A scanning method of a multi-channel touch control system and a touch coordinate determination device

Abstract

The application provides a scanning method of a multi-channel touch control system and a touch coordinate determination device. The method comprises: leading out a first electrode along a first direction and a second electrode along a second direction on a frame of a capacitive screen; controlling a square wave input of any TX port through a code striking module and controlling a signal acceptance of RX through an acceptance module. The scanning process comprises: selecting a starting point of channel scanning of a next frame, finding an effective signal channel, further scanning all effective signals according to the effective signal channel, and finally obtaining a touch coordinate by using a centroid algorithm. The whole process minimizes the scanning time and maintains the touch precision by using a timely multi-channel driving and scanning strategy. The scanning method provided by the application improves the scanning frame rate of the system on the capacitive screen and reduces the touch delay time without affecting the touch precision, so that the touch curve is smoother and the touch response is more rapid.

Description

Technical Field

[0001] This application relates to the field of capacitive touch screen technology, and in particular to a scanning method and a device for determining touch coordinates of a multi-channel touch system. Background Technology

[0002] Capacitive touchscreens, as a widely adopted touch technology, are popular due to their high degree of ease of use. A touchscreen typically consists of two layers of transparent conductive material: one on the surface of the touchscreen and the other underneath. A capacitor is formed between these two layers, which is used to detect touch. When there is no external interference, a uniform electric field is established between the two conductive layers. Current flows between them, forming a capacitor. When a user touches the screen surface with their finger or stylus, their charge is introduced into the capacitor, causing a change in mutual capacitance. By detecting this change in mutual capacitance, the touch status can be determined.

[0003] With the upgrading of capacitive touchscreen products and the increasing demands for user experience, capacitive touchscreens are becoming larger and have more channels. As the number of channels increases, the sampling time for capacitive touchscreen information also increases, and this sampling time largely determines the touch response speed and touch tracking effect of the capacitive touchscreen. Using conventional full-screen scanning methods, once the number of channels reaches a certain level, the scanning frame rate will be insufficient for normal touch operation. Summary of the Invention

[0004] To address this need, this application proposes a scanning method and a touch coordinate determination device for a multi-channel touch system, which solves the problem of excessively long single-frame touch time for large-size multi-channel capacitive screens.

[0005] In a first aspect, this application provides a scanning method for a multi-channel touch system, applied to single-point touch on a multi-channel mutual capacitance touchscreen, the method comprising:

[0006] Step 1: Select the channel scanning start point for the next frame based on the driving channel where the touch coordinates of the previous frame are located. If the touch point was not scanned in the previous frame, the channel start point is selected as the middle channel.

[0007] Step 2: Perform a single-channel scan based on the channel start point. If a valid signal exists at the channel start point (the mutual capacitance of the channel changes), proceed to step 4; otherwise, proceed to step 3.

[0008] Step 3: Select multiple specific channels to drive simultaneously from the starting point of the TX channel to the left and right. The selection of channels is related to the screen itself. When a valid signal is found in a certain multi-channel drive, find the channel corresponding to the valid signal and proceed to step 4.

[0009] Step 4: Based on the channel corresponding to the valid signal, perform single-channel scanning on its left and right channels in sequence. When all valid signal channels have been scanned, the scanning of this frame ends, and the touch coordinates of this frame are obtained according to the centroid algorithm.

[0010] Secondly, this application provides a touch coordinate determining device applied to a capacitive touch screen. A first electrode is led out along a first direction on the edge of the capacitive touch screen, and a second electrode is led out along the edge in a second direction. The device includes:

[0011] The coding module is configured to input a square wave excitation to any port of the first electrode;

[0012] The receiving module is configured to receive the output signals from all ports of the second electrode in parallel and convert them into digital signals;

[0013] The processing module is configured to process the obtained digital signal to obtain the corresponding touch coordinates.

[0014] The touch system in this application embodiment changes from full-channel scanning to gated scanning. That is, it uses the coordinate information of the previous frame and the multi-channel driving method to find the channel containing effective information as soon as possible, and then scans and calculates the coordinates of it. This reduces the scanning time of the touch system in each frame, improves the scanning frame rate and response speed, and thus enhances the user experience. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in this application or related technologies, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a flowchart illustrating the scanning method of the touch system according to an embodiment of this application;

[0017] Figure 2 This is a schematic diagram of the structure of the capacitive touchscreen according to an embodiment of this application;

[0018] Figure 3 This is a schematic diagram of the cyclic scanning data acquisition process according to an embodiment of this application;

[0019] Figure 4 This is a schematic diagram of the structure of the touch coordinate determination device according to an embodiment of this application. Detailed Implementation

[0020] To make the objectives, technical solutions and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0021] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this application should have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," and similar terms used in the embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0022] A capacitive touchscreen is made of a layer of transparent conductive material, typically coated on a glass surface. This conductive material is divided into tiny capacitive electrodes, or sensing units, usually arranged in a matrix. In the non-touch state, these capacitive units have a uniformly distributed charge. When a finger or a capacitive object touches a location on the screen, the charge distribution between the capacitive electrodes changes. This change is sensed, and the control circuitry detects the capacitance change to determine the location of the touch point.

[0023] The horizontal and vertical electrode positions in a capacitive touchscreen form a dense matrix of mutual capacitances in the X and Y directions. By inputting a square wave to the electrode in the X (Y) direction, the signal receiving module connects to the electrode in the Y (X) direction to obtain the mutual capacitance value. When a finger or other capacitive material touches the screen, it will change the mutual capacitance value near that coordinate. The specific location of the touch point can be obtained by calculation.

[0024] The main component of this application is the coding module responsible for generating square wave signals and selecting channels. To improve the scanning rate of a capacitive touchscreen, it is necessary to minimize the time required to acquire mutual capacitance information. Since touch only causes changes in a fixed number of mutual capacitances near the touch point, the calculation process for touch coordinates is relatively fixed. This application reduces unnecessary channel coding to decrease the time required to acquire and receive signals, thereby increasing the system's scanning frame rate for the capacitive screen and reducing touch response, especially applicable to multi-channel, large-size capacitive screens.

[0025] The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0026] This application provides a scanning method for a multi-channel touch system, applied to a capacitive touch screen, wherein a first electrode is led out along the edge of the capacitive touch screen in a first direction, and a second electrode is led out along the edge in a second direction.

[0027] In this embodiment, the capacitive touchscreen structure is as follows: Figure 2As shown, the first direction is set as the positive X-axis direction, the second direction is set as the negative Y-axis direction, the number of TX channels is set to 112, and the number of RX channels is set to 72. When performing full-screen scanning, the TX1 channel is first coded, and all RX channels output signals in parallel. The receiving module obtains all mutual capacitance information of the first column. This process is repeated 112 times to obtain 112*72 mutual capacitance information.

[0028] In some embodiments, the positions of the TX electrode and the RX electrode can be interchanged, and other settings and scanning methods are no different from those in the above embodiments, and will not be described again here.

[0029] The overall idea of ​​the scanning method in this application is as follows:

[0030] The control square wave input is used to the TX channels (assuming N channels), and the RX channels (assuming M channels) are connected to the signal receiving module. The touch information of the current row (column) is obtained from the data received by the module. One TX channel is encoded per unit time. All RX channel signals are received in parallel. Each time one TX channel is encoded per unit time, the change in mutual capacitance (number of signals M, each signal representing one mutual capacitance change) of a row (column) can be obtained. Each time n TX channels are encoded per unit time, the sum of the mutual capacitance changes of the corresponding n rows (columns) can be obtained (number of signals M, each signal representing the sum of n mutual capacitance changes). A single touch on each screen results in a fixed number of channel mutual capacitance changes, and the touch coordinates can be calculated using the centroid algorithm.

[0031] In a preferred example, the scanning process includes the following steps, see Figure 1 and Figure 3 As shown:

[0032] Step S101: Select the channel scanning start point of the next frame according to the driving channel where the touch coordinates of the previous frame are located. If the touch point is not scanned in the previous frame, the channel start point is selected as the middle channel.

[0033] The purpose of selecting the channel starting point for the next frame based on the previous frame is to quickly locate the channel containing the valid signal in the next frame during continuous touches, thereby completing coordinate acquisition as soon as possible. If no touch point is scanned in the previous frame, it generally means that the next touch point is not in the same position as the previous touch point. In this case, selecting the middle channel as the channel starting point is to ensure that touch points in the middle of the touchscreen are scanned faster, because for a screen, more touch operations occur in the middle of the screen rather than on the sides.

[0034] Step S102: Perform a single-channel scan based on the channel start point to determine whether there is a valid signal at the channel start point (the mutual capacitance of the channel changes). If there is, proceed to S104; otherwise, proceed to S103.

[0035] A single touch will cause a fixed number of mutual capacitance changes to a capacitive screen. For example, a single touch will cause K or K+1 channels of mutual capacitance changes to a screen. If there is a valid signal in the starting channel, then the remaining (K-1) or K valid signal channels are continuous with it. If there is no valid signal in the starting channel, it means that the touch point is not near the starting channel and it is necessary to find the channel corresponding to the valid signal.

[0036] Step S103: Select multiple specific channels to drive simultaneously from the starting point of the TX channel to the left and right. The selection of channels is related to the screen itself. When a valid signal is found in a certain multi-channel drive, find the channel corresponding to the valid signal and proceed to step S104.

[0037] The main purpose of this step is to quickly locate the approximate range of the touch coordinates. Since a single touch will generate mutual capacitance changes in K or K+1 channels, if no valid signal is found at the channel starting point, it means that the nearest valid signal channel is K-1 or K channels away from the channel starting point (for example, if the channel starting point is TX1, the nearest valid signal channel is TX(K+1) or TX(K+2)). In order to find the valid signal channel as quickly as possible and to avoid omissions, a channel is selected every K-1 channels from the channel starting point as the test channel for multi-channel driving. The number of multi-channel drives is adjusted according to the distance or power consumption requirements. After a valid signal is found in a multi-channel drive, the channel corresponding to the valid signal is found by binary search, and then the process proceeds to step S104.

[0038] Step S104: Based on the channel corresponding to the valid signal, perform single-channel scanning on its left and right channels in sequence. When all valid signal channels have been scanned, the scanning of this frame ends, and the touch coordinates of this frame are obtained according to the centroid algorithm.

[0039] When a valid signal channel is found, it means that the remaining valid signal channels are continuous with it. At this time, scanning can be performed from the adjacent channels (the left and right order is not fixed) until an invalid signal is scanned. After all valid signal channels have been scanned, the touch coordinates of the frame are obtained according to the centroid algorithm. The scanning of the frame ends and the scanning of the next frame begins.

[0040] Furthermore, the touch coordinates are specifically calculated as follows:

[0041] The first touch coordinate in the first direction is determined based on the TX channel number in the original frame;

[0042] The second touch coordinates in the second direction are determined based on the RX channel information in the original frame;

[0043] The touch coordinates corresponding to the original frame are determined based on the first touch coordinates and the second touch coordinates.

[0044] The following example compares the coordinate determination method proposed in this application with the processing time of a frame of data in the prior art:

[0045] This comparison is based on single-point touch scenarios. Assuming the single-channel scan time of the capacitive touchscreen TX end in this application is 0.25ms, then for a 112*72 channel capacitive touchscreen, regardless of whether it is continuous or discrete touch, the time required to obtain one frame of data under the full-channel scan method is:

[0046] T = 0.25ms * 112 = 28ms

[0047] The frame rate is F = 1000 / 28 = 35.7

[0048] According to the scanning method of this application, assuming that single-point touch will cause capacitance changes in 4 to 5 channels, during continuous touch, the change in touch coordinates per frame will not exceed 4 channels. Therefore, during continuous touch, there are valid signals at the starting point of each channel. In this case, the number of scans required for one frame of data is the number of valid signal channels + 2, where 2 represents the invalid signal channels scanned on the left and right sides respectively. The time taken for one frame is:

[0049] T1 = 0.25 * (5 + 2) = 1.75 ms

[0050] F1 = 1000 / 1.75 = 571

[0051] If it is discrete touch (no touch behavior in the previous frame), then the starting point of the channel is first set to the middle channel, which is TX56. If there is no valid signal in TX56, then select one channel from every 3 channels of TX56 as the channel to be tested for multi-channel driving. At this time, there are 27 channels selected (4, ... 48, 52, 60, 64 ... 112).

[0052] If power consumption is not considered, according to the binary search method, the slowest time required to locate the channel containing the valid signal is 5 (rounded up [log2(27)]). At this time, the number of scans for one frame of data is 1 (channel start scan) + number of multi-channel scans + number of valid signal channels + 2. At this time, the maximum time for one frame is:

[0053] T2 = 0.25 * (1 + 5 + 5 + 2) = 3.25 ms

[0054] In practical operation, considering power consumption, the number of multi-channel drives should not be too large. Assuming 4, then 27 channels under test require a maximum of 7 4-channel scans to determine the range of valid signals. The scanning order is based on the distance from the channel start point (first scan channels 48, 52, 60, 64; second scan channels 40, 44, 68, 72, and so on). Then, a channel containing a valid signal is found using a binary search method (2 scans) among the 4 channels. At this point, the number of scans for one frame of data is 1 (channel start point scan) + number of multi-channel scans + number of valid signal channels + 2. The maximum time for one frame is:

[0055] T3=(1+7+2+5+2)*0.25=4.25ms

[0056] With continuous touch input, the frame rate increased by nearly 15 times, resulting in improved smoothness.

[0057] In discrete touch control, if full-channel scanning is used, in the worst-case scenario, when a finger touches TX1, the frame scan happens to be scanning TX2. This frame will then obtain coordinates that deviate from the actual values ​​because scanning TX1 in this frame is considered to have no valid signal. Therefore, the true coordinates will not be detected until the end of the next frame. In other words, the touch delay at this point is:

[0058] Td=0.25*111+0.25*112=55.75ms

[0059] In the method of this application, if the finger just touches the starting point of channel TX56 when the scan has just started (48, 52, 60, 64) of the 4-channel scan, then when the last 4-channel scan of this frame (4, 8, 108, 112) is performed, if no valid signal is found in any of the 4-channel scans, it will be determined that there is no touch behavior in this frame, and then a valid signal will be obtained at the starting point of the channel in the next frame. The touch delay at this time is:

[0060] Td1 = 0.25 * (7 + 5 + 2) = 3.5 ms

[0061] If a finger touches the first batch of 4-channel range, and the system has just finished scanning the first batch of multi-channels (40, 44, 68, 72), then this frame will be determined as a no-touch action. The coordinates will be obtained in the next frame. This frame requires 6 more 4-channel scans to complete, while the next frame scan requires 1 (channel start-up scan) + 1 (touch position within the first batch of 4-channel range) + 2 (number of times the 4-channel system uses binary search to find valid channels) + 5 (the maximum number of channels corresponding to the touch point causing capacitance change) + 2 (invalid signal channels scanned from the left and right sides). The touch delay at this point is:

[0062] Td2=0.25*(6+1+1+2+5+2)=4.25ms

[0063] Similarly, if a finger touches the Xth batch (X is an integer between 1 and 7), and the system has just finished the Xth 4-channel scan, then it will take 7-X more 4-channel scans to finish this frame. The next frame scan will require 1+X (the touch position is within the 4-channel range of the Xth batch)+2+5+2. In this case, the touch delay is:

[0064] Td3=0.25*(7-X+1+X+2+5+2)=4.25ms

[0065] In other words, regardless of the touch location, the maximum touch latency is 4.25ms, which is a huge improvement in response speed compared to 55.75ms, and it can also avoid calculating incorrect coordinates in the first frame.

[0066] Based on the same inventive concept, and corresponding to any of the above embodiments, refer to... Figure 4 This application also provides a touch coordinate determination device applied to a capacitive touchscreen, wherein a first electrode is led out along a first direction on the edge of the capacitive touchscreen, and a second electrode is led out along the edge in a second direction. The device includes:

[0067] The coding module 401 is configured to input a square wave excitation to any port of the first electrode;

[0068] The receiving module 402 is configured to receive the output signals of all ports of the second electrode in parallel and convert them into digital signals;

[0069] The processing module 403 is configured to process the digital signal obtained from the receiving port to obtain the corresponding touch coordinates.

[0070] In a preferred example, the processing module 403 obtains the touch coordinates specifically as follows:

[0071] The first touch coordinate in the first direction is determined based on the TX channel number in the original frame;

[0072] The second touch coordinates in the second direction are determined based on the RX channel information in the original frame;

[0073] The touch coordinates corresponding to the original frame are determined based on the first touch coordinates and the second touch coordinates.

[0074] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A scanning method for a multi-channel touch system, applied to single-point touch on a multi-channel mutual capacitance touchscreen; characterized in that, The method includes: Step 1: Select the channel scanning start point for the next frame based on the driving channel where the touch coordinates of the previous frame are located. If the touch point was not scanned in the previous frame, the channel scanning start point is selected as the middle channel. Step 2: Perform a single-channel scan based on the channel scan start point. If a valid signal exists at the channel scan start point, proceed to step 4; otherwise, proceed to step 3. The valid signal is the signal in which the mutual capacitance of the channel changes. Step 3: Select multiple channels to the left and right from the channel scanning starting point and drive them simultaneously. When a valid signal is found in a multi-channel drive, find the channel corresponding to the valid signal and proceed to Step 4. Step 4: Based on the channel corresponding to the valid signal, perform single-channel scanning on its left and right channels in sequence. When all valid signal channels have been scanned, the scanning of this frame ends, and the touch coordinates of this frame are obtained according to the centroid algorithm.

2. The scanning method according to claim 1, characterized in that: On the frame of the multi-channel mutual capacitance touch screen, a first electrode is led out along the frame in the first direction to form a TX channel, and a second electrode is led out along the frame in the second direction to form an RX channel.

3. The scanning method according to claim 2, characterized in that: The first direction is set as the positive X-axis direction, and the second direction is set as the negative Y-axis direction.

4. The scanning method according to claim 2 or 3, characterized in that, The touch coordinates are calculated as follows: The first touch coordinate in the first direction is determined based on the TX channel number in the original frame; The second touch coordinates in the second direction are determined based on the RX channel information in the original frame; The touch coordinates corresponding to the original frame are determined based on the first touch coordinates and the second touch coordinates.

5. A touch coordinate determination device, applied to a multi-channel mutual capacitance touch screen, wherein a first electrode is led out along a first direction on the edge of the multi-channel mutual capacitance touch screen, and a second electrode is led out along a second direction on the edge of the edge, for implementing the method according to any one of claims 1-4, characterized in that: The device includes: The coding module is configured to input a square wave excitation to any port of the first electrode; The receiving module is configured to receive the output signals from all ports of the second electrode in parallel and convert them into digital signals; The processing module is configured to process the digital signal to obtain the corresponding touch coordinates.

6. In the touch coordinate determination device according to claim 5, the touch coordinates in the processing module are specifically calculated as follows: The first touch coordinate in the first direction is determined based on the TX channel number in the original frame; The second touch coordinates in the second direction are determined based on the RX channel information in the original frame; The touch coordinates corresponding to the original frame are determined based on the first touch coordinates and the second touch coordinates.

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