Low-power touch button sensing system
A capacitance sensing circuit receives an application of a power supply. The capacitance sensing circuit controls a switch circuit to connect the power supply to a processing device responsive to the application of the power supply. The capacitance sensing circuit receives, via a control interface and from the processing device, control information to configure the capacitance sensing circuit. The capacitance sensing circuit disconnects the power supply from the processing device subsequent to receiving the control information.
1. A method, comprising:
receiving, by a capacitance sensing circuit, an application of a power supply that powers the capacitance sensing circuit;
controlling, by the capacitance sensing circuit, a switch circuit to connect the power supply to a processing device responsive to the application of the power supply;
receiving, from the processing device via a control interface, control information to configure the capacitance sensing circuit; and
responsive to receiving the control information to configure the capacitance sensing circuit from the processing device, disconnecting the power supply from the processing device.
2. The method of claim 1 , wherein controlling the switch circuit to connect the power supply to the processing device is automatically responsive to receiving the application of the power supply.
3. The method of claim 1 , further comprising:
measuring a signal indicative of a capacitance of a touch button to detect a presence of a touch object proximate to the touch button, the touch button operatively coupled to the capacitance sensing circuit; and
connecting the power supply to the processing device in response to detecting the presence of the touch object.
4. The method of claim 3 , wherein measuring the signal indicative of the capacitance of the touch button to detect the presence of the touch object proximate to the touch button occurs at intervals.
5. The method of claim 1 , further comprising:
controlling, by the capacitance sensing circuit, the switch circuit to connect the power supply to the processing device responsive to a timer event and independent of a presence of a touch object detected proximate to a touch button.
6. The method of claim 1 , further comprising:
configuring the capacitance sensing circuit with the control information, wherein the control information configures the capacitance sensing circuit to connect or disconnect the power supply and the processing device in response to events.
7. The method of claim 1 , further comprising:
coupling a plurality of touch buttons to form a composite button; and
measuring a signal indicative of a capacitance of the composite button to detect a presence of a touch object proximate to the composite button.
8. An apparatus, comprising:
a capacitance sensing circuit, operatively coupled to a touch button, to control power supplied to a processing device using a switch circuit, wherein the capacitance sensing circuit, responsive to an application of a power supply that powers the capacitance sensing circuit, to cause the power supply to be connected with the processing device, wherein the capacitance sensing circuit to receive, from the processing device via a control interface, control information to configure the capacitance sensing circuit, and wherein responsive to receiving the control information to configure the capacitance sensing circuit from the processing device, the capacitance sensing circuit to disconnect the power supply from the processing device.
9. The apparatus of claim 8 , wherein the capacitance sensing circuit further comprises:
the control interface to provide an interface to exchange information to and from the capacitance sensing circuit.
10. The apparatus of claim 8 , wherein the capacitance sensing circuit to disconnect a power supply from the processing device until, responsive to a presence of a touch object is detected proximate to the touch button, the capacitance sensing circuit to connect the power supply to the processing device.
11. The apparatus of claim 8 , wherein the capacitance sensing circuit is unresponsive to a presence of a touch object proximate to one or more other touch buttons.
12. The apparatus of claim 8 , wherein the capacitance sensing circuit further comprises:
an analog front end (AFE) to measure a signal indicative of a capacitance of the touch button indicative of a presence of a touch object;
a bias generator, oscillator, timer (BOT) circuit to generate a clock signal; and
a control circuit, responsive to receiving the clock signal, to turn on the AFE to measure the signal indicative of the capacitance of the touch button.
13. The apparatus of claim 8 , wherein the capacitance sensing circuit further comprises:
a delay timer circuit to cause the capacitance sensing circuit to connect the power supply to the processing device independent of a presence of a touch object detected proximate to the touch button.
14. The apparatus of claim 8 , wherein the capacitance sensing circuit is to be configured, via the control interface, with the control information, wherein the control information configures the capacitance sensing circuit to connect or disconnect the power supply and the processing device in response to events, wherein the control interface comprises a serial interface.
15. The apparatus of claim 8 , wherein the capacitance sensing circuit further comprises:
a plurality of button switches to connect the capacitance sensing circuit to a plurality of touch buttons, wherein at least two or more of the plurality of touch buttons, using at least two or more of the plurality of switches, to be electrically coupled to form a composite button, wherein the capacitance sensing circuit to measure a signal indicative of a capacitance of the composite button.
16. The apparatus of claim 8 , wherein the touch button comprises a capacitive button operatively coupled to the capacitance sensing circuit.
17. A method, comprising:
receiving, by a capacitance sensing circuit, an application of a power supply that powers the capacitance sensing circuit;
responsive to receiving control information to configure the capacitance sensing circuit from the processing device, disconnecting the power supply from the processing device;
detecting, by the capacitance sensing circuit, a presence of a touch object proximate to a touch button; and
controlling, by the capacitance sensing circuit, a switch circuit to connect the power supply to the processing device responsive to the detected presence of the touch object, wherein the capacitance sensing circuit consumes an average of less than 100 nanoamperes during operation.
18. The method of claim 17 , further comprising:
receiving, by the capacitance sensing circuit, the application of the power supply at power-up;
controlling, by the capacitance sensing circuit, the switch circuit to connect the power supply to the processing device;
receiving, from the processing device via a control interface, control information to configure the capacitance sensing circuit; and
disconnecting, subsequent to receiving the control information, the power supply from the processing device.
19. The method of claim 17 , further comprising:
coupling a plurality of touch buttons to form a composite button; and
measuring a signal indicative of a capacitance of the composite button to detect the presence of the touch object proximate to the composite button.
20. The method of claim 17 , further comprising:
controlling, by the capacitance sensing circuit, the switch circuit to connect the power supply to the processing device responsive to a timer event and independent of the presence of the touch object detected proximate to the touch button.