# US 2020/0401265 A1 · Absorption correction for fabric touch sensing layer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2020/0401265 A1 - Document ID: US20200401265A1 - Status: Published application - Kind: A1 - Application number: 17/009,671 - Filed: 2020-09-01 - Published: 2020-12-24 - Earliest claimed: 2017-07-17 - Assignees: Apple Inc. - Applicants: Apple Inc. - Inventors: Karan JAIN; Nandita VENUGOPAL - Web page: https://patentgrep.com/patent/US20200401265A1 ## CPC - G06F 3/0418: {for error correction or compensation, e.g. based on parallax, calibration or alignment} - B32B 5/26: another layer {next to it} also being fibrous or filamentary {(relative arrangement of fibres or filaments of different layers B32B5/12)} - G06F 3/0202: {Constructional details or processes of manufacture of the input device} - G06F 3/023: Arrangements for converting discrete items of information into a coded form, e.g. arrangements for interpreting keyboard generated codes as alphanumeric codes, operand codes or instruction codes - G06F 3/044: by capacitive means - G06F 3/0488: using a touch-screen or digitiser, e.g. input of commands through traced gestures - G06F 3/04886: by partitioning the display area of the touch-screen or the surface of the digitising tablet into independently controllable areas, e.g. virtual keyboards or menus - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM ## Abstract Fabric touch-sensitive layers provided for electronic devices can absorb moisture, liquids or chemicals, which can cause drift in measurements of touch nodes formed in the fabric layer. In some examples, reference nodes formed in a fabric layer can be used to account for drift due to the absorption of moisture, liquids or chemicals. The reference nodes can be isolated from the effects of proximate or touching objects and from absorption of moisture, liquids or chemicals. The reference nodes can also be formed in a fabric layer having the same or similar properties as the fabric touch-sensitive layers. When measurements of touch nodes drift due to changes in absorption, the measurements can be adjusted based on measurements of reference nodes. ## Claims ### Claim 1 An input device comprising: a first fabric layer including one or more touch nodes; and a second fabric layer, separate from the first fabric layer, including one or more reference nodes; wherein at least a portion of the first fabric layer forms at least a portion of an external surface of the input device and wherein the second fabric layer is disposed within the input device. ### Claim 2 (depends on 1) The input device of claim 1, wherein the first fabric layer and the second fabric layer are formed from a same type of fabric. ### Claim 3 (depends on 1) The input device of claim 1, wherein the first fabric layer is formed from a different type of fabric than the second fabric layer. ### Claim 4 (depends on 3) The input device of claim 3, wherein changes in a dielectric property of the first fabric due to changes in absorption are within a threshold amount of changes in a dielectric property of the second fabric due to changes in absorption. ### Claim 5 (depends on 1) The input device of claim 1, further comprising a plurality of keyboard keys, wherein the first fabric layer overlaps the keyboard keys. ### Claim 6 (depends on 5) The input device of claim 5, further comprising keycaps disposed over the first fabric layer in positions corresponding to the plurality of keyboard keys. ### Claim 7 (depends on 1) The input device of claim 1, further comprising: processing circuitry coupled to the one or more touch nodes and the one or more reference nodes, the processing circuitry configured to: sense the one or more reference nodes; sense the one or more touch nodes; detect a drift in a touch node measurement of at least one of the one or more touch nodes based on measurements of the one or more reference nodes; and in accordance with detecting the drift in the touch node measurement of the at least one of the one or more touch nodes, adjust the touch node measurement of the at least one of the one or more touch nodes in accordance with the measurements of the one or more reference nodes. ### Claim 8 (depends on 1) The input device of claim 1, wherein the first fabric layer includes an array of row electrodes and column electrodes, and each of the one or more touch nodes is formed at an adjacency of one of the row electrodes and one of the column electrodes separated by a portion of the first fabric layer. ### Claim 9 (depends on 1) The input device of claim 1, wherein the second fabric layer includes an array of row electrodes and column electrodes, and each of the one or more reference nodes is formed at an adjacency of one of the row electrodes and one of the column electrodes separated by a portion of the second fabric layer. ### Claim 10 (depends on 1) The input device of claim 1, further comprising: a plurality of keyboard keys disposed on a support surface; and a frame; wherein the second fabric layer is disposed between the support surface and the frame. ### Claim 11 (depends on 1) The input device of claim 1, wherein the one or more reference nodes are isolated from absorption of liquids and from changes in capacitance due to objects touching or in proximity to the one or more reference nodes. ### Claim 12 (depends on 1) The input device of claim 1, further comprising: one or more sense channels; wherein the processing circuitry is further configured to adjust a gain of at least one of the one or more sense channels corresponding to the at least one of the one or more touch nodes to adjust the touch node measurements. ### Claim 13 (depends on 1) The input device of claim 1, wherein adjusting the touch node measurement of the at least one of the one or more touch nodes comprises scaling a value of the touch node measurement. ### Claim 14 (depends on 1) The input device of claim 1, wherein the one or more reference nodes comprises a plurality of reference nodes and adjusting the touch node measurement is based on an average of measurements of the plurality of reference nodes. ### Claim 15 A method comprising: sensing one or more touch nodes included in a first fabric layer of an input device, wherein at least a portion of the first fabric layer forms at least a portion of an external surface of the input device; and sensing one or more reference nodes included in a second fabric layer of the input device, wherein the second fabric layer is disposed within the input device. ### Claim 16 (depends on 15) The method of claim 15, further comprising: detecting a drift in a touch node measurement of at least one of the one or more touch nodes based on measurements of the one or more reference nodes; and in accordance with detecting the drift in the touch node measurement of the at least one of the one or more touch nodes, adjusting the touch node measurement of the at least one of the one or more touch nodes in accordance with the measurements of the one or more reference nodes. ### Claim 17 (depends on 16) The method of claim 16, further comprising: in accordance with detecting no drift in a touch node measurement of at least a second of the one or more touch nodes based on the measurements of the one or more reference nodes, forgoing adjusting the touch node measurement of the least the second of the one or more touch nodes. ### Claim 18 (depends on 16) The method of claim 16, wherein the one or more reference nodes comprises a plurality of reference nodes, the method further comprising: averaging the measurements of the plurality of reference nodes. ### Claim 19 (depends on 18) The method of claim 18, further comprising: excluding at least one measurement of one of the plurality of reference nodes which exhibits more than a threshold amount of drift. ### Claim 20 A non-transitory computer readable storage medium storing instructions, which when executed by an input device, cause the input device to: sense one or more touch nodes included in a first fabric layer of the input device, wherein at least a portion of the first fabric layer forms at least a portion of an external surface of the input device; and sense one or more reference nodes included in a second fabric layer of the input device, wherein the second fabric layer is disposed within the input device.