(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2008/0158167 A1
`Hotelling et al.
`(43) Pub. Date:
`Jul. 3, 2008
`
`US 2008O1581 67A1
`
`(54) SIMULTANEOUS SENSING ARRANGEMENT
`
`Publication Classification
`
`(75) Inventors:
`
`Steven P. Hotelling, San Jose, CA
`(US); John Greer Elias, Townsend,
`DE (US); Kapil Vinod Sakariya,
`Sunnyvale, CA (US)
`
`Correspondence Address:
`APPLE C/O MORRISON AND FOERSTERLLP
`LOS ANGELES
`555 WEST FIFTH STREETSUITE 3500
`LOS ANGELES, CA 90013-1024
`
`(73) Assignee:
`
`APPLE COMPUTER, INC.,
`CUPERTINO, CA (US)
`
`(21) Appl. No.:
`
`11/619,433
`
`(22) Filed:
`
`Jan. 3, 2007
`
`(51) Int. Cl.
`(2006.01)
`G06F 3/04
`(52) U.S. Cl. ........................................................ 345/173
`(57)
`ABSTRACT
`Multi-touch touch-sensing devices and methods are
`described herein. The touch sensing devices can include mul
`tiple sense points, each located at a crossing of a drive line and
`a sense line. In some embodiments, multiple drive lines may
`be simultaneously or nearly simultaneously stimulated with
`drive signals having unique characteristics, such as phase or
`frequency. A sense signal can occur on each sense line that
`can be related to the drive signals by an amount of touch
`present at sense points corresponding to the stimulated drive
`lines and the senseline. By using processing techniques based
`on the unique drive signals, an amount of touch correspond
`ing to each sense point can be extracted from the sense signal.
`The touch sensing methods and devices can be incorporated
`into interfaces for a variety of electronic devices such as a
`desktop, tablet, notebook, and handheld computers, personal
`digital assistants, media players, and mobile telephones.
`
`Y 1004
`
`
`
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`Patent Application Publication
`
`Jul. 3, 2008 Sheet 1 of 7
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`US 2008/O158167 A1
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`Patent Application Publication
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`Jul. 3, 2008 Sheet 2 of 7
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`US 2008/O158167 A1
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`Patent Applicat
`ion Publication
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`Jul. 3, 2008 Sheet 3 of 7
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`US 2008/O158167 A1
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`Patent Application Publication
`
`Jul. 3, 2008 Sheet 4 of 7
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`US 2008/O158167 A1
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`Fig. 7
`(Prior Art)
`
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`Patent Application Publication
`
`Jul. 3, 2008 Sheet 5 of 7
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`US 2008/O158167 A1
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`Patent Application Publication
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`Jul. 3, 2008 Sheet 6 of 7
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`Patent Application Publication
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`Jul. 3, 2008 Sheet 7 of 7
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`US 2008/O158167 A1
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`A
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`US 2008/O1581 67 A1
`
`Jul. 3, 2008
`
`SIMULTANEOUS SENSING ARRANGEMENT
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`0001. This is related to the following U.S. patents and
`patent applications, each of which is hereby incorporated by
`reference in its entirety:
`0002 U.S. Pat. No. 6,323,846, titled “Method and Appa
`ratus for Integrating Manual Input issued Nov. 27, 2001;
`0003 U.S. patent application Ser. No. 10/840,862, titled
`“Multipoint Touchscreen,” filed May 6, 2004;
`0004 U.S. patent application Ser. No. 1 1/381,313, titled
`“Multipoint TouchSurface Controller” filed May 2, 2006.
`
`BACKGROUND
`0005 Recently, interest has developed in touch and/or
`proximity-based input systems for electronic devices and
`computer systems that are capable of recognizing multiple
`touch and/or hover events simultaneously. Many of these
`systems, for example those based on mutual capacitance or
`certain optical sensing arrangements, involve applying peri
`odic stimulus waveforms to a plurality of sense points and
`detecting sense waveforms that can be related to the periodic
`stimulus waveform by the amount of touch and/or proximity
`present at the sense point. In some embodiments, these sys
`tems apply periodic stimulus waveforms to drive lines that are
`coupled to sense lines at the sense points. Typically, stimulus
`waveforms have been applied to these drive lines one at a
`time. Because devices typically include a plurality of these
`drive lines, each drive line has been driven sequentially.
`
`SUMMARY
`0006. According to one embodiment of the invention, a
`method of deriving touch information from a touch sensitive
`surface is provided. The touch sensitive device can include a
`plurality of sensing points. Each sensing point can be located
`at or near a crossing of a drive line and a sense line. For
`example, the method can include simultaneously (or Substan
`tially simultaneously) stimulating a plurality of the drive lines
`with one or more unique drive signals. For example, the
`signals may have predetermined phase and/or frequency rela
`tionships. The method can further include sensing a sense
`signal on at least one of the sense lines. The sense signal can
`relate to the drive signals by touch or proximity of one or more
`objects to one or more sensing points located at or near the
`crossing of the plurality of drive lines and the at least one
`sense line. The method can also include, for example, deriv
`ing touch information from the sense signal. Touch may be
`derived from the sense signal by deriving a plurality of values
`from the sense signal, e.g., by integrating the sense signal
`over one or more time periods and deriving touch information
`from a mathematical combination of the plurality of values.
`0007. In another embodiment, the invention can relate to a
`multi-touch sensing device. The touch sensing device can
`include, for example, a touch sensitive surface with a plurality
`of sensing points located at a crossings of drive lines and
`sense lines. The touch sensing device can also include drive
`circuitry configured to simultaneously apply unique drive
`signals to a plurality of the drive lines. For example, the
`signals may have predetermined phase and/or frequency rela
`tionships. The touch sensing device can also include sense
`circuitry that is configured to detect a sense signal in at least
`one sense line and derive touch information from this sense
`
`signal for one or more of the sense points. Such a touch
`sensing device may be based, for example, on self or mutual
`capacitance.
`0008. In yet another embodiment, the invention can relate
`to an electronic device or computer system incorporating a
`touch sensing arrangement or implementing a touch sensing
`method, as discussed above. The electronic device can take a
`variety of forms, including, for example, a desktop computer,
`a tablet computer, a notebook computer, a handheld com
`puter, a personal digital assistant, a media player, or a mobile
`telephone. Other form factors are also possible.
`0009. In still another embodiment, the present invention
`can relate to a method of deriving touch information from a
`touch sensitive Surface. The method can include performing a
`coarse scan of a region of the touch sensitive Surface to
`determine whether a touch is present within the first region. If
`a touch is present, fine Scanning of the region may be per
`formed to determine more exact data about the touch or
`touches that are present within the region. If a touch is not
`present, fine Scanning any be omitted, and a coarse scan of
`another region may begin. By eliminating unnecessary fine
`scans, time and power savings can result.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`0010. The aforementioned and other aspects of the inven
`tion may best be understood by reference to the following
`description taken in conjunction with the accompanying
`drawings in which:
`0011
`FIG. 1 illustrates a multi-touch sensing device used
`as an input device to a computer system in accordance with an
`embodiment of the present invention.
`0012 FIG. 2 illustrates a plurality of contact patch areas
`corresponding to an object in proximity to a plurality of sense
`points of a multi-touchSurface in accordance with an embodi
`ment of the present invention.
`0013 FIG. 3 illustrates a simplified schematic diagram of
`a mutual capacitance sensing circuit that may be used in an
`embodiment of the present invention.
`0014 FIG. 4 illustrates a process for operating a multi
`touch sensing device in accordance with an embodiment of
`the present invention.
`0015 FIG. 5 illustrates a multi-touch sensing device in
`accordance with an embodiment of the present invention.
`0016 FIG. 6 illustrates a process for performing multi
`line stimulation in accordance with an embodiment of the
`present invention.
`0017 FIG. 7 illustrates a single-line stimulation arrange
`ment according to the prior art.
`0018 FIG. 8 illustrates a two-line simultaneous stimula
`tion arrangement in accordance with an embodiment of the
`present invention.
`0019 FIG. 9 illustrates a four-line simultaneous stimula
`tion arrangement in accordance with an embodiment of the
`present invention.
`0020 FIG. 10 illustrates a variety of electronic device and
`computer system form factors that may be used in accordance
`with an embodiment of the present invention.
`0021
`FIG. 11 illustrates a frequency-based four-line
`simultaneous stimulation arrangement in accordance with an
`embodiment of the present invention.
`0022 FIG. 12 illustrates generally various alternatives for
`stimulus windows in accordance with an embodiment of the
`present invention.
`
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`US 2008/O1581 67 A1
`
`Jul. 3, 2008
`
`DETAILED DESCRIPTION
`0023 Recognizing multiple simultaneous or near-simul
`taneous touch events may be accomplished with a multi
`touch sensing arrangement as illustrated in FIG. 1. Mulit
`touch sensing arrangement 100 can detect and monitor
`multiple touch attributes (including, for example, identifica
`tion, position, Velocity, size, shape, and magnitude) across
`touch sensitive Surface 101, at the same time, nearly the same
`time, at different times, or over a period of time. Touchsen
`sitive surface 101 can provide a plurality of sensor points,
`coordinates, or nodes 102 that function substantially indepen
`dently of one another and that represent different points on a
`touch sensitive surface. Sensing points 102 may be positioned
`in a grid or a pixel array, with each sensing point capable of
`generating a signal at the same time. Sensing points 102 may
`be considered as mapping touch sensitive Surface 101 into a
`coordinate system, for example, a Cartesian or polar coordi
`nate system.
`0024. A touch sensitive surface may, for example, be in the
`form of a tablet or a touch screen. To produce a touch screen,
`the capacitance sensing points and other associated electrical
`structures can beformed with a Substantially transparent con
`ductive medium, such as indium tin oxide (ITO). The number
`and configuration of sensing points 102 may be varied. The
`number of sensing points 102 generally depends on the
`desired resolution and sensitivity. In touch-screen applica
`tions, the number of sensing points 102 may also depend on
`the desired transparency of the touch screen.
`0025. Using a multi-touch sensing arrangement, like that
`described in greater detail below, signals generated at nodes
`102 of multi-touch sensor 101 may be used to produce an
`image of the touches at a particular point in time. For
`example, each object (e.g., finger, stylus, etc.) in contact with
`or in proximity to touch sensitive surface 101 can produce
`contact patch area 201, as illustrated in FIG. 2. Each of
`contact patch area 201 may cover several nodes 102. Covered
`nodes 202 may detect the object, while remaining nodes 102
`do not. As a result, a pixilated image of the touch surface
`plane (which may be referred to as a touch image, a multi
`touch image, or a proximity image) can be formed. The sig
`nals for each contact patch area 201 may be grouped together.
`Each contact patch area 201 may include high and low points
`based on the amount of touch at each point. The shape of
`contact patch area 201, as well as the high and low points
`within the image, may be used to differentiate contact patch
`areas 201 that are in close proximity to one another. Further
`more, the current image can be compared to previous images
`to determine how the objects may be moving over time, and
`what corresponding action should be performed in a host
`device as a result thereof.
`0026. Many different sensing technologies can be used in
`conjunction with these sensing arrangements, including
`resistive, capacitive, optical, etc. In capacitance-based sens
`ing arrangements, as an object approaches touch-sensitive
`surface 101, a small capacitance forms between the object
`and sensing points 102 in proximity to the object. By detect
`ing changes in capacitance at each of the sensing points 102
`caused by this Small capacitance, and by noting the position
`of the sensing points, a sensing circuit 103 can detect and
`monitor multiple touches. The capacitive sensing nodes may
`be based on self capacitance or mutual capacitance.
`0027. In self capacitance systems, the “self capacitance
`ofa sensing point is measured relative to some reference, e.g.,
`ground. Sensing points 102 may be spatially separated elec
`trodes. These electrodes are coupled to driving circuitry 104
`and sensing circuitry 103 by conductive traces 105a (drive
`lines) and 105b (sense lines). In some self-capacitance
`embodiments, a single conductive trace to each electrode may
`be used as both a drive and sense line.
`
`0028. In mutual capacitance systems, the “mutual
`capacitance between a first electrode and a second electrode
`can be measured. In mutual capacitance sensing arrange
`ments, the sensing points may be formed by the crossings of
`patterned conductors forming spatially separated lines. For
`example, driving lines 105a may be formed on a first layer
`and sensing lines 105b may beformed on a second layer 105b
`such that the drive and sense lines cross or “intersect' one
`another at sensing points 102. The different layers may be
`different substrates, different sides of the same substrate, or
`the same side of a Substrate with some dielectric separation.
`Because the drive and sense lines are separated, there is a
`capacitive coupling node at each “intersection.”
`0029. The manner in which the drive and sense lines are
`arranged may vary. For example, in a Cartesian coordinate
`system (as illustrated), the drive lines may be formed as
`horizontal rows, while the sense lines may be formed as
`Vertical columns (or vice versa), thus forming a plurality of
`nodes that may be considered as having distinct X and y
`coordinates. Alternatively, in a polar coordinate system, the
`sense lines may be a plurality of concentric circles with the
`drive lines being radially extending lines (or vice versa), thus
`forming a plurality of nodes that may be considered as having
`distinct r and angle coordinates. In either case, drive lines
`105a may be connected to drive circuit 104, and sensing lines
`105b may be connected to sensing circuit 103.
`0030. During operation, a drive signal (e.g., a periodic
`voltage) is applied to each drive line 105.a. When driven, the
`charge impressed on drive line 105a can capacitively couple
`to the intersecting sense lines 105b through nodes 102. This
`can cause a detectable, measurable current and/or Voltage in
`sense lines 105b. The relationship between the drive signal
`and the signal appearing on sense lines 105b is a function of
`the capacitance coupling the drive and sense lines, which, as
`noted above, may be affected by an object in proximity to
`node 102. Capacitance sensing circuit (or circuits) 103 may
`sense sensing lines 105b and may determine the capacitance
`at each node as described in greater detail below.
`0031. As discussed above, conventional drive lines 105a
`were driven one at a time, while the other drive lines were
`grounded. This process was repeated for each drive line 105a
`until all the drive lines had been driven, and a touch image
`(based on capacitance) was built from the sensed results.
`Once all the lines 105a had been driven, the sequence would
`repeat to build a series of touch images. However, in some
`embodiments of the present invention, multiple drive lines
`may be driven simultaneously or nearly simultaneously, as
`described, for example, below. As used herein, “simulta
`neously encompasses precisely simultaneous as well as
`nearly simultaneous events. For example, simultaneous
`events may begin at about the same time, end at about the
`same time, and/or take place over at least partially overlap
`ping time periods.
`0032 FIG. 3 illustrates a simplified schematic diagram of
`mutual capacitance circuit 300 corresponding to the arrange
`ment described above. Mutual capacitance circuit 300 may
`include drive line 105a and sense line 105b, which are spa
`tially separated thereby forming capacitive coupling node
`102. Drive line 105a may be electrically (i.e., conductively)
`coupled to drive circuit 104 represented by voltage source
`301. Senseline 105b may be electrically coupled to capacitive
`sensing circuit 103. Both drive line 105a and sense line 105b
`may, in some cases, include some parasitic capacitance 302.
`
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`US 2008/O1581 67 A1
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`Jul. 3, 2008
`
`0033. As noted above, in the absence of a conductive
`object proximate the intersection of drive line 105a and sense
`line 105b, the capacitive coupling at node 102 stays fairly
`constant. However, if an electrically conductive object (for
`example, a user's finger, stylus, etc.) comes in proximity to
`node 102, the capacitive coupling (i.e., the capacitance of the
`local system) changes. The change in capacitive coupling
`changes the current (and/or Voltage) carried by sense line
`105b, Capacitance sensing circuit 103 may note the capaci
`tance change and the position of node 102 and report this
`information in some form to processor 106 (FIG. 1).
`0034. With reference to FIG. 1, sensing circuit 103 may
`acquire data from touch surface 101 and Supply the acquired
`data to processor 106. In some embodiments, sensing circuit
`103 may be configured to send raw data (e.g., an array of
`capacitance values corresponding to each sense point 102) to
`processor 106. In other embodiments, sensing circuit 103
`may be configured to process the raw data itself and deliver
`processed touch data to processor 106. In either case, the
`processor may then use the data it receives to control opera
`tion of computer system 107 and/or one or more applications
`running thereon. Various implementations along these lines
`are described in the applications referenced above, and
`include a variety of computer systems having touch pads and
`touch screens.
`0035. In some embodiments, sensing circuit 103 may
`include one or more microcontrollers, each of which may
`monitor one or more sensing points 102. The microcontrol
`lers may be application specific integrated circuits (ASICs),
`that work with firmware to monitor the signals from touch
`sensitive surface 101, process the monitored signals, and
`report this information to processor 106. The microcontrol
`lers may also be digital signal processors (DSPs). In some
`embodiments, sensing circuit 103 may include one or more
`sensor ICs that measure the capacitance in each sensing line
`105b and report measured values to processor 106 or to a host
`controller (not shown) in computer system 107. Any number
`of sensor ICs may be used. For example, a sensor IC may be
`used for all lines, or multiple sensor ICs may be used for a
`single line or group of lines.
`0036 FIG. 4 illustrates at a high level process 400 for
`operating a multi-touch sensing arrangement, like that
`described above. The process may begin at block 401 where
`plurality of sensing points 102 are driven. Following block
`401, the process flow can proceed to block 402, where the
`outputs from sensing points 102 are read. For example, a
`capacitance value for each sensing point 102 can be obtained.
`Following block 402, the process can proceed to block 403
`where an image or otherform of data (signal or signals) of the
`touch at one moment in time can be produced and thereafter
`analyzed to determine where objects touching or in proximity
`to the touch sensor may be located. Following block 403, the
`process can proceed to block 404, where the current image or
`signal may be compared to one or more past images or signals
`to determine a change in one or more of the shape, size,
`location, direction, speed, acceleration, pressure, etc. for each
`object. This information can be subsequently used (in step
`405) to perform an action in computer system 107, ranging
`from moving a pointer or cursor to complex gesture-based
`interactions.
`0037. As noted above, enhanced operation of multi-touch
`sensing arrangements may be achieved by driving multiple
`rows simultaneously. An example multi-touch sensing device
`500 with which multi-row stimulation may be employed is
`
`illustrated in FIG. 5 and has reference numerals generally
`corresponding to sensing arrangement 101 illustrated in FIG.
`1. In the given example, touch sensitive surface 501 has
`sixteen drive rows 505a, although any number of drive rows
`could be used. The drive rows may be divided, for example,
`into four groups, e.g., Group 1, Group 2, Group 3, and Group
`4, each including four drive rows 505a. Other numbers of
`groups and numbers of rows per group may also be employed.
`0038 Scanning of multi-touch sensor arrays is described
`in various references, including U.S. patent application Ser.
`No. 1 1/381.313, which is hereby incorporated by reference.
`The process may be briefly summarized by reference to FIG.
`7. In general, a periodic waveform (e.g., a series of square
`wave pulses) is applied sequentially to drive rows 505a. For
`example, a first group of pulses 701 may be applied to Row A,
`followed by a second group of pulses 702 applied to row B,
`followed by a third group of pulses 703 applied to Row C.
`followed by a fourth group of pulses 704 applied to Row D.
`These periodic waveforms are capacitively coupled into
`sense lines 505b, generally resulting in sensed waveform 705
`on each sense line. Sensed waveform 705 can be input inte
`grated over a predetermined time period to measure the
`capacitive coupling between drive lines 505a and sense lines
`505b at each node 502. Other processing, such as filtering,
`demodulation, etc., may also occur.
`0039. In sensed waveform 705, the time period from to to
`t corresponds to the stimulus of Row A. Integrating the
`sensed waveform over this time period results in a numerical
`value X1, which can correspond to the capacitance of a node
`at the intersection of Row A and the column being sensed.
`Similarly, the time period from t to t, corresponds to Row B,
`the time period from t to t corresponds to Row C, and the
`time period from t to ta corresponds to Row D. Integrating
`the sensed waveform over each of these time periods can give
`numerical values X2, X3, and X4 corresponding to the
`capacitance of nodes at the intersection of the Rows B, C, and
`D and the column being sensed.
`0040 FIG. 8 illustrates a multi-line stimulation arrange
`ment in which two lines may be stimulated simultaneously.
`Specifically, Row A and Row B may be simultaneously (or
`nearly simultaneously) stimulated with waveforms 801 and
`802. As can be seen, the phase of waveform 801 may be
`adjusted, e.g., after the fourth pulse. As a result, the remaining
`pulses of waveforms 801 and 802 may be 180° out of phase.
`Similarly, Row C and Row D may be simultaneously (or
`nearly simultaneously) stimulated with waveforms 806 and
`807. Again, the phase of waveform 806 may be adjusted, e.g.,
`after the fourth pulse. As a result, the remaining pulses of
`waveforms 806 and 807 may be 180° out of phase. The phase
`relationships between the waveforms may be easily under
`stood with reference to the + and - signs above.
`0041
`Unlike the example described above with reference
`to FIG. 7, the time periods to to t t to t t to t. and t to ta.
`may no longer uniquely correspond to Rows A-D. Likewise,
`the measured values X1, X2, X3, and X4 resulting from
`integrating the sensed waveform (not shown) over these time
`periods no longer uniquely correspond to the capacitance of a
`node at the intersection of a particular row and the column
`being sensed. In the example of FIG. 8, time periods to to t
`and t to t, along with their corresponding measured values
`X1 and X2, correspond together to both Row A and Row B.
`Similarly, time periods t to t and t to ta, along with their
`corresponding measured values X3 and X4, correspond
`together to both Row C and Row D. However, because of the
`
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`US 2008/O1581 67 A1
`
`Jul. 3, 2008
`
`phase difference between the stimulus waveforms 801 and
`802, the effects of stimulating Row A only and Row B only
`can be isolated from each other. Similarly, because of the
`phase difference between the stimulus waveforms 806 and
`807, the effects of stimulating Row C only and Row D only
`can be isolated from each other.
`0042 Specifically, because stimulus waveforms 801 and
`802 are in phase over time period to to t and out of phase over
`time period t to t, the integration result X1 plus the integra
`tion result X2 (i.e., X1+X2) can yield a value corresponding
`to the capacitance of a node at the intersection of Row A and
`the line being sensed, i.e., only the effect of the stimulus of
`Row A. Similarly, the integration result X1 minus the inte
`gration result X2 (i.e., X1-X2) can yield a value correspond
`ing to the capacitance of a node at the intersection of Row B
`and the line being sensed, i.e., only the effect of the stimulus
`of Row B.
`0043. The same applies to Rows C and D. Because stimu
`lus waveforms 806 and 807 are in phase over time periodt to
`ts and out of phase over time period t to ta, the integration
`result X3 plus the integration result X4 (i.e., X3+X4) can
`yield a value corresponding to the capacitance of a node at the
`intersection of Row C and the line being sensed, i.e., only the
`effect of the stimulus of Row C. Similarly, the integration
`result X3 minus the demodulation result X4 (i.e., X3-X4) can
`yield a value corresponding to the capacitance of a node at the
`intersection of Row D and the line being sensed, i.e., only the
`effect of the stimulus of Row D.
`0044 FIG. 9 illustrates an exemplary multi-line stimula
`tion arrangement in which four lines are stimulated simulta
`neously. During a first period from to to t, the periodic wave
`forms 901-904 applied to Rows A-D are in phase. At time t,
`e.g., after the fourth pulse, the phase of waveforms 901 and
`902 can be adjusted so that waveforms 901 and 902 are 1800
`out of phase with respect to waveforms 903 and 904. Simi
`larly at time t, e.g., after the next four pulses, the phases of
`waveforms 901 and 903 are adjusted. This can result in wave
`forms 901 and 904 being 180° out of phase with respect to
`waveforms 902 and 903. Finally, at time t, e.g., after four
`more pulses, the phase of waveforms 901 and 902 can again
`be adjusted. This can result in waveforms 901 and 903 being
`180° out of phase with respect to waveforms 902 and 904. The
`phase relationships between the various waveforms can be
`understood with reference to the + and - signs in the figure.
`0045. As in the preceding example, the phase relationships
`between waveforms 901-904 allow the effects of the Stimulus
`on each individual row to be isolated as mathematical com
`binations of the measured integration results. Specifically, the
`effects of the stimulus of Row A can be determined by the
`expression X1+X2+X3+X4. The effects of the stimulus of
`Row B can be determined by summing X1+X2-X3-X4. The
`effects of the stimulus of Row C can be determined by
`X1-X2-X3+X4. The effects of the stimulus of row D can be
`determined by X1-X2+X3-X4.
`0046. The process of operation 600 of the multi-touch
`sensing arrangement 500 with multi-row stimulation may be
`further understood with reference to the flow chart of FIG. 6.
`First, the DC content for a group of rows can be obtained 601.
`In the example of FIG. 8, the DC content of the group of rows
`including Rows A and B can be obtained by integrating the
`sensed waveform over time period to to t. This DC content
`can indicate (somewhat coarsely) whether there is any touch
`present within a given group, e.g., Rows A and B, correspond
`ing to a particular region of touch surface 501. If at decision
`block 602, it is determined that there is no touch within a
`given group/region the next group (e.g., Rows C and D) can
`
`be similarly scanned. This may be implemented, for example,
`by implementing counter 603. If at decision block 602, it is
`determined that there is touch within a given group/region as
`indicated by the DC content of the group, a fine scan of the
`group is performed in block 604. The results of the fine scan
`may be combined to extract the signals corresponding to each
`row as described above. Once all groups have been scanned,
`the process repeats.
`0047 Turning back to FIGS. 5 and 6, each group of rows
`may be scanned according to the principles described in the
`foregoing paragraphs. A multi-touch sensing arrangement
`may comprise any number of rows and any number of groups.
`In some embodiments, a multi-touch sensing arrangement
`can employ multi-line stimulation on a single group, i.e., all
`lines of the device may be stimulated simultaneously or
`nearly simultaneously. Additionally, although described in
`terms of rows and columns, the drive and sense lines may be
`arranged in any geometric arrangement.
`0048 Multi-line stimulation as described above may pro
`vide a number of advantages. For example, when multiple
`rows are stimulated simultaneously, the stimulus Voltage can
`be reduced. Specifically, the additive effect of multiple-row
`stimulus can result in the same sensed waveform amplitude
`for a lower per row stimulus Voltage. For example, a single
`line scanning arrangement using an 18 Vpp (volts peak-to
`peak) stimulus Voltage could use a 9 Vpp Stimulus Voltage
`with two lines being simultaneously stimulated or with a 4.5
`Vpp stimulus Voltage with four lines being simultaneously
`stimulated, etc., to obtain similar sensed waveform ampli
`tude.
`0049 Reducing the stimulus voltage can allow drive sig
`nals to be supplied directly from a driver chip without requir
`ing a high Voltage booster. The reduced Voltage can also help
`to avoid fringe field and transistor breakdown issues. The
`reduced Voltage can also result in reduced power consump
`tion. Because power scales as square of Voltage, cutting Volt
`age by a factor of four (for four row simultaneous stimulation)
`cuts the power per row by a factor of 16. However, because
`there are four rows being driven, the actual power savings
`may only be a factor of 4. However, additional power may
`also be saved by not doing a fine-scan when there is no touch
`detected during a DC scan of the region, as described above.
`0050 A variation on the multi-row stimulation techniques
`described above may be referred to as differential multi-row
`stimulation. Differential multi-row stimulation may be
`understood with reference to the table below, which shows the
`polarities of the stimulating waveforms for the multi-row
`stimulation example of FIG. 9 above (Multi-Row Stimula
`tion) compared to the polarities of the stimulating waveforms
`for a differential multi-row stimulation example (Differential
`Multi-Row Stimulation). Differential multi-row stimulation
`may ge