronic device.