Short-term noise suppression

Abstract

The invention relates to "short-term noise rejection". A processing system is configured to drive a transmitter electrode with a repetitive multi-burst pattern. The repetitive multi-burst pattern includes a first plurality of bursts of a sensing waveform and a second plurality of bursts of the sensing waveform. The second plurality of bursts is a repetition of the first plurality of bursts. The processing system is further configured to receive a result signal from a receiver electrode in response to the repetitive multi-burst pattern, and to identify, in the result signal, a segment that is least affected by noise and that coincides in time with a burst of the first plurality of bursts or a burst of the second plurality of bursts that matches the burst of the first plurality of bursts. The processing system is further configured to decode the result signal using the segment.

Description

Technical Field

[0001] The described embodiments generally relate to electronic devices, and more specifically, to noise suppression for capacitive imaging sensors. Background Technology

[0002] Input devices, including proximity sensor devices (e.g., touchpads or touch sensor devices), are widely used in a variety of electronic systems. Proximity sensor devices typically include a sensing area, usually defined by a surface, within which the proximity sensor device determines the presence, location, and / or movement of one or more input objects. Proximity sensor devices can be used to provide interfaces for electronic systems. For example, proximity sensor devices are commonly used as input devices in larger computing systems, such as opaque touchpads integrated into or surrounding laptops or desktops. Proximity sensor devices are also commonly used in smaller computing systems, such as touchscreens integrated into cellular phones.

[0003] Proximity sensor devices are typically used in conjunction with other components, such as power supplies or battery chargers. These components may emit noise that could impair the sensing capabilities of the proximity sensor device.

[0004] Therefore, it is desirable to perform proximity sensing in a noise-robust manner. Summary of the Invention

[0005] Typically, in one aspect, one or more embodiments relate to a processing system configured to: drive transmitter electrodes using a repetitive multiburst pattern, wherein the repetitive multiburst pattern includes: a first plurality of bursts of a sensed waveform, and a second plurality of bursts of a sensed waveform, wherein the second plurality of bursts are repetitions of the first plurality of bursts; receive a result signal from receiver electrodes in response to the repetitive multiburst pattern, identify in the result signal a segment least affected by noise, and the segment coincides in time with a burst in the first plurality of bursts or a burst in the second plurality of bursts that matches a burst in the first plurality of bursts; and use the segment to decode the result signal.

[0006] Generally, in one aspect, one or more embodiments relate to an input device including: a transmitter electrode and a receiver electrode; and a processing system configured to: drive the transmitter electrode using a repetitive multiburst pattern, wherein the repetitive multiburst pattern includes: a first plurality of bursts of a sensed waveform, and a second plurality of bursts of a sensed waveform, wherein the second plurality of bursts is a repetition of the first plurality of bursts; receive a result signal from the receiver electrode in response to the repetitive multiburst pattern, identify in the result signal a segment least affected by noise, and the segment: coincides in time with a burst in the first plurality of bursts or a burst in the second plurality of bursts that matches a burst in the first plurality of bursts; and use the segment to decode the result signal.

[0007] Typically, in one aspect, one or more embodiments relate to a method comprising: driving transmitter electrodes using a repetitive multiburst pattern, wherein the repetitive multiburst pattern includes: a first plurality of bursts of a sensed waveform, and a second plurality of bursts of a sensed waveform, wherein the second plurality of bursts is a repetition of the first plurality of bursts; receiving a result signal from receiver electrodes in response to the repetitive multiburst pattern, identifying in the result signal a segment least affected by noise, and the segment temporally overlapping with a burst in the first plurality of bursts or a burst in the second plurality of bursts that matches a burst in the first plurality of bursts; and decoding the result signal using the segment.

[0008] Other aspects of the embodiments will become apparent from the following description and the appended claims. Attached Figure Description

[0009] Figure 1 A block diagram of an input device according to one or more embodiments is shown.

[0010] Figure 2 A sensing scenario according to one or more embodiments is illustrated.

[0011] Figure 3 A noise emission pattern according to one or more embodiments is shown.

[0012] Figure 4A The sensing timing diagram is shown.

[0013] Figure 4B A sensing timing diagram according to one or more embodiments is shown.

[0014] Figure 5 A flowchart illustrating a method for capacitive sensing according to one or more embodiments is shown.

[0015] Figure 6 A flowchart illustrating a method for short-term noise suppression sensing according to one or more embodiments is shown. Detailed Implementation

[0016] The following specific embodiments are merely exemplary in nature and are not intended to limit the disclosed technology or its application and use. Furthermore, they are not intended to be construed as being bound by any express or implied theories presented in the foregoing technical fields, background technology, or the following specific embodiments.

[0017] In the following detailed embodiments, numerous specific details are set forth to provide a more thorough understanding of the disclosed technology. However, it will be apparent to those skilled in the art that the disclosed technology can be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0018] Throughout the application, ordinal numbers (e.g., first, second, third, etc.) may be used as adjectives for elements (i.e., any noun in this application). The use of ordinal numbers does not imply or create any particular ordering of elements, nor does it limit any element to a single element, unless explicitly disclosed, such as through the use of terms like “before,” “after,” “single,” and others. Rather, the use of ordinal numbers is for distinguishing elements. As an example, a first element is distinct from a second element, and a first element may contain more than one element and be ordered after (or before) the second element.

[0019] Various embodiments of this disclosure provide input devices and methods for achieving capacitive sensing in the presence of noise. More specifically, embodiments of this disclosure suppress short-term noise, such as noise emission occurring in short bursts with a duration of a few milliseconds (ms) or less. Short-term noise can be emitted at a variety of frequencies. An example of such noise emission is the noise emitted by a battery charger. Because noise can be emitted at a variety of rapidly alternating frequencies, frequency hopping may not be a feasible method to avoid noise emission.

[0020] In one or more embodiments, a repetitive multi-burst pattern is used as the capacitive sensing signal to resolve noise emission. Each burst in the multi-burst pattern includes the sensing waveform described below. Each burst in the repetitive multi-burst pattern can be emitted twice. Because the duration of noise emission is short, with proper configuration of the repetitive multi-burst pattern, a segment of the received response associated with one of the two bursts should not be affected by noise emission, even if a segment of the resulting signal associated with the other of the two bursts may be affected by noise emission. Embodiments of this disclosure then identify clean segments of the response to perform touch decoding. Clean segments are segments determined to be unaffected by noise emission. Each of these aspects is discussed in detail below.

[0021] Figure 1This is a block diagram of an example of an input device (100) according to one or more embodiments. The input device (100) may be configured to provide input to an electronic system (not shown). As used in this document, the term "electronic system" (or "electronic device") broadly refers to any system capable of processing information electronically. Some non-limiting examples of electronic systems include personal computers, such as desktop computers, laptop computers, netbook computers, tablet computers, web browsers, e-book readers, smartphones, personal digital assistants (PDAs), gaming devices, automotive infotainment systems, etc.

[0022] exist Figure 1 In this design, the input device (100) is shown as a proximity sensor device (e.g., a "touchpad" or "touch sensor device") configured to sense input provided by one or more input objects (140) in the sensing area (120). Example input objects include styluses, active pens, and fingers. Furthermore, the specific input objects in the sensing area can change during one or more gestures.

[0023] The sensing area (120) covers any space above, around, in, and / or near the input device (100), where the input device (100) is capable of detecting user input (e.g., user input provided by one or more input objects). The size, shape, and location of a particular sensing area can vary widely depending on the embodiment.

[0024] The input device (100) can utilize any combination of sensor components and sensing technologies to detect user input in the sensing area (120). The input device (100) includes one or more sensing elements for detecting user input. As a non-limiting example, the input device (100) may use capacitive technology.

[0025] In some capacitive implementations of the input device (100), a voltage or current is applied to create an electric field. A nearby input object causes a change in the electric field and produces a detectable change in capacitive coupling, which can be detected as a change in voltage, current, etc.

[0026] Some capacitive implementations utilize arrays or other regular or irregular patterns of capacitive sensing elements to create an electric field. In some capacitive implementations, individual sensing elements can be ohmically shorted together to form a large sensor electrode. Some capacitive implementations utilize resistive sheets, which can have uniform resistance.

[0027] Some capacitive implementations utilize a "self-capacitance" (or "absolute capacitance") sensing method based on changes in capacitive coupling between sensor electrodes and an input object. In various embodiments, the input object near the sensor electrodes alters the electric field near the sensor electrodes, thereby changing the measured capacitive coupling. In one implementation, the absolute capacitance sensing method operates by modulating the sensor electrodes relative to a reference voltage (e.g., system ground) and by detecting the capacitive coupling between the sensor electrodes and the input object. The reference voltage can be a substantially constant voltage or a varying voltage, and in various embodiments, the reference voltage can be system ground. Measurements obtained using the absolute capacitance sensing method can be referred to as absolute capacitance measurements.

[0028] Some capacitive implementations utilize a "mutual capacitance" (or "cross-capacitance") sensing method based on changes in capacitive coupling between sensor electrodes. In various embodiments, an input object near the sensor electrodes alters the electric field between the sensor electrodes, thereby changing the measured capacitive coupling. In one implementation, the mutual capacitance sensing method operates by detecting the capacitive coupling between one or more transmitter sensor electrodes (also referred to as "transmitter electrodes" or "transmitters," Tx) and one or more receiver sensor electrodes (also referred to as "receiver electrodes" or "receivers," Rx). The transmitter sensor electrodes may be modulated relative to a reference voltage (e.g., system ground) to transmit a transmitter signal. The receiver sensor electrodes may be kept substantially constant relative to the reference voltage to facilitate reception of the resulting signal. The reference voltage may be a substantially constant voltage, and in various embodiments, the reference voltage may be system ground. The resulting signal may include one or more effects corresponding to one or more transmitter signals and / or one or more sources of environmental interference (e.g., other electromagnetic signals, including noise emissions). One or more effects may be the transmitter signal, changes in the transmitter signal caused by one or more input objects and / or environmental interference, or other such effects. The sensor electrodes can be dedicated transmitters or receivers, or they can be configured to both transmit and receive. Measurement results obtained using mutual capacitance sensing methods can be referred to as mutual capacitance measurements.

[0029] exist Figure 1In this embodiment, a processing system (110) is shown as part of an input device (100). The processing system (110) is configured to operate the hardware of the input device (100) to detect input in a sensing area (120). The processing system (110) includes part or all of one or more integrated circuits (ICs) and / or other circuit components. For example, a processing system for a mutual capacitance sensor device may include transmitter circuitry configured to transmit signals using transmitter sensor electrodes, and / or receiver circuitry configured to receive signals using receiver sensor electrodes. Furthermore, a processing system for an absolute capacitance sensor device may include driver circuitry configured to drive absolute capacitance signals onto sensor electrodes, and / or receiver circuitry configured to receive signals using those sensor electrodes. In one or more embodiments, a processing system for a combined mutual capacitance and absolute capacitance sensor device may include any combination of the aforementioned mutual capacitance and absolute capacitance circuitry. In some embodiments, the processing system (110) also includes electronically readable instructions, such as firmware code, software code, and / or the like.

[0030] The processing system (110) can be implemented as a set of modules that perform different functions. For example, the processing system (110) may include determining circuitry (150) to determine when at least one input object is in the sensing area, determine the signal-to-noise ratio, determine the position information of the input object, recognize gestures, determine the action to be performed based on the gesture, a combination of gestures, or other information, and / or perform other operations. Modules may include hardware and / or software that can be executed on a processor.

[0031] The sensor circuit (160) may include functionality to drive a sensing element to transmit a transmitter signal and receive a result signal. For example, the sensor circuit (160) may include sensing circuitry coupled to the sensing element. The sensor circuit (160) may include, for example, a transmitter module and a receiver module. The transmitter module may include transmitter circuitry coupled to a transmitting portion of the sensing element. The receiver module may include receiver circuitry coupled to a receiving portion of the sensing element and may include functionality to receive a result signal.

[0032] although Figure 1 The determination circuit (150) and sensor circuit (160) are shown, but alternative or additional modules may be present according to one or more embodiments. Example alternative or additional modules include a hardware operation module for operating hardware such as sensor electrodes and a display screen (155), a data processing module for processing data such as sensor signals and location information, a reporting module for reporting information, a recognition module configured to recognize gestures such as mode-changing gestures, and a mode-changing module for changing the operating mode.

[0033] In some embodiments, the processing system (110) responds directly to user input (or the absence of user input) in the sensing area (120) by inducing one or more actions. Example actions include changing operating modes and graphical user interface (GUI) actions such as cursor movement, selection, menu navigation, and other functions. In some embodiments, the processing system (110) provides information about the input (or the absence of input) to a part of the electronic system (e.g., to a central processing unit of the electronic system separate from the processing system (110), if such a separate central processing unit exists). In some embodiments, a part of the electronic system processes the information received from the processing system (110) to act on the user input, such as to facilitate a full range of actions, including mode-changing actions and GUI actions.

[0034] Although Figure 1 The configuration of the components is shown, but other configurations may be used without departing from the scope of the invention. For example, various components may be combined to create a single component. As another example, functionality performed by a single component may be performed by two or more components.

[0035] Figure 2 A sensing scenario (200) according to one or more embodiments is illustrated. Figure 2 The diagram shows a set of transmitter (Tx) electrodes (210) and a set of receiver (Rx) electrodes. The Tx and Rx electrodes intersect at the capacitive sensing element, thereby forming the capacitive sensing element (230) in a rectangular pattern. Figure 2 In the example, the capacitive sensing element (230) is arranged in a rectangular grid. Those skilled in the art will understand that this disclosure is not limited to a particular electrode pattern. Any electrode configuration suitable for capacitive sensing can be used. For example, the electrode configuration can be provided by a matrix pad sensor having multiple sensing pads and traces connected to the sensing pads in a metal mesh layer across the sensing area.

[0036] Transcapacitive coupling C tIt is present at a capacitive sensing element (230). In one or more embodiments, the capacitive sensing element (230) is "scanned" to determine transcapacitive coupling. For example, assume a configuration with 20 Tx electrodes and 40 Rx electrodes. Each of the 20 Tx electrodes may emit a capacitive sensing signal in the form of a repetitive multi-burst pattern, and each of the 40 Rx electrodes may receive a result signal associated with each of the emitted repetitive multi-burst patterns. The result signal may be used to determine the measurement result of transcapacitive coupling at the capacitive sensing element (230), which is used to determine the presence and location information of an input object, as described above. A set of values ​​of the capacitive sensing element (230) forms a "capacitive image" (also referred to as a "sensing image") representing transcapacitive coupling at the sensing element. In one or more embodiments, the sensing image, or capacitive image, includes data received during the process of measuring the result signal received using at least a portion of the capacitive sensing element (230) distributed across the sensing area (120). The result signal can be received at one moment, or by scanning rows and / or columns of capacitive sensing elements (230) distributed across the sensing area (120) in a raster scan mode (e.g., polling each sensing element individually in a desired scan mode), a row scan mode, a column scan mode, or other useful scanning techniques.

[0037] When an input object (290) (e.g., a finger) approaches the capacitive sensing element (230), C T It is possible to provide changes to C T The grounded input object (290) and the change in amount ΔC T In other words, C T It may be sensitive to finger-to-ground voltage, which may be caused by another capacitive coupling C from the finger (290) to ground (240). GND Generate. ΔC T It can be measured by sensing the charge that shifts to or from the Rx electrode in response to the drive of the Tx electrode.

[0038] In real-world scenarios, the finger (290) not only via C F Capacitive coupling to ground (240), and also via C N Capacitive coupling is applied to a noise source (250). The noise source (250) can be, for example, a battery charger or power supply, which may have unique noise emission characteristics, as referenced. Figure 3 As shown. Therefore, when the finger (290) approaches the capacitive sensing element (230), ΔC TThe measurement results are affected not only by grounding but also by noise emitted by the noise source (250), which may cause charge to shift toward or away from the Rx electrode. Therefore, the ability to sense the presence or absence of a finger (290) near the capacitive sensing element (230) may be impaired by noise emission. Various methods discussed below can be used to address noise emission. For simplicity, the following discussion pertains to operations performed on a single capacitive sensing element (230). The same techniques can be applied to any number of capacitive sensing elements (230) in the sensed image. Furthermore, while the operations are described in the context of cross-capacitance sensing, similar operations can be performed in absolute capacitance scenarios, as referenced in [reference missing]. Figure 1 The subject of discussion.

[0039] Figure 3 An example noise emission pattern according to one or more embodiments is shown. The noise emission pattern (300) may be associated with a noise source, such as a battery charger. The battery charger (or any other noise source) may be internal or external to an electronic device equipped with an input device. For example, the battery charger may be a USB-connected charger.

[0040] The example noise emission pattern (300) includes 24 different emissions at discrete frequencies (shown in kHz). Each emission may have a specific amplitude (shown in V, peak to peak). Higher amplitudes may result in more interference. Each emission at the discrete frequencies may occur for a finite duration. In the example noise emission pattern (300), each emission may occur for approximately 0.5 ms. In other noise emission patterns, the noise emissions may have different durations without departing from this disclosure. The noise emission pattern may repeat over time, cycling through the frequencies shown in the figure.

[0041] When the frequency of the emitted noise coincides with or is close to the frequency of the signal used to drive the Tx electrode, interference with capacitive sensing performed by the input device may occur. The signal used to drive the Tx electrode (“sensing signal”) can be an alternating current (AC) signal, such as a square wave. Multiple periods of the square wave can be grouped into bursts, and multiple bursts can be grouped into a burst mode or a repeating burst mode. Various frequencies can be used to drive the Tx electrode, for example, in the range between 100 kHz and 250 kHz. In the example of the noise emission mode (300), the frequency that can be used for sensing overlaps with the frequency of the noise emission mode, thus potentially causing interference with capacitive sensing.

[0042] Figure 4A An example sensing timing diagram illustrating how noise emission can affect the received signal is shown. In the sensing timing diagram (400), the signal used to drive the Tx electrode overlaps in time with the noise emission (406).

[0043] The sensing signal includes a multi-burst pattern (412). When sensing is performed continuously, the multi-burst pattern (412) can be emitted sequentially. The multi-burst pattern includes a series of bursts (416). The combination of all bursts (416) in the multi-burst pattern can, for example, be encoded using code division multiplexing (CDM) to provide a capacitive sensing signal for a single capacitive sensing operation. For example, 18 bursts can be used for CDM encoding with an 18th order. When acquired by the Rx electrode at the capacitive sensing element, the resulting signal can be decoded using CDM demodulation.

[0044] In C T The resulting signal may be affected by the presence or absence of the input object. Therefore, the resulting signal allows for the detection of the presence or absence of the input object. However, if noise emission overlaps with one or more bursts, the resulting signal may become corrupted by the noise emission.

[0045] Each burst (416) comprises multiple signal cycles, such as a square wave. In one example, assume the signal has a frequency of 170 kHz. Therefore, a single cycle has a duration of ~6 μs. Each burst can comprise 40 cycles, resulting in a burst duration of ~240 μs. Therefore, a burst pattern with 18 bursts can have a duration of ~4.32 ms. In another example, assume the signal has a frequency of 204 kHz. Therefore, a single cycle has a duration of ~5 μs. Each burst can comprise 50 cycles, resulting in a burst duration of ~250 μs. Therefore, a multi-burst pattern with 18 bursts can have a duration of ~4.5 ms.

[0046] As mentioned above, and as Figure 4A As shown, noise emission can overlap with burst patterns in time. In this example, first and second repetitions (402, 404) of the noise emission pattern are shown. The noise emission pattern corresponds to... Figure 3 The noise emission modes are shown. Therefore, each of the noise emission modes (402, 404) includes... Figure 3 Noise emission (406) is shown at the frequency indicated. Each noise emission (406) lasts for 0.5 ms. Based on the above example with bursts (416) having a duration of ~240 μs or ~250 μs, noise emission can therefore overlap with two or three bursts (416) (as shown, bursts 9, 10, and 11 are affected). Figure 4AIn the example shown, one of the noise emissions (406) is at 200 kHz. Assuming the sensed signal is at 204 kHz, the 200 kHz noise emission could potentially affect any sensing performed using bursts 9, 10, and 11 due to overlap. Since demodulation for obtaining the resulting signal depends on a combination of bursts 1-18, the resulting signal could potentially be corrupted by the noise emission. Although other noise emissions are also present in the example (at 182 kHz and 218 kHz), these other noise emissions are sufficiently far from the sensed signal at 204 kHz to be unlikely to cause interference.

[0047] Figure 4B An example sensing timing diagram according to one or more embodiments is shown. In the sensing timing diagram (450), the sensing signal overlaps with noise emission in time, similar to... Figure 4A The scene shown is similar. Figure 4A The diagram shows a repetitive noise emission pattern with first and second repetitions (402, 404).

[0048] and Figure 4A Unlike other methods, the sensing signal is a repetitive multi-burst pattern (452). In the repetitive multi-burst pattern (452), bursts (476) within the repetitive multi-burst pattern are repeated. In one or more embodiments, the repetition of bursts is interleaved. Specifically, in Figure 4B In the example, 18 bursts are repeated in groups of three. For the first repetition of the 18 bursts, bursts (476) are labeled T1B1, T1B2, T1B3, ..., T1B18, and for the second repetition of the 18 bursts, bursts (476) are labeled T2B1, T2B2, T2B3, ..., T2B18. Thus, a total of 36 bursts form a repetitive multi-burst pattern (452). Based on the organization of bursts (476) in groups of three, in a repetitive multi-burst pattern (452), the order of bursts is T1B1, T1B2, T1B3, T2B1, T2B2, T2B3, T1B4, T1B5, T1B6, T2B4, T2B5, T2B6, ..., T1B16, T1B17, T1B18, T2B16, T2B17, T2B18.

[0049] exist Figure 4BThe diagram illustrates four different time alignments (462, 464, 466, 468) for a repetitive multiburst mode. Because a 204kHz sensing signal is used, a burst (476) that temporally overlaps with a 200kHz noise emission (406) is affected by the noise emission. If the frequency of the noise emission is substantially the same as the frequency of the sensing signal (within a few kHz, e.g., 1, 2, 3, 4, or 5kHz), any sensing signal at a particular frequency may be affected by the noise emission. Depending on the time alignment, the affected bursts can be different bursts. For example, in the first time alignment (462) of the repetitive multiburst mode, bursts T1B1, T1B2, and T1B3 are affected. In the second time alignment (464) of the repetitive burst mode, bursts T1B2, T1B3, and T2B1 are affected. Figure 4B As shown, regardless of timing, there are always three bursts affected by the example noise in this example. However, which bursts are affected by the example noise can change.

[0050] In one or more embodiments, because the 18 bursts in the repeating multiburst mode are repeated in groups of three, it is possible that while some bursts may be affected by noise, there are unaffected bursts for each of the affected bursts. Consider a first time alignment (462) of the repeating multiburst mode, where bursts T1B1, T1B2, and T1B3 are affected. In this case, bursts T2B1, T2B2, and T2B3 are unaffected. Similarly, consider a second time alignment (464) of the repeating burst mode, where bursts T1B2, T1B3, and T2B1 are affected. In this case, bursts T1B1, T1B2, and T1B3 are unaffected.

[0051] While the repetitive multi-burst mode (462) is discussed as having bursts repeated in groups of three, in other embodiments, a single burst may be repeated, and bursts may be repeated in groups of two, four, etc. In one or more embodiments, the selected repetition mode depends on the duration of the noise emission (406) relative to the duration of a single burst. If the noise emission (406) affects no more than one burst, a single burst may be repeated. If the noise emission (406) affects no more than two bursts, bursts may be repeated in groups of two. If the noise emission (406) affects no more than four bursts, bursts may be repeated in groups of four. Generally, a subset of consecutive bursts may have a cardinality based on the duration of the noise emission. The cardinality is chosen to allow the minimum number of consecutive bursts required to obtain a combined duration exceeding the duration of the noise emission (of the subset of consecutive bursts). A subset of consecutive bursts may be followed by a corresponding subset of repetitive bursts.

[0052] In this way, it is possible that for a burst affected by noise, there exists a repeating burst unaffected by noise. Therefore, instead of selecting the burst affected by noise, touch can be decoded by selecting the burst unaffected by noise. The flowchart below provides additional details on the selection of a suitable repeating multi-burst pattern, the application of repeating multi-burst patterns, and touch decoding.

[0053] Figure 5 and Figure 6 A flowchart according to one or more embodiments is shown. Although the various steps in the flowchart are presented and described sequentially, those skilled in the art will understand that some or all of the steps may be performed in a different order, some or all of the steps may be combined or omitted, and some or all of the steps may be performed in parallel. Additional steps may be further performed. Therefore, the scope of this disclosure should not be considered limited to... Figure 5 and Figure 6 The specific arrangement of the steps shown.

[0054] Although the steps of the method have been discussed with reference to a capacitive sensing element, those skilled in the art will understand that at least some of the steps can be repeated for multiple or all capacitive sensing elements in the sensing area to obtain a capacitive image.

[0055] Figure 5 A flowchart illustrating a method for capacitive sensing according to one or more embodiments is shown. The method may be repeated in a loop, for example, at a fixed rate, to provide periodically updated touch output.

[0056] In step 502, the noise amplitude of the emitted noise is obtained. Obtaining the noise amplitude may involve emitting a noise sensing burst to measure the interference caused by the noise emission. Electrodes located in the sensing area can be used to perform the noise emission measurement. In one or more embodiments, the noise sensing burst includes a signal similar to the signal intended for touch sensing. For example, if touch sensing is to be performed at 204 kHz, the signal of the noise sensing burst is also at 204 kHz. In step 502, a different number of noise sensing bursts may be emitted. For example, when the system performs touch sensing using a default sensing frequency (as described in step 506), or when the system performs touch sensing using frequency hopping (as described in step 508), only a few (e.g., 1, 2, 3, or 4) noise sensing bursts may be emitted to determine the noise amplitude. When the noise is present within an extended interval, using only a few noise sensing bursts may be sufficient, and the use of the default sensing frequency method (step 506) or the frequency hopping method (step 508) may be appropriate for that extended interval. However, when the system needs to perform short-term noise suppression sensing (as described in step 512), more noise sensing bursts can be emitted in step 502, such as 20 noise sensing bursts. When a sufficient number of noise sensing bursts are emitted (e.g., 20 noise sensing bursts), in addition to the amplitude, the duration of the noise emission can also be determined, as referenced below. Figure 6 As stated above.

[0057] In step 504, a test is performed to determine whether the noise amplitude is higher or lower than a specified threshold. If the noise amplitude is lower than the specified threshold, the execution of the method can proceed to step 506. If the noise amplitude reaches or exceeds the specified threshold, the execution of the method can proceed to step 508.

[0058] In step 506, touch sensing is performed using the default sensing frequency and a multi-burst mode. The multi-burst mode can be as follows: Figure 4A As described above. Referring to the previously discussed example, sensing at the capacitive sensing element can be performed with, for example, an assumed default frequency of 204 kHz (cycle period ~5 μs), a burst size of 50, and a result burst duration of ~250 μs. Using 18 bursts for the CDM scheme, the duration of transcapacitive sensing at the capacitive sensing element can be performed in ~4.5 ms. A low-pass filter and demodulator circuitry can generate a result signal indicating a touch while eliminating or reducing noise interference that is not directly close to the default frequency used for sensing (e.g., within a few kHz). The output of step 506 can be used as a result of touch sensing, indicating the presence or absence of a touch, and after step 506 is completed, the execution of the method can return to step 502 to continue to the next sensing cycle.

[0059] In step 508, touch sensing is performed using a frequency hopping method. In this method, a sensing frequency can be selected from a set of possible sensing frequencies (e.g., in the range of 100-250 kHz). The frequency to be used can be chosen to avoid frequencies emitting noise. For example, suppose the frequency hopping method provides two sensing frequencies: 204 kHz and 170 kHz. If a noise-emitting frequency is found to be at 200 kHz, the frequency hopping method will use the 170 kHz sensing frequency. Specifically, in this example, step 502 can be performed first for the 204 kHz sensing frequency. In step 504, it is determined that the noise amplitude exceeds a specified threshold, and therefore, the 170 kHz sensing frequency is selected to repeat steps 502-508. Frequency hopping can be performed for any number of available sensing frequencies, e.g., until a suitable sensing frequency is found. The multi-burst pattern used can be non-repetitive. Referring to the previously discussed example, sensing at a capacitive sensing element can be performed with a burst size of 40 (cycle period ~6 μs) and a resulting burst duration of ~240 μs. Using 18 bursts for the CDM scheme, the duration of transcapacitive sensing at the capacitive sensing element can be performed in ~4.3 ms. A low-pass filter and demodulator circuitry can generate a result signal indicating a touch, while eliminating or reducing noise interference that is not directly close to the default frequency used for sensing (e.g., within a few kHz).

[0060] In step 510, a test is performed to determine whether the frequency hopping method of step 508 was successful or failed. If all available sensing frequencies have been tested (through repeated execution of steps 502-508) without producing noise amplitudes below a specified threshold, it can be determined that the frequency hopping method has failed. If the frequency hopping method is found to have failed, the method can proceed to step 512. If the frequency hopping method is found to have succeeded, the output of step 508 can be used as the result of touch sensing, indicating the presence or absence of a touch, and the execution of the method can return to step 502 to continue the next sensing cycle.

[0061] In step 512, short-term noise suppression sensing is used to perform touch sensing, as shown below. Figure 6 Further description. In short, a repetitive multi-burst pattern can be used for sensing. In the repetitive multi-burst pattern, each of the bursts can occur twice. Of the two of the same bursts, the burst less affected by noise emission can then be selected for further processing to determine the presence or absence of a touch. The output of step 512 can be used as the result of touch sensing, indicating the presence or absence of a touch, and after step 512 is completed, the execution of the method can return to step 502 to continue the next sensing cycle.

[0062] Figure 6A flowchart illustrating a method for short-term noise suppression sensing according to one or more embodiments is shown. Figure 6 The method, when executed, allows for touch decoding even in the presence of noise, as shown in the reference. Figure 4B The discussion focuses on what can be performed at a specific sensing frequency (e.g., the default sensing frequency). Figure 6 The method involves emitting all bursts of the repetitive multi-burst pattern used for sensing at the default sensing frequency. Figure 6 The method can alternatively be executed at any other sensing frequency, for example, if execution at the default sensing frequency does not result in successful decoding of the touch. In such a scenario, bursts of the repetitive multi-burst pattern used for sensing are emitted at the selected sensing frequency. Figure 6 The method can alternatively be implemented using multiple sensing frequencies. In this scenario, one or more bursts of a repetitive multi-burst pattern are emitted at a first selected sensing frequency, and one or more bursts of the repetitive multi-burst pattern are emitted at a second selected sensing frequency. Any number of sensing frequencies can be used in this scenario. The selection of one or more sensing frequencies can depend on frequencies known to be present / absent in the noise emission. Where possible, selecting a sensing frequency different from the frequency of the noise emission can improve the robustness of touch sensing.

[0063] In step 602, the duration of the noise emission is determined. The duration of the noise emission can be determined based on the noise measurement performed in step 502. The duration can be a measured time interval during which the amplitude exceeds a previously specified threshold at a frequency close to the sensing frequency.

[0064] In step 604, a repetitive multiburst pattern is defined based on the duration of noise emission. In one or more embodiments, the arrangement of repetitive bursts in the repetitive multiburst pattern depends on the duration of the bursts and the duration of noise emission. In one or more embodiments, the bursts and their repetitions are interleaved. Specifically, as referenced... Figure 4B The repetitive bursts discussed are arranged such that, if one burst is affected by noise emission, repetition of the same burst may be unaffected by the noise emission. For example, if the noise emission has a duration sufficient to affect up to three consecutive bursts, the repetitive burst pattern includes bursts repeating in groups of three, such as... Figure 4B As shown in the image.

[0065] In step 606, a repetitive multiburst mode is emitted on the Tx electrode.

[0066] In step 608, concurrently with the execution of step 606, a result signal in response to the emitted repetitive multiburst pattern is received on the Rx electrode. The result signal may include a repetitive multiburst pattern modulated by the presence or absence of the input object and / or by noise occurring during the reception of the result signal.

[0067] In step 610, clean segments with bursts unaffected by noise emission are identified in the resulting signal obtained in step 608. A clean segment is a segment unaffected by noise emission. (Reference) Figure 4B When sensing using a repetitive multi-burst pattern, bursts may be affected by noise emission. However, because each burst in the pattern occurs twice, each burst affected by noise emission has a matching burst unaffected by noise emission. Therefore, clean segments can be identified in the resulting signal. Clean segments are determined to be unaffected by noise emission or minimally affected by noise emission, and coincide temporally with bursts or burst repetitions.

[0068] Previously received result signals (e.g., from) Figure 5 Previous executions of the method can be used as a reference to determine, for two matching bursts (bursts and burst repetitions), the burst affected by noise emission compared to the burst unaffected by noise emission. Figure 5 In previous executions of the method, bursts unaffected by noise emission are known. To make this determination, a comparison can be performed between the current resulting signal and the previous resulting signal. More specifically, in the resulting signal, two segments with two matching bursts are compared with segments in the previous resulting signal that have bursts without noise emission to determine which of the segments associated with the two bursts is more similar to the segment in the previous resulting signal assumed to be noise-free. The segment more similar to the segment in the previous resulting signal can be considered a clean segment.

[0069] Consider, for example, including Figure 4B The result signal of the repeated multi-burst mode (452) in the middle. In the example of the first alignment (462), the segment of the result signal associated with T2B1, T2B2 and T2B3 will be selected compared with the segment associated with T1B1, T1B2 and T1B3. In the example of the second alignment (464), the segment of the result signal associated with T1B1, T2B2 and T2B3 will be selected compared with the segment associated with T2B1, T1B2 and T1B3.

[0070] In one embodiment, a minimum-maximum distance operation is used to perform the comparison, which can be performed as follows. When a sensing operation is performed by emitting a sensing signal on the Tx electrode, a resulting signal can be obtained from the Rx electrode at each capacitive sensing element associated with the Tx electrode. Each of these resulting signals may include a low-pass filtered, undemodulated signal obtained from the corresponding Rx electrode. For example, consider... Figure 2 The sensing scenario (200) is described. In this example, three Rx electrodes can obtain a response to a sensing signal emitted on a Tx electrode. Each of the three obtained result signals can be different, for example, depending on whether the input object is present in the vicinity of the corresponding capacitive sensing element. Furthermore, each of the three result signals includes two of the repeating bursts. To obtain the minimum-maximum distance, for each of the three result signals, the signal amplitudes of the first and second obtained result signals in the two bursts are calculated. Next, for a segment with a burst known to be unaffected by noise emission, the absolute difference of each of the signal amplitudes is calculated compared to the signal amplitude of the previous result signal. Among the three result signals associated with the Rx electrodes, for the first burst, the maximum value of the absolute difference is identified, and for the second burst, the maximum value of the absolute difference is identified. The two maximum values ​​can be associated with different electrodes. For example, the maximum value of the first burst can be associated with the first Rx electrode, while the maximum value of the second burst can be associated with the third Rx electrode. The segment of the result signal associated with the lower of the two maximum values ​​is then selected as the clean segment for further processing. Subsequently, although a portion of the resulting signal may be corrupted, the complete resulting signal, detected as free of noise artifacts, is assembled by selecting only clean segments. In certain cases, two bursts in a pair can overlap due to noise emission. This can occur, for example, when the duration of the noise emission is longer than the duration assumed when determining the repetitive multi-burst pattern in step 604.

[0071] In step 612, the touch is decoded from the result signal obtained in step 610. In addition to the previously mentioned low-pass filtering, touch decoding may also involve demodulation. The demodulated result signal can be converted from analog to digital (A / D) for further processing, including detecting the presence or absence of the touch. If both bursts are affected by noise, touch decoding in step 612 may fail and can be skipped. In this case, Figure 5 Step 510 ensures that an alternative method for touch sensing is implemented.

[0072] Embodiments of this disclosure can have various features. Embodiments of this disclosure can perform touch sensing in the presence of noise with various characteristics, including short, repetitive bursts of noise at discrete frequencies. Embodiments of this disclosure can perform touch sensing in the presence of high-amplitude noise. Embodiments of this disclosure do not require narrow-bandpass filtering, which would increase the burst period. Embodiments of this disclosure do not require an increase in the amplitude of the sense signal, which would increase power consumption and may cause interference with other components, such as a display.

[0073] While the invention has been described with respect to a limited number of embodiments, those skilled in the art who benefit from this disclosure will understand that other embodiments can be devised without departing from the scope of the invention as disclosed herein. Therefore, the scope of the invention should be limited only by the appended claims.

Claims

1. A processing system configured to: The transmitter electrodes are driven using a repetitive multi-burst mode. The repetitive multiburst mode mentioned above includes: The first multiple bursts of the sensed waveform, and The second plurality of bursts of the sensed waveform The second plurality of bursts is a repetition of the first plurality of bursts; Receive the result signal in response to the repetitive multiburst pattern from the receiver electrodes. Identifying the segment least affected by noise in the resulting signal, wherein the segment temporally overlaps with a burst in the first plurality of bursts or a burst in the second plurality of bursts matching the burst in the first plurality of bursts, wherein identifying the segment least affected by noise includes: The first segment and the second segment of the result signal are compared with the third segment. The first segment of the resulting signal coincides temporally with the burst in the first plurality of bursts, the second segment of the resulting signal coincides temporally with the burst in the second plurality of bursts, and the third segment is associated with a previously repeated multi-burst pattern obtained in the absence of the noise. Select, between the first segment and the second segment, the segment least affected by the noise that is more similar to the third segment; and Use the segment to decode the resulting signal.

2. The processing system of claim 1, wherein selecting the segment least affected by the noise between the first segment and the second segment comprises: Perform a minimum-maximum distance operation on the amplitudes of the first segment, the second segment, and the third segment.

3. The processing system according to claim 1, wherein the second plurality of bursts interleaves with the first plurality of bursts, wherein the second plurality of bursts interleaves with the first plurality of bursts includes: A first subset of consecutive bursts selected from the first plurality of bursts, wherein the first subset has a cardinality based on the duration of the noise; as well as A second subset of consecutive bursts selected from the second plurality of bursts, corresponding to the first subset of consecutive bursts, wherein the second subset has the cardinality. The cardinality is selected as the minimum cardinality necessary for the combined duration of the first subset of consecutive bursts to exceed the duration of the noise, and / or the duration of the noise is determined based on noise measurements performed using multiple noise sensing bursts emitted on the transmitter electrodes.

4. The processing system according to claim 1, The frequency of the noise is substantially the same as the frequency of the sensed waveform, and / or The sensed waveforms of different bursts in the first plurality of bursts have different frequencies in the different bursts.

5. The processing system of claim 1, wherein decoding the result signal includes code division multiplexing (CDM) decoding of the result signal.

6. An input device, comprising: Transmitter electrodes and receiver electrodes; as well as The processing system is configured as follows: The transmitter electrodes are driven using a repetitive multi-burst mode. The repetitive multiburst mode mentioned above includes: The first multiple bursts of the sensed waveform, and The second plurality of bursts of the sensed waveform The second plurality of bursts is a repetition of the first plurality of bursts; Receive the result signal in response to the repetitive multiburst pattern from the receiver electrodes. Identifying the segment least affected by noise in the resulting signal, wherein the segment temporally overlaps with a burst in the first plurality of bursts or a burst in the second plurality of bursts matching the burst in the first plurality of bursts, wherein identifying the segment least affected by noise includes: The first segment and the second segment of the result signal are compared with the third segment. The first segment of the resulting signal coincides temporally with the burst in the first plurality of bursts, the second segment of the resulting signal coincides temporally with the burst in the second plurality of bursts, and the third segment is associated with a previously repeated multi-burst pattern obtained in the absence of the noise. Select, between the first segment and the second segment, the segment least affected by the noise that is more similar to the third segment; and Use the segment to decode the resulting signal.

7. The input device according to claim 6, The noise is coupled to the resulting signal by an input object close to the capacitive sensing element formed by the transmitter electrodes and the receiver electrodes. And / or It further includes a battery charger, wherein the battery charger is a noise source associated with the noise.

8. The input device according to claim 6, The frequency of the noise is substantially the same as the frequency of the sensed waveform.

9. A method for operating an input device, the method comprising: The transmitter electrodes are driven using a repetitive multi-burst mode. The repetitive multiburst mode mentioned above includes: The first multiple bursts of the sensed waveform, and The second plurality of bursts of the sensed waveform The second plurality of bursts is a repetition of the first plurality of bursts; Receive the result signal in response to the repetitive multiburst pattern from the receiver electrodes. Identifying the segment least affected by noise in the resulting signal, wherein the segment temporally overlaps with a burst in the first plurality of bursts or a burst in the second plurality of bursts matching the burst in the first plurality of bursts, wherein identifying the segment least affected by noise includes: The first segment and the second segment of the result signal are compared with the third segment. The first segment of the resulting signal coincides temporally with the burst in the first plurality of bursts, the second segment of the resulting signal coincides temporally with the burst in the second plurality of bursts, and the third segment is associated with a previously repeated multi-burst pattern obtained in the absence of the noise. Select, between the first segment and the second segment, the segment least affected by the noise that is more similar to the third segment; and The resulting signal is decoded using the aforementioned segment.

10. The method according to claim 9, The second plurality of bursts intersects with the first plurality of bursts, wherein the second plurality of bursts intersects with the first plurality of bursts includes: A first subset of consecutive bursts selected from the first plurality of bursts, wherein the first subset has a cardinality based on the duration of the noise; as well as A second subset of consecutive bursts selected from the second plurality of bursts and corresponding to the first subset of consecutive bursts, wherein the second subset has the cardinality, wherein the cardinality is selected as the minimum cardinality necessary for the joint duration of the first subset of consecutive bursts to exceed the duration of the noise.

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