Sensor controller

Abstract

The invention provides a sensor controller capable of preventing interference between symbols of a downlink signal even if a deviation occurs in synchronization with a stylus. In this sensor controller (31), for each of a plurality of symbols constituting a downlink signal (DS) transmitted by a stylus (2), the downlink signal (DS) is received by performing a reception operation of the symbol within a window time, the time length of which is shorter than the time length (T1) of the transmission duration of the symbol generated by the stylus (2).

Description

Technical Field

[0001] The present invention relates to a sensor controller, and in particular to a sensor controller for receiving a downlink signal sent by a stylus pen. Background Art

[0002] In a position detection system that implements pen input based on a stylus, a downlink signal is sent from the stylus to a sensor controller. The stylus generates a string of code elements (a set of digital data sent through one modulation) based on the data sent by the pen pressure value, etc. For each code element, a carrier signal is modulated based on its value, thereby generating and sending a downlink signal. The sensor controller restores the code elements contained in the downlink signal by demodulating the received signal. An example of a position detection system that performs such transmission and reception of a downlink signal is disclosed in Patent Document 1.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2020 / 008638 Summary of the invention

[0006] Problems to be solved by the invention

[0007] As the modulation method of the carrier signal, differential modulation methods such as differential binary phase shift modulation (DBPSK) and differential quaternary phase shift modulation (DQPSK) can be appropriately used. If the differential modulation method is used, the sensor controller can demodulate the downlink signal even when the constellation is rotated due to synchronization deviation or other reasons, thereby reducing the transmission and reception errors of the downlink signal.

[0008] The previous sensor controller is configured to set a window of the same length as the time length of the code element, and use the signal received in the window to perform demodulation of the downlink signal. In this case, if the synchronization between the sensor controller and the stylus pen deviates, inter-code element interference occurs. That is, the signals of other adjacent code elements enter the window and become noise. Therefore, a technology that can prevent interference between code elements of the downlink signal is needed.

[0009] Therefore, one of the objects of the present invention is to provide a sensor controller that can prevent interference between symbols of a downlink signal even if synchronization with a stylus pen deviates.

[0010] Means for solving problems

[0011] In the sensor controller of the present invention, for each of the multiple code elements constituting the downlink signal sent by the stylus pen, the code element is received within a window time, thereby receiving the downlink signal, and the time length of the window time is shorter than the time length of the transmission duration of the code element generated by the stylus pen.

[0012] Effects of the Invention

[0013] According to the present invention, since a period during which the sensor controller does not perform a receiving operation occurs at a boundary between symbols constituting a downlink signal, interference between symbols of the downlink signal can be prevented even if synchronization with the stylus pen deviates. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a diagram showing the configuration of a position detection system 1 according to an embodiment of the present invention.

[0015] Figure 2 It is a diagram showing the transmission and reception timing of the uplink signal US and the downlink signal DS according to the embodiment of the present invention.

[0016] Figure 3 (a) is a diagram showing a modulation signal based on DBPSK, and (b) is a diagram showing a modulation signal based on DQPSK.

[0017] Figure 4 is a diagram showing a downlink signal DS based on DBPSK and a window for receiving the downlink signal DS.

[0018] Figure 5 is a diagram showing a downlink signal DS based on DQPSK and a window for receiving the downlink signal DS.

[0019] Figure 6 1 is a processing flowchart showing the operation of the sensor controller 31 related to the transmission of the uplink signal US and the reception of the downlink signal DS.

[0020] Description of symbols

[0021] 1 Position detection system

[0022] 2 Stylus

[0023] 3 Position detection device

[0024] 3a Panel surface

[0025] 20 Core

[0026] 21 Pen tip electrode

[0027] 22. Pressure sensor

[0028] 23 Switch

[0029] 24 Processing circuit

[0030] 30 Sensors

[0031] 31 Sensor Controller

[0032] 32 Main processor

[0033] DS Downlink Signal

[0034] F Frame

[0035] T0 Minimum sending duration

[0036] T1 Sending duration

[0037] TS Time Slot

[0038] US uplink signal DETAILED DESCRIPTION

[0039] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0040] Figure 1 1 is a diagram showing a configuration of a position detection system 1 according to the present embodiment. As shown in the diagram, the position detection system 1 is configured to include a stylus pen 2 and a position detection device 3 .

[0041] First, let's focus on the position detection device 3. The position detection device 3 is a computer that has the function of detecting the stylus 2. Figure 1 As shown in FIG. 1 , the position detection device 3 is configured to include a panel surface 3a (touch surface), a sensor 30 disposed immediately below the panel surface 3a, a sensor controller 31, and a main processor 32. In a typical example, the position detection device 3 is a personal computer such as a smartphone, a tablet terminal, or a notebook computer. The panel surface 3a may also serve as a display surface of a display, in which case the display is disposed overlapping the sensor 30.

[0042] The sensor 30 is a device used for communication between the sensor controller 31 and the stylus pen 2, and is configured to have a sensor electrode group arranged in the panel surface 3a. Specifically, the sensor electrode group is configured to include a plurality of X electrodes extending in the y direction in the panel surface 3a and arranged side by side at equal intervals in the x direction, and a plurality of Y electrodes extending in the x direction in the panel surface 3a and arranged side by side at equal intervals in the y direction. The plurality of X electrodes and the plurality of Y electrodes are independently connected to the sensor controller 31. One of the plurality of X electrodes and the plurality of Y electrodes can be used as a common electrode in the display, and the position detection device 3 in this case is called an "In-cell type". On the other hand, the plurality of X electrodes and the plurality of Y electrodes may not be used as a common electrode in the display, and the position detection device 3 in this case is called an "On-cell type" or an "Out-cell type".

[0043] The sensor controller 31 is an integrated circuit having a function of deriving the position of the stylus pen 2 within the panel surface 3a (hereinafter referred to as "pen position") and acquiring data (hereinafter referred to as "pen data") from the stylus pen 2 by communicating with the stylus pen 2 via the sensor 30, and a function of sequentially supplying reports including the derived pen position and acquired pen data to the main processor 32. The sensor controller 31 is configured to realize these functions and execute various processes described below by executing a program installed as hardware or a program stored in a built-in memory.

[0044] The communication between the sensor controller 31 and the stylus pen 2 via the sensor 30 is performed, for example, by an active electrostatic capacitance method. The active electrostatic capacitance method is a communication method that performs signal transmission and reception via capacitive coupling between the sensor electrode group constituting the sensor 30 and the pen tip electrode 21 of the stylus pen 2. Hereinafter, the signal sent by the sensor controller 31 to the stylus pen 2 via the sensor 30 is referred to as an "uplink signal US", and the signal sent by the stylus pen 2 to the sensor controller 31 via the sensor 30 is referred to as a "downlink signal DS".

[0045] Figure 2 is a diagram showing the timing of sending and receiving the uplink signal US and the downlink signal DS. As shown in the figure, the sensor controller 31 is configured to communicate with the stylus pen 2 in units of frames F of a predetermined time length. At the beginning of each frame F, the uplink signal US is sent from the sensor controller 31 to the stylus pen 2. In addition, a plurality of time slots TS are set in the remaining time after the uplink signal US is sent in each frame F, and the time slot TS is a unit time for the stylus pen 2 to send the downlink signal DS.

[0046] The uplink signal US has the function of notifying the stylus pen 2 of the time position of the frame F and one or more time slots TS in which the stylus pen 2 should send the downlink signal DS. The stylus pen 2 detects the time position of the frame F based on the reception timing of the uplink signal US, and uses the time slot TS notified by the uplink signal US among the multiple time slots TS contained therein to send the downlink signal DS.

[0047] The communication between the stylus pen 2 and the sensor controller 31 is performed in a paired state. The stylus pen 2 is paired with the sensor controller 31 by receiving the uplink signal US sent by the sensor controller 31. In addition, the sensor controller 31 is paired with the stylus pen 2 by receiving the downlink signal DS sent by the stylus pen 2 as a reply to the uplink signal US. The sensor controller 31 is configured to be able to be paired with multiple styluses 2 at the same time, and assigns different local IDs to each stylus 2 in the pairing. When the command in the uplink signal US is a command for a specific stylus pen 2, the sensor controller 31 sends the command together with the local ID. The stylus pen 2 determines whether the command contained in the uplink signal US is a command sent to itself by referring to the local ID in the received uplink signal US, and only performs processing corresponding to the command when it is a command sent to itself.

[0048] The downlink signal DS sent by the stylus pen 2 may include a position signal for the sensor controller 31 to detect the pen position and a data signal modulated by the pen data sent to the sensor controller 31. The sensor controller 31 receives the position signal using the plurality of X electrodes and the plurality of Y electrodes constituting the sensor 30, approximates the distribution of the received intensity of the position signal in the x direction and the y direction respectively by a normal distribution curve, derives the respective peak positions, and thereby derives the pen position. In addition, the sensor controller 31 receives the data signal using the X electrode or the Y electrode closest to the pen position derived immediately before, performs demodulation, and thereby obtains the pen data sent by the stylus pen 2. The pen data thus obtained may include, in addition to the response to the command in the uplink signal US, the pen pressure value detected by the pressure sensor 22 described later and the on / off information indicating the on / off state of the switch 23 described later.

[0049] The pen data also includes a free-running flag. This is information that becomes true when the stylus pen 2 paired with the sensor controller 31 fails to receive the uplink signal US at the beginning of the frame, and becomes false in other cases. The stylus pen 2 is unpaired when it fails to receive the uplink signal US for a specified number of consecutive times, but the pairing is not unpaired until the number of consecutive reception failures of the uplink signal US reaches the specified number, and the downlink signal DS is continuously sent in a self-running state (free-running state) based on the loss of synchronization. The free-running flag being true means that the stylus pen enters this free-running state.

[0050] return Figure 1 The main processor 32 is a central processing unit of the position detection device 3 having a function of controlling each unit of the position detection device 3. The main processor 32 is configured to execute various application programs including a drawing application program in addition to the operating system of the position detection device 3 by executing programs stored in a built-in memory.

[0051] The series of reports supplied by the sensor controller 31 to the main processor 32 are used by the main processor 32 for processing by the operating system and the drawing application. These processes include the generation and display of digital ink, movement of the cursor, and detection of various gestures such as tapping and dragging.

[0052] Next, let's focus on the stylus 2. The stylus 2 is a pen-shaped device, such as Figure 1 As shown in FIG. 1 , the stylus pen 2 is configured to include a core 20, a pen tip electrode 21, a pressure sensor 22, a switch 23, and a processing circuit 24. In addition to these, the stylus pen 2 also includes a battery for supplying operating power to the processing circuit 24, a memory for storing identification information of the stylus pen 2, etc., but in Figure 1 Illustration omitted.

[0053] The core 20 is a rod-shaped member constituting the tip of the stylus pen 2. The tip electrode 21 is an electrode provided at the tip of the stylus pen 2, and is used to receive the uplink signal US and transmit the downlink signal DS through capacitive coupling with the X electrode and the Y electrode in the sensor 30. The pressure sensor 22 is a sensor that detects the pressure applied to the tip of the stylus pen 2 by detecting the force transmitted through the core 20. The value of the pressure detected by the pressure sensor 22 is supplied to the processing circuit 24 as a writing pressure value. The switch 23 is a switch provided on the surface of the stylus pen 2, and is configured to be turned on / off by the user. The processing circuit 24 is also supplied with on / off information indicating the on / off state of the switch 23.

[0054] The processing circuit 24 is the central processing unit of the stylus pen 2, and performs the following processing: based on the uplink signal US received from the sensor controller 31, a downlink signal DS is generated and supplied to the pen tip electrode 21, thereby sending the downlink signal DS to the sensor controller 31. Specifically, first, regarding the position signal, the processing circuit 24 generates and sends the position signal by supplying an unmodulated carrier signal to the pen tip electrode 21. Next, regarding the data signal, the processing circuit 24 generates a symbol string representing the pen data, and modulates the carrier signal using the generated symbol to generate a modulated signal. Then, the generated modulated signal is supplied to the pen tip electrode 21, thereby generating and sending the data signal.

[0055] Figure 3 (a) is a diagram showing a modulation signal based on DBPSK, and (b) is a diagram showing a modulation signal based on DQPSK. When generating a data signal, the processing circuit 24 selects either DBPSK or DQPSK according to the contact state of the pen tip with the panel surface 3a, and modulates the carrier signal using the selected modulation method.

[0056] like Figure 3 As shown in (a), DBPSK is a modulation method that uses three states: "Base", "1", and "0". In DBPSK, "1" is represented by a phase difference of 0° with respect to the phase of the carrier signal corresponding to the "Base" representing the reference of the phase (hereinafter referred to as "Base phase"), and "0" is represented by a phase difference of 180° with respect to the Base phase. On the other hand, Figure 3 As shown in (b), DQPSK is a modulation method that uses five states: Base, "11", "01", "10", and "00". In DQPSK, "11" is represented by a phase difference of 0° relative to the Base phase, "01" is represented by a phase difference of 270° relative to the Base phase, "10" is represented by a phase difference of 90° relative to the Base phase, and "00" is represented by a phase difference of 180° relative to the Base phase. DBPSK has a characteristic of being more resistant to noise than DQPSK because the number of states used is relatively small. On the other hand, DQPSK has a characteristic of having a higher data rate than DBPSK because the number of states used is relatively large.

[0057] The processing circuit 24 is configured to select DBPSK when the pen pressure value supplied from the pressure sensor 22 indicates that the pen is in hovering (the pen tip is not in contact with the panel surface 3a) (for example, the pen pressure value = 0), and select DQPSK when the pen pressure value supplied from the pressure sensor 22 indicates that the pen is in touch (the pen tip is in contact with the panel surface 3a) (for example, the pen pressure value>0). As a result, the possibility that the sensor controller 31 can receive the downlink signal DS in the hovering state where the reception strength of the downlink signal DS in the sensor controller 31 is relatively weak can be increased, and a high data rate can be achieved in the pen touch state where the reception strength of the downlink signal DS in the sensor controller 31 is relatively strong and the possibility of reception failure is low.

[0058] Figure 4 2 is a diagram showing the transmission and reception of a downlink signal DS during hovering. Figure 5 2 and 3 are diagrams showing transmission and reception of downlink signals DS during pen touch. Hereinafter, with reference to these diagrams, generation of downlink signals DS by the stylus pen 2 will be described in more detail, and reception of downlink signals DS by the sensor controller 31 will also be described in detail.

[0059] First refer to Figure 4 , the processing circuit 24 of the hovering stylus pen 2 is configured to send 6 bits of pen data in one time slot TS. To this end, the processing circuit 24 first generates a codeword string consisting of 7 codewords. The first codeword of the codeword string is "Base", and the values ​​of the second and subsequent codewords become the values ​​corresponding to the bits of the transmission object.

[0060] Next, the processing circuit 24 generates a sub-symbol string consisting of n times the number of symbols constituting the symbol string by replicating each symbol constituting the generated symbol string n times (n ≥ 2). Figure 4 In FIG. 5 , an example where n=5 is shown, and the following description will continue using this example.

[0061] The processing circuit 24 that generates the sub-symbol string modulates the carrier signal using each symbol included in the sub-symbol string. The time T0 shown in the figure represents the minimum time required to send one symbol, that is, the minimum transmission duration. Usually, it is sufficient to send one symbol for each minimum transmission duration T0, but in order to improve the accuracy of the sensor controller 31 receiving the downlink signal DS, in this embodiment, the same symbol is continuously sent 5 times. As a result, the transmission duration T1 of each symbol constituting the symbol string becomes 5 times the minimum transmission duration T0.

[0062] The sensor controller 31 receives the downlink signal DS by performing a receiving operation for each symbol contained in the downlink signal DS within a specified window time for each symbol. The receiving operation for each symbol is performed by synchronous detection. That is, the sensor controller 31 has an oscillator that generates two or four reference signals having phases corresponding to the values ​​of each symbol, and the sensor controller 31 multiplies these reference signals with the received signal supplied from the sensor 30. The multiplication is performed using the received signal and the reference signal of the length of the window time. Then, the sensor controller 31 uses a low-pass filter to remove high-frequency components from the signal obtained by the multiplication. As a result of the above processing, a DC component remains only in the signal corresponding to the value of the received symbol, so the sensor controller 31 determines the value of the received symbol based on the residual DC component.

[0063] The sensor controller 31 is configured to perform the above-described reception operation of each symbol in either a normal mode or a shortened window mode in which specific time lengths of the window time are different from each other.

[0064] The normal mode is a mode in which the window time is equal to the transmission duration T1. In this case, the sensor controller 31 uses 5 times the minimum transmission duration T0 to perform the receiving operation, so it can receive the downlink signal DS with high accuracy. On the other hand, if the synchronization between the sensor controller 31 and the stylus pen 2 deviates, such as Figure 4 As shown in the middle grid line, the signals of other adjacent code elements will become noise when they enter the window time.

[0065] The shortened window mode is a mode in which the time length of the window time is shorter than the time length of the symbol transmission duration T1. In a typical example, the time length of the window time is set to the length obtained by subtracting the minimum transmission duration T0 from the transmission duration T1. When the time length of the window time is set in this way, Figure 4 In the example, the window time is four times the minimum transmission duration T0. In addition, the sensor controller 31 operating in the shortened window mode is configured to start the receiving operation with a delay of 1 / 2 of the minimum transmission duration T0 from the start of the period in which each symbol should be received. Figure 4 As can be understood, even if there is a slight deviation between the code element reception time and the window time due to synchronization deviation, if the deviation is within T0 / 2, it is possible to prevent the signals of other adjacent code elements from entering the window time.

[0066] Next refer to Figure 5, the processing circuit 24 of the stylus pen 2 in pen touch is configured to send 12 bits of pen data in one time slot TS. The fact that the processing circuit 24 generates a symbol string consisting of 7 symbols is similar to Figure 4 The case is the same, but the value of the mth (m≥2) symbol becomes the value corresponding to the 2m-3th and 2m-2th 2 bits of the transmission object. Figure 4 As explained.

[0067] Figure 6 1 is a processing flow chart showing the operation of the sensor controller 31 related to the transmission of the uplink signal US and the reception of the downlink signal DS. In this figure, the operation of the sensor controller 31 in one frame F is shown. Hereinafter, the operation of the sensor controller 31 will be described again in more detail with reference to this processing flow chart.

[0068] like Figure 6 As shown, the sensor controller 31 first sends an uplink signal US (step S1), and then determines whether it is communicating with multiple styluses 2 (whether it is in a multi-pen state) (step S2). In the case where it is determined in step S2 that it is communicating with multiple styluses 2, the sensor controller 31 further determines whether there is a stylus 2 that has entered a free-running state (step S3). The sensor controller 31 can make the determination in step S3 by referring to the free-running flag in the downlink signal DS received from each stylus 2 in the previous frame F.

[0069] If it is determined in step S3 that there is a stylus pen 2 that has entered the free running state, the sensor controller 31 performs the downlink signal DS reception operation in each time slot TS in the shortened window mode (step S4). On the other hand, if it is determined in step S2 that there is not communication with a plurality of stylus pens 2 and if it is determined in step S3 that there is no stylus pen 2 that has entered the free running state, the sensor controller 31 performs the downlink signal DS reception operation in each time slot TS in the normal mode (step S5).

[0070] After that, the sensor controller 31 derives the pen position of each paired stylus 2 and acquires the pen data sent by each paired stylus 2 based on the reception result of the downlink signal DS in step S4 or step S5 (step S6). As described above, the derived pen position and acquired pen data are provided to the main processor 32 as a report.

[0071] As described above, according to the sensor controller 31 of this embodiment, when operating in the shortened window mode, a period during which no receiving operation is performed occurs at the boundary of the code elements constituting the downlink signal DS. Therefore, it is possible to prevent the signals of other adjacent code elements from entering the window time, and thus, even if the synchronization with the stylus pen 2 deviates, it is possible to prevent interference between the code elements of the downlink signal DS.

[0072] In addition, according to the sensor controller 31 of this embodiment, when pairing with multiple stylus pens 2 and one or more of them are in a free-running state, the downlink signals DS of all stylus pens 2 are received in a shortened window mode, so that the downlink signals DS from each stylus 2 can be received uniformly.

[0073] As mentioned above, although the preferred embodiment of the present invention has been described, the present invention is not limited to such embodiment at all, and the present invention can be implemented in various forms within the scope not departing from the gist of the present invention.

[0074] For example, in the above embodiment, the example of using the shortened window mode is described only when pairing with multiple styluses 2 is being performed, but the sensor controller 31 may also use the shortened window mode when pairing with only one stylus 2. By doing so, when the stylus 2 is in a free-running state, the reception state of the downlink signal DS sent by the stylus 2 can be improved.

[0075] In addition, in the above embodiment, an example is described in which the sensor controller 31 is configured to receive the downlink signal DS of all stylus 2 in the shortened window mode when pairing is being performed with multiple stylus 2 and one or more of them are in the free running state. However, the sensor controller 31 may also be configured to receive the downlink signal DS in the shortened window mode only in the time slot TS allocated to the stylus 2 in the free running state, and receive the downlink signal DS in the normal mode in the other time slots TS. In this case, it becomes difficult to uniformly receive the downlink signal DS from each stylus 2, but the downlink signal DS sent by the stylus 2 that is not in the free running state can be received with high accuracy.

Claims

1. A sensor controller, wherein: For each of the multiple code elements constituting the downlink signal sent by the stylus, the code element is received within a window time, thereby receiving the downlink signal, and the time length of the window time is shorter than the time length of the transmission duration of the code element generated by the stylus.

2. The sensor controller according to claim 1, wherein: The transmission duration is a transmission duration of a modulated signal modulated by using the code element.

3. The sensor controller according to claim 1 or 2, wherein: The time length of the transmission duration is a multiple of the minimum transmission duration of the code element, The time length of the window time is a length obtained by subtracting the minimum sending duration from the sending duration.

4. The sensor controller according to claim 3, wherein: The sending of the downlink signal is performed in a state where the stylus pen and the sensor controller are synchronized, For each of the plurality of symbols, a reception operation is started with a delay of 1 / 2 of the minimum transmission duration from the start of a period in which the symbol should be received.

5. The sensor controller according to claim 1 or 2, wherein: The sensor controller is configured to be able to selectively operate in either a normal mode or a shortened window mode, wherein the normal mode is a mode in which the length of the window time is equal to the length of the sending duration, and the shortened window mode is a mode in which the length of the window time is shorter than the length of the sending duration.

6. The sensor controller according to claim 5, wherein: When the sensor controller is pairing with a plurality of styluses and one or more of the plurality of styluses enters a free-running state, the downlink signal is received in the shortened window mode.

7. The sensor controller according to claim 6, wherein: Whether one or more of the plurality of stylus pens enters a free-running state is determined based on information included in the received downlink signal.

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