Patent Publication Number: US-9430107-B2

Title: Determining touch locations and forces thereto on a touch and force sensing surface

Description:
RELATED PATENT APPLICATION 
     This application is a continuation-in-part of U.S. patent application Ser. No. 13/830,891; filed Mar. 14, 2013; which claims priority to U.S. Provisional Patent Application No. 61/617,831; filed Mar. 30, 2012. This application is a continuation-in-part of U.S. patent application Ser. No. 14/097,370; filed Dec. 5, 2013; which claims priority to U.S. Provisional Patent Application Ser. No. 61/777,910; filed Mar. 12, 2013; wherein all of which are hereby incorporated by reference herein for all purposes. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to capacitive touch sensing, and more particularly, to touch sensing that determines both touch locations and pressure (force) applied at the touch locations. 
     BACKGROUND 
     Human interface devices include touch control systems that are based on touch sensing surfaces, e.g., pads, screens, etc., using capacitive sensors that change capacitance values when touched. Transforming the touch(es) on the touch sensor into one or more touch locations is non-trivial. Tracking one or more touches on the touch sensor is also challenging. Advanced touch control systems are capable of detecting not only a single touch and/or movement on a touch sensing surface such as a touch screen, but also so-called multi-touch scenarios in which a user touches more than one location and/or moves more than one finger over the respective touch sensing surface, e.g., gesturing. 
     Key challenges of multi-touch systems are: limited processing speed of low cost systems, such as processing capabilities of, for example but not limited to, 8-bit microcontroller architectures as these architectures may be unable to do advanced math for processing the respective signals generated by the touch sensing device. There may also exist limited touch scanning performance, for example the entire system may be unable to reasonably sample the entire plane of the touch sensor or screen every “frame.” Other challenges include having enough program memory space to provide for touch location determination programs that are concise, modular and general purpose. Limited random access memory (RAM) space may make the touch determination system unable to store multiple entire “images” of the touch detection and location(s) thereof simultaneously. 
     Hence, there exists a need to improve and simplify touch determination methods. Conventional solutions were threshold based and required complex computations. Hence, there is a need for touch determination methods that are more robust and less computation intensive. Furthermore, there exists a need for high quality multi-touch decoding, in particular, a method and/or system that can be implemented with, for example but not limited to, a low-cost 8-bit micro controller architecture. 
     Present technology touch sensors generally can only determine a location of a touch thereto, but not a force value of the touch to the touch sensing surface. Being able to determine not only the X-Y coordinate location of a touch but also the force of that touch gives another control option that may be used with a device having a touch sensing surface with such force sensing feature. 
     SUMMARY 
     The aforementioned problems are solved, and other and further benefits achieved by a touch location and force determining method and system disclosed herein. 
     According to an embodiment, a method for decoding multiple touches and forces thereof on a touch sensing surface may comprise the steps of: scanning a plurality of channels aligned on an axis for determining self capacitance values of each of the plurality of channels; comparing the self capacitance values to determine which one of the channels has a local maximum self capacitance value; scanning a plurality of nodes of the at least one channel having the local maximum self capacitance value for determining mutual values of the nodes; comparing the mutual values to determine which one of the nodes has the largest mutual capacitance value, wherein the node having the largest mutual capacitance value on the local maximum self capacitance value channel may be a potential touch location; and determining a force at the potential touch location from a change in the mutual capacitance values of the node at the potential touch location during no touch and during a touch thereto. 
     According to a further embodiment, the method may comprise the steps of: determining if at least one of the self values may be greater than a self touch threshold, wherein if yes then continue to the step of scanning a plurality of nodes of the at least one channel having the largest self value, and if no then end a touch detection frame as completed. According to a further embodiment, the method may comprise the steps of: determining left and right slope values for the at least one self value, wherein: the left slope value may be equal to the at least one self value minus a self value of a channel to the left of the at least one channel, and the right slope value may be equal to the at least one self value minus a self value of a channel to the right of the at least one channel. 
     According to a further embodiment, the method may comprise the steps of: determining if the left slope value may be greater than zero (0) and the right slope value may be less than zero (0), wherein if yes then return to the step of scanning the plurality of nodes of the at least one channel, and if no then continue to next step; determining if the left slope value may be greater than zero (0) and greater than the right slope value, wherein if yes then return to the step of scanning the plurality of nodes of the at least one channel, and if no then continue to next step; determining if the left slope value may be less than zero (0) and greater than a percentage of the right slope value, wherein if yes then return to the step of scanning the plurality of nodes of the at least one channel, and if no then continue to next step; determining if there may be another self value, wherein if yes then return to the step of determining if at least one of the self values may be greater than the self touch threshold value using the another self value, and if no then end a touch detection frame as completed. 
     According to a further embodiment, the method may comprise the steps of: determining if at least one of the mutual values may be greater than a mutual touch threshold, wherein if yes then continue to the step of scanning a plurality of nodes of the at least one channel having the largest self value, and if no then end the touch detection frame as completed. According to a further embodiment, the method may comprise the steps of: determining a next slope value, wherein the next slope value may be equal to a current mutual value minus a next mutual value of a next node; and determining a previous slope value, wherein the previous slope value may be equal to the current mutual value minus a previous mutual value of a previous node. 
     According to a further embodiment, the method may comprise the steps of: determining if the next slope value may be less than zero (0) and the previous slope value may be greater than zero (0), wherein if yes then begin the step of validating the node, and if no then continue to next step; determining if the next slope value may be greater than zero (0) and less than a percentage of the previous slope value, wherein if yes then begin the step of validating the node, and if no then continue to next step; determining if the next slope value may be less than zero (0) and greater than the previous slope value, wherein if yes then begin the step of validating the node, and if no then continue to next step; determining if there may be another mutual value, wherein if yes then return to the step of determining if at least one of the mutual values may be greater than the mutual touch threshold, and if no then continue to the next step; and determining if there may be another self value, wherein if yes then examine another self value and return to the step of determining if at least one of the self values may be greater than a self touch threshold, and if no then end the touch detection frame as completed. 
     According to a further embodiment of the method, the step of validating the node may comprise the steps of: identifying the node having a local maximum mutual value as a current node; determining if there may be a valid node north of the current node, wherein if no then continue to the step of determining if there may be a valid node south of the current node, and if yes then perform a mutual measurement on the north node and continue to the next step; determining if the north node may be greater then the current node, if yes then make the north node the current node and continue to the step of determining whether a touch point already exists at this node, and if no then continue to the next step; determining if there may be a valid node south of the current node, wherein if no then continue to the step of determining if there may be a valid node east of the current node, and if yes then perform a mutual measurement on the south node and continue to the next step; determining if the south node may be greater then the current node, wherein if yes then make the south node the current node and continue to the step of determining whether a touch point already exists at this node, and if no then continue to the next step; determining if there may be a valid node east of the current node, wherein if no then continue to the step of determining if there may be a valid node west of the current node, and if yes then perform a mutual measurement on the east node and continue to the next step; determining if the east node may be greater then the current node, if yes then make the east node the current node and continue to the step of determining whether a touch point already exists at this node, and if no then continue to the next step; determining if there may be a valid node west of the current node, wherein if no then continue to the step of determining if there may be a valid node left of the current node, and if yes then perform a mutual measurement on the west node and continue to the next step; determining if the west node may be greater then the current node, if yes then make the west node the current node and continue to the step of determining whether a touch point already exists at this node, and if no then continue to the next step; determining if there may be a valid node left of the current node, wherein if no then define a left mutual value as a center mutual value minus a right mutual value and continue to the step of determining a fine position for the node, and if yes then perform a mutual measurement on the left node and continue to the next step; determining if there may be a valid node right of the current node, wherein if no then define the mutual value as the center mutual value minus the left mutual value and continue to the step of determining the fine position for the node, and if yes then perform a mutual measurement on the right node and continue to the next step; defining a fine position of the node by subtracting the left value from the right value, dividing this difference by the center value and multiplying the result thereof by 64 and continue to the next step; and determining whether interpolation was performed for each axis, wherein if yes, then add another touch point to a list of all detected touch points and return to the step of determining if there may be additional mutual values, and if no, then interpolate an other axis by using left and right nodes of the other axis for starting again at the step of determining if there may be a valid node left of the current node. 
     According to another embodiment, a system for determining gesturing motions and forces thereof on a touch sensing surface having a visual display may comprise: a first plurality of electrodes arranged in a parallel orientation having a first axis, wherein each of the first plurality of electrodes may comprise a self capacitance; a second plurality of electrodes arranged in a parallel orientation having a second axis substantially perpendicular to the first axis, the first plurality of electrodes may be located over the second plurality of electrodes and form a plurality of nodes may comprise overlapping intersections of the first and second plurality of electrodes, wherein each of the plurality of nodes may comprise a mutual capacitance; a flexible electrically conductive cover over the first plurality of electrodes, wherein a face of the flexible electrically conductive cover forms the touch sensing surface; a plurality of deformable spacers between the flexible electrically conductive cover and the first plurality of electrodes, wherein the plurality of deformable spacers maintains a distance between the flexible electrically conductive cover and the first plurality of electrodes; a digital processor and memory, wherein digital outputs of the digital processor may be coupled to the first and second plurality of electrodes; an analog front end coupled to the first and second plurality of electrodes; an analog-to-digital converter (ADC) having at least one digital output coupled to the digital processor; wherein values of the self capacitances may be measured for each of the first plurality of electrodes by the analog front end, the values of the measured self capacitances may be stored in the memory; values of the mutual capacitances of the nodes of at least one of the first electrodes having at least one of the largest values of self capacitance may be measured by the analog front end, the values of the measured mutual capacitances may be stored in the memory; and the digital processor uses the stored self and mutual capacitance values for determining a gesturing motion and at least one force associated therewith applied to the touch sensing surface. 
     According to a further embodiment, the digital processor, memory, analog front end and ADC may be provided by a digital device. According to a further embodiment, the digital device may comprise a microcontroller. According to a further embodiment, the flexible electrically conductive cover may comprise a flexible metal substrate. According to a further embodiment, the flexible electrically conductive cover may comprise a flexible non-metal substrate and an electrically conductive coating on a surface thereof. According to a further embodiment, the flexible electrically conductive cover may comprise a substantially light transmissive flexible substrate and a coating of Indium Tin Oxide (ITO) on a surface of the flexible substrate. According to a further embodiment, the flexible electrically conductive cover may comprise a substantially light transmissive flexible substrate and a coating of Antimony Tin Oxide (ATO) on a surface of the flexible substrate. 
     According to yet another embodiment of the method for determining the gesturing motion and the at least one force associated therewith may comprise the step of selecting an object shown in the visual display by touching the object with a first force. According to a further embodiment, the method may comprise the step of locking the object in place by touching the object with a second force. According to a further embodiment, the method may comprise the step of releasing the lock on the object by touching the object with a third force and moving the touch in a direction across the touch sensing surface. According to a further embodiment, the method may comprise the step of releasing the lock on the object by removing the touch at a first force to the object and then touching the object again at a second force. According to a further embodiment of the method, the second force may be greater than the first force. 
     According to still another embodiment, a method for determining the gesturing motion and the at least one force associated therewith may comprise the steps of: touching a right portion of an object shown in the visual display with a first force; touching a left portion of the object with a second force; wherein when the first force may be greater than the second force the object rotates in a first direction, and when the second force may be greater than the first force the object rotates in a second direction. 
     According to a further embodiment of the method, the first direction may be clockwise and the second direction may be counter-clockwise. According to a further embodiment of the method, when the touch at the left portion of the object moves toward the right portion of the object the object rotates in a third direction, and when the touch at the right portion of the object moves toward the left portion of the object may rotate in a fourth direction. According to a further embodiment of the method, the first and second directions may be substantially perpendicular to the third and fourth directions. 
     According to a further embodiment of the method for determining the gesturing motion and the at least one force associated therewith may comprise the step of: changing a size of an object shown in the visual display by touching a portion of the object with a force, wherein the greater the force the large the size of the object becomes. According to a further embodiment of the method, the size of the object may be fixed when the touch and the force may be moved off of the object. According to a further embodiment of the method, the size of the object varies in proportion to the amount of force applied to the object. 
     According to a further embodiment of the method for determining the gesturing motion and the at least one force associated therewith may comprise the step of: handling pages of a document shown in the visual display by touching a portion of the document with a force sufficient to flip through the pages. According to a further embodiment of the method, the step of removing a currently visible page may further comprise the step of moving the touch at the currently visible page in a first direction parallel with the touch sensing surface. According to a further embodiment of the method, the step of inserting the removed page into a new document may comprise the step of touching the removed page with the force near the new document. 
     According to a further embodiment of the method for determining the gesturing motion and the at least one force associated therewith may comprise the step of changing values of an alpha-numeric character shown in the visual display by touching the alpha-numeric character with different forces, wherein a first force will cause the alpha-numeric character to increment and a second force will cause the alpha-numeric character to decrement. According to a further embodiment of the method, the value of the alpha-numeric character may be locked when the touch may be moved off of the alpha-numeric character and parallel to the touch sensing surface. 
     According to a further embodiment of the method for determining the gesturing motion and the at least one force associated therewith may comprise the steps of: incrementing a value of an alpha-numeric character shown in the visual display by touching an upper portion of the alpha-numeric character with a force; and decrementing the value of the alpha-numeric character by touching an lower portion of the alpha-numeric character with the force. According to a further embodiment of the method, the value of the alpha-numeric character may be locked when the touch may be moved off of the alpha-numeric character and parallel to the touch sensing surface. According to a further embodiment of the method, a speed of incrementing or decrementing the value of the alpha-numeric character may be proportional to a magnitude of the force applied to upper portion or lower portion, respectively, of the alpha-numeric character. According to a further embodiment of the method, the alpha-numeric character may be a number. According to a further embodiment of the method, the alpha-numeric character may be a letter of an alphabet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present disclosure thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings wherein: 
         FIG. 1  illustrates a schematic block diagram of an electronic system having a capacitive touch sensor, a capacitive touch analog front end and a digital processor, according to the teachings of this disclosure; 
         FIG. 2  illustrates schematic elevational views of metal over capacitive touch sensors, according to the teachings of this disclosure; 
         FIG. 3  illustrates a schematic elevational view of a touch sensor capable of detecting both locations of touches thereto and forces of those touches, according to the teachings of this disclosure; 
         FIGS. 4A to 4D  illustrate schematic plan views of touch sensors having various capacitive touch sensor configurations, according to the teachings of this disclosure; 
         FIGS. 4E and 4F  illustrate schematic plan views of self and mutual capacitive touch detection of a single touch to a touch sensor, according to the teachings of this disclosure; 
         FIGS. 4G to 4K  illustrate schematic plan views of self and mutual capacitive touch detection of two touches to a touch sensor, according to the teachings of this disclosure; 
         FIG. 5  illustrates a schematic process flow diagram for multi-touch and force decoding of a touch sensor as shown in  FIG. 1 , according to specific example embodiments of this disclosure; 
         FIG. 6  illustrates a graph of single touch peak detection data, according to specific example embodiments of this disclosure; 
         FIG. 7  illustrates a schematic plan diagram of potential touch and mutual touch locations of a touch sensor, according to specific example embodiments of this disclosure; 
         FIG. 8  illustrates a schematic plan view diagram of a touch sensor showing a cache data window thereof, according to specific example embodiments of this disclosure; 
         FIG. 9  illustrates a graph of self scan values and a table of mutual scan values for two touch peak detection data, according to specific example embodiments of this disclosure; 
         FIGS. 10 and 11  illustrate schematic diagrams of historic and current point locations used for a point weighting example, according to the teachings of this disclosure; 
         FIG. 12  illustrates schematic drawings of a normal finger touch and a flat finger touch, according to the teachings of this disclosure; 
         FIGS. 13 to 23  illustrate schematic process flow diagrams for touch decoding and force determination of the decoded touch(es), according to specific example embodiments of this disclosure; 
         FIG. 24  illustrates a schematic plan view of a finger of a hand touching a surface of a touch sensor, according to a specific example embodiment of this disclosure; 
         FIG. 25  illustrates a schematic plan view of two fingers of a hand touching a surface of a touch sensor, according to another specific example embodiment of this disclosure; 
         FIG. 26  illustrates a schematic plan view of a finger of a hand touching an object projected on a surface of a touch sensor, according to yet another specific example embodiment of this disclosure; 
         FIG. 27  illustrates a schematic plan view of a finger of a hand touching a document projected on a surface of a touch sensor, according to still another specific example embodiment of this disclosure; and 
         FIG. 28  illustrates a schematic plan view of a finger of a hand touching one digit of a number projected on a surface of a touch sensor, according to another specific example embodiment of this disclosure. 
     
    
    
     While the present disclosure is susceptible to various modifications and alternative forms, specific example embodiments thereof have been shown in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific example embodiments is not intended to limit the disclosure to the particular forms disclosed herein, but on the contrary, this disclosure is to cover all modifications and equivalents as defined by the appended claims. 
     DETAILED DESCRIPTION 
     According to various embodiments, a series of optimized processes may be provided that scan a plurality of (electrically) conductive columns and rows arranged in a matrix on a surface, e.g., touch sensor display or panel, and which identify and track a plurality of touches thereto and forces thereof. These processes may be further optimized for operation with a low cost 8-bit microcontroller, according to specific embodiments of this disclosure. 
     Once a touch has been established, a force thereof may be assigned to the touch based upon the magnitude of change of the capacitance values determined during scans of a touch sensor, as more fully described hereinabove. Also the touch forces applied to the touch sensor from the associated tracked touch points may be utilized in further determining three dimensional gesturing, e.g., X, Y and Z positions and forces, respectively. For example, proportional force at a touch location(s) allows three dimensional control of an object projected onto a screen of the touch sensor. Differing pressures on multiple points, e.g., during more then one touch (multiple fingers touching face of touch sensor), allows object rotation control. A touch at a certain force may allow selecting an object(s) and a touch at a difference, e.g., greater force, may be used to fix the location(s) of the object(s) on the display of the touch sensor. 
     Rocking multi-touch presses to produce varying touch forces may be used for rotation of an object. A vertical motion, e.g., vertical sliding, press may be used to scale a vertical size of an object. A horizontal motion, e.g., horizontal sliding, press may be used to scale a horizontal size of an object. Touches with varying force may be used to flip through pages of a document. A varying force may be used to insert a page into a stack of pages of a document. A vertical or horizontal gesture and force may be used to activate a function, e.g., empty trash bin icon. Varying touch pressure may be used to lift a page off of a document for transmission to another display. Varying touch pressure may change the scope of a gesture movement, e.g., selecting a picture instead of the full document. Pressing with a sweeping gesture may be used for an object release and discard. Varying touch pressures may be used to select alpha-numeric characters or drop function boxes. 
     According to various embodiments, these processes utilize both self and mutual scans to perform an optimized scan of the plurality of conductive columns and rows used for touch sensing. Using that as the basis, the proposed processes may use a subset of the data from the plurality of conductive columns and rows in order to do all necessary processing for touch location identification and tracking. The various embodiments specifically focus on a low-resource requirement solution for achieving touch location identification and tracking. 
     According to various embodiments, self capacitances of either the conductive columns or rows may be measured first then mutual capacitances of only those conductive columns or rows may be measured in combination with the other axis of conductive rows or columns. The various embodiments disclosed herein overcome the problem of transforming these self and mutual capacitance measurements into one or more touches and forces thereof, and tracking these one or more touches and forces thereof through multiple frames of the capacitance measurements of the conductive columns or rows as described hereinabove. 
     According to various embodiments, at least one process may scan a plurality of conductive columns and rows arranged in a matrix, detect and track up to N touches, using various unique techniques disclosed and claimed herein. A process of peak detection examines slope ratios to accurately and quickly determine peak measurements. According to various embodiments, the challenge of tracking multiple touch locations may be solved through time on associated ones of the plurality of conductive columns or rows. 
     The various embodiments may allow for N touches to compensate for touches of different finger positions, e.g., such as a flat finger, that prevents missed touches and substantially eliminates incorrect touches. 
     According to various embodiments, a process is provided for quickly identifying accurate touches instead of only looking at true peaks, wherein a “virtual” peak may be found by examining slope ratios using various techniques disclosed herein for touch identification. A combination of unique processes, according to the teachings of this disclosure, may be used to achieve better accuracy and speed improvements for multi-touch decoding. For example, a peak detection process may be implemented as a “fuzzy” peak detection process that examines slope relationships, not just signs of the slopes between the conductive columns measured. Furthermore, a so-called “nudge technique” may be used that “nudges” a potential touch location to a best location by examining adjacent values thereto. “Windowed” data cache may be used to accelerate processing in a low capacity RAM environment, e.g., 8-bit microcontroller. Interpolation may be used to increase the touch location resolution based upon measured values adjacent thereto. Multi-touch tracking may be used to identify N touches through time. Multi-touch tracking may be used to track N touches through time. Weighted matching may be used in a weighting method to best match touch points over time. “Area” detection may use a process that allows easy area and/or pressure detection based upon the sum of the nudged values for a given touch location. 
     Significant accuracy and speed of decoding improvements may use a combination of novel techniques for use in a low memory capacity and low cost digital processor, e.g., microcontroller, microprocessor, digital signal processor (DSP), application specific integrated circuit (ASIC), programmable logic array (PLA), etc. Various embodiments may track eight or more touches and forces thereof on, for example but not limited to, a 3.5 inch touch sensor capacitive sensor array. For example when using a Microchip PIC18F46K22 (64K ROM, &lt;4K RAM) microcontroller. 
     Referring now to the drawings, the details of example embodiments are schematically illustrated. Like elements in the drawings will be represented by like numbers, and similar elements will be represented by like numbers with a different lower case letter suffix. 
     Referring to  FIG. 1 , depicted is a schematic block diagram of an electronic system having a capacitive touch sensor, a capacitive touch analog front end and a digital processor, according to the teachings of this disclosure. A digital device  112  may comprise a digital processor and memory  106 , an analog-to-digital converter (ADC) controller  108 , and a capacitive touch analog front end (AFE)  110 . The digital device  112  may be coupled to a touch sensor  102  comprised of a plurality of conductive columns  104  and rows  105  arranged in a matrix and having a flexible electrically conductive cover  103  thereover. It is contemplated and within the scope of this disclosure that the conductive rows  105  and/or conductive columns  104  may be, for example but are not limited to, printed circuit board conductors, wires, Indium Tin Oxide (ITO) or Antimony Tin Oxide (ATO) coatings on a clear substrate, e.g., display/touch screen, etc., or any combinations thereof. The flexible electrically conductive cover  103  may comprise metal, conductive non-metallic material, ITO or ATO coating on a flexible clear substrate (plastic), etc. The digital device  112  may comprise a microcontroller, microprocessor, digital signal processor, application specific integrated circuit (ASIC), programmable logic array (PLA), etc., and may further comprise one or more integrated circuits (not shown), packaged or unpackaged. 
     Referring to  FIG. 2 , depicted are schematic elevational views of metal over capacitive touch sensors, according to the teachings of this disclosure. A capacitive sensor  238  is on a substrate  232 . On either side of the capacitive sensor  238  are spacers  234 , and an electrically conductive flexible cover  103 , e.g., metal, ITO or ATO coated plastic, etc.; is located on top of the spacers  234  and forms a chamber  236  over the capacitive sensor  238 . When a force  242  is applied to a location on the flexible cover  103 , the flexible cover  103  moves toward the capacitive sensor  238 , thereby increasing the capacitance thereof. The capacitance value(s) of the capacitive sensor(s)  238  is measured and an increase in capacitance value thereof will indicate the location of the force  242  (e.g., touch). The capacitance value of the capacitive sensor  238  will increase the closer the flexible cover  103  moves toward the face of the capacitive sensor  238 . Metal over capacitive touch technology is more fully described in Application Note AN1325, entitled “mTouch™ Metal over Cap Technology” by Keith Curtis and Dieter Peter, available www.microchip.com; and is hereby incorporated by reference herein for all purposes. 
     Referring to  FIG. 3 , depicted is a schematic elevational view of a touch sensor capable of detecting both locations of touches thereto and forces of those touches, according to the teachings this disclosure. A touch sensor capable of detecting both a location of a touch(es) thereto and a force(s) of that touch(es) thereto, generally represented by the numeral  102 , may comprise a plurality of conductive rows  105 , a plurality of conductive columns  104 , a plurality of deformable spacers  334 , and a flexible electrically conductive cover  103 . 
     The conductive columns  104  and the conductive rows  105  may be used in determining a location(s) of a touch(es), more fully described in Technical Bulletin TB3064, entitled “mTouch™ Projected Capacitive Touch Screen Sensing Theory of Operation” referenced hereinabove, and the magnitude of changes in the capacitance values of the conductive column(s)  104  at and around the touch location(s) may be used in determining the force  242  (amount of pressure applied at the touch location). The plurality of deformable spacers  334  may be used to maintain a constant spacing between the flexible conductive cover  103  and a front surface of the conductive columns  104  when no force  242  is being applied to the flexible electrically conductive cover  103 . When force  242  is applied to a location on the flexible electrically conductive cover  103 , the flexible electrically conductive cover  103  will be biased toward at least one conductive column  104 , thereby increasing the capacitance thereof. Direct measurements of capacitance values and/or ratios of the capacitance values may be used in determining the magnitude of the force  242  being applied at the touch location(s). 
     Referring back to  FIG. 1 , digital devices  112 , e.g., microcontrollers, now include peripherals that enhance the detection and evaluation of such capacitive value changes. More detailed descriptions of various capacitive touch system applications are more fully disclosed in Microchip Technology Incorporated application notes AN1298, AN1325 and AN1334, available at www.microchip.com, and all are hereby incorporated by reference herein for all purposes. 
     One such application utilizes the capacitive voltage divider (CVD) method to determine a capacitance value and/or evaluate whether the capacitive value has changed. The CVD method is more fully described in Application Note AN1208, available at www.microchip.com; and a more detailed explanation of the CVD method is presented in commonly owned United States Patent Application Publication No. US 2010/0181180, entitled “Capacitive Touch Sensing using an Internal Capacitor of an Analog-To-Digital Converter (ADC) and a Voltage Reference,” by Dieter Peter; wherein both are hereby incorporated by reference herein for all purposes. 
     A Charge Time Measurement Unit (CTMU) may be used for very accurate capacitance measurements. The CTMU is more fully described in Microchip application notes AN1250 and AN1375, available at www.microchip.com, and commonly owned U.S. Pat. No. 7,460,441 B2, entitled “Measuring a long time period;” and U.S. Pat. No. 7,764,213 B2, entitled “Current-time digital-to-analog converter,” both by James E. Bartling; wherein all of which are hereby incorporated by reference herein for all purposes. 
     It is contemplated and within the scope of this disclosure that any type of capacitance measurement circuit having the necessary resolution may be used in determining the capacitance values of the plurality of conductive columns  104  and nodes (intersections of columns  104  and rows  105 ), and that a person having ordinary skill in the art of electronics and having the benefit of this disclosure could implement such a capacitance measurement circuit. 
     Referring to  FIGS. 4A to 4D , depicted are schematic plan views of touch sensors having various capacitive touch sensor configurations, according to the teachings of this disclosure.  FIG. 4A  shows conductive columns  104  and conductive rows  105 . Each of the conductive columns  104  has a “self capacitance” that may be individually measured when in a quiescent state, or all of the conductive rows  105  may be actively excited while each one of the conductive columns  104  has self capacitance measurements made thereof. Active excitation of all of the conductive rows  105  may provide a stronger measurement signal for individual capacitive measurements of the conductive columns  104 . 
     For example, if there is a touch detected on one of the conductive columns  104  during a self capacitance scan, then only that conductive column  104  having the touch detected thereon need be measured further during a mutual capacitance scan thereof. The self capacitance scan may only determine which one of the conductive columns  104  has been touched, but not at what location along the axis of that conductive column  104  where it was touched. The mutual capacitance scan may determine the touch location along the axis of that conductive column  104  by individually exciting (driving) one at a time the conductive rows  105  and measuring a mutual capacitance value for each one of the locations on that conductive column  104  that intersects (crosses over) the conductive rows  105 . There may be an insulating non-conductive dielectric (not shown) between and separating the conductive columns  104  and the conductive rows  105 . Where the conductive columns  104  intersect with (crossover) the conductive rows  105 , mutual capacitors  120  are thereby formed. During the self capacitance scan above, all of the conductive rows  105  may be either grounded or driven with a logic signal, thereby forming individual column capacitors associated with each one of the conductive columns  104 . 
       FIGS. 4B and 4C  show interleaving of diamond shaped patterns of the conductive columns  104  and the conductive rows  105 . This configuration may maximize exposure of each axis conductive column and/or row to a touch (e.g., better sensitivity) with a smaller overlap between the conductive columns  104  and the conductive rows  105 .  FIG. 4D  shows receiver (top) conductive rows (e.g., electrodes)  105   a  and transmitter (bottom) conductive columns  104   a  comprising comb like meshing fingers. The conductive columns  104   a  and conductive rows  105   a  are shown in a side-by-side plan view, but normally the top conductive rows  105   a  would be over the bottom conductive columns  104   a . Self and mutual capacitive touch detection is more fully described in Technical Bulletin TB3064, entitled “mTouch™ Projected Capacitive Touch Screen Sensing Theory of Operation” by Todd O&#39;Connor, available at www.microchip.com; and commonly owned United States Patent Application Publication No. US 2012/0113047, entitled “Capacitive Touch System Using Both Self and Mutual Capacitance” by Jerry Hanauer; wherein both are hereby incorporated by reference herein for all purposes. 
     Referring to  FIGS. 4E and 4F , depicted are schematic plan views of self and mutual capacitive touch detection of a single touch to a touch sensor, according to the teachings of this disclosure. In  FIG. 4E  a touch, represented by a picture of a part of a finger, is at approximately the coordinates of X 05 , Y 07 . During self capacitive touch detection each one of the rows Y 01  to Y 09  may be measured to the determine the capacitance values thereof. Note that baseline capacitance values with no touches thereto for each one of the rows Y 01  to Y 09  have been taken and stored in a memory (e.g., memory  106 — FIG. 1 ). Any significant capacitance change to the baseline capacitance values of the rows Y 01  to Y 09  will be obvious and taken as a finger touch. In the example shown in  FIG. 4E  the finger is touching row Y 07  and the capacitance value of that row will change, indicating a touch thereto. However it is still unknown from the self capacitance measurements where on this row that the touch has occurred. 
     Once the touched row (Y 07 ) has been determined using the self capacitance change thereof, mutual capacitive detection may be used in determining where on the touched row (Y 07 ) the touch has occurred. This may be accomplished by exciting, e.g., putting a voltage pulse on, each of the columns X 01  to X 12  one at a time while measuring the capacitance value of row Y 07  when each of the columns X 01  to X 12  is individually excited. The column (X 05 ) excitation that causes the largest change in the capacitance value of row Y 07  will be the location on that row which corresponds to the intersection of column X 05  with row Y 07 , thus the single touch is at point or node X 05 , Y 07 . Using self and mutual capacitance touch detection significantly reduces the number of row and column scans to obtain the X,Y touch coordinate on the touch sensor  102 . In this example, nine (9) rows were scanned during self capacitive touch detection and twelve (12) columns were scanned during mutual capacitive touch detection for a total number of 9+12=21 scans. If individual x-y capacitive touch sensors for each node (location) were used then 9×12=108 scans would be necessary to find this one touch, a significant difference. It is contemplated and within the scope of this disclosure that the self capacitances of the columns X 01  to X 21  may be determined first then mutual capacitances determined of a selected column(s) by exciting each row Y 01  to Y 09  to find the touch location on the selected column(s). 
     Referring to  FIGS. 4G to 4K , depicted are schematic plan views of self and mutual capacitive touch detection of two touches to a touch sensor, according to the teachings of this disclosure. In  FIG. 4G  two touches, represented by a picture of parts of two fingers, are at approximately the coordinates of X 05 , Y 07  for touch #1 and X 02 , Y 03  for touch #2. During self capacitive touch detection each one of the rows Y 01  to Y 09  may be measured to the determine the capacitance values thereof. Note that baseline capacitance values with no touches thereto for each one of the rows Y 01  to Y 09  have been taken and stored in a memory (e.g., memory  106 — FIG. 1 ). Any significant capacitance changes to the baseline capacitance values of the rows Y 01  to Y 09  will be obvious and taken as finger touches. In the example shown in  FIG. 4H  the first finger is touching row Y 07  and the second finger is touching row Y 03 , wherein the capacitance values of those two rows will change, indicating touches thereto. However it is still unknown from the self capacitance measurements where on these two row that the touches have occurred. 
     Once the touched rows (Y 07  and Y 03 ) have been determined using the self capacitance changes thereof, mutual capacitive detection may be used in determining where on these two touched rows (Y 07  and Y 03 ) the touches have occurred. Referring to  FIG. 4I , this may be accomplished by exciting, e.g., putting a voltage pulse on, each of the columns X 01  to X 12  one at a time while measuring the capacitance value of row Y 07  when each of the columns X 01  to X 12  is individually excited. The column (X 05 ) excitation that causes the largest change in the capacitance value of row Y 07  will be the location on that row that corresponds to the intersection of column X 05  with row Y 07 . Referring to  FIG. 4J , likewise measuring the capacitance value of row Y 03  when each of the columns X 01  to X 12  is individually excited determines where on column Y 03  the touch #2 has occurred. Referring to  FIG. 4K , the two touches are at points or nodes (X 05 , Y 07 ) and (X 02 , Y 03 ). It is contemplated and within the scope of this disclosure that if the capacitances of more then one of the selected rows, e.g., Y 07  and Y 03 , can be measured simultaneously, then only one set of individual column X 01  to X 12  excitations is needed in determining the two touches to the touch sensor  102 . 
     Referring to  FIG. 5 , depicted is a schematic process flow diagram for multi-touch and force decoding of a touch sensor as shown in  FIG. 1 , according to specific example embodiments of this disclosure. A process of multi-touch decoding may comprise the steps of Data Acquisition  502 , Touch Identification  504 , Force Identification  505 , Touch and Force Tracking  506 , and Data Output  508 . The step of Touch Identification  504  may further comprise the steps of Peak Detection  510 , Nudge  512  and Interpolation  514 , more fully described hereinafter. 
     Data Acquisition. 
     Data Acquisition  502  is the process of taking self capacitance measurements of the plurality of conductive columns  104  or conductive rows  105 , and then mutual capacitance measurements of selected ones of the plurality of conductive columns  104  or conductive rows  105 , and intersections of the plurality of conductive rows  105  or conductive columns  104 , respectively therewith, to acquire touch identification data. The touch identification data may be further processed to locate potential touches and forces thereto on the touch sensor  102  using the process of Touch Identification  504  and Force Identification  505 , respectively, as more fully described hereinafter. 
     Touch Identification 
     Touch Identification  504  is the process of using the touch identification data acquired during the process of Data Acquisition  502  to locate potential touches on the touch sensor  102 . The following are a sequence of process steps to determine which ones of the plurality of conductive columns  104  or conductive rows  105  to select that have a touch(es) thereto using self capacitance measurements thereof, and where on the selected conductive columns  104  or conductive rows  105  the touch(es) may have occurred using mutual capacitance measurements thereof. 
     Peak Detection 
     Peak detection  510  is the process of identifying where potential touch locations may be on the touch sensor  102 . However according to the teachings of this disclosure, instead of only looking at actual detected “peaks,” peak detection may purposely be made “fuzzy,” e.g., identifying potential peaks by looking for ratios of differences of slope values as well as slope “signs,” not just a low-high-low value sequence. A “virtual” peak may be detected by examining slope ratios, e.g., 2:1 slope ratio, wherein a change in slope may be identified as a potential peak. This may be repeated until no additional peaks are detected. 
     Nudge 
     Nudge  512  is the process of examining each adjacent location of a potential touch location once it has been identified. If the adjacent location(s) has a greater value than the existing touch potential location then eliminate the current potential touch location and identify the adjacent location having the greater value as the potential touch location (see  FIG. 8  and the description thereof hereinafter). 
     Interpolation 
     Once a touch location has been identified, Interpolation  514  is the process that examines the adjacent values to generate a higher resolution location. 
     Force Identification 
     Force Identification  505  is the process of using some of the touch identification data acquired during the process of Data Acquisition  502  in combination with the potential touch locations identified during the process of Touch Identification  504 . The mutual capacitance measurements associated with the potential touch locations, determined during the process of Touch Identification  504 , may be compared with reference capacitance values of those same locations with no touches applied thereto (smaller capacitance values). The magnitude of a capacitance change may thereby be used in determining the force applied by the associated potential touch previously determined. 
     Touch and Force Tracking 
     Touch and Force Tracking  506  is the process of comparing time sequential “frames” of touch identification data and then determining which touches are associated between sequential frames. A combination of weighting and “best guess” matching may be used to track touches and forces thereof through multiple frames during the process of Data Acquisition  502  described hereinabove. This is repeated for every peak detected and every touch that was identified on the previous frame. A “frame” is the set of self and mutual capacitive measurements of the plurality of conductive columns  104  or conductive rows  105  in order to capture a single set of touches at a specific time. Each full set of scans (a “frame”) of the self and mutual capacitance measurements of the plurality of conductive columns  104  or conductive rows  105  to acquire touch identification data of the touch sensor  102  at a given time associated with that frame. 
     Touch and Force Tracking  506  associates a given touch in one frame with a given touch in a subsequent frame. Touch and Force tracking may create a history of touch frames, and may associate the touch locations of a current frame with the touch locations of a previous frame or frames. In order to associate a previous touch location to a current potential touch location a “weighting” function may be used. The weight values (“weight” and “weight values” will be used interchangeably herein) between time sequential touch locations (of different frames) represent the likelihood that time sequential touch locations (of different frames) are associated with each other. Distance calculations may be used to assign weight values between these associated touch locations. A “true” but complex and processor intensive calculation for determining weight value between touch locations is:
 
Weight value=SQRT[( X   previous   −X   current ) 2 +( Y   previous   −Y   current ) 2 ]  Eq. (1)
 
A simplified distance (weight value) calculation may be used that measures ΔX and ΔY and then sums them together:
 
Weight value′= ABS ( X   previous   −X   current )+ ABS ( Y   previous   −Y   current )  Eq. (2)
 
     The above simplified weight value calculation, Eq. (2), creates a diamond shaped pattern for a given weight value instead of a circular pattern of the more complex weight value calculation, Eq. (1). Use of Eq. (2) may be optimized for speed of the weight value calculations in a simple processing system, distance may be calculated based upon the sum of the change of the X-distances and the change in the Y-distances, e.g., Eq. (2) herein above. A better weight value may be defined as a smaller distance between sequential touch locations. 
     For each new touch location a weight value may be calculated for all touch locations from the previous frame. The new touch location is then associated with the previous touch location having the best weight value therebetween. If the previous touch location already has an associated touch location from a previous frame, a secondary second-best weight value for each touch location may be examined. The touch location with the lower-cost second-best weight value may then be shifted to its second best location, and the other touch location may be kept as the best touch location. This process is repeated until all touch locations have been associated with previous frame touch locations, or have been identified as “new touches” having new locations with no touch locations from the previous frame being close to the new touch location(s). 
     An alternative to the aforementioned weighting process may be a vector-based process utilizing a vector created from the previous two locations to create the most likely next location. This vector-based weighting process may use the same distance calculations as the aforementioned weighting process, running it from multiple points and modifying the weight values based upon from which point the measurement was taken. 
     By looking at the previous two locations of a touch, the next “most likely” location of that touch may be predicted. Once the extrapolated location has been determined that location may be used as the basis for a weighting value. To improve matching on the extrapolated location an “acceleration model” may be used to add weighting points along the vector to the extrapolated locations and past the extrapolated locations. These additional points assist in detecting changes in speed of the touch movement, but may not be ideal for determining direction of the touch motion. 
     Once the touch locations have been established, forces thereto may be assigned to these touch locations based upon the magnitude of change of the capacitance values determined during the process of Data Acquisition  502 , as more fully described hereinabove. Also the forces applied to the touch sensor  102  from the associated tracked touch points may be utilized in further determining three dimensional gesturing, e.g., X-Y and Z directions. 
     Referring to  FIGS. 10 and 11 , depicted are schematic diagrams of historic and current point locations used for a point weighting example, according to the teachings of this disclosure. Once weights have been generated, the best combination of weight values and associated touches may be generated. Certain touch scenarios may cause nearly identical weight values, in which case the second best weight values should be compared and associations appropriately shifted. Depending upon the order of operations, points A and D may be associated first. As the weight values for B are generated BD is a better match then BC. In this case look at secondary weight values. Is it less costly to shift A to be associated with C or to shift B to be associated with C? 
     By extending this sequence of operations, all points can have associations shifted for the best overall match, not just the best local match. Some caution may be needed to prevent infinite loops of re-weighing. This may be accomplished by limiting the number of shifts to a finite number. Referring now to  FIG. 11 , points A and B are existing points, and points  1  and 2 are “new” points that need to be associated. 
     Step 1) Calculate weight values between touch locations: 
     
         
         
           
             A 1 weight=5 ((ΔX=2)+(ΔY=3)=5) 
             A 2 weight=4 
             B 1 weight=10 
             B 2 weight=5
 
Step 2) Select the “best” pair (lowest weight) for each existing touch location:
 
             A &gt;2 weight=4 and B &gt;2 weight=5
 
Step 3) If more than one existing touch location pairs with a given new touch location, then look at the second-best touch locations for each and the difference in weight values from the best to the second best pair (the “cost”).
 
             A 1 (weight: 5) Cost=1: (A 1 weight)−(A 2 weight 4) 
             B 1 (weight: 10) Cost=5: (B 1 weight)−(B 2 weight 5)
 
Step 4) Shift the pairing to the lowest cost pair thereby allowing the other touch location to maintain the original pairing.
 
             A 1 
             B 2
 
Step 5) Repeat steps 2) through 4) until all pairing are 1:1. If there are more touch locations than existing touch locations then start tracking a new touch location. If fewer new touch locations than existing “worst match” touch locations then these worst match touch locations may be lost and no longer tracked.
 
           
         
       
    
     Flat Finger Identification 
     Referring to  FIG. 12 , depicted are schematic drawings of a normal finger touch and a flat finger touch, according to the teachings of this disclosure. One challenge of identifying a touch is the “flat finger” scenario. This is when the side or flat part of a finger  1020 , rather then the finger tip  1022 , is placed on the touch sensor  102 . Note that a flat finger  1020  may generate two or more potential touch locations  1024  and  1026 . It is possible using the teaching of this disclosure to detect a flat finger  1020  by accumulating the sum of the values of all nodes nudged to each peak. If the sum of these values surpasses a threshold then it is likely caused by a flat finger touch. If a flat finger touch is detected then other touches that are near the flat finger peak(s) may be suppressed. In addition, comparing the forces associated with the two or more potential touch locations  1024  and  1026  may also be used in detecting a flat finger  1020  situation. 
     Data Output 
     Referring back to  FIG. 5 , Data Output  508  is the process of providing determined touch location coordinates and associated forces applied thereto in a data packet(s) to a host system for further processing. 
     Touch Determination 
     Given an array of touch data, examine the differences between the values thereof and flag certain key scenarios as potential peaks for further examination. All touch data values below a threshold value may be ignored when determining touch locations. 
     Key Scenario 1: True Peak 
     Referring to  FIG. 6 , identify the transition from a positive to a negative slope as a potential peak. This would be the point circled in column  7  of the example data values shown in  FIG. 6 . 
     Key Scenario 2: Slope Ratio Beyond Threshold (“Fuzzy” Peak Detection) 
     A key threshold of slope ratios may be used to flag additional peaks. The threshold value used may be, for example but is not limited to, 2:1; so instances where there is a change of slope greater than 2:1 may be identified as potential peaks. This applies to positive and negative slopes. This would be the point circled in column  6  of the example data values shown in  FIG. 6 . 
     Why not Just Look at the Slope Signs? 
     Since the self scan is only one axis of a two-axis sensor array (e.g., conductive rows  105  and conductive columns  104  of touch sensor  102 ,  FIG. 1 ), it is possible for two touches that are off by a single “bar” (e.g., column) to only show a single peak. With the example data, there could be two touches, one at 6,6 and another at 7,7 (see  FIGS. 6 and 9 ). Without the additional peak detection, the touch at 6,3 may not be detected. 
     Nudge Location Refinement 
     Once a potential touch location is identified, each adjacent touch location may be examined to determine if they have a greater value. If a greater value is present, eliminate the current potential touch location and identify the touch location of the greater value as a potential touch location. This process is repeated until a local peak has been identified. 
     Referring to  FIG. 6 , depicted is a graph of single touch peak detection data, according to specific example embodiments of this disclosure. An example graph of data values for one column (e.g., column  7 ) of the touch sensor  102  is shown wherein a maximum data value determined from the self and mutual capacitance measurements of column  7  occurs at the capacitive touch sensor  104  area located a row  7 , column  7 . All data values that are below a threshold value may be ignored, e.g., below about 12 in the graphical representation shown in  FIG. 6 . Therefore only data values taken at row  6  (data value=30) and at row  7  (data value=40) need be processed in determining the location of a touch to the touch sensor  102 . Slope may be determined by subtracting a sequence of adjacent row data values in a column to produce either a positive or negative slope value. When the slope value is positive the data values are increasing, and when the slope value is negative the data values are decreasing. A true peak may be identified as a transition from a positive to a negative slope as a potential peak. A transition from a positive slope to a negative slope is indicated at data value  422  of the graph shown in  FIG. 6 . 
     However another touch may have occurred at column  6  and was not directly measured in the column  7  scan, but shows up as data value  420  during the column  7  scan. Without another test besides the slope sign transition, the potential touch at column  6  may be missed. Therefore a threshold of slope ratios may further be used to flag additional potential peaks. Slope is the difference between two data values of adjacent conductive columns  104 . This threshold of slope ratios may be, for example but is not limited to, 2:1 so instances where there is a change of slope greater than 2:1 may be identified as another potential peak. This may apply to both positive and negative slopes. For example, the data value  420 , taken at row  6 , has a left slope of 23:1 (30−7) and a right slope of 10:1 (40−30). The data value  422 , taken at row  7 , has a left slope of 10:1 (40−30) and right slope of −30:1 (10−40). The slope ratio for row  6  of 23:10, exceeds the example 2:1 threshold and would be labeled for further processing. All other data values are below the data value threshold and may be ignored. 
     Referring to  FIG. 7 , depicted is a schematic plan diagram of potential touch and mutual touch locations of a touch sensor, according to specific example embodiments of this disclosure. Once a potential touch location is identified, each adjacent location thereto may be examined to determine whether any one of them may have a greater data value than the current potential touch location (labeled “C” in  FIGS. 7( a )  &amp;  7 ( b )). If a greater data value is found, then the current potential touch location may be eliminated and the touch location having the greater value may be identified as a potential touch location. This is referred to herein as the process of Nudge  512  and may be repeated until a data peak has been identified. 
     During a data acquisition scan of a column of rows, only tier one nodes (labeled “1” in  FIGS. 7( a ) and 7( b ) —adjacent locations to the current potential touch location) are examined. If any of these tier one nodes has a larger data value than the data value of the current potential touch location, a new current touch location is shifted (“nudged”) to that node having the highest data value and the process of Nudge  512  is repeated. If a tier one node is already associated with a different potential peak, then no further searching is necessary and the current data peak may be ignored. Tier two nodes (labeled “2” in  FIGS. 7( a )  &amp;  7 ( b )—adjacent locations to the tier one nodes) are examined when there is a potential of a large area activation of the touch sensor  102 . 
     After one conductive column  104  has been scanned for mutual capacitance values, the process of Nudge  512  may be speeded up by storing the mutual capacitance data values of that one column in a cache memory, then doing the Nudge  512  first on the tier one nodes, and then on the tier two nodes of that one column from the mutual capacitance data values stored in the cache memory. Then only after there are no further nudges to do in that one column will the process of Nudge  512  examine the tier one and tier two nodes from the mutual capacitance measurement scans of the two each adjacent columns on either side of the column having the process of Nudge  512  performed thereon. 
     Interpolation of the potential touch location may be performed by using the peak data value node (touch location) as well as each adjacent node thereto (e.g., tier one nodes from a prior Nudge  512 ) to create sub-steps between each node. For example, but not limited to,  128  steps may be created between each node. Referring to  FIG. 7( c ) , node A is the potential touch location and nodes B, C, D and E are tier one nodes adjacent thereto. The interpolated X, Y location may be found using the following equations:
 
Location x =( D   Value   −B   Value )/ A   Value *64
 
Location y =( E   Value   −C   Value )/ A   Value *64
 
It is contemplated and within the scope of this disclosure that variations of the above equations may be used based upon the ratio of values and the signs of the numerator of the division.
 
     Referring to  FIG. 8 , depicted is a schematic plan view diagram of a touch sensor showing a cache data window thereof, according to specific example embodiments of this disclosure. The conductive columns  104  of the touch sensor  102  may be scanned column by column for self capacitance values until all conductive columns  104  have been scanned. Each conductive column  104  indicating a potential touch from the self capacitance data may be sequentially scanned for determining mutual capacitive values thereof (touch data) and when peaks are discovered they may be processed contemporaneously with the column scan. Furthermore, touch data may be stored in a cache memory for further processing. Since the Nudge  512  looks at the first tier nodes then the second tier nodes, if necessary, not all of the touch data from all of the conductive columns  104  need be stored at one time. This allows a simple caching system using a minimum amount of random access memory (RAM). For example, storing five columns of touch data in a cache. The five columns are contiguous and a cache window may move across the columns  104  of the touch sensor  102  one column  104  at a time. It is contemplated and within the scope of this disclosure that more or fewer than five columns of touch data may be stored in a cache memory and processed therefrom, and/or self capacitance scanning by rows instead of columns may be used instead. All descriptions herein may be equally applicable to self capacitance scanning of rows then mutual capacitance scanning by columns of those row(s) selected from the self capacitance scan data. 
     Whenever a Mutual Scan of a first or second tier node (capacitive sensor  104 ) is requested, it may be called first from the cache memory. If the requested node touch data is present in the cache memory, the cache memory returns the requested touch data of that first or second tier node. However, if the requested touch data is not present in the cache memory then the following may occur: 1) If the column of the requested touch data is in the range of the cache window then perform the mutual scan of that column and add the touch data to the cache memory, or 2) If the column of the requested touch data is not in the range of the present cache window then shift the cache window range and perform the mutual scan of the new column and add the resulting touch data from the new cache window to the cache memory. 
     Referring to  FIG. 9 , depicted are a graph of self scan values and a table of mutual scan values for two touch peak detection data, according to specific example embodiments of this disclosure. Since a self scan is performed in only one axis (e.g., one column), it is possible for two touches that are off by a single column to only show a single peak. For the example data values shown in  FIG. 9 , two touches may have occurred, one at self scan data value  422  and the other indicated at self scan data value  420 . Without being aware of change of slopes greater than 2:1, the potential touch represented by self scan data value  420  may have been missed. A first touch may cause data value  422  and a second touch may cause data value  420 . The processes of Peak Detection  510  and Nudge  512  ( FIG. 5 ), as described hereinabove, may further define these multiple touches as described herein. Once each multiple touch has been defined a force thereof may be determined and associated its respective touch. 
     Referring to  FIG. 24 , depicted is schematic plan view of a finger of a hand touching a surface of a touch sensor, according to a specific example embodiment of this disclosure. A hand of a user, generally represented by the numeral  2400 , may hover over a face of a touch sensor  102 , e.g., touch screen or panel, having a plurality of locations that when at least one of the plurality of locations is touched by a finger  2402  of the hand  2400 , the location and on the face of the touch sensor  102  force thereto is detected and stored for further processing as disclosed herein. For example, a light touch of the finger  2402  on the face of the touch sensor  102  may select an object (not shown) displayed by a visual display integral therewith. Upon the finger  2402  pressing a little harder at the touch location the selected object may be locked in place. Pressing even harder on the locked object and then gesturing to move the object may release the lock on the object. Another example, pressing on the object (not shown) selects the object, then pressing harder fixes the object&#39;s location. Releasing the pressure (force) on the object then pressing hard on the object again would release the object to move again. 
     Referring to  FIG. 25 , depicted is schematic plan view of two fingers of a hand touching a surface of a touch sensor, according to another specific example embodiment of this disclosure. A finger  2504  over a left portion of the touch sensor  102  and another finger  2506  over a right portion of the touch sensor  102  may be used to rotate an object (not shown) displayed by a visual display integral therewith. For example, when the left oriented finger  2504  presses harder than the right oriented finger  2506  the object may rotate counterclockwise about an axis parallel with the axis of the wrist/arm. When the right oriented finger  2506  presses harder than the left oriented finger  2504  the object may rotate clockwise about the axis parallel with the axis of the wrist/arm. When the wrist is rotated while the fingers  2504  and  2506  are touching the face of the touch sensor  102 , the object (not shown) may rotate substantially perpendicular to the axis of the wrist/arm (substantially parallel with the face of the touch sensor  102 ) and in the direction of the rotation of the fingers  2504  and  2506 . 
     Referring to  FIG. 26 , depicted is schematic plan view of a finger of a hand touching an object projected on a surface of a touch sensor, according to yet another specific example embodiment of this disclosure. Pressing on the face of the touch sensor  102  over an object  2608  with a finger  2402  may be used to scale the size of the object. For example, the greater the force of the press (touch) by the finger  2402  the larger in size that the object may be displayed. The object may remain at the new larger size or may vary in size in proportion to the force applied to the face of the touch sensor, e.g., a harder press will result in a larger in size object and a softer press will result in a smaller in size object. The size of the object may follow the amount of force applied by the finger  2402  to the face of the touch sensor  102 . 
     Referring to  FIG. 27 , depicted is schematic plan view of a finger of a hand touching a document projected on a surface of a touch sensor, according to still another specific example embodiment of this disclosure. A document  2710  may displaced on a face of the touch sensor  102 . A touch of sufficient force by the finger  2402  to a portion of the document  2710  may be used to flip through pages thereof. A finger  2402  movement, for example but not limited to, the right may remove currently visible page(s) of the document  2710 . Pressing on a removed page near another new document (not shown) may be used to flip through the new document (not shown) and/or may allow insertion of the remove page into the new document. For example, pressing on a document  2710  flips through a stack of document pages. If the finger  2402  then moves off the document the selected page may be removed. Pressing on a single page next to a document may flip through the document and then may insert the page when it is drug over the document. 
     Referring to  FIG. 28 , depicted is schematic plan view of a finger of a hand touching one digit of a number projected on a surface of a touch sensor, according to another specific example embodiment of this disclosure. At least one number or letter, e.g., alpha-numeric character  2814 , may be displayed on the face of the touch sensor. A finger  2402  may press on a portion of the character  2814  wherein the amount of force by the finger  2402  may cause the character  2814  to increase or decrease alpha-numerically in value, accordingly. When the character  2814  is a desired value then the finger  2402  may slide off, e.g., up, down or sideways, to leave editing of the character  2814 . An increase in the alpha-numeric value may be controlled by pressing the finger  2402  on an upper portion of the character  2814 , and a decrease in the alpha-numeric value may be controlled by pressing the finger  2402  on a lower portion of the character  2814 . The speed of increase or decrease of the alpha-numeric value may be proportional to the amount of force applied by the finger  2402  to surface of the touch sensor  102 . More than one finger may be used to contemporaneously increase and or decrease more than one alpha-numeric character. For example, a finger  2402  may be pressed on a single digit  2814  of a number (124779 shown), whereby the single digit  2814  sequentially flips through numerical values, e.g., 0-9. When a desired numerical value is displaced, the finger  2402  may be dragged off the digit to leave the selected numerical value. 
     Referring to  FIGS. 13 to 23 , depicted are schematic process flow diagrams for touch decoding and force determination of the decoded touch(es), according to specific example embodiments of this disclosure.  FIG. 13  shows a general overview of possible processes for multi-touch decoding and force determination for a touch sensor  102  enabled device. It is contemplated and within the scope of this disclosure that more, fewer and/or some different processes may be utilized with a touch sensor  102  enabled device and still be within the scope, intent and spirit of this disclosure. In step  1050  a device is started, actuated, etc., when in step  1052  power is applied to the device. In step  1054  the device may be initialized, and thereafter in step  1056  the process of Touch Identification  504  may begin. Once the process of Touch Identification  504  in step  1056  has determined the touch locations, step  1057  determines the force applied at each of those touch locations. In step  1058  touch and force tracking may be performed on those touches identified in step  1056 . In step  1060  the touch and force data may be further processed if necessary, otherwise it may be transmitted to the processing and control logic of the device for display and/or control of the device&#39;s intended purpose(s) in step  1062 . 
     In the descriptions of the following process steps references to “top” or “north” channel or node will mean the channel or node above another channel or node, “bottom” or “south” channel or node will mean the channel or node below another channel or node, “left” or “west” channel or node will mean the channel or node to the left of another channel or node, and “right” or “east” channel or node will mean the channel or node to the right of another channel or node. 
     Referring to  FIG. 14 , a flow diagram of a process of Touch Identification  504  is shown and described hereinafter. In step  1102  the process of Touch Identification  504  ( FIG. 5 ) begins. In step  1104  a self scan of all channels on one axis may be performed, e.g., either all columns or all rows. In step  1106  the first self scan value may be examined. In step  1108  the (first or subsequent) self scan value may be compared to a self touch threshold value. 
     A self peak detection process  1100  may comprise steps  1110  to  1118 , and is part of the overall process of Peak Detection  510  ( FIG. 5 ). If the self scan value is less than the self touch threshold value as determined in step  1108 , then step  1238  ( FIG. 15 ) may determine whether there are any additional self scan values to be examined. However, if the self scan value is equal to or greater than the self touch threshold value as determined in step  1108 , then step  1110  may calculate a left slope between the self scan value and a self scan value of the channel to the left of the present channel. Then step  1112  may calculate a right slope between the self scan value and a self scan value of the channel to the right of the present channel. 
     Step  1114  determines whether the left slope may be greater than zero (positive slope) and the right slope may be less than zero (negative slope), identifying a peak. If a yes result in step  1114 , then step  1120  may perform mutual scan measurements on each node of the channel selected from the self scan data. If a no result in step  1114 , then step  1116  determines whether the left slope may be greater than zero (positive slope) and greater than the right slope may be, for example but is not limited to, two times (twice) greater than the right slope. If a yes result in step  1116 , then in step  1120  mutual scan measurements may be performed on each node of the selected self scan channel. If a no result in step  1116 , then step  1118  determines whether the left slope may be, for example but is not limited to, less than zero (negative slope) and greater than a percentage of the right slope, e.g., fifty (50) percent. If a yes result in step  1116 , then step  1120  may perform mutual scan measurements on each node of the channel selected from the self scan data. If a no result in step  1116 , then step  1238  ( FIG. 15 ) may determine whether there are any additional columns to be examined based upon the self scan values thereof. Step  1122  may examine a first mutual scan value. 
     Referring to  FIG. 15 , a mutual peak detection process  1244  may comprise steps  1226  to  1234 , and is part of the overall Peak Detection process  510  ( FIG. 5 ). Step  1224  may compare the (first or subsequent) mutual scan value to a mutual touch threshold value, wherein if the mutual scan value is less than the mutual touch threshold value then step  1236  may determine whether there are any additional mutual scan values to be examined. However, if the mutual scan value is equal to or greater than the mutual touch threshold value then step  1226  may calculate a slope to the next mutual scan value node, then step  1228  may calculate a slope to the previous mutual scan value node. 
     Step  1230  determines whether the next slope may be less than zero (negative slope) and the previous slope may be greater than zero (positive slope). If a yes result in step  1230 , then step  1350  ( FIG. 16 ) may start the process of Nudge  512  and/or the process of Interpolation  514  ( FIG. 5 ). If a no result in step  1230 , then step  1232  determines whether the next slope may be, for example but is not limited to, greater than zero (positive slope) and less than a percentage of the previous slope. If a yes result in step  1232 , then step  1350  ( FIG. 16 ) may start the process of Nudge  512  and/or the process of Interpolation  514  ( FIG. 5 ). If a no result in step  1232 , then step  1234  determines whether the next slope may be, for example but is not limited to, less than zero (negative slope) and greater than the previous slope. If a yes result in step  1234 , then step  1350  ( FIG. 13 ) may start the process of Nudge  512  and/or the process of Interpolation  514  ( FIG. 5 ). If a no result in step  1234 , then step  1236  determines whether there may be any additional mutual values to be examined. If a yes result in step  1236 , then step  1242  may examine a next mutual value. If a no result in step  1236 , then step  1238  determines whether there may be any additional self scan values to be examined. If a yes result in step  1238 , then step  1240  examines a next self scan value that may be returned to step  1108  ( FIG. 14 ) for further processing thereof. If a no result in step  1238 , then in step  1244  a touch detection frame may be complete. 
     Referring to  FIGS. 16-18 , flow diagrams of processes for Nudge  512  and Interpolation  514  ( FIG. 5 ) are shown and described hereinafter. Step  1350  may start the process of Nudge  512  and/or the process of Interpolation  514  by using a peak location from the process of Touch Identification  504  ( FIG. 5 ) and may comprise the following process steps: Step  1352  determines whether there may be a valid node to the north. If a no result in step  1352 , then continue to step  1360 . If a yes result in step  1352 , then step  1354  may make a mutual scan measurement of the node to the north. Step  1356  determines whether the mutual scan data of the north node may be greater than the current node. If a no result in step  1356 , then continue to step  1360 . If a yes result in step  1356 , then in step  1358  the north node may become the current node, and then continue to step  1486  ( FIG. 17 ). 
     Step  1360  determines whether there may be a valid node to the south. If a no result in step  1360 , then continue to step  1470  ( FIG. 17 ). If a yes result in step  1360 , then step  1362  may make a mutual scan measurement of the node to the south. Step  1364  determines whether the mutual scan data of the south node may be greater than the current node. If a no result in step  1364 , then continue to step  1470  ( FIG. 17 ). If a yes result in step  1364 , then in step  1366  the south node may become the current node, and then continue to step  1486  ( FIG. 17 ). 
     Referring to  FIG. 17 , step  1470  determines whether there may be a valid node to the east. If a no result in step  1470 , then continue to step  1478 . If a yes result in step  1470 , then step  1472  may make a mutual scan measurement of the node to the east. Step  1474  determines whether the mutual scan data of the east node may be greater than the current node. If a no result in step  1474 , then continue to step  1478 . If a yes result in step  1474 , then in step  1476  the east node may become the current node, and then continue to step  1486 . 
     Step  1478  determines whether there may be a valid node to the west. If a no result in step  1478 , then continue to step  1502  ( FIG. 18 ). If a yes result in step  1478 , then step  1480  may make a mutual measurement of the node to the west. Step  1482  determines whether the mutual scan data of the west node may be greater than the current node. If a no result in step  1482 , then continue to step  1502  ( FIG. 18 ). If a yes result in step  1482 , then in step  1484  the west node may become the current node. Step  1486  determines whether a touch point may already exist at the selected node. If a no result in step  1486 , then continue to step  1352  ( FIG. 16 ). If a yes result in step  1486 , then step  1488  may eliminate the current peak, and then continue to step  1236  ( FIG. 15 ). 
     Referring to  FIG. 18 , a flow diagram of a process of Interpolation  514  may comprise steps  1502  to  1518 . Step  1502  determines whether there may be a valid node to the left. If a no result in step  1502 , then continue to step  1510  wherein the left node value may be defined as a center value minus a right value then continue to step  1506 . If a yes result in step  1502 , then step  1504  may perform a mutual scan measurement on the node to the left. Then step  1506  determines whether there may be a valid node to the right. If a no result in step  1506 , then continue to step  1512  wherein the right node value may be defined as a center value minus a left value then continue to step  1516 . If a yes result in step  1506 , then step  1508  may perform a mutual scan measurement on the node to the right. Step  1516  may determine a fine position by subtracting the left value from the right value, dividing the difference thereof by the center value, and then multiplying the result by, for example but is not limited to, the number 64. It is contemplated and within the scope and spirit of this disclosure that many ways of determining valid peaks and nodes may be used as one having ordinary skill in the art of touch detection and tracking could readily implement by having knowledge based upon the teachings of this disclosure 
     After step  1516  has completed the aforementioned calculations, step  1514  determines whether an Interpolation  514  may have been performed for each axis. If a no result in step  1514 , then step  1518  may interpolate another axis, thereafter steps  1502  to  1516  may be repeated, with “above” replacing “left” and “below” replacing “right” in each step. If a yes result in step  1514 , then step  1520  may add this touch point to a list of all detected touch points. Then step  1522  may return to step  1236  ( FIG. 15 ) for any additional mutual scan values to be examined. 
     Referring to  FIG. 19 , a flow diagram of a process of Force Identification  505  is shown and described hereinafter. After a new touch point is added in step  1520  ( FIG. 18 ), step  1550  starts the process of determining the force applied to the touch sensor  102  at that touch point. Untouched mutual capacitances of each point on the touch sensor  102  may be stored in a memory of the digital processor  106  after a “no touch” calibration scan of all points of the touch sensor  102  is performed. When a force is applied to a touch location, the value of the mutual capacitance of that touch location will increase. In step  1552  that mutual capacitance change may be determined, and in step  1554  the mutual capacitance change may be converted into a force value. Once this force value is determined, in step  1556  the force value may then be associated with the new touch point and stored in the list of all detected touches. 
     Referring to  FIGS. 20, 21 and 22 , flow diagrams of a process of Touch and Force Tracking  506  are shown and described hereinafter. In step  1602  the process of Touch and Force Tracking  506  may start by using the previously found and current touch locations. Step  1604  determines whether there may be any current touch locations. If a yes result in step  1604 , then step  1606  may select the first of the current touch locations, and thereafter may continue to step  1722  ( FIG. 21 ). If a no result in step  1604 , then step  1610  determines whether there may be any previous touch location(s). If a yes result in step  1610 , then step  1612  may select the first previous touch location. If a no result in step  1610 , then at step  1611  tracking is complete. 
     Step  1614  determines whether the previous touch location may be associated with a current touch location. If a no result in step  1614 , then step  1608  may assert an output of “touch no longer present at previous touch location, stop tracking,” and then return to step  1616 . If a yes result in step  1614 , then step  1616  determines whether there may be any more previous touch locations. If a no result in step  1616 , then at step  1620  tracking touch locations is complete and the touch location data may be transmitted as Data Output  508  ( FIG. 5 ) for further processing by the microcontroller  112  ( FIG. 1 ). If a yes result in step  1616 , then step  1618  may select the next previous touch location, and thereafter return to step  1614 . 
     Referring to  FIG. 21 , step  1722  determines whether there may be any previous touch locations. If a no result in step  1722 , then continue to step  1868  ( FIG. 22 ) wherein a “New Touch to track is identified” at current location, and thereafter continue to step  1856  ( FIG. 22 ). If a yes result in step  1722 , then step  1724  may set a temporary weight value to a maximum weight value. Step  1726  may select the first of the previous touch locations. Then step  1728  may measure a distance between the selected current touch location and the selected previous touch location to determine a current distance (weight value) therebetween. Step  1730  determines whether the current weight value may be less than the temporary weight value. If a yes result in step  1730 , then step  1732  may set the temporary weight value to the current weight value and thereafter may record the selected previous touch location as a temporary location and continue to step  1734 . If a no result in step  1730 , then step  1734  determines whether there may be more previous touch locations. If a yes result in step  1734 , then step  1736  may select the next previous touch location, and thereafter return to step  1728 . If a no result in step  1734 , then step  1738  determines whether the temporary location may have already been assigned to a different current location. If a yes result in step  1738 , then step  1740  may calculate a next worst weight value for the current location and for an assigned current location, and thereafter continue to step  1860  ( FIG. 22 ). If a no result in step  1738 , then continue to step  1850  ( FIG. 22 ). 
     Referring to  FIG. 22 , step  1850  determines whether the weight value may be below a maximum association threshold. If a no result in step  1850 , then step  1854  may identify a new touch location for tracking. If a yes result in step  1850 , then step  1852  may assign a new temporary location to the current location and then continue to step  1856 . Step  1860  determines whether the next worst weight value for the current location may be less than the next worst weight value for the assigned location. If a yes result in step  1860 , then step  1862  may set the temporary location to the next worst location and thereafter continue to step  1856 . If a no result in step  1860 , then step  1864  may set the assigned location to the next worst weight value. Step  1866  may select a moved assignment location and thereafter return to step  1722  ( FIG. 21 ). Step  1856  determines whether there may be more current touch locations. If a yes result in step  1856 , then step  1858  may select the next current touch location and thereafter return to step  1722  ( FIG. 21 ). 
     Referring to  FIG. 23 , depicted is a process flow diagram for a column cache, according to specific example embodiments of this disclosure. Step  1902  may received a mutual scan location request. Step  1904  determines whether the mutual scan area location requested may be stored in the cache memory. If a yes result in step  1904 , then step  1920  determines whether the mutual scan data stored in the cache memory may be valid. If a yes result in step  1920 , then step  1922  may return mutual scan data to the cache memory. If a no result in step  1920 , then step  1918  may perform a mutual scan at the requested location, wherein step  1916  may write the mutual scan data to a location in the cache memory and then return back to step  1922 . 
     If a no result in step  1904 , then step  1906  determines whether the requested touch location may be beyond the right edge of the cache. If a yes result in step  1906 , then step  1908  may de-allocate the left-most column of mutual scan data from the cache memory. In step  1910  the de-allocated mutual scan data may be allocated to the right edge of the cache memory so as to move the edge values thereof, and thereafter return to step  1904 . If a no result in step  1906 , then step  1914  may de-allocate the right-most column of data from the cache memory. In step  1912  the de-allocated mutual scan data may be allocated to the left edge of the cache memory so as to move the edge values thereof, and thereafter return to step  1904 . 
     While embodiments of this disclosure have been depicted, described, and are defined by reference to example embodiments of the disclosure, such references do not imply a limitation on the disclosure, and no such limitation is to be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those ordinarily skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and are not exhaustive of the scope of the disclosure.