Patent Publication Number: US-10775929-B2

Title: Suppressing noise in touch panels using a shield layer

Description:
RELATED APPLICATIONS 
     This application is a Continuation of U.S. patent application Ser. No. 16/122,014, filed on Sep. 5, 2018, which claims the benefit of U.S. Provisional Application No. 62/557,472, filed Sep. 12, 2017, which are hereby incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to sensing systems, and more particularly to capacitance measurement systems configurable to suppress noise in touch panels using shield layers. 
     BACKGROUND 
     Capacitance sensing systems can sense electrical signals generated on electrodes that reflect changes in capacitance. Such changes in capacitance can indicate a touch event (i.e., the proximity of an object to particular electrodes). Capacitive sense elements may be used to replace mechanical buttons, knobs, and other similar mechanical user interface controls. The use of a capacitive sense element allows for the elimination of complicated mechanical switches and buttons, providing reliable operation under harsh conditions. In addition, capacitive sense elements are widely used in modern consumer applications, providing user interface options in existing products. Capacitive sense elements can range from a single button to a large number arranged in the form of a capacitive sense array for a touch-sensing surface of a touch panel. 
     Capacitive sense arrays and touch buttons are ubiquitous in today&#39;s industrial and consumer markets. They can be found on cellular phones, GPS devices, set-top boxes, cameras, computer screens, MP3 players, digital tablets, and the like. The capacitive sense arrays work by measuring the capacitance of a capacitive sense element and evaluating for a delta in capacitance indicating a touch or presence of a touch object. When a touch object (e.g., a finger, hand, or other conductive object) comes into contact or close proximity with a capacitive sense element, the capacitance changes and the conductive object is detected. The capacitance changes can be measured by an electrical circuit. The electrical circuit converts the signals corresponding to measured capacitances of the capacitive sense elements into digital values. The measured capacitances are generally received as currents or voltages that are integrated and converted to the digital values. 
     There are two typical types of capacitance: 1) mutual capacitance where the capacitance-sensing circuit measures a capacitance formed between two electrodes coupled to the capacitance-sensing circuit; 2) self-capacitance where the capacitance-sensing circuit measure a capacitance of one electrode. A touch panel may have a distributed load of capacitance of both types (1) and (2) and some touch solutions sense both capacitances either uniquely or in hybrid form with its various sense modes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present embodiments are illustrated by way of example, and not of limitation, in the figures of the accompanying drawings. 
         FIG. 1  is a block diagram illustrating a touch panel stack up, in accordance with aspects of the disclosure. 
         FIG. 2  is a block diagram illustrating system to suppress noise of a touch panel, in accordance with aspects of the disclosure. 
         FIG. 3  is a block diagram illustrating a system to suppress noise of a touch panel and includes a circuit model of the touch panel stack-up, in accordance with aspects of the disclosure. 
         FIG. 4  is a block diagram illustrating a system to suppress noise of a touch panel with an alternative circuit implementation, in accordance with aspects of the disclosure. 
         FIG. 5  is a block diagram illustrating a system to suppress noise of a touch panel including a filter, in accordance with aspects of the disclosure. 
         FIG. 6  is a block diagram illustrating the path of the noise signal in a system to suppress noise of a touch panel, in accordance with aspects of the disclosure. 
         FIG. 7  is a block diagram illustrating a system to suppress noise of a touch panel with a filter in an alternative circuit implementation, in accordance with aspects of the disclosure 
         FIG. 8  is a block diagram illustrating a system to suppress noise of a touch panel with an alternative hardware circuit implementation, in accordance with aspects of the disclosure. 
         FIG. 9  is a block diagram illustrating a system to suppress noise of a touch panel with another alternative circuit implementation, in accordance with aspects of the disclosure. 
         FIG. 10  is a block diagram illustrating a system to suppress noise of a touch panel with an alternative circuit implementation, in accordance with aspects of the disclosure. 
         FIG. 11  is a flow diagram illustrating method for suppressing a noise signal from a touch panel, in accordance with aspects of the disclosure. 
         FIG. 12  is a flow diagram illustrating method for determining an attenuation coefficient used to generate the estimated noise signal, in accordance with aspects of the disclosure. 
         FIG. 13  is a block diagram illustrating an electronic system that processes touch data, in accordance with aspects of the disclosure. 
         FIG. 14  illustrates an embodiment of a core architecture of the Programmable System-on-Chip (PSoC®) processing device, in accordance with aspects of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present embodiments. It will be evident, however, to one skilled in the art that the present embodiments may be practiced without these specific details. In other instances, well-known circuits, structures, and techniques are not shown in detail, but rather in a block diagram in order to avoid unnecessarily obscuring an understanding of this description. 
     Reference in the description to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The phrase “in one embodiment” located in various places in this description does not necessarily refer to the same embodiment. 
     In some touch sensing systems, such as capacitive touch sensing systems, a noise source of a touch panel may generate noise signals that interfere with the detection of a touch object proximate the touch panel. For example, an electrode layer (also referred to as a “sense array” herein) may be disposed above a display device, such as a liquid crystal display of a touch panel. A noise signal from the operation of the display device may couple to the electrode layer via parasitic capacitive coupling. The coupled noise signal may interfere with the measuring signal (e.g., a transmission (Tx) signal) at the electrode layer used to detect a touch object proximate the electrode layer. 
     In some touch sensing systems, a shield layer disposed between the electrode layer and display device is used to help shield the electrode layer from the noise signal generated by the display device. The shield layer may be coupled to a ground potential. However, the shield layer has sheet resistance that creates a voltage potential in the presence of the noise signal. Thus, the noise signal is coupled to the electrode layer via parasitic capacitive coupling between the electrode layer and shield layer, which obscures with the measuring signal used to detect a touch object. 
     Some touch sensing systems, may use a first electrode of the electrode layer to sample the noise signal. After sampling the noise signal, a second different electrode (or same electrode) may be used to subsequently measure a touch using a measuring signal. The sampled noise signal from the first electrode may be used to reduce the noise from the measuring signal measured at the second electrode. However such systems may suffer from linearity and accuracy degradation. Such systems may be highly sensitive to a touch by a touch object. Sampling and measuring may be performed sequentially for systems that are highly sensitive to a touch. For example, if the above system concurrently measures the first electrode for the noise signal and the second electrode for the measuring signal, the first electrode samples a large amount of the measuring signal and the touch data associated therein. Using the signal from the first electrode, which includes a large amount of the measuring signal, to reduce the noise of the measuring signal of the second electrode eliminates a large portion of the usable data (e.g., touch data) from the measuring signal leading to inaccurate touch measurements. 
     Aspects of the disclosure address the above and other challenges by measuring, at a first channel of a processing device, a first signal indicative of a touch object proximate to an electrode layer. A channel may refer to hardware, firmware, software, or combination thereof use to receive, manipulate, or measure a received signal. The first channel is coupled to the electrode layer. The first signal includes a touch data component and a first noise component generated by a noise source. The second channel of the processing device measures a second signal including a second noise component generated by the noise source. The second channel is coupled to a shield layer disposed between the noise source and the electrode layer. An estimated noise signal is generated using the second noise component of the second signal that is associated with the second channel. The estimated noise signal is an estimation of the first noise component of the first signal. The estimated noise signal is subtracted from the measured first signal to obtain the touch data component of the first signal. In an embodiment, measuring the first signal at the first channel is performed concurrently with the measuring of the second signal. 
     The noise signal sampled at the shield layer includes a negligible amount of the measuring signal because the shield layer is further away from the touch object, is partially shielded by the above electrode layer. The measuring signal that is injected from the electrode layer to the shield layer may be significantly attenuated (e.g., by an order of magnitude). This reduces the amount of the measuring signal (and touch data component therein) that is coupled to the shield layer and sampled a the second channel. The signal obtained from the shield layer can be used to reduce the noise from the measuring signal without significantly impacting the usable touch data of the measuring signal. 
     Aspects of the disclosure may be applied to self-capacitance measuring techniques or mutual capacitance measuring techniques. 
       FIG. 1  is a block diagram illustrating a touch panel stack up, in accordance with aspects of the disclosure. System  100  shows a touch panel stack-up  101  that illustrates various layers that are included in a touch panel. A touch panel may display images and video to users and be included in various electronic devices, such as mobile devices or front panel displays. A touch panel may also be used in conjunction with processing device  116  to detect a touch (also referred to as a “touch event”) by a touch object  102  (e.g., a human finger or other touch object) proximate to the touch panel. For example, a touch by touch object  102  in physical contact with overlay may be detected. In another example, a touch by touch object some distance above overlay  104  (e.g., hovering approximately 35 millimeters (mm) above overlay  104 ) may also be detected. It can be noted that a touch object proximate the touch panel may be detected at distances greater than 35 mm using aspects of the present disclosure. 
     In an embodiment, the touch panel stack-up  101  may include one or more of an overlay  104 , an electrode layer  106 , a shield layer  108  or a noise source  112 . As illustrated, each of the aforementioned layers may be disposed above the subsequently mentioned layer(s). For example, the overlay  104  is disposed above electrode layer  106 , shield layer  108 , and noise source  112 . In another example, shield layer  108  may be disposed between the electrode layer  106  and noise source  112 . 
     In an embodiment, overlay  104  may be a transparent or semi-transparent material that is disposed above the electrode layer  106 . The overlay  104  may provide protection or other functionality, such as filtering, to the underlying layers. 
     In an embodiment, the electrode layer  106  (also referred to as a “sense array” herein) includes one or more electrodes. In an embodiment, the electrode layer  106  may be a capacitive sense array. For purposes of illustration, rather than limitation, touch panel stack-up  101  is illustrated with a single electrode (i.e., a receiving (Rx) electrode). If can be appreciated that the electrode layer  106  may include many electrodes, such as multiple transmission (Tx) electrodes and multiple Rx electrodes. The electrode layer  106  can be used to sense touch object  102  proximate to the electrode layer  106 . For example, in mutual capacitance mode a Tx signal may be generated and coupled to a Tx electrode. From the Tx electrode the Tx signal may be capacitively coupled to a respective Rx electrode. A change in the capacitance between the Tx electrode and respective Rx electrode is measured (e.g., the measuring signal) at the Rx electrode of electrode layer  106  in the presence of a touch object  102 . The measuring signal may include a touch data component indicative of a touch object  102  proximate to the Rx electrode of electrode layer  106 . In mutual capacitance mode, the measuring signal may be an induced current at the Rx electrode caused by the Tx signal from the respective Tx electrode. In another example, in self-capacitance mode an Rx electrode can be excited using an excitation signal (e.g., by varying the ground potential). A touch object proximate the Rx electrode can capacitively couple with the respective Rx electrode and change the capacitance sensed at the Rx electrode. A change in the capacitance at the Rx electrode (e.g., from having no touch object proximate the Rx electrode to having a touch object proximate the Rx electrode) can be measured using the measuring signal. The measuring signal may include a touch data component indicated of a touch object  102  proximate to the Rx electrode of the electrode layer. In self-capacitace mode, the measuring signal may be an induced signal at the Rx electrode caused by the excitation signal. 
     In embodiments, the electrode layer  106  may be a transparent or semi-transparent conductive material, such as indium tin oxide (ITO). Electrode layer  106  (i.e., sense array) and touch detection is further described with respect to  FIG. 11 . 
     In an embodiment, the shield layer  108  may be used to help shield electrode layer  106  from parasitic noise signals. For example, noise from noise source  112  may be injected into the electrode layer  106  via parasitic capacitive coupling. The noise that is injected into the electrode layer  106  by noise source  112  may be combined with a measuring signal that includes touch data and decrease the accuracy of touch detection. A shield layer  108  may be used to help de-couple one or more noise sources, such as noise source  112 , from the electrode layer  106  and increase the accuracy of a measuring signal. In the current example, shield layer  108  is coupled to system ground  114 , which may refer to the ground potential of the device in which the touch panel stack-up  101  is implemented. For example, in a mobile device the system ground  114  may be battery of the mobile device. In embodiments, the shield layer  108  may be a transparent or semi-transparent conductive material. The material of the shield layer may be a similar material as described with respect to electrode layer  106 . For example, the shield layer may include indium tin oxide (ITO). In an embodiment, the shield layer  108  is a contiguous, planar, and conductive material. 
     In an embodiment, the noise source  112  is disposed below the shield layer  108 . In an embodiment, the noise source  112  may generate a noise signal, as illustrated by noise signal  126 . The noise signal  126  generated by noise source  112  may be injected into the shield layer  108  and the electrode layer  106  via parasitic coupling. For example, a first noise component of noise signal  126  may be injected into the electrode layer  106  (e.g., the Rx electrode) and a second noise component of the noise signal  126  may be injected into the shield layer  108 . The noise signal  126  may include both the first noise component and the second noise component. The first and second noise components may be proportional to one another. The property of proportionality of the first and second noise components of the noise signal  126  may be used to help cancel the first noise component received at the Rx electrode, as illustrated below and in aspects of the disclosure. 
     In an embodiment, a measuring signal is measured by an Rx channel, such as channel  124 A. The injected noise signal  126  may become a part of the measuring signal, e.g., noise component of the measuring signal. The measuring signal may also include a touch data component (e.g., a voltage or current indicating a change in capacitance), which may be obscured by the noise signal and lead to decreased accuracy in touch detection. 
     In some embodiments, the noise source  112  may include a display device, such as a liquid crystal display (LCD). In other embodiments, the display device may be a different type of display, such as an organic light emitting diode (OLED) display or other type of display device. 
     In an embodiment, the electrode layer  106  is coupled to processing device  116 . Processing device  116  may measure signal changes, such as capacitance changes, of electrode layer  106  and produce digital outputs (also referred to as “counts” or “digital counts” herein) indicative of a touch proximate to a touch panel. In an embodiment, each Rx electrode may be coupled to a separate channel  124 A- 124 N of processing device  116 . It can be noted that in other embodiments, a channel may be coupled to more than one Rx electrode at a single instance in time. In still other embodiments, a channel may couple to multiple Rx electrodes but only to one Rx electrode at a particular time (e.g., via a multiplexer). 
     In an embodiment, a channel, such as channel  124 A, may include hardware or firmware to measure a signal, such as a measuring signal, received from the respective Rx electrode of electrode layer  106 . For example, the measuring signal may be received by a buffer  118 . The buffer may buffer or amplify the received measuring signal. In an embodiment, the buffer  118  may be a unity-gain buffer. In other embodiments, the buffer  118  may have some amount of gain. In an embodiment, the positive terminal of buffer  118  may be connected to the output of buffer  118 . The negative terminal of buffer  118  may be coupled to a reference voltage. In other embodiments, a buffer with different configurations may be implemented. 
     In an embodiment, the buffered measuring signal at the output of buffer  118  may be integrated by integrator  120 . Integrator  120  may integrate the buffered measuring signal to combine the buffered measuring signal to produce a raw measuring signal. In an embodiment, the integrated measuring signal is an analog voltage or current. In one embodiment, the measuring signal may include a current (e.g., charge) that is integrated (e.g., accumulate the charge) on a capacitor. The integrated current can be detected as a voltage change. In embodiments, integrator  120  may be a hardware circuit, firmware, or a combination thereof. In some embodiments, a particular channel  124 A- 124 N may include the same, different, more, or fewer components in different or the same configuration as illustrated in  FIG. 1 . It can be noted that the components illustrated with respect to channel  124 A are provided for purposes of illustration, rather than limitation. 
       FIG. 2  is a block diagram illustrating system  200  to suppress noise of a touch panel, in accordance with aspects of the disclosure. Components of  FIG. 1  are used to help describe aspects of  FIG. 2 .  FIG. 2  shows the touch panel stack-up  101  as illustrated in  FIG. 1 . Channel  224 A and the components therein may be similar to channel  124 A of  FIG. 1 . Buffer  218 A and  218 B may be similar to buffer  118  of  FIG. 1 . Integrator  220 A and  220 B may be similar to integrator  120  of  FIG. 1 . 
     As shown in  FIG. 2 , Rx electrode of electrode layer  106  is coupled to channel  224 A and shield layer  108  is coupled to channel  224 B. Both channels  224 A and  224 B are part of processing device  116 . In an embodiment, channel  224 A and channel  224 B (generally referred to as “channel(s)  224 ” herein) are physically separate channels (e.g., coupled to two distinct output pins of processing device  116 ). Each channel  224  may include its own hardware. In an embodiment, different channels may be coupled to single pin of the processing device  116  at different instances in time using for example, a switch or multiplexer. For example, the shield layer  108  can be coupled to channel  224 B during times when reducing the touch panel noise from the measuring signal is determined to be important. At other times, channel  224 B can be coupled to an Rx electrode of the electrode layer  106  to measure a respective measuring signal. 
     The output of integrator  220 B of the channel  224 B is coupled to the input of attenuator  230 . The output of attenuator  230  is coupled to a subtraction module  228  capable of subtracting one signal from another signal. In embodiments, attenuator  230  may include an attenuator circuit, firmware, or a combination thereof In embodiments, subtraction module  228 , may include circuitry, firmware, or a combination thereof In an embodiment, attenuator  230  or subtraction module  228  is part of a channel  224 A or  224 B. In other embodiments, attenuator  230  or subtraction module  228  may be outside channels  224 . 
     Noise signal  126  is coupled to both the shield layer  108  and the Rx electrode of the electrode layer  106 . The coupled noise signal  126  is illustrated having a first noise component  232 A coupled to the Rx electrode of electrode layer  106  and a second noise component  232 B coupled to the shield layer  108 . First noise component  232 A is coupled to channel  224 A and second noise component  232 B is coupled to  224 B. 
     In an embodiment, a measuring signal  234  is received at channel  224 A. The measuring signal  234  may be indicative of a touch by touch object  102  proximate to the electrode layer  106 . The measuring signal  234  may include a touch data component indicative of a touch proximate to the electrode layer  106  and a first noise component  232 A. For example, in a mutual capacitance implementation a Tx transmission signal may be transmitted to a Tx electrode. The presence of touch object  102  changes the capacitance between the Tx electrode and the respective Rx electrode of electrode layer  106 . The information of the change in capacitance is included in the touch data component of the measuring signal  234 . The noise component  232 A injected by the noise source  112  is also coupled to the Rx electrode of the electrode layer  106  and included in the measuring signal  234 . 
     In an embodiment, a shield signal  236  is received at channel  224 B. The shield signal  236  can include the second noise component  232 B. 
     In an embodiment, the measuring signal  234  is measured at channel  224 A of processing device  116 . In an embodiment, the measuring can include buffering the measuring signal  234  at buffer  218 A and integrating the buffered measuring signal at integrator  220 A, as further described with respect to  FIG. 1 . 
     In an embodiment, the shield signal  236  that includes the second noise component  232 B is measured at channel  224 B of processing device  116 . In an embodiment, the measuring can include buffering the shield signal  236  at buffer  218 B and integrating the buffered shield signal at integrator  220 B. 
     In an embodiment, processing device  116  may generate an estimated noise signal using the second noise component  232 B of the shield signal  236 . The estimated noise signal may be an estimation of the first noise component  232 A of the measuring signal  234  received at channel  224 A. In an embodiment, generating the estimated noise signal using the second noise component  232 B of the shield signal  236  includes multiplying the shield signal  236  (e.g., the integrated shield signal) at an attenuator  230  by an attenuation coefficient (K). It can be noted that an attenuation coefficient may be any real number. Attenuation may include reducing a signal, amplifying a signal, or buffering a signal (e.g., attenuation coefficient of 1). 
     In an embodiment, the estimated noise signal may be subtracted from the measuring signal  234  (e.g., the integrated measuring signal) by subtraction module  228 . 
     For example, the second noise component  232 B may be proportional to the first noise component  232 A of the noise signal  126 . As such, the shield signal  236  (e.g., integrated shield signal) that includes the second noise component  232 B may be attenuated (or amplified) by an attenuation coefficient (K) to generate an estimated noise signal. The estimated noise signal may be attenuated so that the estimated noise signal may be similar in magnitude as the first noise component  232 A of the measuring signal  234  received at channel  224 A. The estimated noise signal can be subtracted from the measuring signal  234  to remove or reduce the first noise component  232 A of the measuring signal  234 . The remaining touch data component of the measuring signal  234  can be used to detect a touch proximate to the electrode layer  106 . The above operations can be performed in the presence of a touch object proximate the touch panel or with no touch object present. 
       FIG. 3  is a block diagram illustrating a system  300  to suppress noise of a touch panel and includes a circuit model of the touch panel stack-up, in accordance with aspects of the disclosure. Components of  FIGS. 1 and 2  are used to help describe aspects of  FIG. 3 .  FIG. 3  illustrates a circuit model of touch panel stack-up  101 . Rx electrode of electrode layer  106  is represented by multiple resistors (R rx ) coupled in series to channel  224 A of processing device  116 . The shield layer  108  is represented by multiple resistors (R s ) coupled in series to channel  224 B of processing device  116 . Coupling capacitors  336  (C s2n ) represent the parasitic capacitive coupling between the shield layer  108  and the noise source  112 . Coupling capacitors  334  (C rx2s ) represent the parasitic capacitive coupling between the Rx electrode of the electrode layer  106  and the shield layer  108 . 
       FIG. 4  is a block diagram illustrating a system  400  to suppress noise of a touch panel with an alternative circuit implementation, in accordance with aspects of the disclosure. Components of  FIGS. 1 and 2  are used to help describe aspects of  FIG. 4 . Integrator  420 A and  420 B may be similar to integrator  120  of  FIG. 1 . 
     Channel  424 A and channel  424 B may each include integrator  420 A and integrator  420 B, respectively. Integrator  420 A and  420 B may be similar to integrator  120  of  FIG. 1 . Channel  424 A and channel  424 B (generally referred to as “channel(s)  424 ” herein) may each include an analog-to-digital converter (ADC)  438 A and  438 B, respectively (generally referred to as “ADC(s)  438 ” herein). The ADC  438  may convert an analog signal into an equivalent digital signal. For example, measuring signal  234  at channel  224 A may be integrated by integrator  420 A. The integrated measuring signal  234  maybe converted from an analog signal to a digital signal by ADC  438 A. Similarly, the shield signal  236  at channel  224 B may be integrated by integrator  420 A. The integrated shield signal  236  may be converted from an analog signal to a digital signal by ADC  438 B. 
     System  400  may provide similar noise suppression as described with respect to the previous figures. In an embodiment, the digital shield signal  236  may be attenuated by attenuator  230 . The attenuated digital shield signal  236  may be subtracted from digital measuring signal  234  using subtraction module  228 . In an embodiment, attenuator  230  or subtraction module  228  is part of a channel  424 A or  424 B. In other embodiments, attenuator  230  or subtraction module  228  may be outside channels  424 . 
       FIG. 5  is a block diagram illustrating a system  500  to suppress noise of a touch panel including a filter, in accordance with aspects of the disclosure. Components of  FIG. 1-4  are used to help describe aspects of  FIG. 5 . It can be noted that any unlabeled components may be similar to their labelled counterparts in previous Figures. 
     In an embodiment, system  500  may implement a filter  540  between the shield layer  108  and the input of buffer  218 B. The filter  540  may be used to create a similar transfer function between the first noise component  232 A of the measuring signal  234  and the second noise component  232 B of the shield signal  236 , as will be further described with respect to  FIG. 6 . 
     In an embodiment, filter  540  may include a capacitor  541  (C f ) coupled in series with channel  224 B and the shield layer  108 . In an embodiment, filter  540  may include a resistor  542  (R f ). Resistor  542  may include a first terminal coupled between the shield layer  108  and channel  224 B. Resistor  542  may include a second terminal coupled to a ground potential, such as system ground  114 . In an embodiment, the filter  540  includes both the capacitor  541  and the resistor  542 . In an embodiment, one or more of capacitor  541  and resistor  542  are implemented as discrete components outside of processing device  116 . In another embodiment, one or more of capacitor  541  and resistor  542  are integrated as on-chip components of processing device  116 . 
     In an embodiment, resistor  544 A (R i ) may be coupled between the Rx electrode of electrode layer  106  and buffer  218 A. In an embodiment, resistor  544 B (R i ) may be coupled between the shield layer  108  and the input of buffer  218 B. In embodiments, one or more resistor  544 A and  544 B (generally referred to as “resistor(s)  544 ”) may be off-chip or on-chip components. Resistors  544  may assist with immunity, such as transient immunity or radio-frequency immunity. 
     It can be noted that one or more channels may have similar immunity resistors. For example, each channel may have a similar immunity resistor coupled between the respective Rx electrode of the electrode layer  106  and the respective channel of processing device  116 . 
       FIG. 6  is a block diagram illustrating the path of the noise signal in a system  600  to suppress noise of a touch panel, in accordance with aspects of the disclosure. Components of  FIG. 1-5  are used to help describe aspects of  FIG. 6 . It can be noted that any unlabeled components may be similar to their labelled counterparts in previous Figures. 
     In  FIG. 6 , the noise signal  126  of noise source  112  is shown propagating through system  600 . Signal waveforms  644 A- 644 E (generally referred to as “signal waveform(s)  644 ” herein) show noise signal  126  or noise components thereof at different nodes (e.g., nodes A-E) in system  600 . It can be noted that the signal waveforms are provided for illustration, rather than limitation. Other signal waveform may be present in different applications. 
     At node A, the noise signal  126  is shown as series of triangular waveforms as illustrated by signal waveform  644 A. Noise signal  126  propagates from node A to node B via a coupling capacitance  336  between the shield layer  108  and noise source  112 . 
     From node A to node B, the noise signal  126  changes shape (e.g., phase change) as illustrated by signal waveform  644 B. The shape change may be caused by coupling capacitance  336  between the shield layer  108  and noise source  112 . From node B, the noise signal  126  propagates to both node C and node D. 
     From node B to node C, the noise signal  126  is slightly attenuated by the resistance of shield layer  108  as shown by signal waveform  644 C. 
     From node B to node D, the noise signal  126  (e.g. first noise component  232 A of the noise signal  126 ) is coupled to the Rx electrode of the electrode layer  106  via a coupling capacitance  334  between the Rx electrode of the electrode layer  106  and the shield layer  108 . From node B to D, the noise signal  126  undergoes another transition (e.g., phase change) as illustrated by signal waveform  644 D. 
     From node C to node E, the inclusion of capacitor  541  shapes the noise signal  126  at node E (e.g., second noise component  232 B of noise signal  126 ) to be similar in shape as the noise signal  126  at node D (as illustrated by signal waveform  644 E and  644 D). The second noise component  232 B noise signal  126  having the shape of signal waveform  644 E can be attenuated by a particular attenuation coefficient at attenuator  230 , and can be subtracted from the first noise component  232 A of noise signal  126  having the shape of signal waveform  644 D. 
       FIG. 7  is a block diagram illustrating a system  700  to suppress noise of a touch panel with a filter in an alternative circuit implementation, in accordance with aspects of the disclosure. Components of  FIG. 1-6  are used to help describe aspects of  FIG. 7 . It can be noted that any unlabeled components may be similar to their labelled counterparts in previous Figures. Components of  FIG. 7  may be similar to components of  FIG. 4 . A filter  740  may be included and be similar to filter  540  of  FIG. 5 . 
       FIG. 8  is a block diagram illustrating a system  700  to suppress noise of a touch panel with an alternative hardware circuit implementation, in accordance with aspects of the disclosure. Components of  FIG. 1-7  are used to help describe aspects of  FIG. 8 . It can be noted that any unlabeled components may be similar to their labelled counterparts in previous Figures. 
     In an embodiment, a compensation circuit  850  can be used to minimize the noise injected into a channel, such as channel  224 A of processing device  116 . In an embodiment, the compensation circuit  850  can sample the first noise component  232 A at the input of buffer  218 A. The compensation circuit  850  may filter the first noise component  232 A using filter  840 , and invert the filtered first noise component  232 A using invertor  852 , and inject the inverted first noise component  232 A into the shield layer  108  using invertor  852 , which may reduce the noise component received at the channel  224 A. 
     In an embodiment, one or more components of compensation circuit  850  are off-chip components outside the processing device  116  (as illustrated). In another embodiment, one or more components of compensation circuit  850  are on-chip components of the processing device  116 . In an embodiment, the compensation circuit  850  includes circuit hardware components. It can be noted that compensation circuit  850  may include the same, more, less, or different components configured in the same or different configuration in some embodiments. 
       FIG. 9  is a block diagram illustrating a system  900  to suppress noise of a touch panel with another alternative circuit implementation, in accordance with aspects of the disclosure. Components of  FIG. 1-8  are used to help describe aspects of  FIG. 9 . It can be noted that any unlabeled components may be similar to their labelled counterparts in previous Figures. System  900  of  FIG. 9  is similar to system  400  and system  700  of  FIG. 4  and  FIG. 7 , respectively. 
     In an embodiment, system implements a compensation circuit  950 . Compensation circuit  950  performs operations similar to compensation circuit  850  of  FIG. 8 . In an embodiment, a compensation circuit  950  can be used to minimize the noise injected into a channel, such as channel  224 A of processing device  116 . In an embodiment, the compensation circuit  950  can sample the first noise component  232 A at the input of buffer  218 A. The compensation circuit  850  may filter the first noise component  232 A using filter  940 , invert the filtered first noise component  232 A using an invertor  952 , and inject the inverted first noise component  232 A into the shield layer  108 , which may reduce the noise signal received at channel  224 A. 
     In an embodiment, one or more components of compensation circuit  950  are off-chip components outside the processing device  116  (as illustrated). In another embodiment, one or more components of compensation circuit  950  are on-chip components of the processing device  116 . It can be noted that compensation circuit  950  may include the same, more, less, or different components configured in the same or different configuration in some embodiments. In embodiments one or more components of compensation circuit may be implemented in hardware, firmware, or a combination thereof 
       FIG. 10  is a block diagram illustrating a system  1000  to suppress noise of a touch panel with an alternative circuit implementation, in accordance with aspects of the disclosure. Components of  FIG. 1-9  are used to help describe aspects of  FIG. 10 . It can be noted that any unlabeled components may be similar to their labelled counterparts in previous Figures. 
     In system  1000 , the noise suppression may be performed at a single channel, such as channel  224 A. For example, the measuring signal  234  having a first noise component  232 A may be provided at a first input of buffer  218 A. The shield signal  236  may be filtered by filter  540  and attenuated by attenuator  1030 . The attenuated shield signal  236  is provided to a second input of buffer  218 A, which may allow the buffer  218 A to effectively filter the first noise component  232 A (e.g., common-mode rejection) from measuring signal  234 . The buffered measuring signal  234  is then integrated at integrator  220 . 
     In an embodiment, attenuator  1030  is a hardware integrator and integrated into channel  224 A of processing device. 
       FIG. 11  is a flow diagram illustrating method  1100  for suppressing a noise signal from a touch panel, in accordance with aspects of the disclosure. Method  1100  may be performed by processing logic that includes hardware (e.g., circuitry, dedicated logic, programmable logic, microcode), software (e.g., instructions run on a processing device to perform hardware simulation), or a combination thereof. In other implementations, noise suppression module  1320  of  FIG. 13  can perform some or all the operations. Components of the preceding Figures may be used to help illustrate method  1100 . It may be noted that the in some implementations, method  1100  may include the same, different, fewer, or greater number of operations performed in any order. 
     At block  1102 , processing logic measures, at channel  224 A of a processing device  116 , a first signal (e.g., measuring signal  234 ) indicative of a touch object proximate to an electrode layer  106 . The first signal includes a touch data component and a first noise component  232 A generated by a noise source  112 . 
     In an embodiment, measuring the first signal includes buffering the first signal using buffer  218 A of channel  224 A and integrating the buffered first signal using an integrator  220 A. 
     In another embodiment, measuring the first signal includes integrating the first signal using integrator  420 A and converting the first signal into a digital signal using ADC  438 A. 
     At block  1104 , processing logic measures, at channel  224 B of the processing device  116 , a second signal (e.g., shield signal  236 ) including a second noise component  232 B generated by the noise source  112 . The channel  224 B is coupled to shield layer  108  that is disposed between the noise source  112  and electrode layer  106 . 
     In an embodiment, measuring the second signal includes buffering the second signal using buffer  218 B of channel  224 B and integrating the buffered second signal using an integrator  220 B. 
     In another embodiment, measuring the second signal includes integrating the second signal using integrator  420 B and converting the second signal into a digital signal using ADC  438 B. 
     In an embodiment, the measuring the first signal at channel  224 A is performed concurrently with measuring the second signal at channel  224 B. 
     At block  1106 , processing logic generates an estimated noise signal using the second noise component  232 B of the second signal that is associated with the channel  224 B. The estimated noise signal is an estimation of the first noise component  232 A of the first signal. 
     In an embodiment, generating the estimated noise signal includes attenuating the second signal (e.g., shield signal  236 ) by an attenuation coefficient to generate the estimated noise signal. For example, after the second signal is measured (e.g., buffered and integrated), the second signal can be attenuated by attenuator  230 . 
     At block  1108 , processing logic may subtract the estimated noise signal from the measured first signal to obtain the touch data component of the first signal. For example, a subtraction module  228  may be used to subtract the estimated noise signal from the measured first signal. In an embodiment, the touch data may be used to determine whether a touch by a touch object  102  occurred proximate to an Rx electrode of the electrode layer  106 . 
     As noted above, similar operations may be used for other channels associated with other Rx electrodes of electrode layer  106 . In embodiments, channel  224 A may be used to suppress noise for one or more channels associated with Rx electrodes. 
       FIG. 12  is a flow diagram illustrating method  1200  for determining an attenuation coefficient used to generate the estimated noise signal, in accordance with aspects of the disclosure. Method  1200  may be performed by processing logic that includes hardware (e.g., circuitry, dedicated logic, programmable logic, microcode), software (e.g., instructions run on a processing device to perform hardware simulation), or a combination thereof. In other implementations, noise suppression module  1320  of  FIG. 13  can perform some or all the operations. Components of the preceding Figures may be used to help illustrate method  1200 . It may be noted that the in some implementations, method  1200  may include the same, different, fewer, or greater number of operations performed in any order. 
     At block  1202 , processing logic determines that the noise source  112  is powered on. For example, the processing device  116  may send a signal that turns the display device on. In another example, the processing device  116  received an indication that the display device is powered on, but may not directly control the display device. 
     At block  1204 , processing logic may turn off one or more excitation voltages associated with the electrode layer  106 . For example, in mutual capacitance sensing the Tx excitation voltages may be removed. In another example, in self-capacitance sensing the excitation voltage may be turned off by, for instance, coupling the device ground of the processing device  116  to the system ground used by the noise source  112 . In an embodiment, the excitation voltages are turned off so that a touch does not interfere with measurements of the noise signal  126  at both channel  224 A and channel  224 B of processing device  116 . 
     At block  1206 , processing logic sets the attenuation coefficient to a predetermined number. For example, the attenuation coefficient of attenuator  230  may be set to the  1 , so that the attenuator  230  buffers the second noise component ( 12 )  232 B of the noise source  112 . 
     At block  1208 , processing logic measures, at the channel  224 A of processing device  116 , the third signal including the third noise component (e.g., similar to first noise component  232 A). In an embodiment, the measurement of the third signal may be similar to measurement of the first signal (e.g., measuring signal  234 ) as described above except that the third signal does not include a touch data component because the excitation signal is turned off. 
     At block  1208 , processing logic measures at the channel  224 B of processing device  116 , the fourth signal including the fourth noise component (e.g., similar to second noise component  232 B). In an embodiment, the measurement of the fourth signal may be similar to measurement of the second signal (e.g., shield signal  236 ) as described above. 
     In an embodiment, the third signal and the fourth signal are measured concurrently. 
     At block  1210 , processing logic estimates the attenuation coefficient using the third signal and fourth signal from channel  224 A and channel  224 B, respectively. For example, the third signal represents the noise component (e.g., first noise component  232 A) of the noise source  112  received by the channel  224 A. The fourth signal represents the noise component (e.g., second noise component  232 B) of the noise source  112  received by the channel  224 B. Since the excitation signal is turned off, the signals received by channel  224 A and channel  224 B may be representative of the noise source  112  without interference from signals representative of touch data. 
     In one embodiment, the attenuation coefficient may be estimated using a ratio of the third signal (e.g., first noise component  232 A) received at channel  224 A and the fourth signal (e.g., second noise component  232 B) received at channel  224 B. In another embodiment, the attenuation coefficient can be estimated using a least square method approach using the third signal and the fourth signal. 
     In an embodiment, the attenuator, such as attenuator  230  or attenuator  1030 , may be set using the estimated attenuation coefficient. 
     In an embodiment, determining the attenuation coefficient can be performed once, for example, after manufacture of the system (e.g., mobile device). In another embodiment, determining the attenuation coefficient may be performed more than once, for example periodically based on time, number of on-off cycles of the system, or other criteria. In an embodiment, determining the attenuation coefficient can be performed dynamically, for example when a user is using the system. 
     In another embodiment, the attenuation coefficient can be determined based on a temperature value sensed in the system. In an embodiment, processing logic determines that a temperature value satisfies a temperature threshold. Responsive to determining that a temperature value satisfies a temperature threshold, processing logic determines the attenuation coefficient used to generate the estimated noise signal. For example, processing device  116  may receive or generate a temperature value indicative of the temperature of the electrode layer  106  or shield layer  108 . The temperature value may exceed a predefined threshold or drop below another predefined threshold, responsive to which processing device  116  executes method  1200  to determine a new attenuation coefficient. 
       FIG. 13  is a block diagram illustrating an electronic system that processes touch data, in accordance with aspects of the disclosure.  FIG. 13  illustrates an electronic system  1300  including a processing device  1310  (which may be similar to processing device  116  described herein) that may be configured to measure capacitances from a sense array  1321  (e.g., capacitive-sense array) with noise suppression module  1320 , the sensor array  1321  forming a touch-sensing surface  1316 . In one embodiment, a multiplexer circuit may be used to connect a capacitance-sensing circuit  1301  with a sense array  1321 . The touch-sensing surface  1316  (e.g., a touchscreen or a touch pad) is coupled to the processing device  1310 , which is coupled to a host  1350 . In one embodiment, the touch-sensing surface  1316  is a two-dimensional sense array (e.g., sense array  1321 ) that uses processing device  1310  to detect touches on the touch-sensing surface  1316 . 
     In one embodiment, the sense array  1321  includes electrodes  1322 ( 1 )- 1322 (N) (where N is a positive integer) that are disposed as a two-dimensional matrix (also referred to as an XY matrix). The sense array  1321  is coupled to pins  1313 ( 1 )- 1313 (N) of the processing device  1310  via one or more analog buses  1315  transporting multiple signals. In sense array  1321 , the first three electrodes (i.e., electrodes  1322 ( 1 )-( 3 )) are connected to capacitance-sensing circuit  1301  and to ground, illustrating a self-capacitance configuration. The last electrode (i.e.,  1322 (N)) has both terminals connected to capacitance-sensing circuit  1301 , illustrating a mutual capacitance configuration. It should be noted that the other electrodes  1322  can have both terminals connected to capacitance-sensing circuit  1301  as well. In an alternative embodiment without an analog bus, each pin may instead be connected either to a circuit that generates a transmit or transmission (TX) signal or to an individual receive (RX) sensor circuit. The sense array  1321  may include a multi-dimension capacitive sense array. The multi-dimension sense array includes multiple sense elements, organized as rows and columns. In another embodiment, the sense array  1321  operates as an all-points-addressable (“APA”) mutual capacitive sense array. The sense array  1321  may be disposed to have a flat surface profile. Alternatively, the sense array  1321  may have non-flat surface profiles. Alternatively, other configurations of capacitive sense arrays may be used. For example, instead of vertical columns and horizontal rows, the sense array  1321  may have a hexagon arrangement, or the like. In one embodiment, the sense array  1321  may be included in an indium tin oxide (ITO) panel or a touch screen panel. In one embodiment, sense array  1321  is a capacitive sense array. In another embodiment, the sense array  1321  is non-transparent capacitive sense array (e.g., PC touchpad). In one embodiment, the sense array is configured so that processing device  1310  may generate touch data for a touch detected proximate to the capacitive sense array, the touch data represented as a plurality of cells. 
     In one embodiment, the capacitance-sensing circuit  1301  may include a CDC or other means to convert a capacitance into a measured value. The capacitance-sensing circuit  1301  may also include a counter or timer to measure the oscillator output. The processing device  1310  may further include software components to convert the count value (e.g., capacitance value) into a touch detection decision or relative magnitude. It should be noted that there are various known methods for measuring capacitance, such as current versus voltage phase shift measurement, resistor-capacitor charge timing, capacitive bridge divider, charge transfer, successive approximation, sigma-delta modulators, charge-accumulation circuits, field effect, mutual capacitance, frequency shift, or other capacitance measurement algorithms. It should be noted however, instead of evaluating the raw counts relative to a threshold, the capacitance-sensing circuit  1301  may be evaluating other measurements to determine the user interaction. For example, in the capacitance-sensing circuit  1301  having a sigma-delta modulator, the capacitance-sensing circuit  1301  is evaluating the ratio of pulse widths of the output (i.e., density domain), instead of the raw counts being over or under a certain threshold. 
     In another embodiment, the capacitance-sensing circuit  1301  includes a TX signal generator to generate a TX signal (e.g., stimulus signal) to be applied to the TX electrode and a receiver (also referred to as a “sensing channel” or “receiving (Rx) channel” or “channel”), such as a buffer or an integrator, to measure an RX signal on the RX electrode. In some embodiments, each Rx channel may be coupled to a physical pin of processing device  1310  (or capacitance-sensing circuit  1301 ). In some embodiments, each Rx channel may include hardware such as a buffer or an integrator. In a further embodiment, the capacitance-sensing circuit  1301  includes an analog-to-digital converter (ADC) coupled to an output of the receiver to convert the measured RX signal to a digital value. The digital value can be further processed by the processing device  1310 , the host  1350 , or both. 
     The processing device  1310  is configured to detect one or more touches on a touch-sensing device, such as the sense array  1321 . The processing device can detect conductive objects, such as touch objects (fingers or passive styluses, an active stylus, or any combination thereof). The capacitance-sensing circuit  1301  can measure a touch data on the sense array  1321 . The touch data may be represented as multiple cells, each cell representing an intersection of sense elements (e.g., electrodes) of the sense array  1321 . The capacitive sense elements are electrodes of conductive material, such as copper, silver, indium tin oxide (ITO), metal mesh, carbon nanotubes, or the like. The sense elements may also be part of an ITO panel. The capacitive sense elements can be used to allow the capacitance-sensing circuit  1301  to measure self-capacitance, mutual capacitance, or any combination thereof. In another embodiment, the touch data measured by the capacitance-sensing circuit  1301  can be processed by the processing device  1310  to generate a 2D capacitive image of the sense array  1321  (e.g., capacitive-sense array). In one embodiment, when the capacitance-sensing circuit  1301  measures mutual capacitance of the touch-sensing device (e.g., capacitive-sense array), the capacitance-sensing circuit  1301  determines a 2D capacitive image of the touch-sensing object on the touch surface and processes the data for peaks and positional information. In another embodiment, the processing device  1310  is a microcontroller that obtains a capacitance touch signal data set, such as from a sense array, and finger detection firmware executing on the microcontroller identifies data set areas that indicate touches, detects and processes peaks, calculates the coordinates, or any combination therefore. The firmware can calculate a precise coordinate for the resulting peaks. In one embodiment, the firmware can calculate the precise coordinates for the resulting peaks using a centroid algorithm, which calculates a centroid of the touch, the centroid being a center of mass of the touch. The centroid may be an X/Y coordinate of the touch. Alternatively, other coordinate interpolation algorithms may be used to determine the coordinates of the resulting peaks. The microcontroller can report the precise coordinates to a host processor, as well as other information. 
     In one embodiment, the processing device  1310  further includes processing logic  1302 . Some or all of the operations of the processing logic  1302  may be implemented in firmware, hardware, or software or some combination thereof. The processing logic  1302  may receive signals from the capacitance-sensing circuit  1301 , and determine the state of the sense array  1321 , such as whether an object (e.g., a finger) is detected on or in proximity to the sense array  1321  (e.g., determining the presence of the object), resolve where the object is on the sense array (e.g., determining the location of the object), tracking the motion of the object, or other information related to an object detected at the touch sensor. In another embodiment, processing logic  1302  may include capacitance-sensing circuit  1301 . 
     The processing logic  1302  can be implemented in a capacitive touch screen controller. In one embodiment, the capacitive touch screen controller is the TrueTouch® capacitive controllers and CapSense® technology controllers (touch screens, buttons, sliders, proximity, etc.), such as the CY8C[2|3|4|5|6]xxxx family and CY8CMBRxx family of CapSense controllers, developed by Cypress Semiconductor Corporation of San Jose, Calif. The CapSense® technology can be delivered as a peripheral function in the Programmable System on a Chip (PSoC®) processing device, developed by Cypress Semiconductor Corporation, San Jose, Calif., such as the PSoC® 1, 3, 4, 5, 6 devices. The CapSense® controllers&#39; sensing technology can resolve touch locations of multiple fingers and a stylus on the touch-screens, supports operating systems, and is optimized for low-power multi-touch gesture and all-point touchscreen functionality. Alternatively, the touch position calculation features may be implemented in other touchscreen controllers, or other touch controllers of touch-sensing devices. In one embodiment, the touch position calculation features may be implemented with other touch filtering algorithms as would be appreciated by one of ordinary skill in the art having the benefit of this disclosure. 
     In another embodiment, instead of performing the operations of the processing logic  1302  in the processing device  1310 , the processing device  1310  may send the raw data or partially-processed data to the host  1350 . The host  1350 , as illustrated in  FIG. 13 , may include decision logic  1351  that performs some or all of the operations of the processing logic  1302 . Noise suppression module  1320  may be implemented partially or fully by decision logic  1351 . Noise suppression module  1320  may be a module within decision logic  1351 . Alternatively, noise suppression module  1320  may be an algorithm in decision logic  1351 . Host  1350  may obtain raw capacitance data from processing device  1310 , and determine if a touch has occurred or not occurred on sense array  1321 . Operations of the decision logic  1351  may be implemented in firmware, hardware, software, or a combination thereof. The host  1350  may include a high-level Application Programming Interface (API) in applications  1352  that perform routines on the received data, such as compensating for sensitivity differences, other compensation algorithms, baseline update routines, start-up and/or initialization routines, interpolation operations, or scaling operations. The operations described with respect to the processing logic  1302  may be implemented in the decision logic  1351 , the applications  1352 , or in other hardware, software, and/or firmware external to the processing device  1310 . In some other embodiments, the processing device  1310  is the host  1350 . 
     In another embodiment, the processing device  1310  may also include a non-sensing actions block  1303 . Non-sensing actions block  1303  may be used to process and/or receive/transmit data to and from the host  1350 . For example, additional components may be implemented to operate with the processing device  1310  along with the sense array  1321  (e.g., keyboard, keypad, mouse, trackball, LEDs, displays, or other peripheral devices). 
     As illustrated, capacitance-sensing circuit  1301  may be integrated into processing device  1310 . Capacitance-sensing circuit  1301  may include an analog I/O for coupling to an external component, such as touch-sensor pad (not shown), sense array  1321 , touch-sensor slider (not shown), touch-sensor buttons (not shown), and/or other devices. The capacitance-sensing circuit  1301  may be configurable to measure capacitance using mutual-capacitance sensing techniques, self-capacitance sensing technique, charge coupling techniques, combinations thereof, or the like. In one embodiment, capacitance-sensing circuit  1301  operates using a charge accumulation circuit, a capacitance modulation circuit, or other capacitance sensing methods known by those skilled in the art. In an embodiment, the capacitance-sensing circuit  1301  is of the Cypress controllers. Alternatively, other capacitance-sensing circuits may be used. The mutual capacitive sense arrays, or touch screens, as described herein, may include a transparent, conductive sense array disposed on, in, or under either a visual display itself (e.g. LCD monitor), or a transparent substrate in front of the display. In an embodiment, the TX and RX electrodes are configured in rows and columns, respectively. It should be noted that the rows and columns of electrodes can be configured as TX or RX electrodes by the capacitance-sensing circuit  1301  in any chosen combination. In one embodiment, the TX and RX electrodes of the sense array  1321  are configurable to operate as TX and RX electrodes of a mutual capacitive sense array in a first mode to detect touch objects, and to operate as electrodes of a coupled-charge receiver in a second mode to detect a stylus on the same electrodes of the sense array. The stylus, which generates a stylus TX signal when activated, is used to couple charge to the capacitive sense array, instead of measuring a mutual capacitance at an intersection of an RX electrode and a TX electrode (including one or more sense element) as done during mutual-capacitance sensing. An intersection between two sense elements may be understood as a location at which one sense electrode crosses over or overlaps another, while maintaining galvanic isolation from each other. The capacitance associated with the intersection between a TX electrode and an RX electrode can be sensed by selecting every available combination of TX electrode and RX electrode. When a touch object (i.e., conductive object), such as a finger or stylus, approaches the sense array  1321 , the touch object causes a decrease in mutual capacitance between some of the TX/RX electrodes. In another embodiment, the presence of a finger increases the coupling capacitance of the electrodes. Thus, the location of the finger on the sense array  1321  can be determined by identifying the RX electrode having a decreased coupling capacitance between the RX electrode and the TX electrode to which the TX signal was applied at the time the decreased capacitance was measured on the RX electrode. Therefore, by sequentially determining the capacitances associated with the intersection of electrodes, the locations of one or more inputs can be determined. It should be noted that the process can calibrate the sense elements (intersections of RX and TX electrodes) by determining baselines for the sense elements. It should also be noted that interpolation may be used to detect finger position at better resolutions than the row/column pitch as would be appreciated by one of ordinary skill in the art. In addition, various types of coordinate interpolation algorithms may be used to detect the center of the touch as would be appreciated by one of ordinary skill in the art. 
     It should also be noted that the embodiments described herein are not limited to having a configuration of a processing device coupled to a host, but may include a system that measures the capacitance on the sensing device and sends the raw data to a host computer where it is analyzed by an application. In another embodiment, the processing that is done by processing device  1310  is done in the host. 
     The processing device  1310  may reside on a common carrier substrate such as, for example, an integrated circuit (IC) die substrate, or a multi-chip module substrate. Alternatively, the components of the processing device  1310  may be one or more separate integrated circuits and/or discrete components. In one embodiment, the processing device  1310  may be the Programmable System on a Chip (PSoC®) processing device, developed by Cypress Semiconductor Corporation, San Jose, California. One embodiment of the PSoC® processing device is illustrated and described below with respect to  FIG. 14 . Alternatively, the processing device  1310  may be one or more other processing devices known by those of ordinary skill in the art, such as a microprocessor or central processing unit, a controller, special-purpose processor, digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable device. In an alternative embodiment, for example, the processing device  1310  may be a network processor having multiple processors including a core unit and multiple micro-engines. Additionally, the processing device  1310  may include any combination of general-purpose processing device(s) and special-purpose processing device(s). 
     Capacitance-sensing circuit  1301  may be integrated into the IC of the processing device  1310 , or alternatively, in a separate IC. Alternatively, descriptions of capacitance-sensing circuit  1301  may be generated and compiled for incorporation into other integrated circuits. For example, behavioral level code describing the capacitance-sensing circuit  1301 , or portions thereof, may be generated using a hardware descriptive language, such as VHDL or Verilog, and stored to a machine-accessible medium (e.g., CD-ROM, hard disk, floppy disk, etc.). Furthermore, the behavioral level code can be compiled into register transfer level (“RTL”) code, a netlist, or even a circuit layout and stored to a machine-accessible medium. The behavioral level code, the RTL code, the netlist, and the circuit layout may represent various levels of abstraction to describe capacitance-sensing circuit  1301 . 
     It should be noted that the components of electronic system  1300  may include all the components described above. Alternatively, electronic system  1300  may include some of the components described above. 
     In one embodiment, the electronic system  1300  is used in a tablet computer. Alternatively, the electronic device may be used in other applications, such as a notebook computer, a mobile handset, a personal data assistant (“PDA”), a keyboard, a television, a remote control, a monitor, a handheld multi-media device, a handheld media (audio and/or video) player, a handheld gaming device, a signature input device for point of sale transactions, an eBook reader, global position system (“GPS”) or a control panel, among others. The embodiments described herein are not limited to touch screens or touch-sensor pads for notebook implementations, but can be used in other capacitive sensing implementations, for example, the sensing device may be a touch-sensor slider (not shown) or touch-sensor buttons (e.g., capacitance sensing buttons). In one embodiment, these sensing devices include one or more capacitive sensors or other types of capacitance-sensing circuitry. The operations described herein are not limited to notebook pointer operations, but can include other operations, such as lighting control (dimmer), volume control, graphic equalizer control, speed control, or other control operations requiring gradual or discrete adjustments. It should also be noted that these embodiments of capacitive sensing implementations may be used in conjunction with non-capacitive sensing elements, including but not limited to pick buttons, sliders (ex. display brightness and contrast), scroll-wheels, multi-media control (ex. volume, track advance, etc.) handwriting recognition, and numeric keypad operation. 
     Electronic system  1300  includes capacitive button  1323 . Capacitive button  1323  is connected to processing device  1310 . In one embodiment, capacitive button  1323  may be a single electrode. In another embodiment, capacitive button  1323  may be a pair of electrodes. In one embodiment, capacitive button  1323  is disposed on a substrate. In one embodiment, capacitive button  1323  may be part of sense array  1321 . In another embodiment, capacitive button may be a separate from sense array  1321 . In one embodiment, capacitive button  1323  may be used to in self-capacitance scan mode. In another embodiment, capacitive button  1323  may be used in mutual capacitance scan mode. In one embodiment, capacitive button  1323  may be used in both self-capacitance scan mode and mutual capacitance scan mode. Alternatively, the capacitive button  1323  is used in a multi-stage capacitance measurement process as described herein. Capacitive button  1323  may be one or more distinct buttons. 
       FIG. 14  illustrates an embodiment of a core architecture  1400  of the PSoC® processing device, such as that used in the PSoC3® family of products offered by Cypress Semiconductor Corporation (San Jose, Calif.). In one embodiment, the core architecture  1400  includes a microcontroller  1402 . The microcontroller  1402  includes a CPU (central processing unit) core  1404 , flash program storage  1406 , DOC (debug on chip)  1408 , a prefetch buffer  1410 , a private SRAM (static random access memory)  1412 , and special functions registers  1414 . In an embodiment, the DOC  1408 , prefetch buffer  1410 , private SRAM  1412 , and special function registers  1414  are coupled to the CPU core  1404 , while the flash program storage  1406  is coupled to the prefetch buffer  1410 . 
     The core architecture  1400  may also include a CHub (core hub)  1416 , including a bridge  1418  and a direct memory access (DMA) controller  1420  that is coupled to the microcontroller  1402  via bus  1422 . The CHub  1416  may provide the primary data and control interface between the microcontroller  1402  and its peripherals (e.g., peripherals) and memory, and a programmable core  1424 . The DMA controller  1420  may be programmed to transfer data between system elements without burdening the CPU core  1404 . In various embodiments, each of these subcomponents of the microcontroller  1402  and CHub  1416  may be different with each choice or type of CPU core  1404 . The CHub  1416  may also be coupled to shared SRAM  1426  and an SPC (system performance controller)  1428 . The private SRAM  1412  is independent of the shared SRAM  1426  that is accessed by the microcontroller  1402  through the bridge  1418 . The CPU core  1404  accesses the private SRAM  1412  without going through the bridge  1418 , thus allowing local register and RAM accesses to occur simultaneously with DMA access to shared SRAM  1426 . Although labeled here as SRAM, these memory modules may be any suitable type of a wide variety of (volatile or non-volatile) memory or data storage modules in various other embodiments. 
     In various embodiments, the programmable core  1424  may include various combinations of subcomponents (not shown), including, but not limited to, a digital logic array, digital peripherals, analog processing channels, global routing analog peripherals, DMA controller(s), SRAM and other appropriate types of data storage,  10  ports, and other suitable types of subcomponents. In one embodiment, the programmable core  1424  includes a GPIO (general purpose IO) and EMIF (extended memory interface) block  1430  to provide a mechanism to extend the external off-chip access of the microcontroller  1402 , a programmable digital block  1432 , a programmable analog block  1434 , and a special functions block  1436 , each configured to implement one or more of the subcomponent functions. In various embodiments, the special functions block  1436  may include dedicated (non-programmable) functional blocks and/or include one or more interfaces to dedicated functional blocks, such as USB, a crystal oscillator drive, JTAG, and the like. 
     The programmable digital block  1432  may include a digital logic array including an array of digital logic blocks and associated routing. In one embodiment, the digital block architecture is comprised of UDBs (universal digital blocks). For example, each UDB may include an ALU together with CPLD functionality. 
     In various embodiments, one or more UDBs of the programmable digital block  1432  may be configured to perform various digital functions, including, but not limited to, one or more of the following functions: a basic I2C slave; an I2C master; a SPI master or slave; a multi-wire (e.g., 3-wire) SPI master or slave (e.g., MISO/MOSI multiplexed on a single pin); timers and counters (e.g., a pair of 8-bit timers or counters, one 16 bit timer or counter, one 8-bit capture timer, or the like); PWMs (e.g., a pair of 8-bit PWMs, one 16-bit PWM, one 8-bit deadband PWM, or the like), a level sensitive I/O interrupt generator; a quadrature encoder, a UART (e.g., half-duplex); delay lines; and any other suitable type of digital function or combination of digital functions which can be implemented in a plurality of UDBs. 
     In other embodiments, additional functions may be implemented using a group of two or more UDBs. Merely for purposes of illustration and not limitation, the following functions can be implemented using multiple UDBs: an I2C slave that supports hardware address detection and the ability to handle a complete transaction without CPU core (e.g., CPU core  1404 ) intervention and to help prevent the force clock stretching on any bit in the data stream; an I2C multi-master which may include a slave option in a single block; an arbitrary length PRS or CRC (up to 32 bits); SDIO; SGPIO; a digital correlator (e.g., having up to 32 bits with 4× over-sampling and supporting a configurable threshold); a LINbus interface; a delta-sigma modulator (e.g., for class D audio DAC having a differential output pair); an I2S (stereo); an LCD drive control (e.g., UDBs may be used to implement timing control of the LCD drive blocks and provide display RAM addressing); full-duplex UART (e.g., 7-, 8- or 9-bit with 1 or 2 stop bits and parity, and RTS/CTS support), an IRDA (transmit or receive); capture timer (e.g., 16-bit or the like); deadband PWM (e.g., 16-bit or the like); an SMbus (including formatting of SMbus packets with CRC in software); a brushless motor drive (e.g., to support 6/12 step commutation); auto BAUD rate detection and generation (e.g., automatically determine BAUD rate for standard rates from 1200 to 115200 BAUD and after detection to generate required clock to generate BAUD rate); and any other suitable type of digital function or combination of digital functions which can be implemented in a plurality of UDBs. 
     The programmable analog block  1434  may include analog resources including, but not limited to, comparators, mixers, PGAs (programmable gain amplifiers), TIAs (trans-impedance amplifiers), ADCs (analog-to-digital converters), DACs (digital-to-analog converters), voltage references, current sources, sample and hold circuits, and any other suitable type of analog resources. The programmable analog block  1434  may support various analog functions including, but not limited to, analog routing, LCD drive IO support, capacitance-sensing, voltage measurement, motor control, current to voltage conversion, voltage to frequency conversion, differential amplification, light measurement, inductive position monitoring, filtering, voice coil driving, magnetic card reading, acoustic doppler measurement, echo-ranging, modem transmission and receive encoding, or any other suitable type of analog function. 
     In an embodiment, programmable core  1424  may include noise suppression module  1320  to perform one or more aspects of the disclosure. Some are all of component or operations of noise suppression module  1320  may be performed by one or more of the subcomponents of programmable core  1424 . It can be noted that other components of core architecture  1400  may perform some or all of the operations of noise suppression module  1320  or include some or all the components used by noise suppression module  1320 . 
     The embodiments described herein may be used in various designs of mutual-capacitance sensing systems, in self-capacitance sensing systems, or combinations of both. In one embodiment, the capacitance sensing system detects multiple sense elements that are activated in the array and can analyze a signal pattern on the neighboring sense elements to separate noise from actual signal. The embodiments described herein are not tied to a particular capacitive sensing solution and can be used as well with other sensing solutions, including optical sensing solutions, as would be appreciated by one of ordinary skill in the art having the benefit of this disclosure. 
     In the above description, numerous details are set forth. It will be apparent, however, to one of ordinary skill in the art having the benefit of this disclosure, that embodiments of the present disclosure may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the description. 
     Some portions of the detailed description are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here and generally, conceived to be a self-consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like. 
     It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the above discussion, it is appreciated that throughout the description, discussions utilizing terms such as “measuring,” “generating,” “subtracting,” “buffering,” “integrating,” “multiplying,” “determining,” “causing,” “setting,” “estimating,” or the like, refer to the actions and processes of a computing system, or similar electronic computing device, that manipulates and transforms data represented as physical (e.g., electronic) quantities within the computing system&#39;s registers and memories into other data similarly represented as physical quantities within the computing system memories or registers or other such information storage, transmission or display devices. 
     The words “example” or “exemplary” are used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the words “example” or “exemplary” is intended to present concepts in a concrete fashion. As used in this application, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless specified otherwise, or clear from context, “X includes A or B” is intended to mean any of the natural inclusive permutations. That is, if X includes A; X includes B; or X includes both A and B, then “X includes A or B” is satisfied under any of the foregoing instances. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form. Moreover, use of the term “an embodiment” or “one embodiment” or “an implementation” or “one implementation” throughout is not intended to mean the same embodiment or implementation unless described as such. 
     Embodiments descried herein may also relate to an apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a non-transitory computer-readable storage medium, such as, but not limited to, any type of disk including floppy disks, optical disks, CD-ROMs and magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, flash memory, or any type of media suitable for storing electronic instructions. The term “computer-readable storage medium” should be taken to include a single medium or multiple media (e.g., a centralized or distributed database and/or associated caches and servers) that store one or more sets of instructions. The term “computer-readable medium” shall also be taken to include any medium that is capable of storing, encoding, or carrying a set of instructions for execution by the machine and that causes the machine to perform any one or more of the methodologies of the present embodiments. The term “computer-readable storage medium” shall accordingly be taken to include, but not be limited to, solid-state memories, optical media, magnetic media, any medium that is capable of storing a set of instructions for execution by the machine and that causes the machine to perform any one or more of the methodologies of the present embodiments. 
     The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct a more specialized apparatus to perform the required method steps. The required structure for a variety of these systems will appear from the description below. In addition, the present embodiments are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the embodiments as described herein. 
     The above description sets forth numerous specific details such as examples of specific systems, components, methods, and so forth, in order to provide a good understanding of several embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that at least some embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known components or methods are not described in detail or are presented in simple block diagram format in order to avoid unnecessarily obscuring the present embodiments. Thus, the specific details set forth above are merely exemplary. Particular implementations may vary from these exemplary details and still be contemplated to be within the scope of the present embodiments. 
     It is to be understood that the above description is intended to be illustrative and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. The scope of the embodiments should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.