Frequency hopping algorithm for capacitance sensing devices
First Claim
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1. A method, performed at a capacitance sensing system having a memory device and a controller coupled to the memory device, comprising:
- monitoring signals on a plurality of electrodes of a sense network at a plurality of operating frequencies;
detecting a noise level on the plurality of electrodes at the plurality of operating frequencies;
selecting one of the plurality of operating frequencies based on the detected noise level on the plurality of electrodes at the plurality of operating frequencies;
using a noise detector to determine whether or not external noise is present;
responsive to a determination that external noise is present, using a first filtering circuit of the controller to filter results of a scan of the plurality of electrodes at the selected one of the plurality of operating frequencies for localized noise events using the detected noise level corresponding to the selected one of the plurality of operating frequencies; and
responsive to a determination that external noise is not present, using a second filtering circuit of the controller to filter results of the scan of the plurality of electrodes at the selected one of the plurality of operating frequencies for common mode noise using the detected noise level corresponding to the selected one of the plurality of operating frequencies.
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Abstract
Apparatuses and methods of frequency hopping algorithms are described. One method listens to a noise level on multiple electrodes of a sense network at multiple operating frequencies. The method then selects one of the frequencies with a lowest noise level for scanning the electrodes to detect a conductive object proximate to the electrodes.
53 Citations
19 Claims
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1. A method, performed at a capacitance sensing system having a memory device and a controller coupled to the memory device, comprising:
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monitoring signals on a plurality of electrodes of a sense network at a plurality of operating frequencies; detecting a noise level on the plurality of electrodes at the plurality of operating frequencies; selecting one of the plurality of operating frequencies based on the detected noise level on the plurality of electrodes at the plurality of operating frequencies; using a noise detector to determine whether or not external noise is present; responsive to a determination that external noise is present, using a first filtering circuit of the controller to filter results of a scan of the plurality of electrodes at the selected one of the plurality of operating frequencies for localized noise events using the detected noise level corresponding to the selected one of the plurality of operating frequencies; and responsive to a determination that external noise is not present, using a second filtering circuit of the controller to filter results of the scan of the plurality of electrodes at the selected one of the plurality of operating frequencies for common mode noise using the detected noise level corresponding to the selected one of the plurality of operating frequencies. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A capacitance sensing system, comprising:
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a memory device; and a controller coupled to the memory device, wherein the controller is configured to receive signals from a sense network comprising a plurality of electrodes to detect a conductive object proximate to the plurality of electrodes, wherein the controller comprises; a noise listening circuit configured to detect a noise level on the plurality of electrodes at a plurality of operating frequencies; a frequency hopping state machine configured to select one of the plurality of operating frequencies based on the detected noise level at the plurality of operating frequencies; a noise detector configured to determine whether or not external noise is present; a first filtering circuit configured to filter, responsive to a determination that external noise is present, results of a scan of the plurality of electrodes at the selected one of the plurality of operating frequencies for localized noise events using the detected noise level corresponding to the selected one of the plurality of operating frequencies; and a second filtering circuit configured to filter, responsive to a determination that external noise is not present results of the scan of the plurality of electrodes at the selected one of the plurality of operating frequencies for common mode noise using the detected noise level corresponding to the selected one of the plurality of operating frequencies. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A host device, comprising:
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a display; a capacitance sensing array disposed in connection with the display; a touchscreen controller coupled to the capacitance sensing array, wherein the touch screen controller comprises; a capacitance sensing circuit coupled to the capacitance sensing array; a noise listening circuit coupled to the capacitance sensing array, wherein the noise listening circuit is configured to detect noise on the capacitance sensing circuit from at least one noise source at a plurality of operating frequencies, wherein the touchscreen controller is configured to select one of the plurality of operating frequencies with a lowest noise level for subsequent scanning of the capacitance sensing array; a first filtering circuit configured to filter, when noise from the at least one noise source is detected, a first output of the capacitance sensing circuit for localized noise events using the lowest noise level, wherein the first output of the capacitance sensing circuit includes results of a scan of the capacitance sensing array at the selected one of the plurality of operating frequencies; and a second filtering circuit configured to filter, when noise from the at least one noise source is not detected, a second output of the capacitance sensing circuit. - View Dependent Claims (18, 19)
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Specification