# US 8,542,208 B2 · Multi-touch auto scanning > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,542,208 B2 - Document ID: US8542208B2 - Status: Granted - Kind: B2 - Application number: 13/405,221 - Filed: 2012-02-24 - Published: 2012-06-28 - Granted: 2013-09-24 - Earliest claimed: 2007-01-03 - Assignees: Apple Inc. - Applicants: Christoph Horst Krah; Minh-Dieu Thi Vu; Thomas James Wilson - Inventors: Christoph Horst Krah; Minh-Dieu Thi Vu; Thomas James Wilson - Web page: https://patentgrep.com/patent/US8542208B2 ## CPC - G06F 3/0418: {for error correction or compensation, e.g. based on parallax, calibration or alignment} - G06F 1/3203: Power management, i.e. event-based initiation of a power-saving mode - G06F 1/3262: {Power saving in digitizer or tablet} - G06F 3/041: Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means - G06F 3/04166: {Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving (Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184)} - G06F 3/0445: {using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer} - G06F 3/0446: {using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes} - G06F 2203/04104: Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) ## Abstract A system and method for autonomously scanning a sensor panel device is disclosed. A sensor panel processor can be disabled after a first predetermined amount of time has elapsed without the sensor panel device sensing any events. One or more system clocks can also be disabled to conserve power. While the processor and one or more system clocks are disabled, the sensor panel device can periodically autonomously scan the sensor panel for touch activity. If one or more results from the autonomous scans exceed a threshold, the sensor panel device re-enables the processor and one or more clocks to actively scan the sensor panel. If the threshold is not exceeded, the sensor panel device continues to periodically autonomously scan the sensor panel without intervention from the processor. The sensor panel device can periodically perform calibration functions to account for any drift that may be present in the system. ## Claims ### Claim 1 An apparatus for scanning a sensor panel for events, comprising: driver logic configured for generating one or more input signals; and channel scan logic configured for disabling touch detection after a first predetermined amount of time elapses without any events being detected on the sensor panel, enabling touch detection, controlling the driver logic to drive at least one row in the sensor panel with the one or more input signals, and acquiring an image of the sensor panel upon expiration of a second predetermined amount of time, and determining if any events are detected on the sensor panel; wherein the acquiring of the image includes measuring a capacitance of one or more sensors in the sensor panel. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the driver logic and channel scan logic are further configured for acquiring the image by measuring a change in a mutual capacitance of one or more rows of sensors in the sensor panel. ### Claim 3 (depends on 2) The apparatus of claim 2, wherein the channel scan logic is further configured for controlling the driver logic to drive every other row of the sensor panel with a stimulation signal. ### Claim 4 (depends on 2) The apparatus of claim 2, wherein the channel scan logic is further configured for controlling the driver logic to drive rows in selected areas of the sensor panel with a stimulation signal. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the driver logic and channel scan logic are further configured for acquiring the image by measuring a change in a stray capacitance of one or more columns of sensors in the sensor panel. ### Claim 6 (depends on 5) The apparatus of claim 5, wherein the channel scan logic is further configured for controlling the driver logic to drive every row with a DC voltage. ### Claim 7 (depends on 5) The apparatus of claim 5, wherein the channel scan logic is further configured for controlling the driver logic to acquire the image by measuring the change in the stray capacitance of the one or more columns in a single scan. ### Claim 8 (depends on 5) The apparatus of claim 5, wherein the driver logic and channel scan logic are further configured for measuring a change in a mutual capacitance of one or more rows of sensors in the sensor panel after measuring a change in the stray capacitance in the sensor panel to determine where an event occurred on the sensor panel. ### Claim 9 (depends on 1) The apparatus of claim 1, the apparatus incorporated into a computing system. ### Claim 10 (depends on 9) The apparatus of claim 9, the computing system incorporated into a handheld computing device. ### Claim 11 A method for scanning a sensor panel for events, comprising: disabling touch detection after a first predetermined amount of time elapses without any events being detected on the sensor panel, enabling touch detection, driving at least one row on the sensor panel with one or more input signals, and acquiring an image of the sensor panel by measuring a capacitance of one or more sensors in the sensor panel upon expiration of a second predetermined amount of time, and determining if any events are detected on the sensor panel. ### Claim 12 (depends on 11) The method of claim 11, further comprising acquiring the image by measuring a change in a mutual capacitance of one or more rows of sensors in the sensor panel. ### Claim 13 (depends on 12) The method of claim 12, further comprising driving every other row of the sensor panel with a stimulation signal. ### Claim 14 (depends on 12) The method of claim 12, further comprising driving rows in selected areas of the sensor panel with a stimulation signal. ### Claim 15 (depends on 11) The method of claim 11, further comprising acquiring the image by measuring a change in a stray capacitance of one or more columns of sensors in the sensor panel. ### Claim 16 (depends on 15) The method of claim 15, further comprising driving every row with a DC voltage. ### Claim 17 (depends on 15) The method of claim 15, further comprising acquiring the image by measuring the change in the stray capacitance of the one or more columns in a single scan. ### Claim 18 (depends on 15) The method of claim 15, further comprising measuring a change in a mutual capacitance of one or more rows of sensors in the sensor panel after measuring a change in the stray capacitance in the sensor panel to determine where an event occurred on the sensor panel.