Digital-to-analog controller reference touch sensing system and related systems, methods and devices

Abstract

Some disclosed embodiments generally relate to shaping the waveform of a reference signal used by a driver of a touch sensor to limit electromagnetic emissions (EME) emitted by the touch sensor during sensing operations. Some disclosed embodiments generally relate to a DAC reference touch sensor driver, and using the shape of a reference signal used by a touch detector to detect touch at a touch sensor to control the amount of EME emitted at the touch sensor. Some disclosed embodiments generally relate to compensating for the effects of external noise at a touch sensor. And more specifically, to changing the shape of a reference signal based on changes made to a sampling rate to compensate for external noise.

Description

[0001] Priority declaration

[0002] This application claims the benefit of the filing date of U.S. Provisional Patent Application Serial No. 62 / 785,141, filed on December 26, 2018, entitled “DIGITAL-TO-ANALOG CONTROLLER-REFERENCED TOUCH SENSING SYSTEM, AND RELATED SYSTEMS, METHODS, AND DEVICES,” and claims the benefit of the filing date of pending U.S. Patent Application Serial No. 16 / 379,687, filed on April 9, 2019, entitled “DIGITAL-TO-ANALOG CONTROLLER-REFERENCED TOUCHSENSING SYSTEM, AND RELATED SYSTEMS, METHODS, AND DEVICES,” the disclosures of each of which are hereby incorporated by reference in their entirety. Technical Field

[0003] The disclosed systems, methods, and apparatus relate generally to capacitive touch sensing, and more particularly, some embodiments relate to techniques for improved electromagnetic emission control in touch sensors. Background Art

[0004] Typical touch interface systems may incorporate touch sensors (such as, but not limited to, capacitive sensors and / or resistive sensors) that respond to objects that are in close proximity to or in physical contact with a touch-sensitive surface of the touch interface system. Such responses may be captured and interpreted to infer information about the contact, including the position of the object relative to the touch interface system.

[0005] Touchpads used with personal computers (including laptop computers and keyboards for tablet computers) typically incorporate touch interface systems or operate in combination with touch interface systems. Displays typically include touch screens that incorporate elements of touch interface systems (typically at least touch sensors) to enable users to interact with graphical user interfaces (GUIs) and / or computer applications. Examples of devices incorporating touch displays include portable media players, televisions, smart phones, tablet computers, personal computers, and wearable devices such as smart watches, to name a few. In addition, control panels for automobiles, household appliances (e.g., ovens, refrigerators, or washing machines), security systems, automated teller machines (ATMs), residential environmental control systems, and industrial equipment can incorporate touch interface systems with displays and housings, including enabling buttons, sliders, wheels, and other touch elements.

[0006] Although touch sensors emit electromagnetic emissions (EME), such as electromagnetic fields and electromagnetic radiation, designers of touch sensors have traditionally focused on minimizing the susceptibility of touch sensors to EME from nearby devices. Touch sensors have been used in environments with very lenient EME limits. However, limits apply to touch sensors based on the function of the touch sensors and the environment in which they are installed. The inventors of the present disclosure recognized that in order to meet the stringent EME limits for new applications of touch sensors, such as automotive applications, techniques and systems are needed to test, calibrate, and operate touch sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] While the present disclosure concludes with claims that particularly point out and distinctly claim specific embodiments, the various features and advantages of embodiments within the scope of the present disclosure may be more readily ascertained from the following description when read in conjunction with the accompanying drawings, in which:

[0008] Figure 1 The period of an exemplary square waveform is shown;

[0009] Figure 2 An exemplary square waveform approximated for a digital-to-analog converter (DAC) is shown;

[0010] Figure 3A shows exemplary edges of a waveform of a signal output from a DAC, wherein the waveform is monotonically increasing;

[0011] Figure 3B illustrates exemplary edges of a waveform of a signal output from a DAC, wherein the waveform includes a non-monotonic portion;

[0012] Figure 4 A system for configuring a touch sensing system to control EME according to the disclosed embodiments is shown;

[0013] Figure 5 shows launch control software according to the disclosed embodiment;

[0014] Figure 6 A method for configuring a touch sensing system such as Figure 4 touch sensing system) to control the EME process;

[0015] Figure 7 A process for evaluating EME at a touch sensor for a particular shape of a reference signal according to a disclosed embodiment is shown;

[0016] Figure 8 A process for collecting a list of acceptable shapes that can be analyzed to determine the shape of a waveform that minimizes EME at a touch sensor is shown in accordance with the disclosed embodiments;

[0017] Fig. 9 A process for obtaining a cost function according to the disclosed embodiment is shown;

[0018] Fig.10 A touch sensing system in accordance with the disclosed embodiments is shown, the touch sensing system being configured to provide driver reference signals that are shaped to control EME emitted by a touch sensor;

[0019] Fig.11 A process for compensating for external noise using a differential reference signal shape according to a disclosed embodiment is shown;

[0020] Fig.12 A DAC controller is shown according to a disclosed embodiment, the DAC controller being configured to change the shape of a waveform of a reference signal (e.g., to compensate for external noise) in response to a touch sensing system changing a sampling rate;

[0021] Fig.13 An EME control circuit that is part of or operates in conjunction with a touch sensing system in accordance with the disclosed embodiments is shown; and

[0022] Fig.14 A process for dynamically selecting a base frequency and a waveform shape in response to an application system according to a disclosed embodiment is shown. DETAILED DESCRIPTION

[0023] In the following detailed description, reference is made to the accompanying drawings which form a part thereof, and in which specific exemplary embodiments in which the present disclosure may be practiced are shown by way of example. These embodiments are described in sufficient detail to enable one of ordinary skill in the art to practice the present disclosure. However, other embodiments may be utilized, and changes in structure, material, and process may be made without departing from the scope of the present disclosure.

[0024] The illustrations presented herein are not intended to be actual views of any particular method, system, device, or structure, but are merely idealized representations for describing embodiments of the present disclosure. The drawings presented herein are not necessarily drawn to scale. For the convenience of the reader, similar structures or components in the various drawings may retain the same or similar numbering; however, the similarity of numbering does not mean that the structures or components must be identical in size, composition, configuration, or any other attribute.

[0025] It is readily understood that the components of the embodiments as described herein as a whole and shown in the accompanying drawings may be arranged and designed in a variety of different configurations. Therefore, the following description of various embodiments is not intended to limit the scope of the present disclosure, but is merely representative of various embodiments. Although various aspects of the embodiments may be presented in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise indicated.

[0026] The following description may include examples to help those skilled in the art practice the embodiments disclosed in the present invention. The use of the terms "exemplary", "by way of example" and "for example" means that the relevant description is illustrative, and although the scope of the present disclosure is intended to cover examples and legal equivalents, the use of such terms is not intended to limit the scope of the embodiments or the present disclosure to the specified components, steps, features or functions, etc.

[0027] Therefore, unless otherwise specified herein, the specific embodiments shown and described are merely examples and should not be construed as the only way to implement the present disclosure. Elements, circuits, and functions may be shown in block diagram form so as not to obscure the present disclosure with unnecessary details. On the contrary, the specific embodiments shown and described are merely exemplary and should not be construed as the only way to implement the present disclosure, unless otherwise specified herein. In addition, the partitioning of logic between block definitions and individual blocks is an example of a specific embodiment. It will be apparent to one of ordinary skill in the art that the present disclosure can be practiced through many other partitioning solutions. In most cases, details about timing considerations, etc. have been omitted, where such details are not required to obtain a complete understanding of the present disclosure and are within the capabilities of one of ordinary skill in the relevant art.

[0028] The information and signals described herein may be represented using any of a variety of different techniques and technologies. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout this specification may be represented by voltage, current, electromagnetic waves, magnetic fields or particles, light fields or particles, or any combination thereof. For clarity of presentation and description, some of the accompanying drawings may show signals as single signals. It will be appreciated by those of ordinary skill in the art that a signal may represent a bus of signals, wherein the bus may have various bit widths, and the present disclosure may be implemented on any number of data signals including a single data signal.

[0029] It should be understood that any reference to an element using names such as "first", "second", etc. herein does not limit the number or order of these elements, unless such limitations are explicitly stated. On the contrary, these names are used herein as a convenient method to distinguish two or more elements or two or more instances of an element. Therefore, the reference to the first element and the second element does not mean that only two elements can be used, or that the first element must be before the second element in some way. Moreover, unless otherwise stated, a group of elements may include one or more elements. Similarly, an element sometimes mentioned in the singular may also include one or more instances of an element.

[0030] The various exemplary logic blocks, modules, and circuits described in conjunction with the embodiments disclosed herein may be implemented or executed with a general purpose processor, a special purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein. A general purpose processor (also referred to herein as a host processor or simply a host) may be a microprocessor, but in an alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration. A general purpose computer including a processor is considered a special purpose computer when the general purpose computer is configured to execute computing instructions (e.g., software code) associated with the embodiments disclosed herein.

[0031] Moreover, it should be noted that embodiments can be described according to processes depicted as flow charts, flow diagrams, structure diagrams, or block diagrams. Although flow charts can describe operational behaviors as sequential processes, many of these behaviors can be performed in another order, in parallel, or substantially simultaneously. In addition, the order of actions can be rearranged. A process can correspond to a method, a thread, a function, a program, a subroutine, a subprogram, etc. In addition, the methods disclosed herein can be implemented in hardware, software, or both. If implemented in software, these functions can be stored or transmitted to a computer-readable medium as one or more instructions or codes. Computer-readable media include both computer storage media and communication media, and the communication media include any media that is conducive to transferring a computer program from one location to another.

[0032] As understood for the purposes of the embodiments described in this disclosure, a capacitive sensor can respond to an object (such as a finger or stylus) coming into contact with a touch-sensitive area of ​​the capacitive sensor or an object approaching a touch-sensitive area of ​​the capacitive sensor. In this disclosure, "contact" and "touch" are meant to encompass both physical contact of an object with a touch-sensitive area and the presence of an object within proximity of a touch-sensitive area without physical contact. Actual physical contact with the capacitive sensor is not required.

[0033] When an object contacts a capacitive sensor, a capacitance change may occur at or near the contact location within the touch sensor. If the touch meets a certain threshold, the analog acquisition front end may "detect" the touch. "Charge-and-transfer" is a technique implemented in some touch acquisition front ends to detect capacitance changes, in which the sensing capacitor is charged (e.g., faster or slower) in response to the capacitance change, and the charge is transferred to the integration capacitor over multiple charge transfer cycles. The amount of charge associated with this charge transfer can be converted to a digital signal by an analog-to-digital converter (ADC), and a digital controller can process those digital signals to determine the measurement value and whether the object has contacted the sensor.

[0034] A self-capacitance sensor is a capacitive field sensor that detects / responds to changes in capacitance to ground. Self-capacitance sensors are typically arranged in an array of rows and columns that react independently to touch. As a non-limiting example, a self-capacitance sensor may include a circuit that employs a repeated charge-and-transfer cycle using a commonly integrated CMOS push-pull drive circuit with a floating end. A mutual capacitance sensor is a capacitive field sensor that detects / responds to changes in capacitance between two electrodes, a drive electrode and a sense electrode. The drive electrode and sense electrode pair form a capacitor at each intersection of the drive line and the sense line. Self-capacitance technology and mutual capacitance technology can be used for the same touch interface and complement each other, for example, self-capacitance can be used to confirm a touch detected using mutual capacitance.

[0035] The touch sensors may be overlapped in a 2-dimensional (2-D) arrangement for a 2-D touch-sensitive surface that may be incorporated into a touch-sensitive surface (e.g., a touch pad or a display screen) and may facilitate user interaction with an associated home appliance. An insulating protective layer (e.g., resin, glass, plastic, etc.) may be used to cover the touch sensors. As used herein, a "touch display" or "touch panel" is a display (such as a liquid crystal display (LCD), a thin film transistor (TFT) LCD, or a light emitting diode (LED) display) that incorporates a 2-D touch sensor.

[0036] Taking a touch screen using a matrix sensor method of a mutual capacitance sensor using charge transfer technology as an example, the drive electrodes may extend in rows on one side of the substrate, and the sensing electrodes may extend in columns on the other side of the substrate to define a "matrix" array of N*M nodes. Each node corresponds to the intersection between the conductive lines of the drive electrode and the conductive lines of the sensing electrode. The drive electrode drives (i.e., provides alternating current (A / C) excitation) all nodes in a given row at the same time, and the sensing electrode senses all nodes in a given column. The capacitive coupling of the drive electrode and the sensing electrode at the node position can be measured separately or both in response to a capacitance change indicating a touch event. For example, if a drive signal is applied to the drive electrode of row 2 and the sensing electrode of column 3 is active, the node position is: (row 2, column 3). The nodes can be scanned sequentially by different combinations of drive electrodes and sensing electrodes. In one mode, the drive electrodes can be driven sequentially, while the sensing electrodes are all continuously monitored. In another mode, each sensing electrode can be sampled sequentially.

[0037] Taking a touch screen using a matrix sensor method of a self-capacitive sensor as an example, electrodes may extend in rows and columns to define a "matrix" array of N*M nodes. A matrix sensor may be constructed with electrodes at each node, each electrode being individually addressable, or each row and column may be addressable electrodes, and each node corresponds to a unique row / column pair. A drive signal (i.e., A / C excitation) is repeatedly provided to the electrodes of the sensor. When an object contacts the sensor, the coupling between the object and the electrode increases the current consumed on the electrode, which increases the apparent sensor capacitance, and the increase in sensor capacitance may be detected. For example, if an increase in capacitance is detected when a drive signal is applied to electrode row 2 and electrode column 3, the location of the touch may be row 2, column 3. Interpolation techniques may be used to identify locations between nodes. Nodes may be sequentially scanned sequentially by a combination of rows and columns of electrodes.

[0038] The above-mentioned drive signal (i.e., AC excitation) is one cause of EME. Capacitance is usually measured synchronously with the drive signal. Therefore, there is a direct relationship between the sampling rate of the measurement and the emission frequency of EME.

[0039] Electromagnetic emissions (EME) are intended broadly to include energy transmitted in electromagnetic waves of electromagnetic fields (EMFs) propagating through space (e.g., electromagnetic radiation (EMR)), as well as energy transmitted in electric currents conducted through materials (e.g., conducted emissions).

[0040] Emission measurements are intended to broadly include any measurable value indicative of EME. The measurement equipment may utilize techniques for wireless measurement of EME caused by a device (i.e., no physical connection between the measurement equipment and the device), techniques for wired measurement of EME caused by a device (i.e., at least one physical connection between the measurement equipment and the device (such as a wire)), or techniques using a combination of techniques for wireless measurement and techniques for wired measurement.

[0041] The EME of a touch sensor, and more specifically, one or more electrode arrays forming the touch sensor, may exceed EME limits for certain applications. As the area of ​​the N*M touch sensors increases, the EME of the touch sensors also increases. The EMR of a touch sensor is a propagating (i.e., radiating) wave of an electromagnetic field (EMF), which carries electromagnetic radiation energy.

[0042] Among other things, the waveform of the reference signal used by the driver of the touch sensor can affect the amount of EMR emitted by the touch sensor during sensing operations. Sharp transitions from one edge of the waveform to another create harmonics, thereby increasing EMR. Figure 1 A period of an exemplary square waveform 1 is shown including a rising edge 2, a top edge 3, a falling edge 4, and a bottom edge 5. Transitions 6, 7, and 8 correspond to increasing EMR. Figure 1 is a simple example. Figure 2 An exemplary square waveform 10 is shown that is approximated for a DAC. The transitions between edges and the transitions between the monotonic portions of the edges that form the square waveform 10 contribute to EMR.

[0043] The edges of the waveform can be shaped to control the harmonics, and therefore the EMR generated by such harmonics. A conventional technique for shaping the waveform in a touch sensor is to use a passive filter, but using specific hardware ties each touch sensor to a specific solution that may not meet EME limits for different applications or for the same application in different countries. For example, a touch sensor with a passive filter used in an application with a radio frequency (RF) antenna near Europe may not meet EME limits for the same application in the United States, nor may it meet EME limits for an application with an RF antenna using a different frequency band.

[0044] In addition, when a passive filter is used to shape the waveform of the driver reference signal, there is a tradeoff in sensing speed. The sensing speed is the speed at which the touch processor can identify contact with the touch sensor. The sensing speed is affected by the acquisition rate, which is the frequency at which the touch processor can measure the capacitance on the electrodes of the touch sensor (the acquisition rate is also referred to herein as the "sampling rate"). The higher the acquisition rate, the faster the sensing speed. The best acquisition rate is achieved when the driver reference signal has a flat top, but the passive filter provides the signal with a waveform having a top that slopes downward instead of a flat top.

[0045] Finally, passive filtering techniques known to the inventors of the present disclosure do not compensate for non-linearities in the touch sensor driver.

[0046]

[0006] Accordingly, the inventors of the present disclosure have recognized a need for waveform shaping techniques that do not suffer from some or all of the disadvantages of passive filtering techniques.

[0047] The non-monotonic portion of the waveform can be used to control the harmonics and, therefore, the EMR of the driver reference signal. Figure 3A An exemplary edge 12 of a DAC output waveform is shown, where edge 12 may be characterized as monotonically increasing. Figure 3B An exemplary edge 13 of a DAC output waveform is shown, where edge 13 includes a portion 14 that can be characterized as non-monotonic, and thus edge 13 can also be characterized as non-monotonic. In this disclosure, waveforms with intentionally introduced non-monotonic portions are referred to as "arbitrary waveforms," ​​and signals with such waveforms are referred to as "arbitrary signals."

[0048] There is a need for waveform shaping techniques that can be used to generate arbitrary waveforms for reference signals for touch sensor drivers in order to control harmonics and more generally control EME.

[0049] Some disclosed embodiments are generally related to shaping the waveform of a reference signal used by a driver of a touch sensor to limit the EME emitted by the touch sensor during a sensing operation. In the disclosed embodiments, shaping can be performed on one or more frequency bands of a sampling frequency that can be used for a sensing operation. Shaping can be performed on a portion of the waveform of the reference signal or on the entire waveform. One or more shapes detected as corresponding to EME below a predefined limit (or within a predefined range) of one or more frequency bands can be selected. An N-bit digital code (also referred to herein as an "n-bit code") corresponding to the selected shape can be stored. In some embodiments, the selected shape can be an arbitrary shape. In some embodiments, the selected shape can include non-monotonic and / or monotonic portions, and at least some of the n-bit codes in the n-bit code sequence can correspond to such portions.

[0050] It should be appreciated that the disclosed embodiments have many advantages and benefits, including but not limited to those described herein. For example, in some disclosed embodiments, electromagnetic radiation caused at least in part by known and unknown nonlinearities of a DAC that may be used to generate a reference voltage for a driver may be overcome.

[0051] In the disclosed embodiments, the shape of the waveform of the driver reference signal (i.e., "waveform shape") can be described based on the shape of the waveform of the driver reference signal output by the DAC and / or an n-bit code sequence applied to the DAC to generate a signal having such a shape.

[0052] Figure 4 An embodiment of a system 100 for configuring a touch sensing system 110 to control EME is shown. The system 100 may include the touch sensing system 110, touch sensors 130, measurement equipment 140, launch control software 150, and launch requirements 160. The touch sensing system 110 is generally configured to measure capacitance at the touch sensors 130, and detect and report touches in response to those measurements.

[0053] The touch sensing system 110 may include DAC reference drivers 111 and 112, n-bit DACs 113 and 114, a DAC control 115, and a touch detector 116. The N-bit DACs 113 and 114 are configured to receive bit streams 117 and 118, respectively, and to output driver reference signals 119 and 120, respectively, in response to the bit streams 117 and 118. Figure 4 In the example shown, reference signals 119 and 120 are labeled output reference 119 and input reference 120 because this example uses separate drivers for the rows and columns of electrodes of touch sensor 130. In other embodiments, a different number of drivers than in this example may be used, including one driver or more than two drivers.

[0054] DAC control 115 is configured to provide bit streams 117 and 118 to n-bit DACs 113 and 114, respectively. In the disclosed embodiment, bit streams 117 and 118 correspond to signal shapes. DAC control 115 can store the bit stream of the signal shape in a memory (not shown). For example, if a 4-bit DAC is used, DAC control 115 stores a 4-bit code sequence, and the 4-bit code sequence corresponds to a waveform having a desired shape. DAC control 115 can store a first n-bit code sequence to cause n-bit DAC 113 to generate reference signal 119, and store a second n-bit code sequence to cause n-bit DAC 114 to generate reference signal 120.

[0055] exist Figure 4In the example shown, DAC control 115 controls both n-bit DACs 113 and 114. In another embodiment, touch sensing system 110 may include multiple DAC control modules, for example, each n-bit DAC may be controlled (ie, receive a bit stream) by a dedicated DAC control module.

[0056] The measurement equipment 140 is generally configured to measure the EME 132 emitted from the touch sensor 130. More specifically, the measurement equipment 140 is configured to measure the EME 132 emitted from the touch sensor 130 during the sensing operation, and to provide the emission control software 150 with the emission measurement values ​​142 corresponding to the EME 132 during the sensing operation. The measurement equipment 140 may include any suitable sensor for measuring the EME 132 directly or indirectly, such as a spectrum analyzer, a Gauss meter, an EMF meter, a multimeter (mustimeter) for measuring body voltage, an E field sensor, and / or an H field sensor. The emission control software 150 is generally configured to analyze the emission measurement values ​​142 corresponding to the sensing operation, and based on those results, evaluate the shape of the n-bit code sequence and thus the driver reference signals 119 and 120 used during the sensing operation. For example, the emission control software 150 can evaluate the n-bit code sequence by comparing the emission measurement values ​​142 with the applicable EME requirements 160. If the transmit measurement 142 is below the applicable limit, the n-bit code sequence may be stored by the DAC control 115. If the transmit measurement 142 is outside the applicable limit, the transmit control software 150 may provide a new sequence of n-bit codes with a new signal shape to the DAC control 115 for testing. The process of selecting an n-bit code sequence, performing a sensing operation, measuring the EME 132, and evaluating the n-bit code sequence based on the measured EME 132 and the transmit requirements 160 may be repeated until an acceptable signal shape is identified.

[0057] Emission requirements 160 may include standards 162 and / or custom requirements 164. As an example, standard 162 may be an automotive standard, such as CISPR 25, which is a standard for controlling electromagnetic interference in electrical and electronic devices used in automotive applications. Custom requirements 164 may be any requirements, including, for example, customer requirements, requirements beyond standards, and requirements for applications for which no standard or industry-recognized standard exists.

[0058] Figure 5An embodiment of emission control software 150 is shown, which includes a waveform optimizer 152, a code generator 154, and an emission analyzer 156. The waveform optimizer 152 is generally configured to determine a change in the shape of a waveform to theoretically improve the EME emitted from the touch sensor 130 during a sensing operation. In one embodiment, the waveform optimizer 152 can select the change based on an optimization algorithm (and more specifically, according to the output of a cost function described more fully below). It should be understood that the disclosed embodiments do not require that the actual change in the shape of the waveform determined by the waveform optimizer 152 is actually optimal.

[0059] The code generator 154 is generally configured to generate an n-bit code sequence corresponding to the shape of the waveform selected by the waveform optimizer 152. The emission analyzer 156 is generally configured to analyze the emission measurements 142 from the measurement equipment 140 and determine how the EME emitted from the touch sensor 130 compares to various emission requirements.

[0060] In the disclosed embodiment, any suitable global optimization algorithm can be used to find the waveform shape that improves EME. In one embodiment, each sequence of the n-bit code tested is a parameter of the global optimization algorithm. In some cases, the list of n-bit code sequences can be long, and therefore the optimization algorithm can drift over a long period of time, so in one embodiment, in addition to using the list of n-bit code sequences or as an alternative to using the list of n-bit code sequences, a smaller number of parameters can be used to represent the waveform. For example, the waveform can be represented as a polynomial evaluated at different times, and the parameters of the global optimization algorithm are the coefficients of the polynomial at a given time. As another example, the waveform can be represented as the coefficients of a spline curve, a Bezier curve, or a Taylor series, which allows complex shapes to be represented with a limited list of parameters.

[0061] Figure 6A process 200 for configuring a touch sensing system (such as touch sensing system 110) to control EME according to the disclosed embodiments is shown. In operation 201, a reference signal is provided to a driver during a plurality of sensing operations. Each of the reference signals provided during different sensing operations has a different shape. In other words, the reference signal provided during a first sensing operation has a different shape than the reference signal provided during a subsequent sensing operation. In operation 202, an optimal shape of the reference signal is detected in response to the EME emitted by the touch sensor when the reference signal is provided. In one embodiment, the optimal shape of the reference signal can be detected because it is a first shape below the applicable EME limit. In another embodiment, the optimal shape of the reference signal can be detected because it corresponds to the lowest EME measurement value of a plurality of shapes tested (i.e., the shape corresponds to the minimum EME measurement value). In one embodiment, the optimal shape of the reference signal can be detected because it corresponds to the lowest EME measurement value of a plurality of shapes tested below the EME limit. In operation 203, an instruction for causing a DAC to generate a reference signal having an optimal shape is stored. The instruction can be or include an n-bit code sequence corresponding to the optimal shape.

[0062] Figure 7 A process 210 for evaluating the EME at a touch sensor for a particular shape of a reference signal is shown according to the disclosed embodiments. In operation 211, a driver reference signal is provided for a sensing operation, the reference signal having a preselected shape. In operation 212, the EME emitted by the touch sensor during the sensing operation is measured. In operation 213, if the EME is acceptable because the EME measurement is below the applicable limit, an n-bit code sequence corresponding to the current shape of the reference signal is stored in operation 216, and process 210 ends. If not acceptable, in operation 214, a new shape of the reference signal is selected in response to the measured EME, and in operation 215, a new reference signal having the new shape is provided for the driver, and operation 212 is performed again.

[0063] Figure 8 A process 220 for collecting a list of acceptable signal shapes that can be analyzed to determine a signal shape that improves EME at a touch sensor is shown in accordance with the disclosed embodiments. In operation 221, a driver reference signal is provided for a sensing operation, the reference signal having a preselected signal shape. In operation 222, the EME emitted by the touch sensor during the sensing operation is measured. In operation 223, if the EME is acceptable because the EME measurement is below an applicable limit, an n-bit code sequence corresponding to the current shape of the reference signal is stored in operation 227.

[0064] In operation 224, it is determined whether there are more signal shapes to be tested, and if not, the process 220 ends. In one embodiment, the signal shapes tested may be a set of pre-selected signal shapes, and if all pre-selected signal shapes have been tested, the process 220 ends.

[0065] In another embodiment, a cost function may be used, and process 220 ends when a shape is found that minimizes the cost function. The cost function may analyze the emission measurements and return an output that evaluates the compliance of the EME with the emission requirements.

[0066] If more signal shapes should be tested, a new signal shape for the reference signal is selected in operation 225 and a new reference signal with the new signal shape is provided for the driver in operation 226. If there are multiple sequences of n-bit codes stored, the n-bit code sequence with the lowest EME may be selected.

[0067] Fig. 9 A flow chart of a process 230 for obtaining a cost function, such as the cost function used in process 220, is shown in accordance with the disclosed embodiments. Fig. 9 In an embodiment of the present invention, the cost function may return a lower value to indicate improved compliance with the emission requirements, and return a higher value to indicate worsening compliance with the emission requirements. In other embodiments, other conventions may be used.

[0068] In operation 231, a plurality of emission measurements are received. The emission measurements may correspond to a particular waveform shape. In operation 232, a highest emission measurement of the emission measurements is identified. The highest emission measurement may be identified even though the highest emission measurement is above or below a defined emission limit.

[0069] In operation 233, excess values ​​are obtained and stored. For each of the excess values, the excess value may be obtained by calculating a difference between each emission measurement value of operation 231 and a defined emission limit value.

[0070] In operation 234, a margin value is obtained and stored. The margin value may be obtained by calculating the difference between the highest emission measurement value identified in operation 232 and the defined emission limit. In operation 235, the excess values ​​are summed and the summed excess values ​​are used to increase the cost function. If no excess values ​​exist, then in operation 236, the margin value is used to decrease the cost function.

[0071] Other embodiments may additionally or alternatively obtain the cost function by subtracting the margin value from the summed excess value and using the result to increase or decrease the cost function (depending on whether the result is positive or negative).

[0072] In some embodiments, the emission requirements may define emission limits in several frequency bands, and a process such as process 230 may be used to determine a cost function associated with the waveform shape of each of the frequency bands. In other embodiments, the emission requirements may define several frequency bands, and for each frequency band, emission limits for different measurement methods may be defined, and a process such as process 230 may be used to determine a cost function associated with the waveform shape for each combined frequency band and measurement method. For example, the emission requirements may divide the spectrum into an RFID band, a long wave (LW) band, and a medium wave (MW) band; and for each frequency band, an emission limit for peak (PK), quasi-peak (QP), and / or average (AV) emission may be defined. Thus, for each combination of frequency band and measurement method of interest, a cost function may be determined.

[0073] In some embodiments, the configuration process (such as processes 200, 210, and 220) may be performed multiple times for different sampling rates with different base frequencies. Multiple sequences of n-bit codes may be stored, where each sequence of n-bit codes is associated with a signal shape that optimizes EME for a particular sampling rate / base frequency. Fig.10 and Fig.11 Some advantages of storing multiple sequences of n-bit codes for different base frequencies are described.

[0074] Some disclosed embodiments generally relate to a DAC reference touch sensor driver and controlling the amount of EME emitted at a touch sensor. More specifically, a DAC is controlled to generate a shaped reference signal having a waveform shaped to control the amount of EME emitted at a touch sensor to meet EME limits. Such limits may be defined, for example, by a standard or customized for a specific application using a touch sensing system.

[0075] Fig.10 An embodiment of a touch sensing system 300 is shown that is configured to provide reference signals 306 and 307 that are shaped to control the EME emitted by a touch sensor in accordance with the disclosed embodiments. Fig.10In the example shown, the touch sensing system 300 is generally configured to perform self-capacitance sensing technology. The touch sensing system 300 may include drivers 301 and 302, n-bit DACs 303 and 304, and a touch detector 305. The touch controller 310 has stored an n-bit code 311 corresponding to the improved shape of the reference signals 306 and 307. The bitstream generator 312 is logic that enables the DAC controller 310 to generate bitstreams 308 and 309, which enable the n-bit DACs 303 and 304 to cooperate with the received clock signal to output the reference signal with an improved shape. More specifically, the bitstream generator 312 can control the rate at which the bitstreams 308 and 309 are provided to the n-bit DACs 303 and 304 based on, for example, the desired sampling rate used by the touch sensing system 300. The drivers 301 and 302 can respectively output drive signals 315 and 316 for driving electrodes of a touch sensor (not shown) in response to the reference signals 306 and 307, respectively.

[0076] The touch detector 305 is configured to measure the signal level of the drive signal 316 and detect changes in the signal level caused by a touch at a touch sensor operably coupled to the touch sensing system 300. More specifically, the touch detector 305 can detect an increase in current caused by an apparent additional capacitance from an object contacting the touch sensor. If the touch detector 305 detects a change in the signal level that meets or exceeds a threshold, the touch detector reports a touch.

[0077] Although in Fig.10 In the exemplary system shown, touch detector 305 is shown as measuring driver signal 316, but the disclosed embodiments are not limited thereto. Touch detector 305 may also measure driver signal 315 to detect a touch, or measure both driver signal 316 and driver signal 316 to detect a touch. Fig.10 The exemplary system shown includes two drivers 301 and 302, but it should be understood that other numbers of drivers may be used to provide drive signals to the touch sensor (eg, one driver or more than two drivers). Fig.10 The exemplary system shown is configured to perform self-capacitance sensing technology, and the intended operations described herein have been described with reference to self-capacitance sensing, but the disclosed embodiments are not limited thereto. In another embodiment, the touch sensing system 300 can be configured for mutual capacitance sensing, wherein a drive signal and a sense signal are provided to the touch sensor in response to a shaped reference signal, and the touch detector 305 is configured to measure the sense signal to detect a touch at the touch sensor.

[0078] In some cases, the frequency of the sampling rate may cause the measured value to be susceptible to external noise, but a different frequency may not cause the measured value to be susceptible or susceptible to external noise. Some disclosed embodiments are generally related to compensating for the effects of external noise at the touch sensor. In the disclosed embodiments, the sampling rate may be changed from a first sampling rate to a second sampling rate in response to external noise. More specifically, in the disclosed embodiments, the sampling rate may be changed to a second sampling rate that is less susceptible to external noise (i.e., affected by external noise) than the first sampling rate. The first sampling rate may be associated with a first fundamental frequency, and the second sampling rate may be associated with a second fundamental frequency. The shape of the reference signal available to the driver may change in response to the second fundamental frequency.

[0079] Fig.11 An implementation scheme of a process 320 for compensating external noise using different reference signal shapes is shown. In operation 321, a first driver reference signal is output. The driver reference signal has a first shape corresponding to a first fundamental frequency of a first sampling rate. In operation 322, a touch sensor is measured at a first sampling rate associated with the first fundamental frequency. In operation 323, a second fundamental frequency is determined in response to detected interference. In one embodiment, a second sampling rate that reduces the degree of susceptibility to external noise is determined, and the second fundamental frequency is determined based on the second sampling rate. In one embodiment, the second fundamental frequency and the second sampling rate may be one of a plurality of predetermined fundamental frequencies and predetermined sampling rates having a predetermined association, respectively. In operation 324, a second reference signal for a driver is provided. The second reference signal has a second shape different from the first shape, and the second shape is associated with the second fundamental frequency. In operation 325, the touch sensor is sampled at a second sampling rate associated with the first fundamental frequency.

[0080] Fig.12 An embodiment of a DAC controller 400 is shown that is configured to change the shape of a reference signal in response to a touch sensing system changing a sampling rate (e.g., to compensate for external noise). The DAC controller 400 includes a processor 401, a program memory 402, and a data memory 406 (depending on the specific implementation, the data memory 406 may be only a portion of the program memory). The program memory 402 is configured to store programs for various applications related to executing the disclosed embodiments, including controlling the DAC to change the shape of the reference signal. In this example, a code selector 403, a fundamental frequency detection 404, and a bit stream generator 405 are stored at the program memory 402. The data memory 406 is configured to store a sequence of n-bit codes 407 to achieve an improved shape of the reference signal. Each stored sequence 407 of n-bit codes is associated with a specific fundamental frequency (f 0) 408. In one embodiment, the sequence of n-bit codes 407 and base frequencies 408 may be stored as a lookup table (LUT), and the value of base frequencies 408, the values ​​corresponding to the base frequencies F may be used. 0 The sample rate or some other key to search the LUT.

[0081] In the intended operation of the DAC controller 400, the fundamental frequency detection 404 determines that the sampling rate has changed, for example, because the bitstream generator 405 has changed the bitstream rate to accommodate the new sampling rate. The fundamental frequency detection 404 determines the fundamental frequency associated with the new sampling rate. The code selector 403 uses the fundamental frequency to select an n-bit code sequence from a sequence of n-bit codes 407 stored on the data memory 406. In another embodiment, the code selector 403 may use a new sampling rate determined based on the bitstream rate of the bitstream generator 405 (in which case the fundamental frequency detection 404 may be omitted). The code selector 403 provides the selected sequence of n-bit codes to the bitstream generator 405 to generate a bitstream for the DAC.

[0082] For some applications, the EME requirements may be so stringent that not all EME limits may be met by a single fundamental frequency and waveform shape. In other words, multiple EME limits may be associated with an application, and a single fundamental frequency and waveform shape combination may not be found that does not result in undesirable harmonics (i.e., harmonics that cause the touch system to exceed at least one of the EME limits).

[0083] For example, in the intended application, the EME limits of the RFID, LW, and MW bands may be enforced. A touch system operating with a given base frequency and waveform shape may be able to follow (i.e., meet) the EME limits of RFID and LW, but exceed the EME limits of MW. Alternatively, a touch system using a different base frequency and waveform shape or the same base frequency and a different waveform shape may be able to follow the EME limits of RFID and MW, but exceed the EME limits of LW. In other words, in this example, a base frequency and shape that will meet the EME limits of RFID and LW are found; a base frequency and shape that will meet the EME limits of RFID and MW are found; but a base frequency and shape that will meet the EME limits of RFID, MW, and LW are not found.

[0084] Thus, some disclosed embodiments are generally directed to an emission control circuit and a touch sensing system including the emission control circuit, the touch sensing system being configured to perform dynamic selection of a touch sensing fundamental frequency and / or waveform shape of the touch sensing system based at least in part on system-level usage information and qualitative EME information. The system-level usage information may be, for example, information about the current state of other devices in an application system of which the touch sensing system is a part, or the system-level usage information may be instructions on how to prioritize EME limits (e.g., prioritize MW limits over LW limits).

[0085] Qualitative EME information is a qualitative characterization of associated fundamental frequency and waveform shape, and / or can be used to characterize the information of the relevance of fundamental frequency and waveform shape qualitatively according to EME. Qualitative EME information can include various fundamental frequency and waveform shape pairs, for example, information about harmonics, information about EME limits of specific frequency bands and / or regions, information about whether specific EME limits are met or tested, or any other information that can be used to determine whether a given fundamental frequency and waveform shape meet the EME limits associated with an application system. The EME limits met can be expressed as, for example, EME levels that may be generated during operation, meeting parts of spectrum (for example, LW, MW and RFID), and meeting limits of specific geographic regions (for example, North America, South America and Europe). Information about the EME limits met can also include information about unsatisfied EME limits, for example, decomposed by geographic regions or frequency bands.

[0086] Fig.13 An EME control circuit 505 is shown as part of or operating in conjunction with a touch sensing system 502 according to the disclosed embodiments. In the disclosed embodiments, the touch sensing system 502 may include a touch detection circuit 503, a touch sensing circuit 504, and an EME control circuit 505; and is part of a touch system 500 that also includes a touch sensor 501. Fig.13 In the illustrated embodiment, the touch system 500 is a subsystem that is part of a broader application system that may include other devices and / or components (not shown). The touch sensing circuit 504 can be configured to provide and receive a sensing signal 512 (e.g., a drive signal) to the touch sensor 501, and the touch detection circuit 503 can be configured to report a touch 513 in response to a measurement value 511 based on the sensing signal 512.

[0087] In the disclosed embodiment, the EME control circuit 505 can be generally configured to monitor the state of the application system and control the operation of the touch sensing circuit 504 to meet certain EME requirements. The EME control circuit 505 can be configured to: store (e.g., in data memory, registers, buffers, and combinations thereof) state information 508 about the broader application system and qualitative EME information 507 about the improved base frequency and associated waveform shape; select the base frequency and / or waveform shape based at least in part on the stored state information 508 and qualitative EME information 507; and provide a selection signal 510 in response to the selected base frequency and / or waveform.

[0088] In one embodiment, the EME control circuit 505 can be configured to receive system-level usage information 509 about the application system and store the state information 508 based at least in part on the received system-level usage information 509. In one embodiment, the application system can provide the system-level usage information 509 to the touch system 500. For example, the application system can provide the following information as the system-level usage information 509: information about other devices in the system, information about EME limits associated with those devices, and / or information about application-specific settings such as regional settings (e.g., North America, South America, or Europe). In one embodiment, the EME control circuit 505, the touch sensing system 502, or the touch system 500 more generally can include a communication link or communication protocol to collect or receive the system-level usage information 509 from the application system (e.g., from a computer, subsystem, or stack of the application system).

[0089] For example, if the application system includes multiple radio transmitters and receivers, the system level usage information 509 may include information about which bands and / or frequencies the radio is configured to receive / transmit and / or which bands and / or frequencies are actually received / transmitted by the radio.

[0090] exist Fig.13 In the illustrated embodiment, the base frequency and associated waveform shape (e.g., n-bit code sequence) may be stored with the qualitative EME information 507 or in another memory location (not shown) accessible by the selection logic 506. Fig.13 In the embodiment shown, the EME control circuit 505 may be a circuit for controlling a DAC (not shown, but such as Fig.10 DAC 303 or 304) of the DAC controller (such as Fig.10 The DAC controller 310 shown in FIG. 5 is a DAC controller 310 or a part thereof, and the selection signal 510 may be, for example, a driver reference signal. In another embodiment, the EME control circuit 505 may be a separate module (i.e., separate from the DAC controller) and configured to provide the selection signal 510 to a DAC controller that is part of the touch sensing circuit 504. For example, the EME control circuit 505 may be configured to provide information about a selected fundamental frequency and shape having favorable EME characteristics to the DAC controller, and such DAC controller may then select an n-bit code sequence corresponding to the information provided by the EME control circuit 505.

[0091] The EME control circuit 505 may include a base frequency and waveform shape selection logic 506 configured to dynamically select a base frequency and a waveform shape based at least in part on the state information 508 and the qualitative EME information 507. In one embodiment, the base frequency and waveform shape selection logic 506 may be configured to monitor the state information 508 and detect changes in the state information 508. If the base frequency and waveform shape selection logic 506 detects a change, the base frequency and waveform shape selection logic 506 may be configured to select a base frequency and a waveform shape based on the qualitative information 507 and the new state information 508, and provide a selection signal 510 in response to the selection.

[0092] Fig.14 An embodiment of a process 520 for dynamically selecting a base frequency and a waveform shape in response to an application system is shown.

[0093] In operation 521, a first sensing signal is provided in response to a first reference signal. The first reference signal may have a shape corresponding to a first waveform shape associated with a first fundamental frequency. The first fundamental frequency and the first waveform shape may have favorable EME characteristics for the application system, as stated in the qualitative EME information characterizing the association of the first fundamental frequency and the first waveform. In operation 522, a touch sensing measurement is performed in response to the first sensing signal. In one embodiment, the first sensing signal is a drive signal, and the touch sensing measurement value is a self-capacitance measurement value. In operation 523, new state information about the application system is detected. In operation 524, a second fundamental frequency and / or a second waveform shape are selected in response to new state information and qualitative EME information characterizing the association of multiple pairs of fundamental frequencies and waveform shapes (including those selected). The second fundamental frequency and / or the second waveform shape may be selected, for example, because the qualitative EME information characterizes the association more advantageously than the first fundamental frequency and the first waveform shape according to EME in view of the new state information (and preferably more advantageously than other combinations of available fundamental frequencies and waveform shapes). A more favorable EME characteristic may be an indication, for example, that the fundamental frequency and associated waveform shape result in EME within EME limits for various devices within the application system or within a geographic area where the application system is deployed.

[0094] In operation 525, a second reference signal is provided. The second reference signal has a second waveform shape different from the first waveform shape. In operation 526, a second sensing signal is provided in response to the second reference signal, and in operation 527, a touch sensor measurement is performed in response to the second sensing signal.

[0095] Those skilled in the art will appreciate that the disclosed embodiments have many advantages and benefits. For example, compliance with different electromagnetic emission limits based on the location of the radio antenna, based on radio quality, based on the location of use (e.g., but not limited to, countries with specific requirements related to EME), and / or based on the presence of other equipment (e.g., but not limited to, audio systems, remote entry equipment for cars, communication equipment); compliance with EME requirements for allocation of radio frequency bands (e.g., but not limited to frequency bands) worldwide; and the ability to control frequency content through software without using hardware passive filters.

[0096] As another example, the disclosed embodiments enable more general tuning of DAC controllers and touch sensing systems after manufacturing, and thus can accelerate time to market by saving redesign cycles that would otherwise be required for systems using passive filters.

[0097] As yet another example, combining a DAC solution with tuning software (eg, transmit control software 150) may compensate for nonlinearities in the driver stage that would otherwise result in unwanted harmonic signals.

[0098] As yet another example, using software to control a DAC to generate a shaped reference signal for a driver enables faster signal acquisition compared to other solutions such as hardware passive filters.

[0099] Although the present invention is described herein with respect to certain illustrated embodiments, those of ordinary skill in the art will recognize and appreciate that the present invention is not so limited. Rather, many additions, deletions, and modifications may be made to the illustrated embodiments and the described embodiments without departing from the scope of the present invention as claimed below and its legal equivalents. Furthermore, features from one embodiment may be combined with features of another embodiment while still being included within the scope of the present invention as contemplated by the inventor.

[0100] Additional non-limiting embodiments of the present disclosure include:

[0101] Embodiment 1: A touch sensing system comprises: a digital-to-analog converter (DAC) controller, the DAC controller being configured to output a code in a waveform shape, wherein the code or the waveform shape is associated with electromagnetic emission (EME) exhibiting below a limit at the touch sensing system; a DAC, the DAC being configured to output a first shaped reference signal in response to the code output by the DAC controller; a driver, the driver being configured to provide a drive signal to a touch sensor in response to the first shaped reference signal; and a touch detector, the touch detector being configured to report a touch in response to a changing signal level of the drive signal.

[0102] Embodiment 2: A system according to embodiment 1, wherein the DAC controller is configured to store an n-bit code sequence, and wherein the code of the waveform shape output by the DAC controller is a bit stream including one of the stored n-bit code sequences.

[0103] Embodiment 3: The system of any one of Embodiments 1 and 2, wherein at least another of the stored n-bit code sequences is associated with an EME exhibited at the touch sensing system below a different limit.

[0104] Embodiment 4: A system according to any one of Embodiments 1 to 3, wherein the DAC controller is configured to store n-bit code sequences, and each of the stored n-bit code sequences is associated with a different sampling rate.

[0105] Embodiment 5: A system according to any one of embodiments 1 to 4, wherein the DAC controller is configured to output a first code in a first waveform shape in response to a first base frequency, and to output a second code in a second waveform shape in response to a second base frequency, wherein the first base frequency is associated with a first sampling rate and the second base frequency is associated with a second sampling rate.

[0106] Embodiment 6: A system according to any one of embodiments 1 to 5, wherein the DAC controller is configured to: provide a first bit stream based at least in part on a first n-bit code sequence corresponding to the shape of the first shaped reference signal; and provide a second bit stream based at least in part on a second n-bit code sequence corresponding to the shape of a second shaped reference signal.

[0107] Embodiment 7: A system according to any one of Embodiments 1 to 6, wherein the DAC controller is configured to provide the first bit stream at a first rate associated with a first sampling rate, and to provide the second bit stream at a second rate associated with a second sampling rate.

[0108] Embodiment 8: According to the system described in any one of embodiments 1 to 7, it also includes one or more memories, and the one or more memories are configured to store: an n-bit code sequence in a waveform shape; qualitative electromagnetic emission (EME) information, wherein the qualitative EME information characterizes the correlation between the fundamental frequency and at least some sequences in the n-bit code sequence; and status information about the application system.

[0109] Embodiment 9: A system according to any one of embodiments 1 to 8, wherein the first n-bit code sequence and the second n-bit code sequence are associated with the same fundamental frequency, and wherein the qualitative EME information includes: harmonics of the fundamental frequency and a first representation of the first n-bit code sequence; and harmonics of the fundamental frequency and a second representation of the second n-bit code sequence.

[0110] Embodiment 10: The system according to any one of Embodiments 1 to 9 further includes selection logic, wherein the selection logic is configured to select an n-bit code sequence among the n-bit code sequences in response to the state information and the qualitative EME information.

[0111] Embodiment 11: A touch sensing method comprises: providing a first code of a waveform shape to a digital-to-analog converter (DAC), wherein the first code or the waveform shape is associated with electromagnetic emissions (EME) below a limit at a touch sensing system; providing a first shaped reference signal to a driver in response to the first code of the waveform shape; providing a drive signal to a touch sensor in response to the first shaped reference signal; and reporting a touch in response to a changing signal level of the drive signal.

[0112] Embodiment 12: A method according to embodiment 11, wherein providing the first code in the waveform shape includes: providing a bit stream including an n-bit code sequence.

[0113] Embodiment 13: The method according to any one of embodiments 11 and 12 also includes: measuring the drive signal at a first sampling rate; providing a second code in a waveform shape to the DAC in response to detecting that the sampling rate has changed from the first sampling rate to the second sampling rate; providing a second reference signal to the driver in response to the second code in the second waveform shape; providing a second drive signal to the touch sensor in response to the second reference signal; and measuring the second drive signal at the second sampling rate.

[0114] Embodiment 14: A method according to any one of Embodiments 11 to 13, wherein the second sampling rate is associated with a lower degree of susceptibility to external noise compared to the first sampling rate.

[0115] Embodiment 15: According to the method described in any one of embodiments 11 to 14, it also includes: providing a first bit stream of the first code of the first waveform shape at a first rate associated with the first sampling rate; and providing a second bit stream of the second code of the second waveform shape at a second rate associated with the second sampling rate.

[0116] Embodiment 16: According to the method described in any one of embodiments 11 to 15, it includes: performing a first touch measurement in response to providing the drive signal; providing a second code of a second waveform shape to the DAC in response to detecting that the status information of the application system has changed; providing a second shaped reference signal to the driver in response to the second code of the second waveform shape; providing a second drive signal to the touch sensor in response to the second reference signal; and performing a second touch measurement in response to providing the second drive signal.

[0117] Embodiment 17: The method according to any one of Embodiments 11 to 16 also includes: determining that the harmonics associated with the second waveform shape have more favorable electromagnetic emission (EME) characteristics in response to the changed state information about the application system and the qualitative EME information about the harmonics associated with the second waveform shape.

[0118] Embodiment 18: A system for configuring a touch sensing system to control electromagnetic emissions (EME), the system comprising: a touch sensing system, the touch sensing system configured to detect a touch at a touch sensor in response to a sensed signal; and emission control software, the emission control software, when executed by a processor, configured to: receive EME measurements obtained in response to EME emitted by the touch sensor during a sensing operation; evaluate a shape of a reference signal used by the touch sensing system to detect the touch at the touch sensor in response to the EME measurements and one or more emission requirements; and configure the touch sensing system to use an improved shape of the reference signal for detecting touch, the improved shape corresponding to the EME measurement that is lower than the one or more emission requirements.

[0119] Embodiment 19: A system according to Embodiment 18, wherein the shape of the improved shape is characterized by one or more of a substantially flat-top edge, a rising edge having one or more non-monotonic portions, and a falling edge having one or more non-monotonic portions.

[0120] Embodiment 20: A system according to any of Embodiments 18 and 19, wherein the emission control software is configured to select the improved shape in response to detecting that the improved shape minimizes EME relative to other shapes of the reference signal.

[0121] Embodiment 21: A system according to any one of Embodiments 18 to 20, wherein the touch sensing system is configured to store the improved shape of the reference signal.

[0122] Embodiment 22: A system according to any one of Embodiments 18 to 21, wherein the one or more emission requirements include emission requirements defined by a standard.

[0123] Embodiment 23: A system according to any one of Embodiments 18 to 22, wherein the one or more emission requirements include emission requirements defined by customer requirements.

[0124] Embodiment 24: The system of any one of Embodiments 18 to 23, further comprising an emission measurement device configured to provide an EME measurement value in response to the EME exhibited by the touch sensor.

[0125] Embodiment 25: A method for configuring a touch sensing system to control electromagnetic radiation (EME), the method comprising: providing reference signals for a sensing operation, each of the reference signals having a different shape; detecting an improved shape of the reference signal in response to a measured value indicating electromagnetic radiation (EME) emitted by a touch sensor during the sensing operation; and storing instructions for generating the reference signal having an optimal shape.

[0126] Embodiment 26: A method according to embodiment 25, wherein providing the reference signal during the sensing operation includes: providing a first reference signal during a first sensing operation, the first reference signal having a preselected shape; receiving a first EME measurement value during the first sensing operation; determining that the first EME measurement value is greater than the emission requirement; providing a second reference signal during a second sensing operation, the second reference signal having a second shape; receiving a second EME measurement value during the second sensing operation; and determining that the second EME measurement value is less than the emission requirement.

[0127] Embodiment 27: The method of any one of Embodiments 25 and 26, further comprising: selecting one of the first shape and the second shape that corresponds to the smaller of the first EME measurement value and the second EME measurement value.

[0128] Embodiment 28: The method according to any one of embodiments 25 to 27 also includes: detecting that the first EME measurement value is not less than the emission requirement; determining a change in the first shape that may affect the EME emitted by the touch sensor during a sensing operation; and selecting an n-bit code sequence corresponding to the second shape in response to the determined change.

[0129] Embodiment 29: A method according to any one of embodiments 25 to 28, wherein the selecting the n-bit code sequence corresponding to the second shape includes: selecting at least some n-bit codes in the n-bit code sequence corresponding to the determined variation of the first shape.

[0130] Embodiment 30: A method according to any one of Embodiments 25 to 29, wherein the selecting at least some n-bit codes includes: selecting at least some n-bit codes corresponding to a non-monotonic portion of the n-bit code sequence.

Claims

1. A touch sensing system, comprising: a digital-to-analog converter controller configured to output a code in a waveform shape, wherein the code in the waveform shape is associated with electromagnetic emissions exhibiting below a limit at the touch sensing system; a digital-to-analog converter configured to output a first shaped reference signal in response to the code output by the digital-to-analog converter controller; a driver coupled to the digital-to-analog converter and configured to provide a drive signal to a touch sensor in response to the first shaped reference signal, wherein there is no filter between the driver and the digital-to-analog converter; and A touch detector is configured to report a touch in response to a changing signal level of the drive signal.

2. The system of claim 1 , wherein the DAC controller is configured to store an n-bit code sequence, and wherein the code of the waveform shape output by the DAC controller is a bit stream comprising one of the stored n-bit code sequences.

3. The system of claim 2, wherein at least another of the stored n-bit code sequences is associated with an electromagnetic emission that exhibits below a different limit at the touch sensing system.

4. The system of claim 1, wherein the DAC controller is configured to store n-bit code sequences, and each of the stored n-bit code sequences is associated with a different sampling rate.

5. The system of claim 4, wherein the DAC controller is configured to output a first code of a first waveform shape in response to a first base frequency, and to output a second code of a second waveform shape in response to a second base frequency, The first base frequency is associated with a first sampling rate, and the second base frequency is associated with a second sampling rate.

6. The system of claim 5, wherein the digital-to-analog converter controller is configured to: providing a first bit stream based at least in part on a first n-bit code sequence corresponding to a shape of the first shaped reference signal; and A second bit stream is provided based at least in part on a second n-bit code sequence corresponding to a shape of the second shaped reference signal.

7. The system of claim 6, wherein the DAC controller is configured to provide the first bit stream at a first rate associated with a first sampling rate and to provide the second bit stream at a second rate associated with a second sampling rate.

8. The system of claim 1 , further comprising one or more memories configured to store: An n-bit code sequence in the shape of a waveform; qualitative electromagnetic emission information characterizing the association of a fundamental frequency with at least some of the n-bit code sequences; and Information about the status of the application system.

9. The system of claim 8, wherein the first n-bit code sequence and the second n-bit code sequence are associated with the same fundamental frequency, and wherein the qualitative electromagnetic emission information comprises: a harmonic of the fundamental frequency and a first representation of a first n-bit code sequence; and A harmonic of the fundamental frequency and a second representation of the second n-bit code sequence.

10. The system of claim 8, further comprising selection logic configured to select one of the n-bit code sequences in response to the state information and the qualitative electromagnetic emission information.

11. A touch sensing method, comprising: providing a first code of a first waveform shape to a digital-to-analog converter, wherein the first code of the first waveform shape is associated with electromagnetic emissions below a limit at a touch sensing system; providing a first shaped reference signal to a driver coupled to the digital-to-analog converter in response to the first code of the first waveform shape; providing a drive signal to a touch sensor in response to the first shaped reference signal, wherein there is no filter between the driver and the digital-to-analog converter; as well as A touch is reported in response to the changing signal level of the drive signal.

12. The method of claim 11 , wherein providing the first code of the first waveform shape comprises: A bit stream comprising an n-bit code sequence is provided.

13. The method according to claim 11, further comprising: measuring the drive signal at a first sampling rate; providing a second code of a second waveform shape to the digital-to-analog converter in response to detecting that the sampling rate has changed from a first sampling rate to a second sampling rate; providing a second shaped reference signal to the driver in response to the second code of the second waveform shape; providing a second drive signal to the touch sensor in response to the second shaped reference signal; as well as The second drive signal is measured at the second sampling rate.

14. The method of claim 13, wherein the second sampling rate is associated with a lower susceptibility to external noise than the first sampling rate.

15. The method according to claim 13, further comprising: providing a first bit stream of the first code of the first waveform shape at a first rate associated with the first sampling rate; as well as A second bit stream of the second code of the second waveform shape is provided at a second rate associated with the second sampling rate.

16. The method according to claim 11, comprising: performing a first touch measurement in response to providing the drive signal; providing a second code of a second waveform shape to the digital-to-analog converter in response to detecting that the state information of the application system has changed; providing a second shaped reference signal to the driver in response to the second code of the second waveform shape; providing a second drive signal to the touch sensor in response to the second shaped reference signal; as well as A second touch measurement is performed in response to providing the second drive signal.

17. The method according to claim 16, further comprising: A determination is made that the harmonics associated with the second waveform shape have more favorable electromagnetic emission characteristics in response to the changed state information about the application system and qualitative electromagnetic emission information about the harmonics associated with the second waveform shape.

18. A system for controlling electromagnetic emission, the system comprising: A touch sensing system for detecting a touch at a touch sensor in response to a measured sense signal, and comprising: A digital-to-analog converter, the digital-to-analog converter is used to output a shaped reference signal; a touch detector for measuring a sense signal in response to the shaped reference signal; and a driver coupled to the digital-to-analog converter to provide a drive signal to the touch sensor in response to the shaped reference signal, wherein there is no filter between the driver and the digital-to-analog converter; and emission control software, which, when executed by a processor, is configured to: receiving electromagnetic emission measurements obtained in response to electromagnetic emissions emitted by the touch sensor during a sensing operation; evaluating, responsive to the electromagnetic emission measurements and one or more emission requirements, a shape of a reference signal used by the touch sensing system to detect the touch at the touch sensor; and The touch sensing system is configured to use an improved shape of the reference signal for detecting touch, the improved shape corresponding to the electromagnetic emission measurement value being below the one or more emission requirements.

19. The system of claim 18, wherein the shape of the improved shape is characterized by one or more of a substantially flat-top edge, a rising edge having one or more non-monotonic portions, and a falling edge having one or more non-monotonic portions.

20. The system of claim 18, wherein the emission control software is configured to select the modified shape in response to detecting that the modified shape minimizes electromagnetic emissions relative to other shapes of the reference signal.

21. The system of claim 18, wherein the touch sensing system is configured to store the improved shape of the reference signal.

22. The system of claim 18, wherein the one or more emission requirements comprise emission requirements defined by a standard.

23. The system of claim 18, wherein the one or more launch requirements include a launch requirement defined by a customer requirement.

24. The system of claim 18, further comprising an emission measurement device configured to provide electromagnetic emission measurements in response to electromagnetic emissions exhibited by the touch sensor.

25. A method of configuring a touch sensing system to control electromagnetic emissions, the method comprising: providing reference signals for sensing operations to a driver coupled to a digital-to-analog converter, wherein there is no filter between the driver and the digital-to-analog converter, each of the reference signals having a different shape; detecting a modified shape of a reference signal in response to a plurality of measured values ​​indicating shapes of electromagnetic emissions emitted by the touch sensor during the sensing operation that are below an electromagnetic emission limit; as well as Instructions for generating said reference signal having an optimal shape are stored by the digital-to-analog converter controller.

26. The method of claim 25, wherein providing a reference signal comprises: providing a first reference signal during a first sensing operation, the first reference signal having a preselected first shape; receiving a first electromagnetic radiation measurement during the first sensing operation; determining that the first electromagnetic radiation measurement value is greater than an emission requirement; providing a second reference signal during a second sensing operation, the second reference signal having a second shape; receiving a second electromagnetic radiation measurement during the second sensing operation; as well as A determination is made as to whether the second electromagnetic radiation measurement is less than the emission requirement.

27. The method according to claim 26, further comprising: One of the first shape and the second shape is selected that corresponds to a smaller one of the first electromagnetic radiation measurement and the second electromagnetic radiation measurement.

28. The method of claim 26, further comprising: detecting that the first electromagnetic radiation measurement value is not less than the emission requirement; determining a change in the first shape that affects electromagnetic radiation emitted by the touch sensor during a sensing operation; as well as An n-bit code sequence corresponding to the second shape is selected in response to the determined change.

29. The method of claim 28, wherein the selecting the n-bit code sequence corresponding to the second shape comprises: At least some of the n-bit codes in the sequence of n-bit codes are selected that correspond to the determined variations of the first shape.

30. The method of claim 29, wherein said selecting at least some of the n-bit codes comprises: At least some of the n-bit codes are selected that correspond to non-monotonic portions of the n-bit code sequence.

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