Canceling unwanted capacitive effects in a capacitive touch measurement, and related systems, methods, and devices
The embodiments of the present disclosure relate generally to systems and methods for canceling mutual capacitive effects in a capacitive touch measurement, and more specifically, implementing a driven shield using rail-to-rail voltage.
1. A capacitive touch circuitry, the circuitry comprising:
an electrode circuitry;
a driven shield circuitry to:
drive one or more inactive electrodes of the electrode circuitry at a first reference voltage rail for a first period of time; and
drive one or more inactive electrodes of the electrode circuitry in a generally increasing or decreasing manner between the first reference voltage rail and a second reference voltage rail for a second period of time, and at least in part thereby induce cancelling mutual capacitance effects at an active sense electrode;
a sensing circuitry to drive an active drive electrode and at least in part thereby induce self-capacitance effects at the active sense electrode;
a self-capacitance sensing circuitry to provide one or more measurable signals that are indicative of the induced cancelling mutual capacitance effects and the induced self- capacitance effects; and
a measurement circuitry to:
combine a first and second measurement values, the first measurement value corresponding to a measurable signal generated during the first period of time and the second measurement value corresponding to a measurable signal generated during the second period of time; and
obtain a self-capacitance measurement.
2. The circuitry of claim 1 , wherein the sensing circuitry and the driven shield circuitry are to drive the active drive electrode and the one or more inactive electrodes, respectively, at substantially the same time.
3. The circuitry of claim 1 , wherein the driven shield circuitry is to generate a rail-to-rail pulse.
4. A microcontroller package, comprising:
a number of programmable input/output (I/O) pins;
a touch controller to generate a first voltage at one or more programmable I/O pins associated with inactive drive lines and inactive sense lines during a measurement acquisition cycle, the measurement acquisition cycle comprising a positive pre-charge measurement phase and a negative pre-charge measurement phase, wherein providing the shield voltage comprises:
holding the one or more programmable I/O pins associated with inactive drive lines and inactive sense lines to a first voltage rail during one of the positive pre-charge measurement phase and the negative pre-charge measurement phase; and
driving the one or more programmable I/O pins associated with inactive drive lines and inactive sense lines from the first voltage rail to a second voltage rail during the other one of the positive pre-charge measurement phase and the negative pre-charge measurement phase; and
a digital control bus operatively coupled to the touch controller.
5. The microcontroller package of claim 4 , wherein the touch controller is an embedded microcontroller.
6. The microcontroller package of claim 4 , wherein the first voltage rail is equal to ground and the second voltage rail is equal to a supply voltage.
7. The microcontroller package of claim 4 , further comprising general purpose input/output drivers that are operably coupled to the digital control bus.
8. The microcontroller package of claim 7 , wherein the general purpose I/O drivers are configurable responsive to one or more digital control signals provided by the touch controller to the digital control bus.
9. The microcontroller package of claim 4 , wherein the touch controller comprises one or more custom input/output (I/O) drivers that are to control one or more of the number of programmable input/output (I/O) pins.