Nested scanning for capacitive touch sensors

Abstract

A touch detection circuit, with: multiple sensor channels (X0-X4,Y0-Y2); a controller (102) which is connected to the multiple sensor channels (X0-X4,Y0-Y2), wherein the controller (102) is configured as follows: to assign the sensor channels (X0-X4,Y0-Y2) to sensor nodes (101), wherein the sensor nodes (101) form several nested concentrated sensors, wherein at least two of the nested concentrated sensors have a common sensor node (101), and at least one of the nested concentrated sensors comprises a set of non-adjacent sensor nodes (101); to scan the nested concentrated sensors during a sampling period to detect one or more touch inputs; and In response to the detection of one or more touch inputs, to determine the position of at least one touch input.

Description

[0001] The subject matter of this disclosure generally relates to capacitive touch sensing. BACKGROUND

[0002] Human interfaces in devices and equipment may include capacitive touch sensors that allow a user to provide input to control various functions of the device or equipment. The capacitive touch sensors are periodically sampled or polled to detect touch input. The power consumption of the device or equipment is influenced by the number of active sensor nodes being sampled. An example of capacitive touch sensor sensing is described in US 2012 / 0050216 A1.

[0003] Embodiments of the present invention include a touch sensing circuit, a touch sensing method, and a touch sensing system according to the independent claims. Preferred developments are subject to the dependent claims. Fig. 1 shows an illustrative capacitive touch system according to one embodiment. Fig. 2 shows illustrative nested lumped sensors in a capacitive touch system according to one embodiment. Fig. 3 shows an illustrative touch control circuit for sensing nested capacitively arranged lumped sensors according to one embodiment. Fig. 4 shows an illustrative touch control circuit for sensing nested self-capacitive lumped sensors according to one embodiment. Fig.Figure 5 is a flowchart of an illustrative process for nested sampling of nodes from lumped sensors. Fig. Figure 6 shows an illustrative nested sampling of nodes on a 2D touch-sensitive surface.

[0004] Capacitive touch sensors are implemented using one of the following illustrative approaches: self-capacitance and mutual capacitance. A self-capacitance touch sensor node is formed by a single electrode whose capacitance is measured with respect to the circuit's DC ground. Touch sensing is achieved by a change in the capacitance (touch delta) of the sensor node when it is touched. Each mutual capacitance touch sensor node is formed by a drive (X) electrode and a sense (Y) electrode. The capacitance between the two electrodes is measured, and touch sensing is achieved by a characteristic change in the measured capacitance. In both approaches, the capacitance of each sensor node is measured independently to achieve touch sensing.

[0005] In one example, the capacitance for each of the sensor nodes is measured in a sequential order or a hierarchical order to reduce the overall sampling time. In sequential order systems, the sensor node capacitances are measured in a fixed order and individually compared with the previous measurement results. A sequence with an n number of measurement results is established to detect the presence of a touch input at any sensor node. For a relatively large number of sensor nodes, collecting measurements in a sequential order can be a time-consuming process, which may result in unacceptable processing time for touch detection and / or increased power consumption due to the portion of time the measurement system spends actively scanning the sensor nodes for touch input.

[0006] However, according to an example of hierarchical ordering systems, the sensor nodes are grouped into lumped sensors, where multiple drive electrodes are electrically connected or coupled to each other, and multiple sensing electrodes (mutual capacitance) or self-capacitance electrodes are electrically coupled or connected to each other to form a single complex capacitance. For example, if each lumped sensor is configured to include an n number of sensor nodes, the n sensor nodes are divided into m / n lumped sensors as follows: lumped sensor 0 = sensor node 0 to (m-1), lumped sensor 1 = sensor node m to (2m-1), ... lumped sensor (n / m) = sensor nodes (nm-1) to (n-1).

[0007] According to one example, a periodic measurement is performed on the lumped sensors. When one of the lumped sensors detects a touch input, then the m sensor nodes included in the lumped sensor are individually measured to determine which sensor node is being touched. In the pristine state, a total of (n / m) measurements are required to determine that no touch input is present. When a touch input is present, the individual sensor node being touched can be determined with a total of (n / m) + m measurements. For example, assume that lumped sensor 2 is touched, then the buttons comprising lumped sensor 2 are measured: button m → button (m + 1) → button (m + 2) ... → button (2m - 1).If two touch inputs are present on different lumped sensors, the keys constituting each of these lumped sensors are measured, resulting in a total number of (n / m) + 2m measurements. Illustrative nested sampling of nodes

[0008] In one embodiment, as in the hierarchical node sampling method, the individual sensor nodes are grouped into lumped sensors so that preliminary touch sensing can be achieved without sampling all of the individual sensor nodes. However, the nested node sampling method does not require measuring the individual sensor nodes grouped into lumped sensors. The presence and position of one or more touch inputs can be determined using only the measurements from the lumped sensors. To implement nested node sampling, the sensor nodes are grouped into lumped sensors. Different grouping schemes can be used, depending on the application requirements. In one embodiment, touch buttons orTouch-sensitive buttons of a user interface (UI) are divided into concentrated sensors in such a way that a capacitive measurement at the concentrated sensors alone allows a clear detection for each touch button.

[0009] In an illustrative configuration, each lumped sensor contains half of the touch keys, so that 'n' lumped sensors are sufficient for touch sensing on (2n - 1) keys. Each key is a member of one or more lumped sensors, so any individual keypress is uniquely specified by the touch sensing on one or more lumped sensors. Multiple touch contacts can be detected by an enlarged touch delta on a lumped sensor, which implies a touch input on more than one of its constituent keys. The following Table 1 shows an illustrative grouping of touch keys with touch sensing on 15 keys using 4 lumped sensors. Table 1 - Example: Touch detection on 15 keys using 4 concentrated sensors 4 concentrated sensors Keys concentrated sensors (bit field) Concentrated Sensor 3 Concentrated Sensor 2 Concentrated Sensor 1 Concentrated Sensor 0 0 0001 0 0 0 1 1 0010 0 0 1 0 2 0011 0 0 1 1 3 0100 0 1 0 0 4 0101 0 1 0 1 5 0110 0 1 1 0 6 0111 0 1 1 1 7 1000 1 0 0 0 8 1001 1 0 0 1 9 1010 1 0 1 0 10 1011 1 0 1 1 11 1100 1 1 0 0 12 1101 1 1 0 1 13 1110 1 1 1 0 14 1111 1 1 1 1

[0010] As shown in Table I: lumped sensor 0 contains keys 0, 2, 4, 6, 8, 10, 12, 14; lumped sensor 1 contains keys 1, 2, 5, 6, 9, 10, 13, 14; lumped sensor 2 contains keys 3, 4, 5, 6, 11, 12, 13, 14; and lumped sensor 3 contains keys 7, 8, 9, 10, 11, 12, 13, 14.

[0011] For single touch detection, the logic of node grouping is reversed. For example, if only lumped sensor 0 is touched, then button 0 is touched. If lumped sensor 0 and lumped sensor 1 are touched, then button 2 is touched. If lumped sensor 0 and lumped sensor 2 are touched, then button 4 is touched. If lumped sensors 0, 1, and 2 are touched, then button 6 is touched. For multi-touch detection, where multiple buttons are touched simultaneously, further testing can reveal which button or combination of buttons is being detected. The relative magnitude of the capacitance change (touch delta) at the lumped sensors can be used to constrain the chances that a button or combination of buttons is subject to detection.

[0012] For example, if lumped sensors 0, 1, and 3 are subject to sensing, and lumped sensor 3 has twice (or approximately twice) the touch delta of the other two lumped sensors, then at least two touch inputs are present, both of which belong to lumped sensor 3 (buttons 7 through 14). Only one of each of the touch inputs includes lumped sensors 0 and 1, whereas none of the touch inputs belong to lumped sensor 2 (buttons 8 and 9). If lumped sensors 0 and 1 exhibit sensing with similar touch delta, the sensing may be caused by a single touch input to button 2 or by two touch inputs to buttons 0 and 1. The ambiguity can be resolved by measuring only button 2. If button 2 is not touched, then buttons 0 and 1 are touched.If all four lumped sensors show a touch detection with a similar touch delta, the detection can correspond to a single touch input on key 14, two touch inputs on keys (2, 11), three touch inputs on keys (2, 3, 7) or keys (0, 1, 11), or four touch inputs on keys (0, 1, 3, 7). In this case, key 14 is sensed. If key 14 is not touched, keys 2 and 11 are sensed. The status of these three keys is sufficient to determine which of the possible options is the correct one.

[0013] The previously described nested node sampling provides advantages over sequential and hierarchical sampling. The three node sampling techniques described above can be applied to a UI application with 30 touch buttons, including sequential sampling, hierarchical sampling of 5 clustered nodes each with 6 buttons, and nested sampling. For a single touch contact, sequential sampling requires 30 measurements, hierarchical sampling requires 11 measurements, and nested sampling requires 5 measurements. For two touch contacts, sequential sampling requires 30 measurements, hierarchical sampling requires up to 17 measurements, and nested sampling requires up to 6 measurements.For three touch contacts, sequential sensing requires 30 measurements, hierarchical sensing requires up to 23 measurements, and nested sensing requires up to 7 measurements. Touch-sensitive 2D surfaces

[0014] Nested node sensing can be applied to two-dimensional (2D) touch surfaces to reduce the number of capacitance measurements required to resolve the presence and position of a touch input. Sensor nodes are organized into rows and columns, forming a lumped 1D sensor (e.g., a touch-sensitive slider) along each axis of the surface, which can optionally encompass the entire area of ​​the touch-sensitive surface. In this way, the position(s) of the touch input on a surface with mxn sensor nodes can be determined using only m + n measurements.When a single touch input is present, the vertical position is the position of the touch input on the vertical slider, and the horizontal position is the position of the touch input on the horizontal slider. Multiple touch inputs can be detected along each slider, but because the X position and Y position are each calculated independently, it is not possible to immediately determine which X position corresponds to which Y position. Further measurements are required to complete the determination of the touch input position, either by detection (single-node sampling) or by re-interpolation (3-node sampling), as described with reference to . Fig. 6 is described.

[0015] A comparison was conducted of sensing methods for 2D touch surfaces based on an 8 x 8 grid of sensors measured using sequential order sensing, hierarchical order sensing with 8 lumped sensor nodes each consisting of 8 nodes, and nested sensing. For a single touch input, sequential sensing required 64 measurements, hierarchical sensing required 16 measurements, and nested sensing required 16 measurements. For two touch inputs, sequential sensing required 64 measurements, hierarchical sensing required up to 24 measurements, and nested sensing required 17 measurements for low multi-touch resolution and up to 22 measurements for high multi-touch resolution.For three touch inputs, sequential sampling required 64 measurements, hierarchical sampling required up to 32 measurements, and interleaved sampling required 18 measurements for low multi-touch resolution and up to 25 measurements for high multi-touch resolution. Illustrative systems

[0016] Fig.1 shows an illustrative capacitive touch system 100 according to one embodiment. In the illustrated embodiment, the touch sensing system 100 includes a touch controller 102 and capacitive touch sensors 104, 106a-106c. In the illustrative embodiment, the sensor 104 is a slider, and the sensors 106a-106c are touch buttons. Other types of capacitive touch sensors are also applicable in the disclosed embodiments (e.g., a touch-sensitive wheel). The touch sensors 104, 106 include one or more sensor nodes 101 arranged at intersections of sense electrodes 108a-108c and drive electrodes 110a-110e. The sense electrodes 108a-108c are connected to inputs Y0-Y2 of the touch controller 102. The control electrodes 110a-110e are connected to inputs X0-X4 of the touch controller 102.In this illustrative embodiment, the sensor nodes 101 are formed as an N x N grid pattern, referred to as a “sensor grid,” where “N” is a positive integer value greater than 1.

[0017] The illustrative capacitive touch system 100 is configured for sensing mutual capacitances, where an object (e.g., a finger, a conductive stylus) changes the mutual coupling between sense electrodes 108a-108c and drive electrodes 110a-110e. Sensor 104 includes three sensor nodes 101. Sensors 106a-106c each include a single sensor node 101. Other sensor types may include more or fewer sensor nodes depending on the sensor size and shape. Each intersection or sensor node 101 is referred to as an "XY channel." In the illustrative embodiment shown, the touch sensor 104 (a slider) is assigned to channels (X0-Y0), (X1-Y0), and (X2-Y0), and the touch sensors 106a-106c (3 buttons) are assigned to the XY channels (X0-Y1), (X1-Y1), and (X2-Y1), respectively.When an object (e.g., finger or stylus) touches touch sensor 104, one of the 15 XY channels detects a change in mutual capacitance (e.g., a reduced mutual capacitance) at the corresponding sensor node. For example, when an object touches slider 104, one of the XY channels (X0-Y0), (X1-Y0), (X2-Y0) associated with slider 104 measures a change in mutual capacitance (touch delta). In one embodiment, a sensing circuit in touch controller 102 is configured to determine a change in mutual capacitance due to the addition of a capacitance of an object (e.g., finger), such as described with reference to FIG. Fig. 2 and Fig.3. In one embodiment, the touch controller 102 is configured to sample the 15 sensor nodes 101 shown by sampling the XY channels associated with the sensor node at a sampling period (e.g., 25 ms).

[0018] The sampling sequence may be periodically executed by the touch controller 102 during a user-active phase when the user interacts with the device or facility. The user-active phase may begin when a touch input is detected and may end when no touch input is detected for a specified period of time (e.g., 10 seconds). A user-inactive phase is defined as the period of time between two user-active phases. During a user-inactive phase, the device or facility may enter a sleep or low-power state. When a touch input is detected, the device or facility wakes up, a new user-active phase begins, and the touch controller 102 actively samples all 15 XY channels to detect a touch input.Based on the XY channel, which detects a change in mutual capacitance across the sensor nodes, the position of the touch input in the sensor grid can then be determined. In one embodiment, the scanning of the sensor nodes 101 is performed at least in part by firmware executed by the touch controller 102.

[0019] When a device or facility is in sleep mode and during user-inactive mode, all 15 XY channels are periodically sampled to detect touch input, resulting in power consumption. For mobile devices with limited power resources (e.g., battery-powered devices), it is desirable to reduce power consumption. Instead of measuring each XY channel during a sampling period, the sensor nodes 101 can be "lumped" and treated by the touch controller 102 as a single lumped sensor.

[0020] In one embodiment, capacitive touch system 100 may be connected to a microcontroller or other device via interface 112. Raw or processed touch sensing data may be sent to a microcontroller (not shown) via interface 112. A higher-level application running on a central processing unit (CPU) or peripheral to a microcontroller may process the sensor data using software / firmware, hardware, or a combination of software / firmware and hardware. The sensor data may be made accessible to the higher-level application, for example, through one or more application programming interfaces (APIs).Data processing may include, for example, configuring individual sensor parameters (e.g., threshold and position hysteresis, position resolution), acquiring sensor parameters (e.g., filtering, automatic oversampling, gain settings, prescaler), measuring sensor noise, and sensor self-calibration. Touch controller 102 may include registers (not shown) for storing data and commands received and sent via interface 112.

[0021] Fig. Figure 2 shows nested lumped sensors in a capacitive touch system according to one embodiment. In some implementations, the capacitive touch system 100 includes the touch controller 102 and touch buttons K0-K14. In this illustrative embodiment, each of the touch buttons is a sensor node 101, as described with reference to Fig.1. A nested lumped sensor comprises multiple sensor nodes combined to function as a single touch sensor. When multiple sensor nodes are lumped and treated as a single touch sensor by touch controller 102, the time required to execute a sensing sequence can be reduced. For battery-powered applications utilizing multiple touch buttons, a group of touch buttons can be combined, or lumped, to form a single nested lumped sensor, and this nested lumped sensor can be sensed alone, resulting in reduced power consumption.When detecting a touch input on the nested lumped sensor, in most cases the position of the touch input can be determined without sampling the sensor node components of the nested lumped sensor, thus reducing the number of sampled / measured sensor nodes.

[0022] To demonstrate an illustrative embodiment using seven nested lumped sensors L0-L6, we can assume that the touch system 100 is currently in a non-active user state. For example, no touch input is detected for a certain period of time (e.g., 10 seconds). In the user-inactive state, each lumped sensor is periodically sampled or measured to detect touch input. For example, lumped sensor L0 is measured by touch controller 102, followed by lumped sensor L1, followed by lumped sensor L2, followed by lumped sensor L3, and so on. The order here is merely an example; lumped sensors L0-L6 can be measured in any specified order.In general, the lumped sensors L0-L6 can be manufactured by short-circuiting special sensing electrodes connected to the inputs Y0-Y2 and drive electrodes connected to the inputs X0-X4.

[0023] In this illustrative embodiment, the lumped sensors L0-L6 are nested according to Table II below. Table II - Example: Touch detection on 15 keys using 7 concentrated sensors 7 concentrated sensors Keys concentrated sensors (bit field) L6 L5 L4 L3 L2 L1 L0 K0 0001001 0 0 0 1 0 0 1 K1 0010001 0 0 1 0 0 0 1 K2 0100001 0 1 0 0 0 0 1 K3 1000001 1 0 0 0 0 0 1 K4 0000001 0 0 0 0 0 0 1 K5 0001010 0 0 0 1 0 1 0 K6 0010010 0 0 1 0 0 1 0 K7 0100010 0 1 0 0 0 1 0 K8 1000010 1 0 0 0 0 1 0 K9 0000010 0 0 0 0 0 1 0 K10 0001000 0 0 0 1 0 0 0 K11 0010100 0 0 1 0 1 0 0 K12 0100100 0 1 0 0 1 0 0 K13 1000100 1 0 0 0 1 0 0 K14 0000100 0 0 0 0 1 0 0

[0024] As shown in Table II: in the lumped sensor 0, the buttons K0, K1, K2, K3, K4 are combined; in the lumped sensor 1, the buttons K5, K6, K7, K8, K9 are combined; in the lumped sensor 2, the buttons K11, K12, K13, K14, K15 are combined; in the lumped sensor 3, the buttons K0, K5, K10 are combined; in the lumped sensor 4, the buttons K1, K6, K11 are combined; in the lumped sensor 5, the buttons K2, K7, K12 are combined; and in the lumped sensor 6, the buttons K3, K18, K13 are combined. Note that there is no need for an 8th (X4) group, since these 3 buttons are included in L0, L1, L2 and can be detected by their absence in L3, L4, L5, L6.

[0025] For a single touch sensing, if only lumped sensor 0 is subject to the sensing process, then button K4 is touched. If lumped sensor 0 and lumped sensor 1 are touched, then button K9 is touched. If lumped sensor 0 and lumped sensor 3 are touched, then button K0 is touched; if lumped sensor 0 and lumped sensor 4 are touched, then button K1 is touched; if lumped sensor 2 and lumped sensor 4 are touched, then button K11 is touched; and so on. In a multi-touch sensing, where several buttons may be touched simultaneously, further testing can reveal which button or combination of buttons is being sensed.The relative magnitude of the capacitance change (touch delta) at the lumped sensors can be used to constrain the ways in which a key or combination of keys is subject to the sensing process.

[0026] For multi-touch sensing, where multiple buttons may be touched simultaneously, further testing can reveal which button or combination of buttons is being sensed. The relative magnitude of the capacitance change (touch delta) at the lumped sensors can be used to reduce the possibilities of which button or combination of buttons is subject to the touch process, as previously described with reference to Table I. If the lumped sensors being sensed exhibit sensing with similar touch delta, an ambiguity may be introduced. This ambiguity can be resolved by measuring individual lumped sensors during a selection process.

[0027] Fig.Figure 3 shows touch control circuitry 102 for measuring nested touch sensors with mutual capacitance, according to one embodiment. In some implementations, touch control 102 may include input control circuitry 116, sensor channels 107, compensation circuitry 118, access circuitry 120, line driver 122, selection circuitry 124, selection circuitry 126, and series resistor 128 (Rs).

[0028] In this mutual capacitance embodiment, selection circuit 124 is connected to sensor channels 107, and selection circuit 126 is connected to line driver circuit 122. Line driver circuit 122 is configured to individually drive individual drive electrodes connected to inputs X0-X4 during a sampling period using selection circuit 126. Selection circuit 126 is connected to input control circuit 116, which is configured to select individual sensor channels 107 during a sampling period. For example, to sample lumped sensor 112, selection circuit 126 shorts the drive electrodes connected to inputs X0-X4, and selection circuit 124 shorts sense channel Y0.The line driver circuit 122 supplies drive voltages to the drive electrodes and, in one embodiment, receives a selection signal (not shown) from the input control circuit 116.

[0029] The access circuit 120 is connected to a charge channel 105 and measures the change in the capacitance of a sensor node in the sensor grid 103 due to a touch input. In one embodiment, the access circuit 120 converts the measured sensor node capacitance into a digital value (e.g., a 10-bit value). The number can be transmitted via the interface 112 (see Fig.1), for example, to a higher-level processor for further processing by an application running therein. In one embodiment, an interrupt (IRQ) signal is also sent to the higher-level processor via interface 112 to "wake up" the higher-level processor so that it retrieves the number, for example, from a register (not shown) in touch controller 102.

[0030] In one embodiment, access circuit 120 may include a switched-capacitor circuit configured to convert the sensor node capacitance into an equivalent resistance. A sigma-delta modulator circuit converts the measured current flowing through the equivalent resistance into a bit data stream that is supplied to a counter during the sampling period. The counter value determines the "ON" or "OFF" state of the sensor node or lumped sensor. When touch input is received, the counter value increases, and when it exceeds a reference value or a default level, the sensor node is in the "ON" state.

[0031] Compensation circuit 118 is connected to charge channel 105 and performs noise compensation. In one embodiment, compensation circuit 118 may be a capacitor network tuned to match the sensor capacitance to provide the largest dynamic range of an input signal, thereby improving noise tolerance.

[0032] Fig.4 shows a touch control circuit 102 for measuring nested self-capacitance touch sensors according to one embodiment. In this illustrative embodiment, only sense electrodes (e.g., sense electrodes 108a-108c) are connected to self-capacitance sensors and are selected using input control circuit 116. The drive electrodes (e.g., drive electrodes 110a-110e) remain unused and can be used for other general purposes of an input / output function. The other components of touch control 102, including compensation circuit 118 and access circuit 120, operate in a similar manner as described with reference to Fig. 3 is described. Illustrative processes

[0033] Fig.5 is a flowchart of an illustrative process 500 for sensing nested nodes in a capacitive touch system according to one embodiment. The process 500 may be implemented, for example, by the Fig. 1 shown touch system 100 can be implemented.

[0034] In one embodiment, process 500 may begin by classifying sensor nodes into nested lumped sensors (502). For example, for touch buttons with a single sensor node per button, a table similar to Table I or Table II may be created to provide a mapping between the sensor channels and sensor nodes that can be used when sensing nested nodes. A touch controller connected to the sensor nodes may determine which lumped sensors are subject to sensing by comparing a bit field corresponding to the lumped sensors with the table containing the mapping.

[0035] Process 500 may continue by scanning the nested lumped sensors for one or more touch inputs (504). For example, the touch controller may perform a nested scan on the nested lumped sensors.

[0036] The process 500 may continue by determining one or more positions of one or more touch inputs from the scan (506). For example, touch buttons subject to detection may be determined by the mapping and / or by individual node scans to resolve ambiguities, as described with respect to Fig. 2 and Fig. 6 is described.

[0037] Fig.Figure 6 shows sensing of nested nodes on a 2D touch surface. As previously described, sensing for nested nodes can be applied to 2D touch surfaces to reduce the number of capacitive measurements used to detect the presence of a touch input and its positions. In the example shown, the sensor nodes are divided into rows and columns, so that lumped 1D sensors L0, L1 (e.g., touch sliders) are formed along the horizontal axis of the 2D touch surface 600, and lumped 1D sensors L2, L3 are formed along the vertical axis of the 2D touch surface 600. The lumped 1D sensors are in Fig.6 as dashed lines. When a single touch input is present at node A (denoted by the dashed oval), the lumped sensors L0, L2 are subjected to detection, and the position of the single touch input is determined from the X (horizontal) and Y (vertical) coordinates of sensor node A. Similarly, when a single touch input is present at node B, the lumped sensors L1, L3 are subjected to detection, and the position of the single touch input is determined from the horizontal and vertical coordinates of sensor node B. However, when multiple touch inputs are present at sensor nodes A and B, there is a position ambiguity that needs to be resolved. For example, if nodes A and B are touched simultaneously, all four lumped sensors L0, L1, L2, and L3 are detected, and a position ambiguity arises.Simultaneous touches at nodes C and D cannot be distinguished from simultaneous touch inputs at nodes A and B, because both touch inputs result in the lumped sensors L0-L3 being sensed. Multiple touch inputs can be sensed along each lumped sensor, but because each X and Y position is calculated independently, it is not possible to immediately determine which X position corresponds to which Y position. Further measurements are required to complete the position determination for the touch input by sensing using a single sensor node sample.

[0038] The measurements of the concentrated sensor result in two contact positions: horizontally results in X a and X b , vertically results in Y a , Y b , where the subscript “a” in X a denotes the X-coordinate of node A, and the subscript “b” in Yb denotes the Y coordinate of node b. In this case, the XY coordinates of these tangency points can be as follows: A (X a , Y a ) and B (X b , Y b ) or C (X a , Y b ) and D (X b , Y a ). This position ambiguity can be resolved with a single measurement of any of these four nodes. For example, if the A (X a , Y a ) node is subject to detection, then the inputs are at A (X a , Y a ) and B (X b , Y b ). If the (X a , Y a ) node is not subject to detection, then the touch inputs are at nodes C (X a , Y b ) and D (X b , Y a ). In general, n contacts with distinguishable horizontal and vertical positions can be resolved using (n-1) additional measurements.

[0039] If the measurements of the concentrated sensors two touch positions horizontally A (X a , X b ), but only one vertical position (Y a ), then two touch inputs are present, but they are too close vertically to be distinguishable by the measurements of the vertical lumped sensors. Depending on the required positional accuracy, it is often acceptable for the touch controller to interpret these two touch inputs as A (X a , Y a ) and D (X b , Y a ) is reported. If the application requires position accuracy for multiple touch inputs that has a higher resolution than the minimum slider distance, then 6 nodes must be measured for re-interpolation. If X na the middle node in relation to the X a -position is, X nb the one who has the X b -Position concerns, Y nais the middle node that reports the Y a -position, then 3 measurements per touch input are required for accurate interpolation of the position. To interpolate the touch input at the vertical X a To determine the position, the nodes (X na , Y na - 1) (X na , Y na ) (X na , Y na + 1). To enable touch input on the vertical X b To determine the position, the nodes (X nb , Y na - 1) (X nb , Y na ) (X nb , Y na + 1) measured.

[0040] Although this document contains many specific implementation details, these should not be construed as limitations on the claimed scope, but rather as descriptions of features specific to particular embodiments. Certain features presented in this description in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be employed in multiple embodiments separately or in a suitable smaller combination.Furthermore, although features are described above as being effective in certain combinations and are themselves initially claimed in that regard, in some cases one or more features from a claimed combination may be extracted from the combination and the claimed combination may be directed to a subordinate combination or a variation of a subordinate combination.

Claims

[1] A touch detection circuit comprising: several sensor channels (X0-X4,Y0-Y2); a controller (102) connected to the plurality of sensor channels (X0-X4,Y0-Y2), wherein the controller (102) is designed: assigning the sensor channels (X0-X4,Y0-Y2) to sensor nodes (101), wherein the sensor nodes (101) form a plurality of nested lumped sensors, wherein at least two of the nested lumped sensors have a common sensor node (101), and at least one of the nested lumped sensors comprises a set of non-adjacent sensor nodes (101); during a sampling period, sample the nested concentrated sensors to detect one or more touch inputs; and in response to detecting one or more touch inputs, determine a position of at least one touch input. [2] The touch sensing circuit of claim 1, wherein the controller (102) is further configured to: scanning a sensor node (101) in a nested lumped sensor to resolve a detection ambiguity between two or more nested lumped sensors being touched. [3] The touch sensing circuit of claim 1, wherein the controller (102) is further configured to: To compare the change in capacitance measured at two or more nested lumped sensors in order to resolve a detection ambiguity between the two or more nested lumped sensors. [4] The touch sensing circuit of claim 1, wherein the controller (102) is further configured to: to assign the nested lumped sensors to rows and columns of a two-dimensional (2D) surface to form a lumped one-dimensional (1D) sensor. [5] The touch sensing circuit of claim 4, wherein the lumped 1D sensor is a slider element. [6] The touch sensing circuit of claim 4, wherein the controller (102) is further configured to determine a position of a single touch input on the 2D surface based on which lumped 1D sensors are touched. [7] The touch sensing circuit of claim 4, wherein the controller (102) is further configured to sample individual sensor nodes (101) in the lumped 1D sensors to resolve a position ambiguity on the 2D surface. [8] A method for touch sensing, comprising: Assigning (502), by a controller (102) of a touch sensing circuit, sensor channels to sensor nodes (101), wherein the sensor nodes (101) form a plurality of nested lumped sensors, wherein at least two of the nested lumped sensors have a common sensor node (101), and at least one of the nested lumped sensors comprises a set of non-contiguous sensor nodes (101); Sampling (504), during a sampling period, the nested lumped sensors to detect one or more touch inputs; and in response to detecting one or more touch inputs, determining (506) a position of at least one touch input. [9] The method of claim 8, further comprising: Sensing, by the controller (102), a sensor node (101) in a nested lumped sensor to resolve a detection ambiguity between two or more nested lumped sensors being touched. [10] The method of claim 8, further comprising: Comparing, by means of the controller (102), changes in capacitance measured at two or more nested lumped sensors to resolve a detection ambiguity between the two or more nested lumped sensors. [11] The method of claim 8, wherein the controller (102) is further configured to assign the nested lumped sensors to rows and columns of a two-dimensional (2D) surface to form a lumped one-dimensional (1D) sensor. [12] The method of claim 11, wherein the lumped 1D sensor is a sliding element. [13] The method of claim 11, further comprising: Determining, by the controller (102), a position of a single touch input on the 2D surface based on which concentrated 1D sensors are touched. [14] The method of claim 11, further comprising: Scanning, by means of the controller (102), individual sensor nodes (101) in the lumped 1D sensors to resolve a position ambiguity on the 2D surface. [15] A touch sensing system comprising: Sensor node (101); a microcontroller; a controller (102) connected to the microcontroller and the sensor nodes (101), the controller (102) being designed: assigning the sensor channels (X0-X4,Y0-Y2) to the sensor nodes (101), wherein the sensor nodes (101) form a plurality of nested lumped sensors, wherein at least two of the nested lumped sensors have a common sensor node (101), and at least one of the nested lumped sensors comprises a set of non-adjacent sensor nodes (101); during a sampling period, sample the nested lumped sensors to detect one or more touch inputs; in response to the detection of one or more touch inputs, determine a position of at least one touch input; and to report the position to the microcontroller. [16] The touch system according to claim 15, wherein the controller (102) is configured: scanning a sensor node (101) in a nested lumped sensor to resolve a detection ambiguity between two or more nested lumped sensors that are touched. [17] The touch sensing system of claim 15, wherein the controller (102) is configured to: To compare changes in capacitance measured at two or more nested lumped sensors to resolve a detection ambiguity between the two or more nested lumped sensors. [18] The touch sensing system of claim 15, wherein the controller (102) is further configured to assign the nested lumped sensors to rows and columns of a two-dimensional (2D) surface, thereby forming a lumped one-dimensional (1D) sensor. [19] The touch sensing system of claim 18, wherein the controller (102) is configured to determine a position of a single touch input on the 2D surface based on which lumped 1D sensors are touched. [20] The touch sensing system of claim 18, wherein the controller (102) is configured to sample individual sensor nodes (101) in the lumped 1D sensors to resolve a position ambiguity on the 2D surface.

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