Patent Publication Number: US-9405421-B2

Title: Mutual capacitance touch sensing device

Description:
This application is a continuation of U.S. patent application Ser. No. 14/293,843, filed Jun. 2, 2014, which is a continuation of U.S. patent application Ser. No. 12/498,119, filed Jul. 6, 2009, now U.S. Pat. No. 8,743,060, which is a continuation-in-part of U.S. patent application Ser. No. 11/482,286, filed Jul. 6, 2006, the entire contents of which are incorporated herein by reference. 
     This application is related to the following applications, all of which are herein incorporated by reference: 
     U.S. patent application Ser. No. 10/188,182, filed Jul. 1, 2002; U.S. patent application Ser. No. 10/722,948, filed Nov. 25, 2003; U.S. patent application Ser. No. 10/643,256, filed Aug. 18, 2003; U.S. patent application Ser. No. 10/840,862, filed May 6, 2004; U.S. patent application Ser. No. 11/057,050, filed Feb. 11, 2005; U.S. patent application Ser. No. 11/115,539, filed Apr. 26, 2005; and U.S. patent application Ser. No. 11/882,420, filed Aug. 1, 2007. 
    
    
     FIELD 
     This relates generally to touch sensing devices used in portable electronic devices and, more particularly, to an improved mutual capacitance sensing touch device. 
     BACKGROUND 
     There can be many factors that determine the size of compact portable electronic devices such as laptops, PDAs, media players, cell phones, etc. In most cases, the size of the portable electronic device can be limited by the size of the operational components used therein. These components can include for example microprocessor chips, printed circuit boards, displays, memory chips, hard drives, batteries, interconnectivity circuitry, indicators, input mechanisms and the like. As such, there can be a desire to make these operational components smaller and smaller while maintaining or increasing their power and functionality to perform operations as well as decreasing their cost. The placement of these components inside the electronic device can also be a factor in determining the size of the portable electronic device. For thin devices such as cell phones, PDAs and media players, stacking operational components on top of each other can be limited and therefore the operational components may be placed side by side. In some cases, the operational components may even communicate through wires or flex circuits so that they may be spaced apart from one another (e.g., not stacked). 
     There exist today many styles of input mechanisms for performing operations in a portable electronic device. The operations can generally correspond to moving objects and making selections. By way of example, the input devices may include buttons, keys, dials, wheels, mice, trackballs, touch pads, joy sticks, touch screens and the like. Touch devices such as touch buttons, touch pads and touch screens are becoming increasingly popular in portable electronic devices because of their ease and versatility of operation, their declining price as well as their space saving ability (e.g., planarity). Touch devices can allow a user to make selections and move objects by simply moving their finger (or stylus) relative to a touch sensing surface. In general, the touch device can recognize a touch and in some circumstances the characteristics of the touch and a host controller of the portable electronic device can interpret the touch data and thereafter perform action based on the touch data. 
     There are several types of technologies for implementing a touch device including for example resistive, capacitive, infrared, surface acoustic wave, electromagnetic, near field imaging, etc. 
     Capacitive touch sensing devices can work particularly well in portable electronic devices. Generally speaking, whenever two electrically conductive members come close to one another without actually touching, their electric fields can interact to form capacitance. In the case of a capacitive touch device, as an object such as a finger approaches the touch sensing surface, a tiny capacitance can form between the object and the sensing points in close proximity to the object. By detecting changes in capacitance at each of the sensing points and noting the position of the sensing points, the sensing circuit can recognize multiple objects and determine the location, pressure, direction speed and acceleration of the object as it is moved across the touch surface. 
     Although capacitive sensing devices can work particularly well in portable electronic devices, improvements to form, feel and functionality are still desired, such as improvements that can help produce a better portable electronic device. 
     SUMMARY 
     This relates to a touch sensing device, which can include nodes for sensing a touch at the device and for sensing a force applied to the device. The device can include distinct individual drive lines for driving the nodes and separate distinct individual sense lines for transmitting touch or force signals from the nodes. The nodes can form groups, where the nodes in each group can be coupled to the same drive line and to different sense lines and where each node in a group can be coupled to a node in a different group by the same sense line. This device structure can advantageously reduce the number of drive and sense lines, thereby saving device space and reducing device power consumption. Each node can be set up with a different combination of drive and sense lines coupled thereto. 
     This also relates to a touch sensing device, which can include a node having a touch sensor for sensing a touch at the device and a dome switch for sensing a force applied to the device. The dome switch can be coupled to ground to reduce signal error associated with the sensed touch, where the signal error can be introduced by a slight deformation in the dome switch caused by a slight movement of the touch sensing device surface. This device structure can advantageously improve the performance of the device in sensing touch. 
     This also relates to a touch sensing device, which can include some nodes having both a touch sensor for sensing a touch at the device and a dome switch for sensing a force applied to the device and other nodes having just a touch sensor. So that the nodes having both the touch sensor and the dome switch can constructively interact, the conductive pattern of the touch sensor components can substantially match the conductive pattern of its corresponding dome switch. This device structure can advantageously improve the performance of the device in sensing touch. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an exemplary circuit diagram of a mutual capacitive sensing input device according to various embodiments. 
         FIG. 2  illustrates an exemplary circuit diagram of a filter arrangement of a mutual capacitance sensing circuit according to various embodiments. 
         FIG. 3A  illustrates an exemplary block diagram of a mutual capacitive sensing circuit according to various embodiments. 
         FIG. 3B  illustrates another exemplary block diagram of a mutual capacitive sensing circuit according to various embodiments. 
         FIG. 4  illustrates an exemplary mutual capacitive sensing node according to various embodiments. 
         FIG. 5  illustrates another exemplary mutual capacitive sensing node according to various embodiments. 
         FIG. 6  illustrates still another exemplary mutual capacitive sensing node according to various embodiments. 
         FIGS. 7A and 7B  show the embodiment of  FIG. 6  in exemplary circuit diagram form. 
         FIG. 8  illustrates an exemplary circular touch sensing device according to various embodiments. 
         FIG. 9  illustrates an exemplary linear touch sensing device according to various embodiments. 
         FIG. 10  illustrates another exemplary type of linear touch sensing device according to various embodiments. 
         FIG. 11  illustrates an exemplary combined touch sensing device according to various embodiments. 
         FIG. 12  illustrates an exemplary touch sensing device that includes a touch region and one or more distinct buttons according to various embodiments. 
         FIG. 13  illustrates another exemplary touch sensing device that includes a touch region and one or more distinct buttons according to various embodiments. 
         FIG. 14  illustrates still another exemplary touch sensing device that includes a touch region and one or more distinct buttons according to various embodiments. 
         FIG. 15  illustrates an exemplary touch sensing device that only includes a button arrangement according to various embodiments. 
         FIG. 16  illustrates another exemplary linear touch sensing device according to various embodiments. 
         FIG. 17  illustrates another exemplary circular touch sensing device according to various embodiments. 
         FIG. 18  illustrates still another exemplary circular touch sensing device according to various embodiments. 
         FIG. 19  illustrates an exemplary bottom view of a click wheel having touch sensing capabilities according to various embodiments. 
         FIG. 20  illustrates an exemplary top view of a click wheel having touch sensing capabilities according to various embodiments. 
         FIG. 21  illustrates an exemplary controller of a click wheel according to various embodiments. 
         FIG. 22  illustrates an exemplary method for operating a click wheel having touch sensing capabilities according to various embodiments. 
         FIG. 23  illustrates another exemplary bottom view of a click wheel having touch sensing capabilities according to various embodiments. 
         FIG. 24  illustrates another exemplary top view of a click wheel having touch sensing capabilities according to various embodiments. 
         FIG. 25  illustrates an exemplary method for detecting capacitance error in a click wheel according to various embodiments. 
         FIG. 26  illustrates an exemplary touch assembly according to various embodiments. 
         FIG. 27  illustrates an exemplary electronic device according to various embodiments. 
         FIG. 28  illustrates an exemplary digital media player according to various embodiments. 
         FIG. 29  illustrates an exemplary mobile telephone according to various embodiments. 
         FIG. 30  illustrates an exemplary personal computer according to various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of various embodiments, reference is made to the accompanying drawings which form a part hereof, and in which it is shown by way of illustration specific embodiments which can be practiced. It is to be understood that other embodiments can be used and structural changes can be made without departing from the scope of the various embodiments. 
     The simplicity of capacitance can allow for a great deal of flexibility in design and construction of a sensing device. By way of example, the sensing device may be based on self capacitance or mutual capacitance. 
     In self capacitance, each of the sensing points can be provided by an individually charged electrode. As an object approaches the surface of the touch device, the object can capacitively couple to those electrodes in close proximity of the object, thereby stealing charge away from the electrodes. The amount of charge in each of the electrodes can be measured by the sensing circuit to determine the positions of objects as they touch the touch sensitive surface. 
     In mutual capacitance, the sensing device can typically include a two-layer grid of spatially separated wires. In the simplest case, the upper layer can include lines in rows, while the lower layer can include lines in columns (orthogonal). The sensing points can be provided at the intersections of the rows and columns. During operation, the rows can be charged and the charge can capacitively couple to the columns at the intersection. As an object approaches the surface of the touch device, the object can capacitively couple to the rows at the intersections in close proximity to the object, thereby stealing charge away from the rows and therefore the columns as well. The amount of charge in each of the columns can be measured by the sensing circuit to determine the positions of multiple objects when they touch the touch sensitive surface. 
     Each of these capacitive sensing methodologies can have advantages and disadvantages to be taken into account when designing a capacitive touch input device. For example, while self capacitance may be arranged in a wide variety of orientations (both 2D and non 2D arrays), it can tend to produce a large number of I/O contacts especially as the resolution of the touch pad is increased (each electrode can require a separate I/O contact). The large number of I/O contacts can create design difficulties especially in portable devices that are small. For example, the portable devices may require large chips and/or additional chips in order to process the large number of I/O contacts. These chips however can take up valuable space inside the device and create stack up such that the device may need to be larger to accommodate the chip(s). Furthermore, routing the I/O through traces from the electrodes to the chips may further exacerbate this problem as well as create new ones. 
     Unlike self capacitance, mutual capacitance can reduce the number of I/Os for the same resolution (sometimes by a factor of two). However, conventional mutual capacitance circuits can be fixed to a 2D array of rows and columns (e.g., x and y) thus preventing uniquely shaped touch surfaces (e.g., non 2D arrays). Furthermore, while rows and columns that are used in mutual capacitive sensing circuits may be well suited for tracking or pointing, this arrangement may not be as well suited for other less complicated tasks associated with some application specific portable electronic devices. This can be especially true when you consider the desire to maintain a small form factor with limited I/O contacts. Examples of less complicated tasks may include for example selection tasks, such as buttoning, and object movement tasks, such as scrolling. Another problem with mutual capacitance may be in its accuracy due to parasitic capacitance that can be created using this methodology. Yet another problem with both technologies may be that they can only be capable of reporting a single point when multiple objects are placed on the sensing surface. That is, they can lack the ability to track multiple points of contact simultaneously. 
     Various embodiments therefore pertain to improved features for touch devices used in portable electronic devices and more particularly for touch devices that are based on capacitance. In some embodiments, a mutual capacitive sensing touch device can include capacitive sensing nodes that can reduce the number of I/O contacts and be positioned in any orientation (e.g., 2D arrays need not be a requirement). In fact, in some embodiments, the capacitive sensing nodes can be placed in a non 2D array. This can present a paradigm shift in the way that designers think about mutual capacitive sensing touch devices. For example, the capacitive sensing nodes can be positioned at angular positions in a circular manner. 
     These and other embodiments are discussed below with reference to  FIGS. 1-30 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes and not limited to the various embodiments. 
       FIG. 1  illustrates an exemplary circuit diagram of a mutual capacitive touch sensing input device  10  according to various embodiments. The mutual capacitive touch sensing input device  10  can be configured to utilize a limited number of I/O contacts while maximizing its resolution, minimizing its size, and providing a multiplicity of orientations including non 2D arrays. Because of this, the input device may for example be placed in a variety of portable electronic devices and serve a wide variety of functions including for example scrolling, parameter control and buttoning. In fact, the input device can work particularly well in small compact handheld devices such as cell phones and media players (e.g., music players, game players, video players, etc.). 
     The input device  10  can include a mutual capacitive sensing controller  12  that can communicate with a touch sensitive element  14 . The touch sensitive element  14  can include multiple independent and spatially distinct mutual capacitive sensing nodes  20  that can be positioned about a touch surface of the touch sensitive element  14 . The nodes  20  can be dispersed such that each node  20  can represent a different position on the touch surface. During operation, each of the mutual capacitive sensing nodes  20  can produce a capacitance, and the mutual capacitive sensing controller  12  can detect changes in the capacitance at each of the nodes  20 . This information can be used to determine touch events. In most cases, the nodes  20  can be coupled to the sensing controller  12  through traces or other well-known routing technologies such as those associated with printed circuit boards, flex circuits and integrated chips. 
     The touch sensitive element  14  can be widely varied. In some cases, it can be mounted to or within a housing of the portable electronic device. For example, the element  14  may be utilized in a touch pad that is mounted within an opening in the housing of the portable electronic device. The touch pad may be a fixed to the portable electronic device or it may be movable so as to engage one or more actuators such as switches. In other cases, the touch sensitive element  14  can be a thin layer applied over a component of the portable electronic device including for example the housing or a display of the portable electronic device. By way of example, the element  14  may be used to create a touch screen (e.g., over laid on top of a display). The touch screen may be a fixed to the portable electronic device or it may be movable so as to engage one or more actuators such as switches. Alternatively, the element  14  may be a portion of the housing (e.g., nodes are embedded inside the housing or adhered to the inside surface of the housing of the portable electronic device). Examples of various ways of situating the touch sensitive element  14  relative to an electronic device can be found in U.S. patent application Ser. Nos. 10/188,182, 10/722,948, 10/643,256, 10/840,862, 11/057,050 and 11/115,539, which are herein incorporated by reference. 
     The mutual capacitive sensing controller  12  can also be widely varied. In some cases, the mutual capacitive sensing controller  12  can be a separate controller that can be operatively coupled to a host controller of a portable electronic device (e.g., for example using a flex circuit or printed circuit board). In other cases the controller  12  can be integrated into the host controller of the electronic device. That is, the sensing controller  12  can be part of the host controller. Integration may be possible due to the reduced number of I/O contacts required by mutual capacitance technology. 
     Referring to  FIG. 1 , the mutual capacitive sensing controller  12  can communicate with the nodes  20  via multiple distinct drive lines  16  and multiple distinct sense lines  18 . The drive lines  16  can be configured to carry current from the controller  12  to the mutual capacitive coupling nodes  20  and the sensing lines  18  can be configured to carry a current from the mutual capacitive coupling nodes  20  to the capacitive controller  12 . The drives lines  16  can capacitively couple to each of the sense lines  18  at multiple capacitive sensing nodes  20 . Each node  20  can be set up with a different combination of drive and sense line  16  and  18 . For example, in the illustrated embodiment, the circuit  10  can include four chive lines  16  and four sense lines  18  thereby forming sixteen individual nodes  20 . The number of nodes  20  can typically be the number of drive lines multiplied by the number of sense lines. In some cases, the nodes can be formed by an equal number of drive lines and sense lines. For example, the circuit may include the following arrangement of drive/sense-nodes, 2/2-4, 3/3-9, 4/4-16, 5/5-25, 6/6-36, 7/7-49, 8/8-64, 9/9-81, 10/10-100, and so on. In other cases, the nodes can be formed by a different number of drive and sense lines. For example, the circuit may include the following arrangement of drive/sense-nodes 2/3-6, 3/5-15, 4/6-24, 5/8-40, 7/9-63, 9/10-90, and so on. It should be further pointed out that in some limited circumstances, the nodes may not equal the number of drive lines multiplied by the number of sense lines. For example, the number of nodes may be smaller than this number. This may be done in cases where the required number of nodes can be a primary number [e.g., the designer simply does not make a node(s) even though there is a drive line(s) and sense line(s) to do so]. Accordingly, any number of nodes may be produced. 
     As shown, the drive lines  16  can be connected to a voltage source  15  that can separately drive the current through each of the driving lines  16 . That is, the stimulus can only be happening over one line while all the other lines can be grounded. They may be driven similar to a raster scan. The sensing lines  18 , on the other hand, can be connected to a mutual capacitive sensing circuit  17  that can monitor the sensing lines  18 . In one embodiment, this can be accomplished with independent sensing circuits that can each monitor an individual sensing line. In this manner, the mutual capacitive sensing circuit  17  can be capable of continuously monitoring the sensing lines  18  at the same time. That is, the mutual capacitive sensing circuit  17  can always monitor the capacitance through the sensing lines  18 . In another embodiment, instead of the sensing lines being all read at the same time by independent circuits, the sensing lines may be sequentially switched to a common sensing circuit and read one after the other (e.g., multiplexing). This can tend to reduce the silicon area of the chip but it can also increase the scanning time. 
     Although not shown in great detail in  FIG. 1 , each node  20  can include a drive electrode  22  coupled to one of the drive lines  16  and a sense electrode  24  coupled to one of the sense. This may for example be accomplished via traces or other related circuitry. The electrodes  22  and  24  can be spatially separated and can therefore cooperate to capacitively couple a charge therethrough. The electrodes  22  and  24  may be arranged in a variety of ways. In one implementation, the electrodes  22  and  24  can be plates that can be juxtaposed next to one another in a side-by-side relationship thereby creating fringe fields when the drive electrode  22  is driven. In another implementation, the spaced apart electrodes  22  and  24  can be disposed below an electrically isolated “floating” electrode. These and other embodiments will be described below. 
     Unlike conventional mutual capacitance devices, which can have nodes that can be fixed to intersection points of upper rows and lower columns, the electrode arrangement disclosed herein can allow each node  20  to be placed at any location within a touch surface. This can be similar to self capacitance technology that can utilize individual electrodes at each node. However, unlike self capacitance technology, the mutual capacitance technology can reduce the number of I/O contacts required for the desired number of nodes. In self capacitance, each node can include a distinct I/O contact and therefore to achieve sixteen nodes, at least seventeen I/O contacts may be needed (one being for return ground). In essence, the various embodiments described herein can provide the benefits of each type of technology (e.g., nodes that can be placed anywhere while limiting the number of I/O contacts for a given resolution). Furthermore, although the nodes  20  may typically be placed on a planar surface, in some circumstances the nodes  20  may be placed on a contoured surface. Moreover, the nodes  20  may be placed on multiple surfaces such as multiple sides of a portable electronic device. 
     Because the node location is not limited, the nodes  20  may be positioned in a conventional 2D array of rows and columns or alternatively they may be positioned in a non 2D array thereby allowing a wide variety of user interfaces to be created. In fact, non 2D arrays may be beneficial in creating user interfaces that better fit portable electronic devices. For example, different orientations of nodes  20  may be used to provide input functionality that can be directed at the specific applications of the portable electronic device. The user interfaces may for example include scrolling regions or parameter control regions where nodes can be set up in succession along a predetermined path, and/or button regions where individual nodes may represent distinct button functions. With regards to a scrolling or parameter control, the nodes may be placed in an open loop arrangement such as a line, or they may be placed in closed loop arrangement such as a circle. Generally speaking, the nodes can be placed to form any shape whether in a single plane or multiple planes. Examples can include squares, rectangles, circles, semi-circles, ovals, triangles, trapezoids, other polygons, pill shapes, S shapes, U shapes, L shapes, star shapes, plus shape, etc. 
     Any number of nodes  20  may be used. The number of nodes  20  can typically be determined by the size of the touch device as well as the size of the electrodes  22  and  24  used at the nodes  20 . In many cases, it may be desirable to increase the number of nodes  20  so as to provide higher resolution (e.g., more information can be used for such things as acceleration). However, as the number increases, so can the number of I/Os. Therefore a careful balance between resolution and number of I/Os can be made when designing the touch device. 
     Furthermore, the size and shape of the nodes  20  may vary according to the specific needs of the touch device. Generally speaking, the nodes  20  can be formed from almost any shape and size. For example they may be formed as squares, rectangles, circles, semi-circles, ovals, triangles, trapezoids, other polygons and or more complicated shapes such as wedges, crescents, stars, lightning bolts, etc. In some cases, at least a portion and in some cases all the nodes  20  can be identical. That is, they can have the same size and shape. In other cases, at least a portion and in some cases all the nodes  20  can have different sizes and/or shapes. For example, a first set of nodes  20  may have a first shape and a second set of nodes  20  may have a second shape that is different than the first shape. The configuration can typically depend on the functionality that the touch device provides. For example, scrolling or parameter control nodes may be configured similarly within a scrolling or parameter control region, and button nodes may be configured differently than scrolling or parameter control nodes and each other. In essence, the size and shape can depend on the desired functionality. If the functionality is the same then the size and shape the nodes can tend to be same. If one functionality is more dominant than another functionality, then the size and shape can be matched accordingly. In some cases, the size of the nodes can correspond to about the size of a fingertip. In other cases, the size of the nodes can be smaller than the size of a finger tip so as to improve the resolution of the touch device (the finger can influence two of more nodes at anyone time thereby enabling interpolation). 
     During operation, the controller  12  can direct a voltage to be applied to each drive line  16  separately. This can happen sequentially until all the lines have been driven. For example, a voltage may first be applied to the first drive line  16 A, then the second drive line  16 B, then the third drive line  16 C and then the forth drive line  16 D. Once all the lines have been driven, the sequence can start over (continuously repeats). On the other hand, in one embodiment, the capacitive sensing circuit  17  of the controller  12  can sense all of the sensing lines  18  in parallel. That is, each time a drive line is driven, each of the sensing lines  18 A- 18 D can be monitored. This can typically be accomplished with independent circuits. Alternatively, in another embodiment, each sense line may be monitored in sequence, to share the same sensing circuit (e.g. multiplexing each line to the sense circuit on-chip). 
     More particularly, because of the capacitive coupling, when a current is driven through a driving line  16 , the current can be carried through to the sensing lines  18 A-D at each of the nodes  20  coupled to the driving line  16 . The sensing circuit  17  can monitor the change in capacitance that can occur at each of the nodes  20  via the sensing lines  18 A-D. The positions where changes occur and possibly the magnitude of those changes can be used to help recognize touch events. 
     When no object is present, the capacitive coupling at the node  20  can stay fairly constant. When an object such as a finger is placed proximate the node  20 , the capacitive coupling can change through the node  20 . The object can effectively shunt some of the field away so that the charge projected across the node  20  can be less, i.e., the object can steal charge thereby affecting the capacitance. The change in capacitive coupling can change the current carried by the sensing lines  18 A-D. The capacitance circuit  17  can note the current change and the particular node  20  where the current change occurred and can report this information in a raw or in some processed form to the host controller of the portable electronic device. 
     Although not shown in great detail in  FIG. 1 , the circuit  17  may additionally include filters for eliminating parasitic capacitance, which may for example be created when nodes, contacts and/or routing circuitry are located closely together. Generally speaking the filter can reject stray capacitance effects so that a clean representation of the charge transferred across the node can be outputted (and not anything in addition to that). That is, the filter can produce an output that is not dependent on the parasitic capacitance, but rather on the capacitance at the node  20 . As a result, a more accurate output can be produced. In one embodiment, the filters can be embodied as inverting amplifiers that can null the input voltage through each sense line. 
       FIG. 2  illustrates an exemplary circuit diagram of a filter arrangement of a mutual capacitance sensing circuit according to various embodiments. In the example of  FIG. 2 , a filter embodied as inverting amplifier  40  may be used in the circuit  17  of  FIG. 1  in order to reduce the parasitic capacitance. As shown, the inverting amplifier can include a non inverting input that can be held at a constant voltage (in this case ground), an inverting input that can be coupled to the node, and an output that can be coupled to the capacitive sensing circuit  17 . The output can be coupled back to the inverting input through a capacitor and/or resistor. During operation, the input from the node may be disturbed by stray capacitance effects, i.e., parasitic capacitance. If so, the inverting amplifier can be configured to drive the input back to the same voltage that it had been previously before the stimulus. As such, the value of the parasitic capacitance may not matter. 
     Analyzed from the circuit standpoint, the charge Q when injected into the circuit can be proportional to the change in voltage. Because the change in voltage is nulled, the input can be kept at a constant voltage, and therefore the net change that goes in and out of the node can be zero, which means the error signal at output of op amp can be zero contribution related to the parasitics caused by other nodes. 
       FIG. 3A  illustrates an exemplary block diagram of a capacitive sensing circuit  60  according to various embodiments. The capacitive sensing circuit  60  may for example correspond to the capacitive sensing circuits described in  FIG. 1 . The capacitive sensing circuit  60  can be configured to receive input data from multiple sensing points  62  (electrode, nodes, etc.), to process the data and to output processed data to a host controller. 
     The sensing circuit  60  can include a multiplexer  64  (MUX). The multiplexer  64  can be a switch configured to perform time multiplexing. As shown, the MUX  64  can include multiple independent input channels  66  for receiving signals from each of the sensing points  62  at the same time. The MUX  64  can store all of the incoming signals at the same time, but can sequentially release them one at a time through an output channel  68 . 
     The sensing circuit  60  can also include an analog to digital converter  70  (ADC) operatively coupled to the MUX  64  through the output channel  68 . The ADC  70  can be configured to digitize the incoming analog signals sequentially one at a time. That is, the ADC  70  can convert each of the incoming analog signals into outgoing digital signals. The input to the ADC  70  can generally correspond to a voltage having a theoretically infinite number of values. The voltage can vary according to the amount of capacitive coupling at each of the sensing points  62 . The output to the ADC  70 , on the other hand, can have a defined number of states. The states can generally have predictable exact voltages or currents. 
     The sensing circuit  60  can also include a digital signal processor  72  (DSP) operatively coupled to the ADC  70  through another channel  74 . The DSP  72  can be a programmable computer processing unit that can work to clarify or standardize the digital signals via high speed mathematical processing. The DSP  74  can be capable of differentiating between human made signals, which can have order, and noise, which can be inherently chaotic. In most cases, the DSP can perform filtering and conversion algorithms using the raw data. By way of example, the DSP may filter noise events from the raw data, calculate the touch boundaries for each touch that occurs on the touch screen at the same time, and thereafter determine the coordinates for each touch event. The coordinates of the touch events may then be reported to a host controller where they can be compared to previous coordinates of the touch events to determine what action to perform in the host device. 
     Another embodiment of the capacitive sensing circuit is shown in  FIG. 3B . This embodiment is similar to  FIG. 3A , but more simplified. In this embodiment, channel  66  can be followed by its own dedicated demodulator  65  and A/D converter  70 . The demodulator can be basically an analog multiplier with one input tied to the pulse generator signal, and the other input tied to the output of the channel charge amplifier. The output of the demodulator can feed the A/D converter, which can be a delta-sigma type of converter. 
     In one implementation of this embodiment, the circuit can wait until a timer (or host controller) indicates that a sensing cycle should begin. Thereafter, a pulse train can be sent to the first drive line (e.g., 12 pulses which can be each 3 uS period). Then, synchronous charge coupling can be sensed on all sense lines. This may for example be accomplished by demodulating the charge transferred to the sense lines using the pulse train phase and frequency reference. Thereafter, an A/D conversion can be performed on the sensed synchronous charge transfer for each sense line. Then, each data can be associated with the specific capacitor being sensed, which can be identified by the combination of the particular drive line and sense line which can be connected to the capacitor of interest. Then, the data from the A/D converter can be signal processed using techniques such as baseline subtraction, low pass filter, etc. Thereafter, the processed data can be communicated to the host to be acted on in an appropriate manner. This method may be repeated for each drive line. 
     A variety of nodes that can be utilized in the embodiments described above will now be described in conjunction with  FIGS. 4-7 . It should be appreciated that this is by way of example and not by way of limitation of the various embodiments. 
       FIG. 4  illustrates an exemplary mutual capacitive sensing node according to various embodiments. The node  100  can be formed from various layers including a cover film  102 , an electrode layer  104  and a substrate  106 . The cover film  102  can be disposed over the electrode layer  104  and the electrode layer  104  can be disposed over the substrate  106 . The electrode layer  104  can include a drive electrode  108  and a sense electrode  110  that can be spaced apart from one another in order to electrically isolate them from each other. The drive electrode  108  can be coupled to a drive line and the sense electrode  110  can be coupled to a sense line. When the drive electrode  108  is driven with a voltage or current, the voltage or current can be capacitively coupled to the sense electrode  110  via fringe fields  112  that can come up through the cover film  102 . When an object is placed over the node  100 , the object can shortcut or steal some of the field lines  112  away effectively reducing the capacitance coupled through the node  100 . 
     The electrodes  108  and  110  may be formed from almost any shape and size. For example they may be formed as squares, rectangles, circles, semi-circles, ovals, triangles, trapezoids, other polygons and or more complicated shapes such as wedges, crescents, stars, lightning bolts, etc. The size and shape of the electrodes  108  and  110  can typically depend on the size and shape of the node  100 . In some cases, the electrodes  108  and  110  can be equal pairs having the same size and shape. For example, the node  100  may be divided equally in half. In other cases, the electrodes  108  and  110  can be disparate pairs having different sizes and/or shapes. For example, the drive electrode  108  may have a first size and/or shape and the sense electrode  110  may have a second size and/or shape that is different than the first shape. By way of example, it may be beneficial to have a larger drive electrode and a smaller sense electrode (or vice versa). 
       FIG. 5  illustrates another exemplary mutual capacitive sensing node according to various embodiments. The node  120  can be similar to the node  100  described in  FIG. 4  except that the drive electrode  108  and sense electrode  110  can be interleaved rather than being juxtaposed plates. 
       FIG. 6  illustrates still another exemplary mutual capacitive sensing node according to various embodiments. The node  140  can be similar to the nodes  100  or  120  described in  FIGS. 4 and 5  in that it can use spaced apart electrodes  108  and  110 . However, unlike the embodiments described above, the node  140  can further include a floating (electrically isolated) electrode  142  disposed above the electrode pairs  108  and  110 . As shown, the drive and sense electrodes  108  and  110  can be disposed underneath a substrate  106 , and the floating electrode  142  can be disposed over the substrate  106 . Furthermore, the cover film  102  can be disposed over the floating electrode  142 . In this embodiment, the driving current can be capacitively coupled to the floating electrode from the driving electrode  108  then it can be capacitively coupled to the sense electrode  110 . Moreover, the outer dimension of the floating electrode  142  can typically match the outer dimensions of the electrode pairs  108  and  110 , although in some circumstances it may be desirable to make the outer dimension of the floating electrode  142  smaller or larger than the outer dimension of the electrode pairs  108 / 110 . 
       FIGS. 7A and 7B  show the embodiment of  FIG. 6  in exemplary circuit diagram form. In this illustration, C 1  can be the capacitance between the drive electrode  108  and the floating electrode  142 , C 2  can be the capacitance between the floating electrode  142  and the sense electrode  110 , and C 3  can be the capacitance between a finger  144  and the floating electrode  142 . C 3  can be the only capacitance that changes (only exists when a finger or other related object is present). 
     For illustration purposes, assume that a typical value for C 1  can be 2 pF, C 2  can be 2 pF and C 3  can be 2 pF. When there is no touch, the capacitance C 1  and C 2  can be placed in series thereby creating a total net capacitance of 1 pF. This capacitance can be fed through a sense line and read by the capacitance sensing circuit. When there is a touch, the capacitance C 2  and C 3  can be first combined together (because the sense electrode can be held at virtual ground) then the capacitance C 1  (2 pF) and C 23  (4 pF) can be placed in series thereby creating a total net capacitance of (4 pF*2 pF)/(4 pF+2 pF)=8/6 pF. However, the total charge transfer can split equally between C 2  and C 3 , so the charge transfer through C 2  can be ½ of the total, or ⅔ pF. This capacitance can be fed through a sense line and read by the capacitance sensing circuit. The capacitance sensing circuit can differentiate between a no touch and a touch by checking these values (e.g., no touch=1 pF, touch=something other than 1 pF). The value of the capacitance for a touch may further be used to determine touch pressure as the capacitance can typically change with increased pressure. 
     Referring to all the node designs mentioned above ( FIGS. 4-7 ), the substrate  106  may for example be a printed circuit board or a flexible membrane such as those of a flex circuit or some other suitable material for supporting the electrodes  108  and  110  thereon (e.g., housing of portable electronic device). Furthermore, the electrodes  108  and  110  may be formed from any thin conductive material. By way of example, the electrodes  108  and  110  may be embodied as a metallic foil that can be adhered to the substrate  106 , a conductive paint or ink that can be coated on the substrate  106 , a conductive material that can be printed, deposited or etched on the substrate  106 , plates or bands that can be molded or embedded into the substrate  106  or any other suitable arrangement. Moreover, the cover film  102  may be formed from any suitable dielectric material such as glass or plastic. The cover film  102  can serve to protect the underlayers and provide a surface for allowing an object to slide thereon. The cover film  102  can also provide an insulating layer between the object and the electrode layer  104 . Furthermore, the cover film  102  can be suitably thin to allow sufficient electrode coupling. 
     In some cases, the various layers may further be embodied as transparent or semi transparent materials. For example, the conductive material of the electrodes may be formed from indium tin oxide (ITO), the dielectric material of the film may be formed as clear or partially transparent plastic or glass, and the substrate may be formed as clear or partially transparent plastic or glass (e.g., clear Mylar™ sheet). This may be done to allow visual feedback through the various layers of the touch device. 
     Moreover, the electrode layer  104  may include interconnects for coupling the electrodes  108  and  110  to the driving and sensing lines. Alternatively, the driving and sensing lines may be formed with the electrodes  108  and  110  in the same step/layer. 
     In one implementation, the electrodes can be placed on one side of a printed circuit board (PCB), and the mutual capacitance sensing circuit in the form of an integrated circuit chip can be mounted on the back side of the chip, with conventional PCB routing connecting the I/O contacts of the electrodes to the I/O contacts of the IC chip. The IC chip may for example be an ASIC. In another implementation, the electrodes can be placed on one side of a printed circuit board (PCB) and the I/O contacts can be coupled to the I/O contacts of a floating IC via a flex circuit with printed traces (sensing and driving lines). For example, the PCB containing the electrodes can be connected to one end of a flex circuit and the sensor IC can be attached to the other end of the flex circuit. Alternatively, the electrodes may be applied directly to the flexible member of the flex circuit. 
     Several touch devices  200 - 290  with nodes  202  set up in a non 2D array will now be described in conjunction with  FIGS. 8-17 . It should be appreciated that these are given by way of example and not by way of limiting the various embodiments. 
     In most of these embodiments, the touch devices can include multiple nodes  202  that can be positioned side by side along a predetermined path. This arrangement can work particularly well for performing scrolling operations or parameter control operations. The path may be a closed loop path or an opened loop path. Furthermore, each of the nodes  202  can include an electrode pair of drive electrode  204  and sense electrode  206 . Moreover, the number of drive lines  208  can be equal to the number of sense lines  210 , and further the number of nodes  202  can be the square of this number. Alternatively, the number of drive lines  208  can be different from the number of sense lines  210 , and further the number of nodes  202  can be the multiplicative product of the numbers of drive and sense lines. It should be appreciated however that this is not a limitation. 
       FIG. 8  illustrates an exemplary circular touch device according to various embodiments. The circular touch device  200  can be divided into several independent and spatially distinct nodes  202  that can be positioned in a circular manner. Each of the nodes  202  can represent a different angular position within the circular shape. Although not shown, the nodes may also be placed at radial locations from the center of the touch surface to the perimeter of the touch surface. 
       FIG. 9  illustrates an exemplary linear touch device according to various embodiments. The linear touch device  220  can be divided into several independent and spatially distinct nodes  202  that can be positioned next to one another along a straight line. Each of the nodes  202  can represent a different linear position. Although shown vertical, it should be appreciated that the linear touch device may also be horizontal or at an angle. Moreover, although shown straight, in some cases it may be desirable to use a curved line such as one that is U shaped, S shaped, etc. 
       FIG. 10  illustrates another exemplary type of linear touch device according to various embodiments. The linear touch device  250  can be divided into several independent and spatially distinct nodes  202  that can be positioned in the form of a “+” shape. This embodiment can include both a horizontal line and a vertical line that can cross each other. 
       FIG. 11  illustrates an exemplary combined touch device according to various embodiments. For example, it may combine two sets of scrolling/parameter control regions as, for example, the circular region described in  FIG. 9  and the plus region described in  FIG. 10 . 
       FIGS. 12-14  illustrate exemplary touch sensing devices that can include a touch region and one or more distinct buttons according to various embodiments. The touch devices  250 - 270  can include a scrolling or parameter control set up  282  and one or more distinct buttons  284 . The scrolling or parameter control set up  282  can include nodes  202  configured similarly to any of those previously described  200 - 240 . The buttons  284 , on the other hand, can include additional node(s)  202 . Each button may include one or more nodes. The minimum required node can be one, but in some cases it may be desirable to include multiple nodes. The buttons  284  may be positioned inside and/or outside the scrolling region  282 . They may be placed in close proximity of the scrolling region  282  as, for example, around the periphery of the scrolling region  282  ( FIGS. 12 and 13 ) and/or they may be placed away from the scrolling region  282  ( FIG. 14 ). 
       FIG. 15  illustrates an exemplary touch sensing device that only includes a button arrangement according to various embodiments. The touch device  280  can include a button arrangement having multiple buttons  284 . Each button  284  can have a different task or function assigned thereto. The buttons  284  may be arranged in any manner within a user interface of an electronic device. 
       FIG. 16  illustrates another exemplary linear touch device according to various embodiments. In the example of  FIG. 16 , linear touch device  280  can be similar to the linear touch device  220  of  FIG. 9  with the following exceptions. Several independent and spatially distinct nodes  202  can be grouped into several node groups, where a group of adjacent drive electrodes  204  can be coupled to the same drive line  208  and corresponding adjacent sense electrodes  206  in that same group can be coupled to different sense lines  210 . Each sense electrode  206  in a group can be coupled to a sense electrode in another group by the same sense line  210 . As such, each node  202  can have a different combination of drive and sense lines coupled thereto. Moreover, by coupling multiple nodes to the same drive line or the same sense line, the total number of drive and sense lines can be reduced, thereby reducing the real estate needed for placing the lines. Controller  215  can operate similar to the controller  12  of  FIG. 1 . The controller  215  can communicate with the nodes  202  via the distinct drive lines  208  and the distinct sense lines  210 , where the drive lines  208  can be configured to carry current from the controller  215  to the nodes to drive the nodes and the sense lines  210  can be configured to carry signals from the nodes to the controller indicative of a touch (or other events) at the nodes. 
       FIG. 17  illustrates another exemplary circular touch device according to various embodiments. In the example of  FIG. 17 , circular touch device  290  can be similar to the circular touch device  200  of  FIG. 8  with the following exceptions. Several independent and spatially distinct nodes  202  can be grouped into several node groups, where a group of adjacent drive electrodes  204  can be coupled to the same drive line  208  and corresponding adjacent sense electrodes  206  in that same group can be coupled to different sense lines  210 . Each sense electrode  206  in a group can be coupled to a sense electrode in another group by the same sense line  210 . As such, each node  202  can have a different combination of drive and sense lines coupled thereto. Controller  215  can communicate with the nodes  202  via the distinct drive lines  208  and the distinct sense lines  210 , where the drive lines  208  can be configured to carry current from the controller  215  to the nodes to drive the nodes and the sense lines  210  can be configured to carry signals from the nodes to the controller indicative of a touch (or other events) at the nodes. 
       FIG. 18  illustrates still another exemplary circular touch device according to various embodiments. In the example of  FIG. 18 , circular touch device  292  can be similar to the circular touch device  290  of  FIG. 17  with the following exception. Sense electrodes  206  can be surrounded by drive electrodes  204  to form nodes  202 . Similar to the device  290  of  FIG. 17 , the nodes  202  can be grouped into several groups, where the drive electrodes  204  in a group can be coupled to the same drive line  208  and corresponding sense electrodes  206  in that same group can be coupled to different sense lines  210 . Each sense electrode  206  in a group can be coupled to a sense electrode in another group by the same sense line  210 . As such, each node  202  can have a different combination of drive and sense lines coupled thereto. Controller  215  can communicate with the nodes  202  via the distinct drive lines  208  and the distinct sense lines  210 , where the drive lines  208  can be configured to carry current from the controller  215  to the nodes to drive the nodes and the sense lines  210  can be configured to carry signals from the nodes to the controller indicative of a touch (or other events) at the nodes. 
     A click wheel can include a touch sensing device as described herein so that, in addition to sensing a force applied by an object, e.g., pressing by a finger, on the wheel, the click wheel can also sense a touch by the object on the wheel, thereby performing one or more functions associated with the force, the touch, or both. 
       FIGS. 19 and 20  illustrate exemplary bottom and top views of a click wheel having touch sensing capabilities according to various embodiments. Click wheel  295  can include flexible membrane  296  having touch and force sensing circuitry thereon. The flexible membrane  296  can be positioned beneath a click wheel cover (not shown), either disposed on or proximate to the undersurface of the cover. As such, when an object touches or presses on the click wheel cover, the touch and force sensing circuitry on the flexible membrane can sense the touch or press. The touch sensing circuitry can include touch sensors  203  configured to sense a touch at or near the click wheel, e.g., at or near the click wheel cover. The force sensing circuitry can include force sensors, e.g., dome switches  205 , configured to sense a force applied to the click wheel, e.g., applied to the click wheel cover. 
     In some embodiments, the touch sensors  203  can be disposed on the surface of the flexible membrane  296  facing the undersurface of the click wheel cover (designated herein as the “top” surface of the membrane) in a circular pattern. In some embodiments, the dome switches  205  can be disposed on the surface of the flexible membrane  296  opposite the top surface (designated herein as the “bottom” surface of the membrane) also in a circular pattern. The dome switches  205  on the bottom surface of the membrane  296  can capacitively couple with the touch sensors  203  disposed opposite on the top surface of the membrane. To ensure the same capacitive performance for all the touch sensors  203 , conductive patterns similar to those of the dome switches  205  can be replicated on the bottom surface of the membrane  296  opposite the remaining touch sensors  203 . As such, the replicate conductive patterns on the bottom surface can capacitively couple with the touch sensors  203  disposed opposite on the top surface. This will be described in more detail in  FIG. 19  below. Additionally, to ensure constructive interaction between the dome switches  205  and their oppositely disposed touch sensor  203 , the locations of conductive components of these touch sensors can substantially match the locations of conductive components of the dome switches. Moreover, to ensure the same capacitive performance for all the touch sensors  203 , conductive patterns of the touch sensors  203  disposed opposite the dome switches  205  can be replicated on the top surface of the flexible membrane  296  for the remaining touch sensors. This will be described in more detail in  FIG. 20  below. 
     In the example of  FIG. 19 , the bottom surface of the flexible membrane  296  can have multiple nodes  202  disposed in a circular pattern around the membrane surface. The nodes  202  can include dome switches  205  and replicate portions of touch sensors  203 . In some embodiments, the dome switches  205  can be disposed on the bottom surface of the flexible membrane  296  at the “press” locations of the click wheel  295 , i.e., locations on the click wheel that an object can press or otherwise apply force in order to trigger a function associated with the click wheel. For example, the dome switches  205  can be disposed at the 0°, 90°, 180°, and 270° positions around an iPod™ click wheel coincident with the Forward, Menu, Back, and Play/Pause labels on the click wheel cover. As such, pressing the cover proximate to one of the labels can deform the underlying dome switch  205 , causing the switch to generate a force signal that can trigger the function identified by that label. For example, pressing the click wheel cover at the Menu label can cause the dome switch underlying the label to deform and generate a force signal which can trigger a menu to display on a display screen in communication with the click wheel. Similarly, pressing the click wheel cover at the Play/Pause label can cause the dome switch underlying the label to deform and generate a force signal which can trigger audio and/or video to begin playing or pause playing on a player in communication with the click wheel. Each dome switch  205  can include force sensor  207  at the center of the switch to sense a force applied to the switch, e.g., by an object pressing on the switch, and conductive ring  209  surrounding the sensor to drive the switch. When an object presses on the switch  205 , the dome center of the switch can deform to contact the force sensor  207 , thereby forming a resistance short circuit between the conductive ring  209  and the sensor  207  and generating a force signal indicative of the resistance change caused by the press or applied force. 
     In some embodiments, the replicate portions of the touch sensors  203  can be disposed on the bottom surface of the flexible membrane  296  at locations between the dome switches  205 . For example, portions of the touch sensors  203  can be disposed at the 30°, 60°, 120°, 150°, 210°, 240°, 300°, and 330° positions around an iPod™ click wheel. Each portion of touch sensor  203  can include a portion of sense electrode  206  at the center of the sensor to replicate the force sensor  207  of the dome switch  205  and a portion of drive electrode  204  surrounding the portion of sense electrode  206  to replicate the conductive ring  209  of the dome switch. The portion of sense electrode  206  on the bottom surface of the membrane  296  can capacitively couple with the sense electrode disposed opposite on the top surface. Similarly, the portion of drive electrode  204  disposed on the bottom surface of the membrane  296  can capacitively couple with the drive electrode disposed opposite on the top surface. 
     In the example of  FIG. 20 , the top surface of the flexible membrane  296  can have multiple nodes  202  disposed in a circular pattern around the membrane surface. The nodes  202  can include touch sensors  203 . In some embodiments, the touch sensors  203  can be disposed on the top surface of the flexible membrane  296  to coincide with the dome switches  205  and the replicate portions of the touch sensors disposed opposite on the bottom surface. For example, the touch sensors can be disposed at the 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330° positions around an iPod™ click wheel. Each touch sensor  203  can include sense electrode  206  to sense a touch at or near the sensor and drive electrode  204  to drive the sensor. When an object touches at or near the sensor  203 , the object can block electric fields formed between the drive electrode  204  and the sense electrode  206 , thereby reducing the mutual capacitance between the electrodes and generating a touch signal, as a function of the capacitance change, indicative of the touch. A sensed touch can include a tap, a gesture, a rotational motion, a linear motion, etc., and can trigger a function associated therewith. For example, a rotational motion or a linear motion on the click wheel can trigger a scroll function for scrolling through a menu or list displayed on a display in communication with the click wheel. 
     Each sense electrode  206  on the top surface of the flexible membrane  296  can have a portion that can substantially match either a force sensor  207  of a dome switch  205  or a replicate portion of a sense electrode disposed opposite on the bottom surface of the membrane. Each sense electrode  206  on the top surface can also have a portion that can electrically couple to sense line  210  for transmitting a touch signal. Remaining portions of the touch sensor  203  designated for the sense electrode  206  can be filled with conductive material, such as interdigitated powder, to complete the sense area of the sensor. Each drive electrode  204  on the top surface of the flexible membrane  296  can have a portion that can substantially match either a conductive ring  209  of a dome switch  205  or a replicate portion of a drive electrode disposed opposite on the bottom surface of the membrane. Each drive electrode  204  on the top surface can also have a portion that can electrically couple to drive line  208  for driving the sensor. Remaining portions of the touch sensor  203  designated for the drive electrode  204  can be filled with conductive material, such as interdigitated powder, to complete the drive area of the sensor. This touch sensor structure can ensure constructive interaction between the dome switch components and the touch sensor components disposed opposite and can ensure the same capacitive performance for all the touch sensors. 
     Referring again to the example of  FIG. 19 , the flexible membrane  296  can also include drive lines  208  configured to drive the dome switches  205  and the touch sensors  203  and sense lines  210  configured to transmit a force signal from the dome switches or a touch signal from the touch sensors. In some embodiments, as in this example, the drive lines  208  and the sense lines  210  can be disposed on the bottom surface of the flexible membrane  296 , connecting through vias to the touch sensors  203  on the top surface of the membrane. Other embodiments are also possible, such as both sets of lines  208 ,  210  being on the top surface of the membrane  296 , portions of either or both sets being split between the top and bottom surfaces, or one set being on the top surface and the other set being on the bottom surface. The nodes  202  can be grouped together to form several groups, where at least one dome switch  205  and at least one touch sensor  203  can be included in each group. A group of adjacent drive electrodes  204  of the touch sensors  203  and conductive rings  209  of the dome switches  205  can be coupled to the same drive line  208 . Corresponding adjacent sense electrodes  206  of the touch sensors  203  and force sensors  207  of the dome switches  205  in that same group can be coupled to different sense lines  210 . Each sense electrode  206  of a touch sensor  203  in a group can be coupled to a sense electrode of a touch sensor in another group by the same sense line  210 . Similarly, each force sensor  207  of a dome switch  205  in a group can be coupled to a force sensor of a dome switch in another group by the same sense line  210 . As such, each node  202  can have a different combination of drive and sense lines coupled thereto. Moreover, by coupling multiple nodes to the same drive line or the same sense line, the total number of drive and sense lines can be reduced, thereby reducing the real estate needed for placing the lines. 
     Table 1 shows an example mapping of drive lines to sense lines for the dome switches and the touch sensors as shown in  FIGS. 19 and 20 . 
                     TABLE 1                  Drive and Sense Line Mapping                                 Sense line S1   Sense line S2   Sense line S3               Drive   Dome switch 0°   Touch sensor 30°   Touch sensor 60°       line D1   Touch sensor 0°       Drive   Dome switch 90°   Touch sensor 120°   Touch sensor 150°       line D2   Touch sensor 90°       Drive   Dome switch 180°   Touch sensor 210°   Touch sensor 240°       line D3   Touch sensor 180°       Drive   Dome switch 270°   Touch sensor 300°   Touch sensor 330°       line D4   Touch sensor 270°                    
where drive line D 1  can drive the dome switch and the touch sensor opposite at the 0° location and sense line S 1  can transmit the respective force signal and touch signal, drive line D 1  can drive the touch sensor at the 30° location and sense line S 2  can transmit the touch signal, and so on.
 
     Controller  215  can operate similar to the controller  12  of  FIG. 1 . The controller  215  can communicate with the nodes  202  via the distinct drive lines  208  and the distinct sense lines  210 , where the drive lines  208  can be configured to carry current from the controller  215  to the nodes to drive the nodes and the sense lines  210  can be configured to carry force and/or touch signals from the nodes to the controller  215  indicative of a touch and/or a force at the nodes. 
     Although the nodes can be disposed at 30° intervals around the click wheel as in this example, it is to be understood that other positions and/or intervals are also possible, depending on the needs of the click wheel. 
     Although the click wheel and the arrangement of the nodes thereon can be circular, it is to be understood that other shapes, configurations, and/or orientations are also possible, depending on the needs of the click wheel. For example, the click wheel can be oval or round and can be three-dimensional and the nodes can be arranged in an oval, round, square, rectangle, triangle, diamond, etc. configuration. 
       FIG. 21  illustrates an exemplary controller of a click wheel according to various embodiments. In the example of  FIG. 21 , controller  215  can operate similar to the controller  12  of  FIG. 1 . The controller  215  can include voltage source  216 , which can be coupled to drive lines  208  to drive current through each drive line  208  to drive electrodes  204  and conductive rings  209  of click wheel  295 , as in  FIGS. 19 and 20 . The voltage source  216  can drive current through one drive line  208  at a time, through all the drive lines substantially simultaneously or somewhere in between, depending on the needs of the click wheel. The controller  215  can also include capacitance sensing circuit  217 , which can be coupled to sense lines  210  to receive touch signals from the sense lines indicative of a sensed touch at touch sensors  203 . The capacitance sensing circuit  217  can receive touch signals from one sense line  210  at a time, from all the sense lines substantially simultaneously, or somewhere in between, depending on the needs of the click wheel. The controller  215  can also include force sensing circuit  218 , which can also be coupled to sense lines  210  to receive force signals from the sense lines indicative of a sensed force at dome switches  205 . The force sensing circuit  218  can receive force signals from one sense line  210  at a time, from all the sense lines substantially simultaneously, or somewhere in between, depending on the needs of the click wheel. 
     Since the drive lines  208  and the sense lines  210  can be shared by the touch sensors  203  and the dome switches  205 , the controller  215  can also include control module  219 , which can be coupled to the various components to selectively change the operation of the click wheel between touch detection and force detection. During touch detection, the control module  219  can cause the voltage source  216  to output current through the drive lines  208  to the drive electrodes  204  of the touch sensors  203  and can cause the capacitance sensing circuit to receive touch signals from the sense electrodes  206  through the sense lines  210 . During force detection, the control module  219  can cause the voltage source  216  to output current through the drive lines  208  to the conductive rings  209  of the dome switches  205  and can cause the force sensing circuit  218  to receive force signals from the force sensors  207  through the sense lines  210  when the dome switches  205  are pressed. 
     In some embodiments, the control module  219  can use time multiplexing when changing between touch detection and force detection. That is, the control module  219  can operate touch detection for a certain time period, then operate force detection for a certain time period, and then repeat in order to perform each operation in an effective manner. In some embodiments, the control module  219  can use interrupts when changing between touch detection and force detection. For example, the control module  219  can operate touch detection until it receives an interrupt that a dome switch  205  is about to be, is in the process of being, or has been pressed. Conversely, the control module  219  can operate force detection until it receives an interrupt that a node  202  is about to receive, is in the process of receiving, or has received a touch. Other mechanisms for changing operation of the click wheel are also possible. 
       FIG. 22  illustrates an exemplary method for operating a click wheel having touch sensing capabilities according to various embodiments. In the example of  FIG. 22 , one or more nodes, including at least one dome switch and/or at least one touch sensor, can be driven using one or more drive lines ( 221 ). The nodes can be driven one at a time, substantially simultaneously, or somewhere in between. The sensed output of the nodes can be transmitted using one or more sense lines ( 222 ). A determination can be made as to the type of output ( 223 ). In some embodiments, the location of the node from which the signal came can be used to determine the output type. For example, if the signal came from a node at the 30° position, as in  FIGS. 19 and 20 , it can be determined that the signal is a touch signal since the 30° position includes only a touch sensor. In some embodiments, the sense line on which the signal was transmitted can be used to determine the output type. For example, if the signal was transmitted on sense line S 2 , as in  FIGS. 19 and 20 , it can be determined that the signal is a touch signal since only touch sensors are coupled to sense line S 2 . In some embodiments, the output type can be determined based on whether the click wheel is in a touch detection period or a force detection period. Other determination methods are also possible. If the output is a force signal, the force signal can be received at a force sensing circuit ( 224 ). The received force signal can be processed to trigger a function associated with the signal ( 225 ). For example, the function can be associated with the location, the strength, the timing, etc., of the force signal. If the output is a touch signal, the touch signal can be received at a touch sensing circuit ( 226 ). The received touch signal can be processed to trigger a function associated with the signal ( 227 ). For example, the function can be associated with the location, the motion, the timing, etc., of the touch signal. 
     It is to be understood that operation of a click wheel is not limited to the method illustrated in  FIG. 22 , but can include additional and/or other actions according to various embodiments. 
       FIGS. 23 and 24  illustrate exemplary bottom and top views of another click wheel having touch sensing capabilities according to various embodiments. Click wheel  295  can include flexible membrane  296  having touch and force sensing circuitry thereon. The flexible membrane  296  can be positioned beneath a click wheel cover (not shown), either disposed on or proximate to the undersurface of the cover. As such, when an object touches or presses on the click wheel cover, the touch and force sensing circuitry on the flexible membrane can sense the touch or press. The touch sensing circuitry can include touch sensors  203  configured to sense a touch at or near the click wheel, e.g., at or near the click wheel cover. The force sensing circuitry can include force sensors, e.g., dome switches  205 , configured to sense a force applied to the click wheel, e.g., applied to the click wheel cover. 
     In the example of  FIG. 23 , the bottom surface of the flexible membrane  296  can have multiple nodes  202  disposed in a circular pattern around the membrane surface. The nodes  202  can include dome switches  205 . In some embodiments, the dome switches  205  can be disposed on the bottom surface of the flexible membrane  296  at the “press” locations of the click wheel  295 , i.e., locations on the click wheel that an object can press or apply force in order to trigger a function associated with the click wheel. For example, the dome switches  205  can be disposed at the 0°, 90°, 180°, and 270° positions around an iPod™ click wheel coincident with the Forward, Menu, Back, and Play/Pause labels on the click wheel cover. As such, as described previously, pressing the cover proximate to one of the labels can deform the underlying dome switch  205 , causing the switch to generate a force signal that can trigger the function identified by that label. Each dome switch  205  can include force sensor  207  at the center of the switch to sense a force applied to the switch, e.g., by an object pressing on the switch, and conductive ring  209  surrounding the sensor to drive the switch. When an object presses on the switch  205 , the dome center of the switch can deform to contact the force sensor  207 , thereby forming a short circuit between the conductive ring  209  and the sensor  207  and generating a force signal indicative of the press or applied force. 
     In the example of  FIG. 24 , the top surface of the flexible membrane  296  can have multiple nodes  202  disposed in a circular pattern around the membrane surface. The nodes  202  can include touch sensors  203 . In some embodiments, the touch sensors  203  can be disposed at certain intervals around the top surface of the flexible membrane  296  and some of the sensor locations can coincide with locations of the dome switches  205  on the bottom surface. For example, the touch sensors  203  can be disposed at 15° intervals around an iPod™ click wheel, where the touch sensors at positions 0°, 90°, 180°, and 270° can be disposed opposite the dome switches  205 . Each touch sensor  203  can include sense electrode  206  to sense a touch at or near the sensor and drive electrode  204  to drive the sensor. When an object touches at or near the sensor  203 , the object can block electric fields formed between the drive electrode  204  and the sense electrode  206 , thereby reducing the mutual capacitance between the electrodes and generating a touch signal, as a function of the reduced capacitance, indicative of the touch. As described previously, a sensed touch can include a tap, a gesture, a rotational motion, a linear motion, etc., and can trigger a function associated therewith. 
     Since the click wheel cover is movable, it can sometimes move when not being intentionally moved by the user. In some embodiments, this incidental movement of the click wheel cover can apply a slight force to an underlying dome switch  205  at the point of movement, causing the dome of the switch to slightly deform. The slight deformation can move the dome closer to the underlying force sensor  207  without contacting the sensor and can reduce the air gap between the sensor and the dome. This gap reduction can increase the capacitance of the switch. Since the dome switch can be capacitively coupled to the touch sensor disposed opposite the switch, this increase in capacitance can induce or introduce error in the mutual capacitance measured at the touch sensor, thereby introducing error in the resultant touch signal. To reduce or avoid this error, the dome switches can be coupled to ground, as shown in  FIGS. 23 and 24 , rather than to drive lines, as in other embodiments. As such, the capacitance error can be shunted to ground rather than to the touch signal outputs. 
     Referring again to the example of  FIGS. 23 and 24 , the flexible membrane  296  can also include drive lines  208  configured to drive the touch sensors  203  and sense lines  210  configured to transmit a force signal from the dome switches  205  or a touch signal from the touch sensors. The nodes  202  can be grouped into several groups, where at least one dome switch  205  and at least one touch sensor  203  can be included in each group. A group of adjacent sense electrodes  206  of the touch sensors  203  and force sensors  207  of the dome switches  205  can be coupled to the same sense line  210 . Corresponding adjacent drive electrodes  204  of the touch sensors  203  in that same group can be coupled to different drive lines  208 . Corresponding conductive rings  209  of the dome switches  205  in that group can be coupled to ground  201  so as to avoid inducing error in the capacitance when the dome switches  205  are slightly deformed. Each drive electrode  204  of a touch sensor  203  in a group can be coupled to a drive electrode of a touch sensor in another group by the same drive line  208 . As such, each node  202  can have a different combination of drive and sense lines coupled thereto. Moreover, by coupling multiple nodes to the same drive line or the same sense line, the total number of drive and sense lines can be reduced, thereby reducing the real estate needed for placing the lines. 
     Table 2 shows an example mapping of drive lines to sense lines to ground for the dome switches and the touch sensors as shown in  FIGS. 23 and 24 . 
                     TABLE 2                  Drive and Sense Line Mapping                                     Sense           Sense           line S1   Sense line S2   Sense line S3   line S4                                             Drive   Touch sensor   Touch sensor   Touch sensor   Touch sensor       line D1   45°   135°   225°   315°       Drive   Touch sensor   Touch sensor   Touch sensor   Touch sensor       line D2   67.5°   157.5°   247.5°   337.5°       Drive   Touch sensor   Touch sensor   Touch sensor   Touch       line D3   90°   180°   270°   sensor 0°       Drive   Touch sensor   Touch sensor   Touch sensor   Touch sensor       line D4   112.5°   202.5°   292.5°   22.5°       Ground G   Dome switch   Dome switch   Dome switch   Dome            90°   180°   270°   switch 0°                    
where sense line S 1  can couple to the touch sensor and the dome switch at 90° location, but the touch sensor can couple to drive line D 3  while the dome switch can couple to ground G, and so on.
 
     Controller  215  can operate similar to the controller  12  of  FIG. 1 . The controller  215  can communicate with the nodes  202  via the distinct drive lines  208  and the distinct sense lines  210 , where the drive lines  208  can be configured to carry current from the controller  215  to the nodes to drive the nodes and the sense lines  210  can be configured to carry force and/or touch signals from the nodes to the controller  215  indicative of a touch and/or a force at the nodes. The nodes  202  can also connect to ground  201 . 
     Although the nodes can be disposed at 15° intervals around the click wheel as in this example, it is to be understood that other positions and/or intervals are also possible, depending on the needs of the click wheel. 
     Although the click wheel and the arrangement of the nodes thereon can be circular, it is to be understood that other shapes, configurations, and/or orientations are also possible, depending on the needs of the click wheel. For example, the click wheel can be oval or round and can be three-dimensional and the nodes can be arranged in an oval, round, square, rectangle, triangle, diamond, etc. configuration. 
     In an alternate embodiment, similar to the click wheel of  FIGS. 19 and 20 , the sense electrodes and the drive electrodes of the touch sensors of  FIG. 24  opposite the dome switches can be configured to substantially match the force sensors and conductive rings of the dome switches to provide constructive interaction therebetween. Additionally, the touch sensor conductive patterns can be substantially the same to provide substantially the same capacitive performance. Also, conductive patterns replicating the dome switches can be disposed on the bottom surface of the membrane opposite the touch sensors to provide substantially uniform capacitive performance of all the touch sensors. 
     Also, in an alternate embodiment, similar to the click wheel of  FIGS. 19 and 20 , a group of adjacent touch sensors of  FIGS. 23 and 24  can be coupled to the same drive line and to different sense lines and each touch sensor in a group can be coupled to a touch sensor in another group by the same sense line. Additionally, the dome switches can be coupled to ground and to the same sense line. 
       FIG. 25  illustrates an exemplary method for detecting capacitance error in a click wheel according to various embodiments. In the example of  FIG. 25 , mutual capacitance at a touch sensor can be measured ( 251 ). The measured capacitance can be compared to a predetermined capacitance value ( 252 ). The predetermined capacitance value can be a typical or expected capacitance measurement based on an object touch profile, operation, design, etc., of the click wheel. A determination can be made whether the comparison indicates a capacitance increase of the measured capacitance value above the predetermined capacitance value ( 253 ). If so, this increase can indicate an induced error in the capacitance measurement due to a dome switch being pressed. Accordingly, the dome switch can be identified as being pressed or having a force applied thereto ( 254 ). And the measured capacitance can be ignored ( 255 ). In some embodiments, a signal can be sent to a controller indicating that the dome switch is being pressed. If the comparison indicates a capacitance decrease of the measured capacitance value below the predetermined capacitance value, this can indicate a normal touch at the touch sensor, which can be sent to the controller for further processing. 
     It is to be understood that capacitance error detection is not limited to the method illustrated in  FIG. 25 , but can include additional and/or other actions according to various embodiments. 
       FIG. 26  illustrates an exemplary touch assembly according to various embodiments. The touch assembly  300  can include multiple mutual capacitive sensing nodes  302  coupled to a host controller  304  via flex circuit  306 . The nodes  302  may be disposed on the flexible member of the flex circuit  306  or alternatively on a printed circuit board that can be attached to the flexible member of the flex circuit. The nodes  302  can include a drive electrode  308  and a sense electrode  310  as described above. Although the nodes and electrodes can be arranged in accordance with any of the embodiments described above, in the illustrated embodiment the nodes and electrodes can be set up similarly to  FIG. 8 . 
     The flexible member  307  of the flex circuit  306  can include a first neck  312 , a landing area  314  and a second neck  316 . The first neck  312  can include multiple traces  313  coupling the I/O contacts of the nodes  302  to corresponding I/O contacts of an input controller  318  disposed on the landing area  314  of the flex circuit  306 . The input controller  318  may for example include a capacitive sensing microprocessor. In order to reduce the number of traces and I/O contacts of the input controller, the drive and sense electrodes of the nodes may be configured to share the traces that couple back to the I/O contacts of the input controller. Furthermore, in order to allow sensing, each node may include a different arrangement of drive and sense trace coupled to their corresponding electrodes. In one embodiment, the number of traces and thus the number of I/O contacts can be less than the number nodes  302 . In one implementation of this embodiment, the number of traces and thus the number of I/O contacts of the input controller can be equal to the square root of the number of nodes  302 . This can be in contrast to a self capacitive device where there can typically be one trace for each electrode as well as one for ground. (e.g., in the case of a sixteen electrodes, there would be seventeen traces on the first neck  312 ). Additional traces may be provided for other input means as for example mechanical buttons, switches, etc. 
     The second neck  316  can include multiple traces  317  coupling the I/O contacts of the input controller  318  to corresponding I/O contacts of the host controller  304 . The number of lines can typically depend on the communication protocol being used. By way of example, the second neck  316  may include six traces  317  for power and serial data (e.g., USB). In some cases, the flex circuit  306  can be connected to the host controller  304  through a connector arrangement that can utilize pins or contacts (e.g., male/female). In this way, the touch sensing unit  302  and flex circuit  306  can be a separate unit that can couple to and decouple from the host controller  304  thereby making assembly easier. In other cases, they can be permanently attached thereby creating a single unit. The host controller  304  may be positioned on the flexible member of the flex circuit or alternatively on a printed circuit board such as the main board of the electronic device. 
       FIG. 27  illustrates an exemplary electronic device according to various embodiments. The electronic device  350  can typically include a processor  356  configured to execute instructions and to carry out operations associated with the electronic device. For example, using instructions retrieved for example from memory, the processor  356  may control the reception and manipulation of input and output data between components of the electronic device  350 . The processor  356  can be implemented on a single-chip, multiple chips or multiple electrical components. For example, various architectures can be used for the processor  356 , including dedicated or embedded processor, single purpose processor, controller, ASIC, and so forth. 
     In most cases, the processor  356  together with an operating system can operate to execute computer code and produce and use data. The operating system may correspond to well known operating systems such as OSX, DOS, Unix, Linux, and Palm OS, or alternatively to special purpose operating system, such as those used for limited purpose appliance-type devices (e.g., media players). The operating system, other computer code and data may reside within a memory block  358  that can be operatively coupled to the processor  56 . Memory block  358  can generally provide a place to store computer code and data that can be used by the electronic device  350 . By way of example, the memory block  58  may include Read-Only Memory (ROM), Random-Access Memory (RAM), hard disk drive, flash memory and/or the like. 
     The electronic device  350  can also include a display  368  that can be operatively coupled to the processor  356 . The display  368  can be generally configured to display a graphical user interface (GUI) that can provide an easy to use interface between a user of the electronic device  350  and the operating system or application running thereon. The display  368  may for example be a liquid crystal display (LCD). 
     The electronic device  350  can also include one or more touch sensing devices  380  that can utilize the mutual capacitive sensing technology described herein. The one or more touch sensing devices can be operatively coupled to the processor  356 . The touch sensing devices  380  can be configured to transfer data from the outside world into the electronic device  350 . The touch sensing device  380  may for example be used to perform movements such as scrolling and to make selections with respect to the GUI on the display  368 . The touch sensing device  380  may also be used to issue commands in the electronic device  350 . The touch sensing devices may be selected from fixed and/or movable touch pads, touch screens and/or touch sensitive housings. 
     The touch sensing device  380  can recognize touches, as well as the position and magnitude of touches on a touch sensitive surface. The touch sensing device  380  can report the touches to the processor  356  and the processor  356  can interpret the touches in accordance with its programming. For example, the processor  356  may initiate a task in accordance with a particular touch. Alternatively, a dedicated processor can be used to process touches locally at the touch sensing device and reduce demand for the main processor of the electronic device. 
     In one particular embodiment, the electronic devices described above can correspond to hand-held electronic devices with small form factors. As used herein, the term “hand held” means that the electronic device can typically be operated while being held in a hand and thus the device can be sized and dimensioned for such use. Examples of hand held devices can include PDAs, mobile (or cellular) telephones, media players (e.g., music players, video players, and game players), cameras, GPS receivers, remote controls, and the like. 
     As should be appreciated, the touch sensing device can reduce the number of input devices needed to support the device and in many cases completely eliminate input devices other than the touch sensing devices. The device can therefore be more aesthetically pleasing (e.g., planar smooth surfaces with limited to no breaks gaps or lines), and in many cases can be made smaller without sacrificing screen size and input functionality, which can be very beneficial for hand held electronic device especially those hand held electronic device that can be operated using one hand (some hand held electronic device may require two handed operation while others may not). 
     The touch sensing devices of the various embodiments can be a perfect fit for small form factor devices such as hand held devices, which can have limited space available for input interfaces, and which can require adaptable placement of input interfaces to permit operation while being carried around. This can be especially true when you consider that the functionality of handheld devices has begun to merge into a single hand held device. At some point, there may not be enough real estate on the device for housing all the necessary buttons and switches without decreasing the size of the display or increasing the size of the device, both of which can leave a negative impression on the user. In fact, increasing the size of the device may lead to devices, which can no longer be considered “hand-held.” 
     In one particular implementation, the hand held device can be a music player and the touch sensing device can be configured to generate control signals associated with a music player. For example, the touch sensing device may include list scrolling functionality, volume control functionality and button functionality including, Select, Play/Pause, Next, Previous and Menu. In another particular implementation, the hand held device can be a mobile telephone and the touch sensing device can be configured to generate control signals associated with the mobile telephone. For example, the touch sensing device may include call list scrolling functionality, volume control functionality, call button functionality including alphanumeric inputs, Select, Menu, Talk, End, Speaker, and Redial. 
     The touch sensing devices of the various embodiments can also be a perfect fit for small form factor device such as portable devices. In one particular implementation, the portable device can be a personal computer and the touch sensing device can be configured to generate control signals associated with the personal computer. For example, the touch sensing device may include scrolling, selecting, and moving functionality. 
       FIG. 28  illustrates an exemplary digital media player according to various embodiments. The term “media player” generally refers to computing devices that can be dedicated to processing media such as audio, video or other images, as for example, music players, game players, video players, video recorders, cameras and the like. These devices can be generally portable so as to allow a user to listen to music, play games or video, record video or take pictures wherever the user travels. In one embodiment, the media player can be a handheld device that can be sized for placement into a pocket of the user. By the handheld device being pocket sized, the user may not have to directly carry the device and therefore the device can be taken almost anywhere the user travels (e.g., the user may not be limited by carrying a large, bulky and often heavy device, as in a portable computer). 
     Media players can generally have connection capabilities that can allow a user to upload and download data to and from a host device such as a general purpose computer (e.g., desktop computer, portable computer). For example, in the case of a camera, photo images may be downloaded to the general purpose computer for further processing (e.g., printing). With regards to music players, songs and play lists stored on the general purpose computer may be downloaded into the music player. In the illustrated embodiment, the media player  400  can be a pocket sized hand held MP3 music player that can allow a user to store a large collection of music. By way of example, the MP3 music player may correspond to any of those iPod™ music players manufactured by Apple Computer of Cupertino, Calif. (e.g., standard, mini, iShuffle™, Nano™, etc.). 
     As shown in  FIG. 28 , the media player  400  can include a housing  402  that can enclose internally various electrical components (including integrated circuit chips and other circuitry) to provide computing operations for the media player  400 . The integrated circuit chips and other circuitry may include a microprocessor, memory (e.g., ROM, RAM), a power supply (e.g., battery), a circuit board, a hard drive, and various input/output (I/O) support circuitry. In the case of music players, the electrical components may include components for outputting music such as an amplifier and a digital signal processor (DSP). In the case of video recorders or cameras the electrical components may include components for capturing images such as image sensors (e.g., charge coupled device (CCD) or complimentary oxide semiconductor (CMOS)) or optics (e.g., lenses, splitters, filters). In addition to the above, the housing may also define the shape or form of the media player. That is, the contour of the housing  402  may embody the outward physical appearance of the media player  400 . 
     The media player  400  can also include a display screen  404 . The display screen  404  can be used to display a graphical user interface as well as other information to the user (e.g., text, objects, or graphics). By way of example, the display screen  404  may be a liquid crystal display (LCD). As shown, the display screen  404  can be visible to a user of the media player  400  through an opening  405  in the housing  402 , and through a transparent wall  406  that can be disposed in front of the opening  405 . Although transparent, the transparent wall  406  may be considered part of the housing  402  since it can help to define the shape or form of the media player  400 . 
     The media player  400  can also include a touch pad  410 . The touch pad  410  can be configured to provide one or more control functions for controlling various applications associated with the media player  400 . For example, the touch initiated control function may be used to move an object or perform an action on the display screen  404  or to make selections or issue commands associated with operating the media player  400 . In most cases, the touch pad  410  can be arranged to receive input from a finger moving across the surface of the touch pad  110  in order to implement the touch initiated control function. 
     The manner in which the touch pad  410  receives input may be widely varied. In one embodiment, the touch pad  410  can be configured to receive input from a linear finger motion. In another embodiment, the touch pad  410  can be configured to receive input from a rotary or swirling finger motion. In yet another embodiment, the touch pad  410  can be configured to receive input from a radial finger motion. Additionally or alternatively, the touch pad  410  may be arranged to receive input from a finger tapping on the touch pad  410 . By way of example, the tapping finger may initiate a control function for playing a song, opening a menu and the like. 
     In one embodiment, the control function can correspond to a scrolling feature. For example, in the case of an MP3 player, the moving finger may initiate a control function for scrolling through a song menu displayed on the display screen  404 . The term “scrolling” as used herein can generally pertain to moving displayed data or images (e.g., text or graphics) across a viewing area on a display screen  404  so that a new set of data (e.g., line of text or graphics) can be brought into view in the viewing area. In most cases, once the viewing area is full, each new set of data can appear at the edge of the viewing area and all other sets of data can move over one position. That is, the new set of data can appear for each set of data that moves out of the viewing area. In essence, the scrolling function can allow a user to view consecutive sets of data currently outside of the viewing area. The viewing area may be the entire viewing area of the display screen  404  or it may only be a portion of the display screen  404  (e.g., a window frame). 
     The direction of scrolling may be widely varied. For example, scrolling may be implemented vertically (up or down) or horizontally (left or right). In the case of vertical scrolling, when a user scrolls down, each new set of data can appear at the bottom of the viewing area and all other sets of data can move up one position. If the viewing area is full, the top set of data can move out of the viewing area. Similarly, when a user scrolls up, each new set of data can appear at the top of the viewing area and all other sets of data can move down one position. If the viewing area is full, the bottom set of data can move out of the viewing area. In one implementation, the scrolling feature may be used to move a Graphical User Interface (GUI) vertically (up and down), or horizontally (left and right) in order to bring more data into view on a display screen. By way of example, in the case of an MP3 player, the scrolling feature may be used to help browse through songs stored in the MP3 player. The direction that the finger moves may be arranged to control the direction of scrolling. For example, the touch pad may be arranged to move the GUI vertically up when the finger is moved in a first direction and vertically down when the finger is moved in a second direction 
     To elaborate, the display screen  404 , during operation, may display a list of media items (e.g., songs). A user of the media player  400  may be able to linearly scroll through the list of media items by moving his or her finger across the touch pad  410 . As the finger moves around the touch pad  410 , the displayed items from the list of media items can be varied such that the user may be able to effectively scroll through the list of media items. However, since the list of media items can be rather lengthy, the various embodiments can provide the ability for the user to rapidly traverse (or scroll) through the list of media items. In effect, the user may be able to accelerate traversal of the list of media items by moving his or her finger at greater speeds. 
     In one embodiment, the media player  400  via the touch pad  410  can be configured to transform a swirling or whirling motion of a finger into translational or linear motion, as in scrolling, on the display screen  404 . In this embodiment, the touch pad  410  can be configured to determine the angular location, direction, speed and acceleration of the finger when the finger is moved across the top planar surface of the touch pad  410  in a rotating manner, and to transform this information into signals that can initiate linear scrolling on the display screen  404 . In another embodiment, the media player  400  via the touch pad  410  can be configured to transform radial motion of a finger into translational or linear motion, as in scrolling, on the display screen  404 . In this embodiment, the touch pad  410  can be configured to determine the radial location, direction, speed and acceleration of the finger when the finger is moved across the top planar surface of the touch pad  410  in a radial manner, and to transform this information into signals that can initiate linear scrolling on the display screen  404 . In another embodiment, the media player  400  via the touch pad  410  can be configured to transform both angular and radial motion of a finger into translational or linear motion, as in scrolling, on the display screen  404 . 
     The touch pad can generally include a touchable outer surface  411  for receiving a finger for manipulation on the touch pad  410 . Although not shown in  FIG. 28 , beneath the touchable outer surface  411  can be a sensor arrangement. The sensor arrangement can include multiple sensors that can be configured to activate as the finger performs an action over them. In the simplest case, an electrical signal can be produced each time the finger passes a sensor. The number of produced signals in a given time frame may indicate location, direction, speed and acceleration of the finger on the touch pad, i.e., the more signals, the more the user moved his or her finger. In most cases, the signals can be monitored by an electronic interface that can convert the number, combination and frequency of the signals into location, direction, speed, and acceleration information. This information may then be used by the media player  400  to perform the desired control function on the display screen  404 . By way of example, the sensor arrangement may correspond to any of those described herein. 
     The position of the touch pad  410  relative to the housing  402  may be widely varied. For example, the touch pad  410  may be placed at any external surface (e.g., top, side, front, or back) of the housing  402  that can be accessible to a user during manipulation of the media player  400 . In most cases, the touch sensitive surface  411  of the touch pad  410  can be completely exposed to the user. In the illustrated embodiment, the touch pad  410  can be located in a lower, front area of the housing  402 . Furthermore, the touch pad  410  may be recessed below, level with, or extend above the surface of the housing  402 . In the illustrated embodiment, the touch sensitive surface  411  of the touch pad  410  can be substantially flush with the external surface of the housing  402 . 
     The shape of the touch pad  410  may also be widely varied. For example, the touch pad  410  may be circular, rectangular, triangular, and the like. In general, the outer perimeter of the shaped touch pad can define the working boundary of the touch pad. In the illustrated embodiment, the touch pad  410  can be circular. Circular touch pads can allow a user to continuously swirl a finger in a free manner, i.e., the finger can be rotated through 360 degrees of rotation without stopping. Furthermore, the user can rotate his or her finger tangentially from all sides thus giving it more range of finger positions. For example, when the media player is being held, a left handed user may choose to use one portion of the touch pad  410  while a right handed user may choose to use another portion of the touch pad  410 . More particularly, the touch pad can be annular, i.e., shaped like or forming a ring. When annular, the inner and outer perimeter of the shaped touch pad can define the working boundary of the touch pad. 
     In addition to above, the media player  400  may also include one or more buttons  412 . The buttons  412  can be configured to provide one or more dedicated control functions for making selections or issuing commands associated with operating the media player  400 . By way of example, in the case of an MP3 music player, the button functions may be associated with opening a menu, playing a song, fast forwarding a song, seeking through a menu and the like. The button functions can be implemented via a mechanical clicking action or alternatively via a sensor arrangement such as those described herein. The position of the buttons  412  relative to the touch pad  410  may be widely varied. For example, they may be adjacent one another or spaced apart. In the illustrated embodiment, the buttons  412  can be separated from the touch pad  410  (see for example  FIG. 14 ). As shown, there can be four buttons  412 A in a side by side relationship above the touch pad  410  and one button  412 B disposed in the center or middle of the touch pad  410 . By way of example, multiple buttons  412  may include a menu button, play/stop button, forward seek button and a reverse seek button, select button (enter) and the like. Alternatively or additionally, the buttons may be implemented with a movable touch pad. 
     Moreover, the media player  400  may also include a hold switch  414 , a headphone jack  416  and a data port  418 . The hold switch  414  can be configured to turn the input devices of the media device  400  on and off. The headphone jack  416  can be capable of receiving a headphone connector associated with headphones configured for listening to sound being outputted by the media device  400 . The data port  418  can be capable of receiving a data connector/cable assembly configured for transmitting and receiving data to and from a host device such as a general purpose computer. By way of example, the data port  418  may be used to upload or down load songs to and from the media device  400 . The data port  418  may be widely varied. For example, the data port may be a PS/2 port, a serial port, a parallel port, a USB port, a Firewire port and the like. In some cases, the data port  118  may be a radio frequency (RF) link or optical infrared (IR) link to eliminate the need for a cable. Although not shown in  FIG. 28 , the media player  400  may also include a power port that receives a power connector/cable assembly configured for delivering powering to the media player  400 . In some cases, the data port  418  may serve as both a data and power port. 
       FIG. 29  illustrates an exemplary mobile telephone  500  that can include touch sensor panel  524 , display  536 ; and other computing system blocks according to various embodiments. 
       FIG. 30  illustrates an exemplary personal computer  600  that can include touch sensor panel (trackpad)  624 , display  636 , and other computing system blocks according to various embodiments. 
     The digital media player, mobile telephone, and personal computer of  FIGS. 28 through 30  can realize space savings, power savings, improved performance, and more robustness according to various embodiments. 
     In any of the embodiments described or contemplated herein, the touch sensing devices may be configured to provide visual information to indicate when and where the touches occur, to invoke a touch (location where a user should touch), or as otherwise programmed. In the case of a touch screen, the visual information may be provided by the graphical display positioned behind the touch screen. In the case of the touch sensitive housing, or touch pad (or possibly with the touch screen), this may be accomplished with a visual feedback system that is capable of adjusting the visual stimuli of the touch surface. 
     The visual feedback system may include visual surface changing elements, which can be separate or integral with the sensing elements. In fact, the visual surface changing elements may be mapped to the sensor coordinates such that particular visual surface changing elements are tied to particular sensor coordinates. By way of example, the visual surface changing elements may be light devices such as light emitting diodes that illuminate the touch surface. For example, the light devices may be positioned in an array or matrix similarly to the sensing devices. Alternatively, the visual surface changing elements may be embodied as electronic inks or other color changing surfaces. 
     If used, this visual feedback feature can allow the display of pop-up buttons, characters, and indicators around the touch surface, which can disappear when not in use or required, or glowing special effects that can trace or outline a user&#39;s fingers in contact with the touch surface, or otherwise provide visual feedback for the users of the device. In one implementation, the handheld device can be configured to sense one or more touches and provide visual feedback in the area of the touches. In another implementation, the handheld device can be configured to provide visual feedback on the touch surface, detect a touch in the area of the visual feedback, and perform an action that can be associated with the visual feedback. An example of such an arrangement can be found in U.S. application Ser. No. 11/394,493, which is herein incorporated by reference. 
     Although embodiments have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the various embodiments as defined by the appended claims.