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`IPR2020-00778
`Apple EX1004 Page 1
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`App1ication Data Sheet
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`App1ication Infonnation
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`App1ication Type::
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`Provisional
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`Subject Matter: :
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`Utility
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`Tit1e::
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`_Capacitive Keyboard with Reduced
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`Keying Ambiguity
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`Attorney Docket Number::
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`Tota1 Drawing Sheets::
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`Sma11 Entity?: :
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`PKS
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`4
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`Yes
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`App1icant Information
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`App1icant Authority Type::
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`Inventor
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`Primary Citizenship Country::
`us
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`Status::
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`Given Name: :
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`Fami1y Name: :
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`Full Capacity
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`Harald
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`Philipp
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`City of Residence::
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`Harnble
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`State or Province of Residence::
`Hampshire
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`Country of Residence::
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`GB
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`Street of Mai1ing Address::
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`651 Holiday Drive, Bldg. 1,
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`City of Mai1ing Address::
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`Pittsburgh
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`State or Province of Mai1ing
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`PA
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`Suite 300
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`Address::
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`Country of Mai1ing Address::
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`us
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`Posta1 or ZIP Code of Mai1ing
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`15520
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`Address::
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`07 /12/02 Initial
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`Page 1
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`IPR2020-00778
`Apple EX1004 Page 2
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`Correspondence Information
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`Correspondent Customer Number:: 20191
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`Representative Information
`jRepresentative Customer Number:: I 20191
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`07 /12/02 Initial
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`Pag e2
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`IPR2020-00778
`Apple EX1004 Page 3
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`TITLE: Capacitive Keyboard with Reduced Keying Ambiguity
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`FIELD OF THE INVENTION
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`The invention relates to method and apparatus for controlling an array of capacitive position
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`sensors, and, more specifically for preventing accidental false inputs from keys adjacent to a selected
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`key in a capacitive keyboard ..
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`BACKGROUND INFORMATION
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`Arrays of capacitive proximity sensors are often used in keyboards, keypads and other touch-input
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`.apparatus. Two characteristics of capacitive sensors that lead to their use instead of conventional
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`metallic switches are: 1) Capacitive sensors can be made in small sizes, which is desirable if a small,
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`tightly packed keyboard is required; and 2) Capacitive sensors are particularly easy to
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`environmentally seal, which is desirable if the keyboard is to be used in a wet environment or where
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`there is a concern that contaminants may be spilled on the keyboard.
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`Conventional capacitive sensors, when tightly packed, or when used in the presence of conductive
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`In a small keyboard, for example, a user's finger is
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`liquid films, suffer a keying ambigu ity problem.
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`likely to overlap from a desired key to onto adjacent ones. This is especially problematic if the user
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`has large fingers or if he or she presses on the keyboard surface hard enough to deform his or her
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`finger. The same sort of effect is found when a conducting film is spilled on a keyboard, in which
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`case the user's finger is sensed as though it were the size of the puddle. Problems of this sort are
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`particularly acute in cash register keyboards used in food service establishments where beverage and
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`food sauce spills are a frequent occurrence.
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`In his US Patent 5,730,165, the inventor teaches a capacitive field sensor employing a single
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`coupling plate and a method of detecting a change in capacitance of the coupling plate, Cx, to
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`ground. The apparatus taught in US 5,730,165 comprises pulse circuitry for charging the coupling
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`plate and for subsequently transferring the charge from the plate into a charg e detector,
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`be a sampling capacitor, Cs. The transferring operation is carried out by means of a transfer switch
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`electrically connected between the coupling plate and the charge detector. The disclosure of US
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`5,730,165 is herein incorporated by reference.
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`IPR2020-00778
`Apple EX1004 Page 4
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`the inventor teaches In his US patent application S/N 09/390,869,
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`pulse circuitry for measuring
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`capacitance
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`to ground, the circuitry comprising a plurality of electrical switching elements, each of
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`which has one side electrically connected to either a power supply voltage or to a circuit ground
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`point. lnis circuit arrangement, which may be used with a keyboard as well as for many other
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`applications, is more compatible with available integrated circuit design and manufacturing practices
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`than is prior art pulse circuitry, which commonly had one side of at least one switching element
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`floating. These improved arrangements thereby provide superior performance at a lower
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`manufacturing cost. The disclosure of US patent application S/N 09 /390,869 is herein incorporated
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`by reference.
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`SUMMARY OF THE INVENTION
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`One aspect of the invention provides a method of removing keying ambiguity by measuring a
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`detected signal strength associated with each key in an array, comparing the measured sign al
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`is the strengths to find a ma..ximum, determining that the key having the ma..ximum sign al strength
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`unique user-selected key and suppressing or ign oring sign als from all other keys as long as the signal
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`from the selected key remains above some nominal threshold value. In this aspect , the array under
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`consideration may be a keyboard, or any convenient subset thereof,
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`Another aspect of the invention is a capacitive keyboard in which each key has a respective
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`detection
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`integrator counter (DIC) associated with it. Each DIC is a clocked counter that counts up
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`by one incremental value on each clock cycle during which a signal strength from the associated key
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`is above some nominal threshold value, and that counts down by one value if the sign al strength is
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`less than the nominal value. A controller receives a respective input from each DIC and determines
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`that one of the keys is active, or selected, when the detection integration (DI) count associated with
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`that key exceeds a selected terminal count value, TC. When one of the keys is active, the controller
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`controls all of the detection integrators associated with keys in a selected neighborhood of the active
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`key to stop counting until the count associated with the active key falls below terminal count value -­
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`i.e., until the key that had been active becomes inactive.
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`In another aspect of the invention, the sign al from one key having a DI count close to TC is
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`with the signals from other keys in a neighborhood, and if a sign al from one of the other
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`keys is greater than that from the one selected key during the time period before the one selected
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`detection of its pending is cleared
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`key is determined to be active, the selected key
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`status, which may
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`Apple EX1004 Page 5
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`be done by clearing its DIC. Oo the other hand, if the sign al from the one key is gr eater than that
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`from one of the other key s in the neighborhood before the one key is determined to be in detection,
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`the selected key is declared to be active and the other keys are cleared
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`of their pending active
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`conditions, if any. This may be done by clearing their DIC's.
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`In yet another aspect of the invention, if the signal strengths of two keys that are approaching
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`detection threshold value and that are both in a defined keyboard neighborhood both exceed the
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`tolerance (or are within a selected are equal to each other threshold value and their sign al strengths
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`value) at the same time, an algorithm executed by a controller is used to declare one of the two keys
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`to be active and the other to be inactive. It will be recognized that a wide variety of algorithms are
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`possible and include, but are not limited to, a random, or pseudo-random selection of the active key,
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`or a declaration of activity based on which key was scanned first.
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`The principle also applies in the minimal case where the DIC's terminal count (TC) is chosen to be
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`equal to one. 'This is functionally the same as though there were no DIC, but rather just a simple
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`it. Here, the inputs to the sign al comparison function with an inhibiting logic gate following
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`among the keys in the inhibiting gate also includes the logical comparisons of the sign al strengths
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`neighborhood.
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`Those skilled in the keyboard arts will understand that the above-mentioned neighborhoods can be
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`of all of a given key may consist defined in a wide variety of ways. In some cases, a neighborhood
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`the keys immediately adjacent the given key, or may comprise all the keys having no more than one
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`key between them and the given key. In other cases, the neighborhood may comprise all the keys in
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`a matci..-x array --e.g., in keyboard for use in a numerical data entry application in which only one key
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`is to be active at a time so that the sequence of input digits is uniquely detepnined. In other cases,
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`such as in a typing or computer-input keyboard, the neighborhood of a key may comprise all other
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`keys in the keyboard except for special purpose keys, such as a capitalization shift key, a control key,
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`and the like,-Moreover, some embodiments of the invention provide a keyboard that is configur able
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`by a user who progr ams a controller to selectively consider or ign ore various keys in an array.
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`DESCRIPTION OF THE DRAWING
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`of the invention.
`Figur e 1 is a schematic block diagr am of apparatus
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`method of the carried out in a preferred Figur e 2 is a flow chart showing logical operations
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`invention.
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`Figur e 3 is schematic
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`circuit diagr am of an apparatus of the invention using hardwired logic.
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`Figure 4 is a schematic diagram of a logic block portion of the hardwired logic circuit of Fig. 3.
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`DETAILED DESCRIPTION
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`Turning now to Fig. 1, one finds a schematic representation of apparatus of the invention 10,
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`comprising an array of N capacitive proximity sensors 12 labeled "Key 1", ... , "Key N". Each of
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`by data to and is controlled counter 14 that supplies the sensors 12 has an output to a respective
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`suitable control logic 16. Those skilled in the electronic arts will appreciate that although the
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`counters 14 and control logic 16 are depicted with discrete blocks in the schematic diagr am, these
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`features could be provided either by separate physical circuit elements, or could all be provided by a
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`single microcontroller 18, as depicted by the dashed phantom line in Fig. 1. Moreover, although the
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`array of keys 12 is depicted as being a simple linear array, it will be appreciated by one who reads the
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`completed disclosure contained herein that many other sorts of arrays can be used and will
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`encompass, without being limited to, arrays used as computer keyboards, keypads of the sort
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`commonly used in telephony and automated banking, cash register data input keyboards, etc.
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`As discussed above, prior art capacitive keyboard arrays sense the proximate presence of a user's
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`finger adjacent or abutting a single selected key. A problem arises, however, when the user touches
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`more than one key, or when a conductive film bridges more than one key 12 so as to define an
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`ambigu ous touch area 20 as depicted by the single-dotted phantom curve in Fig. 1. The addition of
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`counters 14, or of the logical function equivalent thereof, when used in the accordance with the
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`teachin
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`gs of this disclosure, can remove or resolve such ambigu ities by methods involving
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`from various keys 12. comparison of sign al strengths
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`Turning now to Fig. 2, one finds a flow chart of a preferred method 22 of the invention for
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`resolve operating apparatus 10 in order to suppress extraneous key sign als or to otherwise
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`keying
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`ambiguities. This method 22 may be carried out by a microprocessor 18 operating under control of
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`a program stored in a, preferably, non-volatile memory, or may be carried out by means of discrete
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`circuit elements connected to provide hardwired logic. Although the chart of Fig. 2 depicts
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`operation
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`in terms of a single sensor 12, variously labeled "Key 1" or "K1", it will be understo
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`and that an algorithm of clarity of presentation that this simplification is solely in the interest
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`controlling an actual keyboard could carry out substantially
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`the depicted method for each of the N
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`keys in a parallel fashion.
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`of sensor outputs, and selects a single sensor
`The depicted method relies on iterated comparisons
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`output based on that sensor both having an output in excess of a detection threshold for some
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`selected number of counter cycles and thereafter having the highest output of all the sensors in the
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`array that have also exceeded the detection threshold for the selected number of cycles of the
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`counters. It will be recogn ized that one could choose to clock all the counters in parallel in order to
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`them one at a time in rapid and operate the counters achieve this, or that one could scan through
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`succession so as to provide the selected number of counter cycles for each sensor within a
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`sufficiently short time period that a user could not perceive a delay in operation of the keyboard.
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`signal threshold with a selected A sign al S1, acquired from sensor key K1 (block 24) is compared
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`value (block 26). If S1 is less than the threshold value, the value,
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`is decremented (block 28) if it is g:reate:r than zero. 'The new value of Dl is then checked to see if it
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`to be OFF (block 32). In keyboards comprising a
`is zero (block 30), and, if so, K1 is determined
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`large number of keys, only one of which should be active at a time, this OFF status will, of course,
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`be the predominant result of an analysis
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`Dl, in the DIC associated with K1
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`the DIC value Dl is compared with a terminal count
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`. If the sign al S1 is above the sign al threshold,
`
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`TC-1 is used to denote a count that is on the TC, as depicted in block 34, where the expression
`
`
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`to a limit of TC and the verge of trigg ering detection. If D1 is below the TC, D1 is incremented
`
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`24 and sign al threshold comparison 26 steps are repeated. If D1 is at the critical value
`acquisition
`
`
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`TC, the program then determines if another key is already ON (block 36). If so, the output from K1
`
`is ign ored and the process is iterated until the other sensor is declared
`
`
`to be OFF. If, on the other
`hand, no other key is on, the output, S1, from K1 is compared
`
`with the outputs from all other keys
`(block 40). If another key, Kj, has an output Sj greater than the output S1, then
`in a neighborhood
`
`
`K1 is declared to OFF and its corresponding DIC is reset to zero (block 42), thus forcing K1 to
`(Sj in the depiction
`of Fig. 2) of
`start the process all over again. If S1 is equal to the ma.x:imum value
`
`
`by block 44), then the counter
`
`Kj has already been declared ON (as depicted
`
`all the other keys, but
`If, however, sign al S1 is greater
`
`
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`D1 is in effect suspended at Dl=(TC-1) and the cycle is repeated.
`
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`than all Sj, then K1 is declared to be ON (block 46).
`
`5
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`IPR2020-00778
`Apple EX1004 Page 8
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`

`

`
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`
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`When K1 is declared ON, its associated DIC value, D1, is forced to equal the TC value (block 46) so
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`as to prevent future comparison with other keys Kj in block 40 by forcing a loop back from block
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`34 to the ST ART step on future iterations. This locks in the state of Kl for as long as it remains ON
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`by virtue of its sign al strength.
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`ON Also, all other keys, Kj, are prevented from being declared
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`
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`because their process flows will never pass further than block 36. Once K1 is found to be OFF, the
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`process of sign al comparison
`
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`in block 40 becomes available to all keys.
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`It should be noted that the case where TC=l also works with the flow of Figure 2. In this case,
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`block 34 always passes flow to block 36 so long as no increment of the appropriate DIC has yet
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`taken place. This is equivalent to the discrete logic flow shown in Figu re 3.
`
`
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`version using voltage comparators and logic gates, although it should be
`
`Figu re 3 shows a hardwired
`
`
`
`
`
`
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`
`
`
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`appreciated that the circuit is best implemented in fully digital form or in software. The following
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`
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`52 discussion is with respect to K1 but applies to the other Kj keys as well. Sign al comparator
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`
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`the output sign al permitted to allow S1 to be ON. a logic block 50 and a gate 54 are used to inhibit
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`the minimum sign al S1 with a fo..:ed threshold voltage Vt, which is set to determine
`
`compares the
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`
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`of the comparator 52. The logic block 50 preferably contains additional voltage comparators 58
`
`which compare S1 with the other sign als Sj. A NOR gate 56 generates
`a logic low when any key, Kj,
`other than Kl has its output ON; this logic level is also fed to the logic block 50.
`
`than S1, or any output Kj is ON;the AND gate 60 in logic block SO will
`If a sign al Sj is larger
`
`
`
`
`output a logic low to the input of D-type flip-flop 64, which is used to prevent race conditions, and
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`
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`which is clocked so as to sample the output of gate 60 at periodic intervals. The Q output, L1, of the
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`flip-flop 64 is fed to a final gate 54, which is arranged to inhibit the output of comparator 52. Thus,
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`sign al
`the Kl output (Kl out) will be inhibited if either another output Kj is already on, or if another
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`Sj is higher than S 1.
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`There are, of course, many possible variations and extensions of the procedure sketched out in Figs.
`
`
`
`
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`2 -4. For example, one may consider
`a rare case in which a user brings his or her finger up to a
`keyboard so that the point 9f touch is exactly between two keys. In this case, one could modify the
`
`
`
`
`
`depicted process to either select just one of those keys (e.g., by means of a known pseudo-random
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`number selection algorithm) or by suppressing the output of both keys until the user move his or
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`
`
`her finger enough that one of the two keys had a higher output than the other.
`
`6
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`IPR2020-00778
`Apple EX1004 Page 9
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`

`

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`|PR2020-00778,
`Apple EX1004 Page ’10
`
`IPR2020-00778
`Apple EX1004 Page 10
`
`

`

`Adjacent Key Suppression
`H_ Philipp
`
`Start
`
`Acquire Signat S114--------�------------,
`
`es
`
`K1 off
`
`no
`
`D1 =01-1
`(Lim O}
`
`Other Sj signal levels
`
`L/o
`
`Compare S1 to Sj; where j=2 ... N
`
`S1 < SJ
`
`51 _.. Sj
`
`S1 -Sj
`
`K1 off;
`D1 � O
`
`K1 on;
`01 � TC
`
`no
`
`IPR2020-00778
`Apple EX1004 Page 11
`
`

`

`SI (from Kl
`
`Klout
`
`Vt
`
`Vt
`
`50
`
`S3
`
`Sj
`
`K3out
`L- .--- -4t---r--�
`
`Kjout
`
`Fig 3
`
`IPR2020-00778
`Apple EX1004 Page 12
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`

`

`SI
`
`• •
`
`S2 S3
`
`Sj
`
`L_----
`
`-�� From 56
`(0 if other key is ON)
`
`Fig. 4
`
`IPR2020-00778
`Apple EX1004 Page 13
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`