I 1111111111111111 11111 lllll 111111111111111 lllll lllll lllll 111111111111111111
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`US005525980A
`5,525,980
`United States Patent
`
`
`[11] Patent Number:
`[19]
`J ahier et al.
`
`[45] Date of Patent:
`Jun. 11, 1996
`
`[54] METHOD AND APPARATUS FOR
`
`
`
`OPERATING A CAPACITIVE TACTILE
`KEYBOARD
`
`4,441,097 4/1984 Anderson .
`
`
`
`
`
`4,550,221 10/1985 Mabusth .
`
`
`
`
`5,012,124 4/1991 Hollaway .................................. 341/33
`
`[75]Inventors: Paris;
`
`
`
`Isabelle Jahier, Patrick Robert,
`
`Sartrouville, both of France
`
`2662528 11/1991 France .
`
`
`
`
`
`58-182746 10/1983 Japan .
`
`
`
`2138567 10/1984 United Kingdom .
`[73]Assignee:
`France
`Sextant Avionique,
`
`FOREIGN PATENT DOCUMENTS
`
`[21]Appl. No.: 49,345
`
`
`L. Coles, Sr.
`Primary Examiner-Edward
`D. Lee
`
`Assistant Examiner-Thomas
`
`
`
`Attorney, Agent, or Firm-Barnes & Thornburg
`
`ABSTRACT
`
`[22]Filed:Apr. 21, 1993
`[30] Foreign Application Priority Data
`
`[57]
`Apr. 24, 1992 [FR] France ................................... 92-05088
`
`
`A method and apparatus for determining a valid selection of
`
`
`
`
`
`
`
`
`
`a capacitance tactile keyboard as a function of a selection
`6 ........................... H03M 11/00
`
`
`[51] Int. Cl.
`H03K 17/94;
`
`
`
`
`
`state and validation state of the keyboard. The selection state
`
`
`
`
`[52]U.S. Cl ................................... 341/22; 341/34 341/33;
`
`
`is determined from measured capacitive values of each key
`
`[58]Field of Search .................................. 341/20, 22, 24,
`
`
`
`
`
`
`by during a first phase of a cycle. The validation state is
`
`341/26, 33, 34; 345/173, 174; 200/600
`
`
`
`
`determined from measured pressure on the keyboard, for
`
`
`
`
`
`certain key selection states only, during a second phase of
`the cycle.
`
`[56]
`
`
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,211,915
`
`
`
`21 Claims, 3 Drawing Sheets
`
`7/1980 Miller et al ............................... 341/33
`
`REAL TIME
`KEYBOARD
`CLOCK
`INITIALIZATION INTERRUPTION
`
`CALCULATION OF
`"""'""'" [ REFERENC�
`)
`VALUES VCR(i)�
`ACQUISITION
`
`-OF CAPACITANCE VALUES
`VCCCi)
`-OF PRESSURE MEASUREMENT
`VER
`
`FUNCTIONAL
`OPERATION
`UPDATE TACTILE
`SURFACE REFERENCE
`
`VALUES VCRCil, n
`
`IDENTIFY SELECTION
`
`CONDITION
`
`UPDATE REFERENCE
`PRESSURE VALUE
`VER,N
`
`IDENTIFY VALIDATION
`
`CONDITION
`
`DECODING
`
`Samsung EX1007 Page 1
`
`

`

`U.S. Patent Jun. 11, 1996 Sheet 1 of 3 5,525,980
`
`KEY NUMBER
`TACTILE/
`I
`SELECTION
`I :)lo SELECTION
`VCCCD, n
`CONTROLLER -
`
`I
`
`I
`
`�
`
`KEY NUMBER
`
`I
`
`I
`
`I
`
`I
`
`l 2J
`
`I
`
`I
`
`I
`
`4
`
`I
`
`I
`
`./
`
`3
`I \ ,�
`VALIDATION
`I PRESSURE/
`- VALIDATION -
`VEC,n
`I
`CONTROLLER
`
`DECODING I -VALID SELECTION
`LOGIC I
`
`I
`
`I
`
`I
`
`I
`
`I
`
`FIG. 1
`� - - - - - - - - - -
`l- - - - - - - - - �
`
`I
`
`I
`
`b
`
`VALIDATED
`ONCE
`STATE
`
`b
`
`VALIDATION
`CONFIRMED
`STATE
`
`a
`
`VALIDATED
`p TIMES
`STATE
`
`FIG. 4
`
`Samsung EX1007 Page 2
`
`

`

`U.S. Patent
`Jun. 11, 1996 Sheet 2 of 3
`
`5,525,980
`
`INITIALIZATION
`
`REAL TIME·
`KEYBOARD
`CLOCK
`INITIALIZATION
`INTERRUPTION
`
`CALCULATION OF
`REFERENCE
`VALUES VCRCD, VER
`
`ACQUISITION
`
`-OF CAPACITANCE VALUES
`VCC(i)
`-OF PRESSURE MEASUREMENT
`VER
`
`YES
`
`NO
`
`FUNCTIONAL
`OPERATION
`
`UPDATE TACTILE
`SURF ACE REFERENCE
`VALUES VCRCD, n
`
`IDENTIFY SELECTION
`CONDITION
`
`UPDATE REFERENCE
`PRESSURE VALUE
`VER, N
`
`IDENTIFY VALIDATION
`
`CONDITION
`
`DECODING
`
`FIG. 2
`
`Samsung EX1007 Page 3
`
`

`

`U.S. Patent
`Jun. 11, 1996 Sheet 3 of 3
`
`5,525,980
`
`FIG. 3
`
`REFERENCE
`VALUE OF
`ASSOCIATED
`PRESSURE
`
`VALUE OF
`CURRENT
`PRESSURE
`ACQUIRED
`
`NO SELECTION
`STATE
`
`2
`
`BEGIN
`SELECTION
`STATE
`
`END
`SELECTION
`STATE
`
`SELECTION
`CONFIRMED
`STATE
`
`e
`
`Samsung EX1007 Page 4
`
`

`

`1
`
`2
`
`5,525,980
`
`METHOD AND APPARATUS FOR
`
`
`OPERATING A CAPACITIVE TACTILE
`KEYBOARD
`
`BACKGROUND AND SUMMARY OF THE
`
`
`
`INVENTION
`
`To adjust for drifts and interference due to environmental
`
`
`
`
`
`
`factors, means may be provided for comparing the measured
`
`
`
`
`
`capacitance and pressure values to reference values and, if
`
`
`
`all measured differences in capacitance are less than a
`
`
`
`
`values. the reference 5 predefined for updating low threshold,
`
`
`
`Consequently, as long as the measured differences in
`
`
`
`
`capacitance are less than the low threshold, the keyboard is
`
`
`considered to be idle and the differences in both the capaci­
`This invention relates to a method of apperature for
`
`
`
`
`
`
`
`tance values and the pressure values are considered to be
`operating a capacitive tactile keyboard and, more particu­
`
`
`
`
`
`
`
`10 attributable to drift or interference. In this case, both refer­
`
`
`
`
`larly, to such a process wherein the position of the operator's
`
`
`
`
`ence values are modified or updated. Conversely, as soon as
`
`
`
`finger on the keyboard and the pressure exerted by that
`
`
`
`the difference in capacitance is greater than or equal to the
`
`
`
`finger are determined cyclically by measuring capacitance
`
`
`
`
`aforesaid low threshold, this difference is considered to be
`and pressure.
`
`
`due to actuation of the keyboard, and the corresponding
`Such tactile keyboards are composed of a capacitive
`
`
`
`
`
`
`
`15 reference capacitance value and reference pressure value are
`
`
`
`
`tactile surface positioned in front of a display, such as a
`
`no longer updated.
`
`
`
`
`
`liquid crystal display, for example, and ma.ke it possible to
`In a particular embodiment of the process of the inven­
`
`
`
`
`
`
`
`designate a specific area of the display by using a finger. To
`
`
`
`
`
`tion, the updated reference capacitance value is obtained by
`
`
`this end, the position of the finger on the surface is deter­
`
`
`
`
`calculating a weighted average using at least the previously
`
`
`
`mined by capacitance measurements and the finger pressure
`
`
`
`
`
`and capacitance value, 20 calculated average and the measured
`
`
`
`exerted on the surface is detected by means of a pressure
`
`
`
`the updated reference pressure value is the last measured
`
`
`
`
`device, consisting of resistance gauges, for
`measuring
`pressure value.
`example.
`The updated reference capacitance value is obtained by
`
`
`
`
`One object of the process according to the invention is to
`
`
`
`
`
`
`
`calculating a weighted average from at least the previously
`
`
`
`make it possible to use the signals generated by the capaci-25
`
`
`
`
`calculated average and the measured capacitance value and
`
`
`
`
`tive tactile surface and the pressure measurement device.
`
`
`
`therefore depend not only on currently measured capaci-
`
`
`
`
`Another object is to provide a fully programmable param­
`
`
`
`tance values, but also on capacitance values measured
`
`
`
`eter keyboard designed to meet the requirements of operat­
`
`
`
`
`during at least one preceding cycle. By weighing the current
`
`
`ing applications and environmental constraints.
`
`
`
`
`capacitive values when calculating the reference capacitive
`
`
`
`
`value, sensitivity can be adjusted to compensate for drift and
`
`A still further object is to provide for the adjustment of 30
`
`
`
`
`
`
`
`interference, mainly of electrical origin.
`
`
`
`
`keyboard sensitivity and to compensate for drifts and inter­
`
`
`
`Conversely, the updated reference pressure value is the
`ference.
`
`
`
`current pressure value which has just been measured. This is
`To this end, the object of the invention is a device for
`
`
`
`
`
`
`possible because this pressure value is not in any event
`
`
`
`
`
`operating a capacitive tactile keyboard wherein the position
`35
`
`
`
`
`updated until the measured differences in capacitance are
`
`
`
`of the operator's finger on the keyboard and the pressure
`
`
`less than the low threshold and, consequently, until the
`
`
`
`exerted by that finger are determined cyclically by capaci­
`
`
`
`
`keyboard is idle. This arrangement makes it possible to
`
`
`
`tance measurements and pressure measurements, character­
`
`
`overcome the load factor problem.
`ized in that:
`In one particular embodiment of the invention, the dif­
`
`
`
`
`
`
`during a first phase of each cycle, the capacitance value of 40
`
`
`
`
`
`ferences between the measured capacitance values and the
`
`
`each key on the keyboard is measured and a keyboard
`
`
`
`
`reference capacitance values are calculated. The keyboard
`
`
`
`selection state is defined based on these measurements;
`
`
`
`has at least one non-selection state, one pre-selection state,
`
`
`
`
`during a second phase of the cycle, for certain keyboard
`
`
`
`and one confirmed selection state. Also, the transitions from
`
`
`
`
`selection states only, the pressure measurements are
`
`
`one state to another are determined by comparing the
`
`
`
`taken into account to define a keyboard validation state;
`45
`
`
`
`differences in capacitance to a low threshold and to a high
`and
`threshold.
`
`
`
`a decision is made on whether a valid selection has
`More particularly, a key may be preselected when its
`
`
`
`
`
`occurred as a function of the selection state and the
`
`
`
`difference in capacitance is greater than the low threshold,
`
`been preselected and a key may be selected if it has already
`
`
`validation state of the keyboard.
`
`
`
`50 and its difference in capacitance is greater than the high
`
`
`
`
`The process according to the invention is implemented by
`threshold.
`
`
`
`
`two controllers operating in a master/slave relationship and
`
`by a decoding logic.
`Measurements may also be made for sorting from among
`
`
`
`
`
`·The first controller is associated with the capacitance
`
`
`
`several keys that are likely to be preselected, to manage
`
`
`
`conflicts, and to compensate for inadvertently brushing
`
`
`
`measuring device. Its input parameters are analog and are
`
`
`
`
`
`composed of the capacitance measurements at each cycle for 55 against the keyboard.
`
`
`
`each key of the keyboard, and its output parameters consist
`More particularly, when the difference in capacitance
`
`
`
`
`
`between two keys is greater than their low threshold, it is
`
`
`
`
`of a positive integer characterizing the selected key and a
`
`
`
`possible to preselect only the key with the highest difference
`
`
`
`logic parameter defining the selection state of this key.
`in capacitance.
`
`
`The second controller is associated with the pressure
`
`
`
`
`measuring device. Its input parameter is also analog and 60
`Moreover, when the keyboard is in the idle state or when
`
`
`
`
`
`
`
`a key has already been preselected, the keyboard remains or
`
`
`
`consists of the value of the pressure measured at each cycle;
`
`
`returns to the non-selection state in capaci­if the difference
`
`
`
`
`and its output parameter is the logic parameter defining the
`
`tance of at least two keys is or was greater than the high
`
`validation state.
`
`threshold, respectively.
`
`
`The two logic parameters of the two controllers, selection
`Finally, when one, and only one, non-preselected key has
`
`
`
`
`
`and validation, are applied at the input of the decoding logic,
`65
`
`
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`a difference in capacitance greater than the high threshold,
`
`
`
`which generates a valid selection logic parameter at its
`
`
`
`and if there is already a preselected key displaying a
`output.
`
`Samsung EX1007 Page 5
`
`

`

`5,525,980
`
`
`
`0
`
`3
`4
`
`difference in capacitance that is less than the high threshold,
`
`controller 2 consist of a positive integer representing the
`
`
`
`
`
`
`
`number of a potentially selected key and a logic parameter
`
`
`the first key is then substituted for the second key and
`
`
`defining the state. of that key.
`
`
`becomes the preselected key.
`
`
`
`Consequently, in the idle state, the low threshold defines
`at its At each cycle n, the validation controller 3 receives
`
`
`
`
`
`
`the range · of signal variations due to drifting and residual
`
`
`
`5 input the value VEC,n of the pressure measured during that
`
`
`cycle n. The output of the selection controller 3 is a logic
`
`
`
`
`noise. Any signal variation above this threshold is consid­
`
`
`
`
`parameter defining the keyboard validation state.
`
`
`
`ered to be the result of an operator action on the keyboard.
`
`
`The high threshold defines the sensitivity of the keyboard,
`
`
`The logic parameters for the selection state and the
`
`
`
`
`that is, the signal variation characterizing a selection. More
`
`
`
`
`validation state are applied at the input of decoding logic
`
`
`10 unit 4, which generates the logic parameter for validated
`
`
`
`particularly, the high threshold may be selected depending
`
`selection at its output.
`
`
`
`on whether the keyboard is designed to be used with a glove
`or without.
`The output of the computer 1 therefore consists of the
`
`
`
`
`
`
`
`
`The keyboard validation state can be determined in the
`
`
`
`number of the potentially selected key and of the following
`logic parameter:
`
`
`
`
`second phase, when the keyboard is in the pre-selection state
`
`
`or confirmed selection state.
`15
`
`
`In a particular embodiment of the invention, the difference
`VALID SELECTION=SELECTIONxVALIDATION.
`
`
`
`between the measured pressure value and a reference pres­
`Moreover, it should be noted that information on the state of
`
`
`
`
`
`
`sure value is calculated. The keyboard has at least one
`
`
`
`
`controller 2 is supplied to controller 3. Indeed, it will be
`
`
`
`
`non-validation state, one pre-validation state, and one con­
`
`
`
`made apparent hereinbelow that controller 3 is a slave
`
`
`
`firmed validation state. Also, the transitions from one state 20
`
`
`
`controller of the master 'Controller 2. A clock and other
`
`
`to the other are determined by comparing the pressure
`
`
`common elements of a computer have not been shown for
`
`. to a predetermined threshold.
`difference
`sake of clarify.
`
`
`More specifically, the keyboard is in the pre-validation
`Referring to FIG. 2, it is apparent that the process accord­
`
`
`
`
`
`state when the pressure difference has been above the
`
`
`
`
`ing to the invention is broken down into two stages, i.e., an
`
`
`
`threshold for a number of cycles below a predetermined 25
`
`
`
`initialization stage and a functional operating stage.
`
`
`
`number, and in the confirmed validation state when the
`
`
`The purpose of the initialization stage is to make adjust­
`
`
`ments to compensate for inaccuracies resulting from hard­
`
`
`pressure difference has been above the threshold for a
`
`
`
`capacitance values ware. tolerances. To this end, reference
`
`
`
`
`number of cycles equal to at least this predetermined num­
`
`
`for each key VCR(i) and a reference pressure value VER are
`ber.
`
`
`
`
`measured during the initialization .stage when the keyboard
`The selection of the high .threshold•
`
`
`
`defines the pressure 30
`
`
`is not in use, and these are stored in. memory. These values.
`
`
`
`
`required for confirming a validation, and the selection of the
`. values. for the tactile
`surface
`
`
`constitute the initial reference
`
`
`
`number of timing cycles. on the validation defines the
`
`
`
`and for the pressure measuring device.
`
`
`minimum duration of a selection.
`
`
`
`The functional operating stage is initiated by an inJerrup
`
`
`
`Other objects, advantages and novel features of the
`
`
`
`tion initiated by a clock, for example every 20 milliseconds.
`
`
`
`present invention will become apparent from the following 35
`
`
`Each cycle starts acquisition of the capacitance values
`
`
`
`detailed description of the . invention when considered in
`
`VCC(i) and the pressure value VEC.
`
`
`conjunction with the accompanying drawings.
`
`
`
`
`A determination of whether the tactile surface is idle is
`
`
`then made, in the manner described hereinafter.
`BRIEF DESCRIPTION.OF THE DRAWINGS
`
`
`
`
`capacitance the reference If the · tactile surface is idle,.
`FIG. 1 is a general diagram of an apparatus capable of 40
`
`
`
`
`
`
`
`
`values of the tactile surface VCR(i), n and the reference
`
`implementing the invention;
`
`pressure value VER,n are updated.
`and If the tactile surface is not idle, the selection condition
`
`
`
`
`
`
`
`FIG. 2 is a flow chart illustrating the processing sequences
`
`
`
`the validation condition are identified in succession. In this
`
`
`
`according to the principles of the present invention;
`
`
`
`
`the idle keysvalues of 45 case, only the reference capacitance
`
`
`
`FIG. 3 represents the states and transitions of the selection
`
`
`are then updated. This is not illustrated in FIG. 2.
`
`
`
`
`controller according to the principles of the present inven­
`
`
`Finally, the cycle is completed by the decoding process
`
`tion; and
`
`described hereinabove.
`
`
`
`of the valida­FIG. 4 illustrates the states and transitions
`
`
`
`
`
`tion controller according to the principles of the present
`
`
`50 described in reference to FIG. 3.
`invention.
`to integrate The selection controller 2 makes it possible
`
`
`
`
`
`
`slow signal drifts generated by the tactile surface (tempera­
`DETAILED DESCRIPTION OF THE DRAWINGS
`
`
`
`ture drift), to level out residual noise, and to manage
`FIG. 1 illustrates a computer I suitable for implementing
`
`
`
`
`
`
`conflicts (several keys selected simultaneously).
`
`the process of the invention.
`
`
`
`
`For this purpose, the program calculates a current differ­
`55
`
`
`ence in capacitance ECC(i), n for each cycle n and for each
`
`
`
`
`This computer consists of a selection controller 2 asso­
`key i, such that:
`
`ciated with the tactile surface, a validation controller
`
`
`
`3
`associated with the pressure measuring device, and a logic
`
`
`
`
`ECC(i),n=VCR(i),n-VCC(i),n
`
`
`
`
`decoding unit 4. The tactile surface and its capacitance and
`
`pressure measuring devices are of a well-known type and
`
`
`
`60 If IECC(i),nl<Low
`Threshold, the keyboard is idle and
`
`
`
`shall not be described in further detail. The controllers 2 and
`
`
`
`
`
`
`
`remains in the NO SELECTION state as illustrated by loop
`
`3 are also known, and only the diagrams illustrating their
`
`
`1 in FIG. 3,
`
`states and transitions shall be described in reference to FIGS.
`
`
`
`
`The current capacitance value of each key VCR(i),n is
`
`
`
`
`
`
`incorporated into the reference capacitance value VCR(i),n
`3 and 4.
`At each cycle n, the selection
`controller
`at its 65 which is updated
`2 receives
`according
`to the following
`formula:
`
`
`input the values VCC(i), n, that is, the capacitance of keys
`
`i measured during the cycle n. The outputs of the selection VCR(i),n=(axVCR(i),n-1 + VCC(i),n)l(a+
`
`
`1),
`
`
`
`
`
`The operation of the selection controller 2 shall now be
`
`Samsung EX1007 Page 6
`
`

`

`5,525,980
`
`
`
`
`
`Low Threshold�ECC(l), n<liigh Threshold
`
`5
`6
`where a is a preselected weight factor. Otherwise, a selection
`
`
`
`
`Key I is then selected.
`
`In this case, the presence of the finger on key I of the
`
`
`phase begins and the controller logic is implemented.
`
`
`
`
`tactile surface is confirmed. The controller shifts to the
`
`
`
`FIG. 3 illustrates the four possible states .of the selection
`SELECTION CONFIRMED state.
`
`controller 2, namely:
`
`
`Transition "2": If the preselected key I meets the follow­
`NO SELECTION
`5
`
`ing condition at cycle n:
`BEGIN SELECTION
`
`SELECTION CONFIRMED
`END SELECTION
`key I remains the preselected key. This occurs when the
`
`
`
`The transitions between these states are the following:
`
`
`
`
`
`
`
`IO operator's finger remains in the vicinity of the key. However,
`
`Transition "a": At least one key i among all keys on the
`
`
`
`the finger's effect on the key is not sufficient to confirm the
`
`
`
`keyboard meets the following condition of the capaci­
`selection.
`
`tive difference ECC(i) at cycle n:
`
`
`
`
`ECC(i),n�Low Threshold or EEC(i),n�High Thresh­
`
`
`meets the following condition at cycle n:
`old
`15
`
`and there are no two keys i and j such that:
`
`
`ECC(i),n�High Threshold and ECC(j),n�High
`and if, of all other keys on the keyboard, one and only one
`
`
`Threshold.
`
`
`key meets the following condition:
`The key displaying the greatest difference is then prese-
`
`
`
`
`
`lected as the selected key I.
`20
`
`
`
`This transition "a" coincides with the detection of the
`
`
`
`proximity (case of low threshold) or the presence (case of
`Key i becomes the preselected key.
`
`
`
`
`high threshold) of a finger on the tactile surface.
`
`
`
`This case occurs when the presence of a finger is detected
`
`
`
`During this transition "a", a check is made to ensure that
`
`on a key other than the preselected key. This other key takes
`25
`
`
`only one key has been pre-selected (conflict management).
`
`
`
`precedence, but the controller remains in the BEGIN
`
`
`
`The high threshold is filtered so as to ensure that the system
`
`
`
`SELECTION state. This makes it possible to compensate for
`
`
`
`is not overly sensitive. Consequently, at the end of this
`
`
`
`signal interference due to the proximity of the other fingers
`
`
`
`phase, only one key I is preselected and the controller shifts
`
`when a selection is made on the keyboard.
`
`
`
`to the BEGIN SELECTION state. Transition "l": This
`
`
`Transition "d": This transition takes place when the
`
`transition coincides with the condition in which all the keys 30
`
`
`
`
`
`selected key I meets the following condition at cycle n:
`
`
`
`on the keyboard meet the following condition at cycle n:
`
`The same transition takes place if the preselected key I
`
`ECC(l), n<High Threshold
`
`
`
`ECC(i),ne:;High Threshold
`
`
`
`ECC(i), n<Low Threshold
`
`
`
`ECC(I), n<Low Threshold
`
`The keyboard then returns to the idle state when the key is
`
`As described hereinabove, this situation occurs when the
`
`
`
`
`
`
`35 released (the controller is in the END SELECTION state),
`
`
`
`keyboard is and remains in the idle state, with the controller
`
`
`
`and when this release is confirmed (the controller is in the
`
`
`
`
`in the NO SELECTION state. The reference values for
`NO SELECTION state).
`
`
`capacitance VCR(i) and pressure VER(i) are updated.
`
`
`
`
`
`Transition "b": This transition takes place when the
`
`
`I meets the following condition at cycle n:
`
`
`
`previously preselected key I meets the following condition
`40
`
`at cycle n:
`
`Transition "e": This is the case wherein the selected key
`
`ECC(l),ne:;Low Threshold
`
`
`
`ECC(I), n<Low Threshold
`
`
`
`ECC(i), ne:;High Threshold
`
`or, if there are two keys i and j, such that
`
`
`
`ECC(i), ne:;High Threshold
`
`and
`
`
`
`ECC(i), ne:;High Threshold
`
`
`
`in The validation controller 3 shall now be described
`
`In this case, there is no confirmation of release and the
`
`
`
`
`controller returns to the SELECTION CONFIRMED state.
`and none of the other keys on the keyboard meets the
`
`
`
`
`Consequently, the values of three parameters, that is, the
`45
`condition:
`
`
`low threshold, the high threshold and factor "a", which are
`
`
`
`used in the formula for updating the reference capacitance
`
`
`
`
`
`values in the operation of the selection controller 2, can be
`set.
`
`
`50
`
`reference to FIG. 4.
`This controller lowers sensitivity to signal fluctuations
`
`
`
`
`
`
`induced by the load factor, the hysteresis of the test objects
`
`
`
`and drifting, and provides filtering by confirming validation
`
`over several cycles.
`
`55 The validation controller
`3 is a slave controller of the
`
`In the first instance, the preselected key returns to the idle
`
`
`
`
`
`
`selection controller 2. As long as the selection controller
`
`
`
`
`
`state; this occurs after something has brushed against the
`
`
`
`remains in the NO SELECTION state, the reference pressure
`
`
`
`
`tactile surface inadvertently, for example.
`
`
`value VER at cycle n becomes the current pressure value
`
`
`No other key is selected and the controller returns to the
`60 VEC at that cycle:
`
`NO SELECTION state.
`
`
`In the second case, there is a conflict, and the controller
`VER,n=VEC,n
`
`returns to the NO SELECTION state.
`
`
`
`Transition "c": This transition coincides with the case
`
`
`
`
`
`wherein the preselected key I meets the following condition
`value VER is fixed:
`65
`at cycle n:
`
`
`
`For all other states of the selection controller 2, the reference
`
`ECC(I),ne:;High Threshold
`
`VER,n=VER,n-1
`
`Samsung EX1007 Page 7
`
`

`

`ECE,n=VEC,n-VER,n
`
`ECE,n�Tbreshold
`
`ECE,n<Tbreshold
`
`
`
`8. An apparatus for operating a capacitive tactile keyboard
`
`means for measuring the capacitive value of each key on
`
`
`
`5,525,980
`
`7
`
`
`
`that:
`
`8
`updating the3.A method according to claim 2, wherein
`
`
`
`and the program computes a current difference ECE,n, such
`
`
`
`
`
`reference capacitance values includes a computing weighted
`
`
`average from at least the previously computed average and
`
`
`the measured capacitance value.
`A method according to claim wherein determine said
`
`
`
`
`5
`4.
`1
`The controller logic 4 is then implemented.
`
`
`
`
`
`selection state includes calculating the difference between
`
`FIG. 4 shows that the state number of the controller 3 is
`
`
`
`each measured capacitance value and a reference capaci­
`
`
`
`
`a direct function of the extent of filtration, due to the
`
`
`
`
`tance value; and wherein determining said validation state
`
`
`existence of the states VALIDATE ONCE, VALIDATE
`
`
`
`
`includes calculating the difference between the measured
`
`TWICE, ... VALIDATE p TIMES. Pis set to determine the
`pressure
`
`
`
`value and a reference pressure value; and, when the
`10
`
`
`
`
`.number of cycles of pressure above a preselected threshold
`
`
`differences in capacitance of all keys are less than a prede­
`
`
`is present to reach a VALIDATION CONFIRMED state.
`
`
`
`
`termined low threshold, updating the a reference pressure
`
`
`The transitions of this controller are the following:
`value.
`S.A method according to claim 4, wherein updating the
`
`
`
`
`
`Transition "a": of this transition takes place when the
`
`
`
`reference pressure value includes setting the reference pres­
`
`
`
`
`following condition for the current difference in pres-
`15
`
`sure value to the last measured pressure value.
`sure ECE is met at cycle n:
`
`
`6.A method according the keyboardto claim 1, wherein
`
`
`
`has at least one non-validation state, one pre-validation state,
`
`
`
`
`and one confirmed validation state; and determining the
`
`keyboard validation state includes calculating the difference
`
`This transition occurs when enough pressure is exerted
`
`
`
`
`
`20 between the measured pressure value and a reference pres­
`
`by the operator on the tactile surface to coincide with
`
`
`
`
`
`
`sure value, and determining transitions from one state to
`
`
`
`
`selection validation. The controller then shifts to the
`
`
`
`
`another by comparing the pressure difference to a predeter­
`
`
`next VALIDATION state. After p VALIDATED states,
`mined threshold.
`
`the VALIDATION CONFIRMED state is searched.
`7.A method according to claim 6, wherein the keyboard
`
`
`
`
`Transition "b": This is the case wherein the following
`
`
`is determined to be in the pre-validation state when the
`25
`
`condition is met at cycle n:
`
`
`
`pressure difference has been greater than the threshold for a
`
`
`
`
`number of cycles below a predetermined number, and in the
`
`
`
`confirmed validation state when the pressure difference has
`
`
`been above the threshold for a number of cycles at least
`This is the case wherein the operator has released the
`
`
`
`30 equal to this number.
`
`
`
`pressure or has not exerted enough pressure to initiate
`
`
`
`
`
`validation. The controller then returns to the
`comprising:
`3
`NO
`
`VALIDATION state.
`
`
`
`
`
`Consequently, it is apparent that the appropriate param­
`the keyboard;
`
`
`
`eters for the threshold and number P of VALIDATION states
`35
`means for determining a keyboard selection state based on
`
`
`
`
`
`
`
`
`can be programmed in the validation controller 3.
`
`
`said capacitive measurement signals;
`
`
`
`
`Although the present invention has been described and
`
`
`means for measuring the pressure on the keyboard;
`
`
`
`
`illustrated in detail, it is to be dearly understood that the
`
`
`same is by way of illustration and example only, and is not
`
`
`
`means for determining a keyboard validation state based
`
`
`to be taken by way of limitation. The spirit and scope of the
`
`
`
`on the pressure measurement signals and independent
`
`present invention are to be limited only by the terms of the 40
`
`
`
`of said selection state mean;
`
`appended claims.
`means for operating said capacitive measuring means and
`
`
`
`What is claimed:
`
`
`
`said selection state means during a first phase of a cycle
`1. A method of operating a capacitive tactile keyboard,
`
`
`
`
`
`
`and for operating said pressure measuring means and
`
`
`
`wherein the position of the operator's finger on the keyboard
`
`
`validation state means for only certain selection status
`45
`
`
`
`and the pressure exerted by that finger are determined
`
`
`
`during a second phase of the cycle; and
`
`
`cyclically by capacitance measurements and pressure mea­
`
`
`means for determining a valid selection as a function of
`
`
`surements, comprising the steps of:
`
`
`the selection state and the validation state of the key­
`during a first phase of each cycle, measuring the capaci­
`
`
`
`
`
`
`board and generating a valid selection signal to be used
`
`tance value of each key on the keyboard and determin-
`by said keyboard.
`50
`
`
`on the capacitive ing a keyboard selection state based
`
`the selection9. An apparatus according to claim 8 wherein
`
`
`
`
`measurement signals;
`
`
`state means includes means for calculating the difference
`
`
`
`
`during a second phase of the cycle, for certain keyboard
`
`
`
`between each measured capacitive value and a reference
`
`selection states only, measuring the pressure on the
`
`
`
`
`
`
`capacitive . value, and means for updating the reference
`
`
`keyboard independent of said measurement during said
`
`
`
`
`
`55 capacitive value when the difference in capacitance of a
`
`
`first phase and determining a keyboard validation state
`
`
`corresponding key is less than a predetermined threshold.
`
`
`based on the pressure measurement signals; and
`
`
`
`10.An apparatus according. to claim 8 wherein said
`
`
`
`selection state means includes means for calculating the
`
`
`
`
`determining whether a valid selection has occurred as a
`
`
`
`
`difference between each measured capacitive value and a
`
`
`
`
`
`function of the selection state and the validation state of
`
`said validation state
`
`
`60 reference capacitive value; and wherein
`
`
`
`
`the keyboard and generating a valid selection signal to
`be used by said keyboard.
`
`
`
`means includes means for calculating the difference between
`
`
`
`
`A method according to claim wherein determining
`
`
`
`the measured pressure value and a reference pressure value
`2.
`1
`
`
`
`
`said selection state, includes calculating the difference
`
`
`
`and means for updating the reference pressure value when
`
`
`
`between each measured capacitance value and a reference
`
`
`
`the difference in capacitance of all keys are less than a
`
`
`
`capacitance value; and, when the difference in capacitance
`
`65 predetermined threshold.
`
`
`of a key is less than a predetermined low threshold, updating
`said11.An apparatus according to claim 8 wherein
`
`
`
`
`
`
`the corresponding reference capacitance value.
`
`
`
`selection state means determines one of at least one non-
`
`Samsung EX1007 Page 8
`
`

`

`5,525,980
`
`key-tactile 19.An apparatus for operating a capacitive
`
`
`
`9
`10
`selection states, one pre-selection state, and one confirmed
`
`
`
`
`preselect­17.A method according to claim 13, including
`
`
`
`
`
`
`
`selection state; and wherein said validation state means
`
`
`
`ing a key when its difference in capacitance is greater than
`
`
`
`
`determines said validation states in the second phase when
`
`
`
`the high threshold and another key is preselected, and this
`
`
`
`
`the keyboard is determined to be in the pre-selection state or
`
`
`other key returns to its non-selection state.
`
`
`the confirmed selection state.
`
`
`the key­18.A method according to claim 13, wherein
`5
`
`
`
`said12.An apparatus according to claim 8 wherein
`
`
`
`
`board validation state is determined in the second phase and
`
`validation state means determining one of at least one
`
`
`
`
`when the keyboard is in the pre-selection state or confirmed
`
`non-validation states, one pre-validation states and one
`
`
`
`
`selection state.
`
`confirmed validation states and determines a confirmed
`
`
`
`
`
`
`
`
`validation state when a predetermined number of cycles
`10
`board comprising:
`
`
`
`having a pre-validation state have been determined.
`
`
`
`
`
`
`keyboard,a capacitive tactile 13.A method of operating
`the keyboard;
`
`
`
`wherein the position of the operator's finger on the keyboard
`
`
`and the pressure exerted by that finger are determined
`means for determining one of at least one non-selection
`
`
`
`
`
`
`cyclically by capacitance measurements and pressure mea-15
`
`
`
`
`keyboard selection states, one pre-selection keyboard
`
`
`surements, comprising the steps of:
`
`
`
`
`selection state, and one confirmed keyboard selection
`
`
`
`
`state based on said capacitive measurement signals by
`
`
`during a first phase of each cycle, a) measuring the
`
`
`capacitance value of each key on the keyboard, b)
`
`
`
`calculating the difference between each measured
`
`
`
`
`determining at least one non-selection keyboard selec­
`
`
`
`capacitive value and a reference capacitive value;
`
`
`
`tion state, one preselection keyboard selection state and 20
`
`
`
`
`
`means determining the transition from one selection state
`
`
`
`
`one confirmed keyboard selection state based on the
`
`
`
`to another by comparing the difference in capacitance
`
`
`
`capacitive measurement signals calculating the differ­
`
`to a low threshold and to a high threshold;
`
`
`
`
`ences between the measured capacitance values and
`means for measuring the pressure on the keyboard;
`
`
`
`
`