Sensor controller and stylus

Abstract

To reduce a load of a sensor controller and influence of noise in reception of an uplink signal by a stylus.SOLUTION: A sensor controller 31 is configured to be able to transmit an uplink signal US having a predetermined preamble in either of a first setting and a second setting different from each other, selects any one of the first setting and the second setting, and transmits the uplink signal US by the selected one setting.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sensor controller and a stylus. [Background technology]

[0002] Some active electrostatic position detection devices are configured to enable bidirectional communication between the sensor controller and the stylus via a group of sensor electrodes embedded in the touch surface. Hereinafter, the signal sent from the sensor controller to the stylus in this bidirectional communication will be referred to as the "uplink signal," and the signal sent from the stylus to the sensor controller will be referred to as the "downlink signal."

[0003] A specific method for generating an uplink signal is disclosed in Patent Document 1. As shown in the document, the uplink signal is generated by adding a predetermined preamble to the beginning of a command to be transmitted, and then spreading the resulting symbol string with a predetermined spreading code (a spreading code having autocorrelation properties).

[0004] Patent document 2 discloses an example of a stylus configured to adjust the frequency of a downlink signal when a received uplink signal includes an interfering signal, thereby avoiding the influence of the interfering signal when a sensor controller receives the downlink signal. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-042867 [Patent Document 2] Chinese Patent Publication No. 112286381 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, position detection devices that place a heavy load on the sensor controller have appeared, such as foldable smartphones and tablet devices that use sensor electrodes made of ITO (indium tin oxide) film, which has higher resistance than metal films. Furthermore, if noise is superimposed on the uplink signal, it can become difficult for the stylus to receive the uplink signal.

[0007] Therefore, one object of the present invention is to provide a sensor controller and a stylus that can reduce the load on the sensor controller and reduce the influence of noise on the reception of uplink signals by the stylus.

[0008] Furthermore, if the sensor controller is configured to transmit an uplink signal using one of two or more different methods, a stylus that is only listening for uplink signals transmitted using the other method will fail to receive them. In this case, the sensor controller will be unable to start communication with the stylus, and so an improvement was needed.

[0009] Therefore, another object of the present invention is to provide a sensor controller that can properly start communication with a stylus while transmitting an uplink signal using one of two or more different methods. [Means for solving the problem]

[0010] A sensor controller according to a first aspect of the present invention is configured to be able to transmit an uplink signal having a predetermined preamble in either a first setting or a second setting that are different from each other, and selects either the first setting or the second setting and transmits the uplink signal in the selected setting.

[0011] A stylus according to a first aspect of the present invention is a stylus comprising a receiver configured to be able to detect both an uplink signal transmitted in a first setting and an uplink signal transmitted in a second setting different from the first setting.

[0012] A sensor controller according to a second aspect of the present invention is a sensor controller that transmits a first uplink signal by a first method, determines whether or not a stylus has failed to detect the first uplink signal, and, if it determines that the stylus has failed to detect the first uplink signal, transmits a second uplink signal by a second method different from the first method. [Effects of the Invention]

[0013] According to the first aspect of the present invention, the sensor controller can transmit an uplink signal by selectively using the first setting and the second setting, thereby reducing the load on the sensor controller and also reducing the effect of noise on the reception of the uplink signal by the stylus.

[0014] According to a second aspect of the present invention, the sensor controller transmits a second uplink signal if the stylus fails to detect the first uplink signal, thereby making it possible to properly initiate communication with the stylus while transmitting uplink signals using one of two or more different methods. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a diagram showing a configuration of a position detection system 1 according to an embodiment of the present invention. [Figure 2] 1 is a diagram showing the transmission and reception timing of an uplink signal US and a downlink signal DS. [Figure 3] 1A is a diagram showing the configuration of an uplink signal US, and FIG. 1B is a diagram showing an example of a spreading code having autocorrelation characteristics. [Figure 4] FIG. 2 is a diagram showing the internal configuration of the stylus 2. [Figure 5] FIG. 2 is a diagram illustrating transitions of operation modes of the MCU 14. [Figure 6] 4 is a flowchart showing processing executed by the sensor controller 31. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0017] 1 is a diagram showing the configuration of a position detection system 1 according to this embodiment. As shown in the figure, the position detection system 1 is configured to include a stylus 2 and a position detection device 3.

[0018] First, focusing on the position detection device 3, the position detection device 3 is a computer having the function of detecting the stylus 2, and as shown in FIG. 1, is configured with a panel surface 3a (touch surface), a sensor 30 arranged directly below the panel surface 3a, a sensor controller 31, a host processor 32, and a wireless communication unit 33. In a typical example, the position detection device 3 is a personal computer such as a smartphone, a tablet terminal, or a laptop computer. The panel surface 3a may also serve as the display surface of a display, in which case the display is arranged overlapping the sensor 30.

[0019] The sensor 30 is a device used by the sensor controller 31 to communicate with the stylus 2, and is configured with a group of sensor electrodes arranged within the panel surface 3a. Specifically, the group of sensor electrodes includes a plurality of X electrodes each extending in the y direction within the panel surface 3a and juxtaposed at equal intervals in the x direction, and a plurality of Y electrodes each extending in the x direction within the panel surface 3a and juxtaposed at equal intervals in the y direction. The plurality of X electrodes and the plurality of Y electrodes are each independently connected to the sensor controller 31. One of the plurality of X electrodes and the plurality of Y electrodes may also serve as a common electrode within the display, in which case the position detection device 3 is called an "in-cell type." On the other hand, the plurality of X electrodes and the plurality of Y electrodes may not also serve as a common electrode within the display, in which case the position detection device 3 is called an "on-cell type" or "out-cell type."

[0020] When the sensor 30 is disposed on the upper surface of a display, the multiple X electrodes and multiple Y electrodes are made of a transparent conductor such as the above-mentioned ITO, or thin wires such as a mesh conductor, in order to ensure the visibility of the display. The X electrodes and Y electrodes configured in this manner have a higher resistance than when they are made of a plate-shaped metal film, and a large load is placed on the sensor controller 31. Furthermore, when the position detection device 3 is a foldable smartphone, which has recently appeared, a large load is placed on the sensor controller 31. One of the objects of the present invention is to reduce the load on the sensor controller 31, which is subject to such a large load, by enabling it to transmit an uplink signal at a slower speed.

[0021] The sensor controller 31 is an integrated circuit that has the functions of deriving the position of the stylus 2 (hereinafter referred to as the "pen position") within the panel surface 3a by performing communication (first communication method) with the stylus 2 via the sensor 30, acquiring data (hereinafter referred to as the "pen data") from the stylus 2, and sequentially supplying reports including the derived pen position and acquired pen data to the host processor 32. The sensor controller 31 realizes these functions by executing a program implemented as hardware or a program stored in an internal memory, and is configured to be able to execute various processes described below.

[0022] Communication between the sensor controller 31 and the stylus 2 via the sensor 30 is performed, for example, by an active capacitance method. The active capacitance method is a communication method that transmits and receives signals via capacitive coupling between a group of sensor electrodes that make up the sensor 30 and the pen tip electrode 10 of the stylus 2. Hereinafter, a signal that the sensor controller 31 transmits to the stylus 2 via the sensor 30 will be referred to as an "uplink signal US," and a signal that the stylus 2 transmits to the sensor controller 31 via the sensor 30 will be referred to as a "downlink signal DS."

[0023] 2 is a diagram showing the transmission and reception timing of 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 2 in units of frames F, each having a predetermined length of time, and transmits an uplink signal US at the beginning of each frame F using multiple X electrodes or multiple Y electrodes. The uplink signal US transmitted in this manner serves to notify the stylus 2 of the time position of the frame F and the timing (time slot) within that frame at which the stylus 2 should transmit the downlink signal DS. The stylus 2 detects the time position of the frame F from the reception timing of the uplink signal US, and transmits the downlink signal DS using one of the multiple time slots contained within that frame that was notified by the uplink signal US.

[0024] 3(a) is a diagram showing the configuration of the uplink signal US. As shown in the figure, the uplink signal US is composed of a preamble PRE and a command COM. The preamble PRE is a portion used by the stylus 2 to detect the uplink signal US, and is composed of a predetermined symbol sequence. On the other hand, the command COM is a portion that includes an instruction (command) from the sensor controller 31 to the stylus 2, and is composed of a symbol sequence that indicates the command.

[0025] The symbol string is composed of one or more symbols. Each symbol may be information associated with "0" or "1" as shown, information associated with a bit string of multiple digits, or information not associated with a bit string (for example, information used only to indicate the position of a preamble PRE). Each symbol is transmitted using a spreading code having autocorrelation properties.

[0026] FIG. 3(b) is a diagram showing an example of such a spreading code. The diagram shows an example of a spreading code associated with the symbol "0" and an example of a spreading code associated with the symbol "1". The spreading code in this example is composed of a chip sequence (pseudo-random numbers) consisting of 32 chips. However, the number of chips constituting one spreading code is not limited to 32. Also, in this example, the spreading code associated with the symbol "1" is the inverse of the spreading code associated with the symbol "0". In the following explanation, the time length Tc of each chip shown in the diagram is referred to as the "chip length", and the reciprocal of the chip length Tc, 1 / Tc, is referred to as the "chip rate".

[0027] The sensor controller 31 transmits the uplink signal US by supplying a pulse signal indicating these spreading codes to the sensor 30. In this case, the value of each chip is represented by the voltage of the pulse signal. However, instead of a pulse signal, a carrier signal (sine wave signal) of a predetermined frequency may be transmitted, in which case the value of each chip is represented by the phase of the carrier signal.

[0028] The sensor controller 31 according to this embodiment is configured to be able to transmit an uplink signal US having a predetermined preamble PRE in any of a plurality of different settings. These settings may have different chip lengths (chip rates), different carrier signal frequencies, or different combinations of chips constituting the spreading codes associated with each symbol (i.e., types of spreading codes). The longer the chip length (i.e., the smaller the chip rate), the lower the carrier signal frequency, and the shorter the spreading code, the smaller the load on the sensor controller 31 for transmitting the uplink signal US. The number of settings for the uplink signal US may be two, or may be three or more. The following description will continue with an example in which a first setting and a second setting with different chip lengths are used.

[0029] The sensor controller 31 is configured to select either the first setting or the second setting and transmit the uplink signal US using the selected setting. It then determines whether the stylus 2 has failed to detect the transmitted uplink signal US, and if it determines that the stylus 2 has failed, transmits the uplink signal US using the other setting. The selection of the setting may be based on the results of communication with the stylus 2 using short-range wireless communication (second communication method) described below, or may be based on a response from the stylus 2 to the transmitted uplink signal US (the contents of the downlink signal DS). The above points will be explained in more detail later with reference to a flowchart showing the processing of the sensor controller 31.

[0030] Returning to FIG. 2, the downlink signal DS may include a position signal for causing the sensor controller 31 to detect the pen position, and a data signal modulated by pen data to be transmitted to the sensor controller 31. The sensor controller 31 receives the position signal from each of the multiple X electrodes and multiple Y electrodes constituting the sensor 30, approximates the distribution of the received strength of the position signal in each of the x and y directions using a normal distribution curve, and derives the respective peak positions, thereby deriving the pen position. The sensor controller 31 also receives and demodulates the data signal from the single X or Y electrode closest to the pen position previously derived, thereby acquiring the pen data transmitted by the stylus 2. The acquired pen data may include a response to a command in the uplink signal US, a writing pressure value indicating the pressure applied to the pen tip of the stylus 2, and switch information indicating the on / off state of a switch provided on the surface of the stylus 2.

[0031] Returning to Figure 1, the host processor 32 is a central processing unit of the position detection device 3 that has the function of controlling each part of the position detection device 3. The host processor 32 is configured to be able to execute not only the operating system of the position detection device 3 but also various applications including a drawing application by executing programs stored in the built-in memory.

[0032] The series of reports provided by the sensor controller 31 to the host processor 32 are used by the host processor 32 for processing by the operating system and drawing applications, including generating and displaying digital ink, moving the cursor, and detecting various gestures such as tapping and dragging.

[0033] The wireless communication unit 33 is a device for communicating with other devices, including the stylus 2, by short-range wireless communication such as Bluetooth (registered trademark). The host processor 32 is configured to be able to communicate with the stylus 2 via this wireless communication unit 33 by short-range wireless communication.

[0034] Next, focusing on the stylus 2, the stylus 2 is a pen-shaped device and, as shown in FIG. 1, is configured to have a pen tip electrode 10 and a wireless communication unit 11. The pen tip electrode 10 is an electrode used to receive an uplink signal US and transmit a downlink signal DS through capacitive coupling with the X electrode and Y electrode in the sensor 30. The wireless communication unit 11 is a device for communicating with other devices, including the position detection device 3, via short-range wireless communication such as Bluetooth (registered trademark). The stylus 2 is configured to be able to communicate with the position detection device 3 via this wireless communication unit 11 via short-range wireless communication.

[0035] Fig. 4 is a diagram showing the internal configuration of the stylus 2. As shown in the figure, the stylus 2 is configured to have, in addition to the pen tip electrode 10 and wireless communication unit 11 described above, a pressure sensor 12, a communication unit 13, and an MCU (Micro Controller Unit) 14. In addition to these, the stylus 2 also has a core that forms the pen tip of the stylus 2, a battery that supplies operating power to each unit within the stylus 2, a switch provided on the surface, a memory that stores identification information for the stylus 2, and the like, but these are not shown in Fig. 4.

[0036] The pen tip electrode 10 includes a pen tip 10a and a pen ring 10b. The pen tip 10a is a rod-shaped electrode provided at the tip of the core. Meanwhile, the pen ring 10b is a ring-shaped electrode provided to surround the core. The stylus 2 is configured to receive an uplink signal US using one or both of the pen tip 10a and the pen ring 10b, and to transmit a downlink signal DS from each of the pen tip 10a and the pen ring 10b. The sensor controller 31 is configured to derive a position based on the downlink signal DS transmitted from the pen tip 10a and the downlink signal DS transmitted from the pen ring 10b, acquire the position derived based on the downlink signal DS transmitted from the pen tip 10a as the pen position, and derive the inclination (tilt angle) of the stylus 2 based on the two derived positions.

[0037] The pressure sensor 12 is a sensor that detects the pressure applied to the pen tip of the stylus 2. The pressure value detected by the pressure sensor 12 is supplied to the MCU 14 as a pen pressure value. When the pen pressure value supplied from the pressure sensor 12 is a predetermined value (for example, 0), the MCU 14 determines that the stylus 2 is not in contact with (hovering over) the panel surface 3a, and when the pen pressure value exceeds the predetermined value (for example, 0), the MCU 14 determines that the stylus 2 is in contact with (touching) the panel surface 3a. Hereinafter, the state in which the pen tip of the stylus 2 is in contact with the panel surface 3a will be referred to as a "pen touch."

[0038] The communication unit 13 is a functional unit that has the function of converting the uplink signal US (spread code) received by the pen tip electrode 10 into a symbol string and supplying it to the MCU 14, and the function of converting the downlink signal DS (symbol string) supplied from the MCU 14 into a spread code similar to the uplink signal US and supplying it to the pen tip electrode 10. Of these, only the function related to the uplink signal US is shown in Figure 4.

[0039] Referring to Figure 4, the functions related to the uplink signal US that the communication unit 13 has will be explained in detail. The communication unit 13 is configured to have an AD converter 20, a custom logic circuit 21, clock generators 22 and 23, and a switch circuit 24.

[0040] The AD converter 20 is a circuit that samples the uplink signal US supplied from the pen tip electrode 10 at a predetermined sampling rate, and then quantizes and encodes it to convert the analog signal received as the uplink signal US into a bit string of "1" or "0" and supplies it to the custom logic circuit 21. The sampling rate of the AD converter 20 is set to a value faster than the chip rate of the uplink signal US. Meanwhile, the time length per bit of the bit string output from the AD converter 20 is set to a value equal to the chip length of the uplink signal US.

[0041] The custom logic circuit 21 is a circuit including a correlator 21a that calculates a correlation value between an input bit string and a predetermined bit string stored in advance. The correlator 21a detects the spreading code that constitutes the symbols of the uplink signal US by calculating a correlation value between the bit string supplied from the AD converter 20 and a predetermined bit string (a bit string indicating a spreading code) stored in advance. The custom logic circuit 21 generates a symbol string based on the detection result of the correlator 21a and supplies the symbol string to the MCU 14.

[0042] Clock generator 22 is a circuit that generates a clock signal that oscillates at a period corresponding to the chip length according to the first setting described above. Clock generator 23 is a circuit that generates a clock signal that oscillates at a period corresponding to the chip length according to the second setting described above. Switch circuit 24 is a circuit that generates a clock signal generated by either clock generator 22 or 23 under the control of MCU 14 and supplies the clock signal to custom logic circuit 21. Custom logic circuit 21 and correlator 21a perform processes such as calculating the correlation value and generating the symbol sequence described above in accordance with the clock signal thus supplied. Therefore, in order for the symbol sequence output from custom logic circuit 21 to correctly reflect the uplink signal US, the period of the clock signal must match the chip length of the uplink signal US.

[0043] The MCU 14 is the central processing unit of the stylus 2, and performs processing to generate a downlink signal DS based on the uplink signal US received from the sensor controller 31 and transmit the signal to the sensor controller 31. The MCU 14 also performs processing to control the switch circuit 24 in order to switch the type (setting) of the uplink signal US that can be received.

[0044] 5 is a diagram showing the transition of operation modes of the MCU 14. As shown in the figure, the MCU 14 is configured to have four operation modes: a normal operation mode, a priority uplink continuous search mode, a non-priority uplink continuous search mode, and a free-running mode.

[0045] The normal operation mode is a mode in which the MCU 14 detects an uplink signal US based on a symbol sequence supplied from the custom logic circuit 21, and generates and transmits a downlink signal in accordance with the detected uplink signal US. When the MCU 14 has not yet detected an uplink signal US, the MCU 14 may perform the operation of detecting the uplink signal US continuously, but it is preferable to perform the operation of detecting the uplink signal US intermittently (i.e., at predetermined time intervals) to conserve battery power.

[0046] As described above, the sensor controller 31 according to this embodiment transmits the uplink signal US in either the first setting or the second setting, which have different chip lengths. The MCU 14 pre-stores one of these settings as a "priority setting," and when operating in the normal operation mode, controls the switch circuit 24 so that a clock signal oscillating at a period corresponding to the priority setting is supplied to the custom logic circuit 21. As a result, the custom logic circuit 21 can correctly convert the uplink signal US transmitted in the priority setting (hereinafter referred to as the "priority uplink signal US") into a symbol sequence, but cannot correctly convert the uplink signal US transmitted in a setting other than the priority setting (hereinafter referred to as the "non-priority setting") (hereinafter referred to as the "non-priority uplink signal US") into a symbol sequence. Therefore, the MCU 14 operating in the normal operation mode can detect the priority uplink signal US based on the symbol sequence supplied from the custom logic circuit 21, but cannot detect the non-priority uplink signal US.

[0047] The settings that the MCU 14 stores as "priority settings" are determined in advance. However, the MCU 14 can share the uplink signal US settings with the sensor controller 31 at any time by short-range wireless communication via the wireless communication unit 11. When the uplink signal US settings are shared with the sensor controller 31, the MCU 14 stores the shared settings as "priority settings."

[0048] If the MCU 14 detects an uplink signal US while operating in the normal operation mode, it continues operating in the normal operation mode and performs operations such as transmitting a downlink signal DS in response to the detected uplink signal US and detecting the next uplink signal US. On the other hand, if the MCU 14 detects a pen touch based on the pen pressure value supplied from the pressure sensor 12 while not detecting an uplink signal US, it enters a priority uplink continuous search mode. The priority uplink continuous search operation mode immediately executes a priority uplink signal US detection operation in response to the detection of a pen touch. This mode is used to quickly detect an uplink signal US when, for example, the uplink signal US is not detected despite contact with the panel surface 3a due to the uplink signal US detection interval. If the MCU 14 detects an uplink signal US while operating in the priority uplink continuous search mode, it returns to the normal operation mode and performs operations such as transmitting a downlink signal DS in response to the detected uplink signal US and detecting the next uplink signal US.

[0049] If the MCU 14 fails to detect the uplink signal US after performing a detection operation for the priority uplink signal US for a predetermined time in the priority uplink continuous search mode, it enters the non-priority uplink search mode. The non-priority uplink search mode is a mode for attempting to detect the non-priority uplink signal US. After entering the non-priority uplink search mode, the MCU 14 controls the switch circuit 24 so that a clock signal oscillating at a period corresponding to the non-priority setting is supplied to the custom logic circuit 21. This enables the MCU 14 to detect the non-priority uplink signal US based on the symbol sequence supplied from the custom logic circuit 21. Note that if there are three or more settings for the uplink signal US, the MCU 14 may sequentially try each setting other than the priority setting in the non-priority uplink search mode.

[0050] If the MCU 14 detects an uplink signal US in the non-priority uplink search mode, it overwrites the priority setting with the current setting and returns to normal operation mode. From then on, the previous non-priority setting becomes the priority setting. On the other hand, if the MCU 14 does not detect an uplink signal US even in the non-priority uplink search mode, it enters the free-running mode. The free-running mode is a mode in which the stylus 2, which is unable to receive an uplink signal US, autonomously transmits a downlink signal DS. Once in the free-running mode, the MCU 14 controls the switch circuit 24 so that a clock signal oscillating at a frequency corresponding to the priority setting is supplied to the custom logic circuit 21, and then periodically detects a priority uplink signal US and transmits a downlink signal DS. The downlink signal DS transmitted in the free-running mode is a special downlink signal DS that includes flag information indicating that the MCU 14 is in the free-running mode.

[0051] If an uplink signal US is detected while in the free-running mode, the MCU 14 enters the normal operation mode. The processing performed by the MCU 14 in the normal operation mode is as described above. The downlink signal DS transmitted by the MCU 14 while in the normal operation mode does not include the above flag information. Furthermore, if, while in the free-running mode, an uplink signal US is not detected and a pen touch is detected based on the pen pressure value supplied from the pressure sensor 12, the MCU 14 enters the priority uplink continuous search mode. The processing performed by the MCU 14 in the priority uplink continuous search mode is as described above.

[0052] 6 is a flow diagram showing the processing executed by the sensor controller 31. Hereinafter, the processing executed by the sensor controller 31 according to this embodiment will be described in detail with reference to the same diagram.

[0053] The sensor controller 31 first determines whether or not a setting has been shared by short-range wireless communication (step S1). If it is determined that a setting has been shared, the sensor controller 31 selects the shared setting (step S2), and if it is determined that a setting has not been shared, the sensor controller 31 selects a predetermined setting (here, the first setting) (step S3).

[0054] Next, the sensor controller 31 transmits an uplink signal US using the selected settings (step S4), and then receives a downlink signal DS (step S5). The sensor controller 31 then determines whether or not a downlink signal DS has been received as a result of the reception (step S6). If it determines that a downlink signal DS has not been received, it re-determines whether or not settings have been shared via short-range wireless communication (step S7). If it determines that settings have been shared, it immediately returns to step S4. If it determines that settings have not been shared, it selects settings different from the current settings (step S8) and then returns to step S4. Thus, until the downlink signal DS is received, if settings have been shared via short-range wireless communication, the sensor controller 31 continues to transmit an uplink signal US using the shared settings. If settings have not been shared via short-range wireless communication, the sensor controller 31 alternately transmits an uplink signal US using the first settings and the second settings.

[0055] If it is determined in step S6 that a downlink signal DS has been received, the sensor controller 31 determines whether the received downlink signal DS is the above-mentioned "special downlink signal DS" (step S9). As a result, if it is determined to be a "special downlink signal DS," the sensor controller 31 selects a setting different from the current setting (step S10) and returns to step S4. The determination of a "special downlink signal DS" in step S9 means that the stylus 2 failed to detect the transmitted uplink signal US and has entered free-running mode. By executing steps S9 and S10, it is possible to increase the possibility that the stylus 2 will be able to receive the uplink signal US again.

[0056] If the sensor controller 31 determines in step S9 that the received downlink signal DS is not a "special downlink signal DS," it derives the position of the stylus 2 and acquires the pen data transmitted by the stylus 2 based on the received downlink signal DS (step S11), and outputs the data to the host processor 32. Next, the sensor controller 31 transmits an uplink signal US again with the selected settings (step S12), and receives the downlink signal DS (step S13).

[0057] Next, the sensor controller 31 determines whether or not a downlink signal DS has been received (step S14). If it is determined that the downlink signal DS has been received, the sensor controller 31 determines whether or not the received downlink signal DS is the above-mentioned "special downlink signal DS" (step S15). If it is determined that the received downlink signal DS is a "special downlink signal DS," the sensor controller 31 selects a setting different from the current setting (step S16) and returns to step S4. The determination of a "special downlink signal DS" in step S15 means that the stylus 2, which was once able to normally detect the uplink signal US, has now begun to fail to detect the uplink signal US and has entered free-running mode. The processing of steps S15 and S16 makes it possible to increase the possibility of returning such a stylus 2 to normal operation mode. If it is determined in step S15 that the received downlink signal DS is not a "special downlink signal DS," the sensor controller 31 returns to step S11 and continues processing.

[0058] If it is determined in step S14 that the downlink signal DS has not been received, the sensor controller 31 determines whether or not the non-reception state of the downlink signal DS has continued for a predetermined number of times (or a predetermined period of time) (step S17). As a result, if it is determined that the non-reception state has not continued, the process returns to step S12 to continue, and if it is determined that the non-reception state has continued, the process returns to step S1.

[0059] As described above, according to the position detection system 1 of this embodiment, the sensor controller 31 can transmit the uplink signal US by selectively using the first setting and the second setting, which have different chip lengths (chip rates) and the like, and can therefore select slow operation when selectable. This makes it possible to reduce the load on the sensor controller 31.

[0060] Furthermore, noise may be superimposed on the uplink signal US, which may result in problems with reception of the uplink signal US by the stylus 2. However, according to the position detection system 1 of this embodiment, the sensor controller 31 can transmit the uplink signal US by selectively using a first setting and a second setting that differ from each other in terms of chip length (chip rate), etc., thereby making it possible to reduce the effects of noise on reception of the uplink signal US by the stylus 2.

[0061] Furthermore, according to the position detection system 1 of this embodiment, when the sensor controller 31 fails to detect the uplink signal US transmitted by the stylus 2 in the first setting, the sensor controller 31 can detect this and transmit the uplink signal US in the second setting. Therefore, the sensor controller 31 can appropriately start communication with the stylus 2 while transmitting the uplink signal US using one of two or more different settings.

[0062] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it goes without saying that the present invention can be embodied in various forms without departing from the spirit of the present invention.

[0063] For example, in the above embodiment, an example has been described in which short-range wireless communication is used without capacitive coupling with the pen tip electrode 10 in order to share the setting of the uplink signal US between the sensor controller 31 and the stylus 2, but an electrode other than the group of sensor electrodes that make up the sensor 30 may be provided in the position detection device 3, and the setting of the uplink signal US may be shared between the sensor controller 31 and the stylus 2 via capacitive coupling between this electrode and the pen tip electrode 10. Examples of such electrodes include sensor electrodes that make up a touchpad provided in a notebook computer and electrodes provided in a garage for storing the stylus 2.

[0064] In addition, in the above embodiment, an example was described in which the stylus 2 enters the non-priority uplink search mode and attempts to receive the non-priority uplink signal US when it is unable to receive the priority uplink signal US in the normal mode and the priority uplink continuous search mode.However, the stylus 2 may also alternate between receiving the priority uplink signal US and receiving the non-priority uplink signal US, for example, when it has not yet detected the uplink signal US.

[0065] Furthermore, in the above embodiment, an example has been described in which the sensor controller 31 transmits an uplink signal US using one of two or more different settings. However, two or more different uplink signals US at a higher level may also be transmitted. For example, one uplink signal US may be transmitted using a version of the active electrostatic system, and the other uplink signal US may be transmitted using a different version of the active electrostatic system. Alternatively, one uplink signal US may be transmitted using the active electrostatic system, and the other uplink signal US may be transmitted using another communication method, such as short-range wireless communication or electromagnetic induction. If we refer to both the case of transmitting two or more uplink signals US with different settings and the case of transmitting two or more different uplink signals US at a higher level than the settings as "transmitting an uplink signal US using one of two or more different methods," then by replacing "setting" with "method" in the above embodiment, it is possible to achieve the same effect as the above embodiment by performing similar processing. [Explanation of symbols]

[0066] 1. Position detection system 2 stylus 3 Position detection device 3a Panel surface 10 Pen tip electrode 10a pen tip 10b Pen Ring 11. Wireless Communication Section 12 Pressure Sensor 13 Communications Department 14 MCU 20 AD converter 21 Custom Logic Circuits 21a Correlator 22,23 Clock Generator 24 Switch Circuit 30 sensors 31 Sensor Controller 32 host processor 33 Radio Communication Department DS downlink signal F Frame PRE Preamble US uplink signal

Claims

1. The uplink signal having a predetermined preamble is configured to be transmittable in either a first setting or a second setting different from each other; selecting one of the first setting and the second setting, and transmitting the uplink signal in the selected setting; Sensor controller.

2. The first setting is a setting in which a chip rate of a spreading code constituting the uplink signal is relatively large, The second setting is a setting in which a chip rate of a spreading code constituting the uplink signal is relatively small. The sensor controller of claim 1 .

3. selecting one of the first setting and the second setting in response to a response from the stylus to the transmitted uplink signal; The sensor controller of claim 1 .

4. alternately transmitting the uplink signal according to the first setting and transmitting the uplink signal according to the second setting; The sensor controller of claim 1 .

5. selecting one of the first setting and the second setting based on a result of communication with the stylus performed using a second communication method different from a first communication method used to transmit the uplink signal; The sensor controller of claim 1 .

6. the first communication method is a communication method performed via capacitive coupling between a group of sensor electrodes arranged on a touch surface and a pen tip electrode of the stylus; The second communication method is a communication method that does not involve capacitive coupling. The sensor controller according to claim 5 .

7. the first communication method is a communication method performed via capacitive coupling between a group of sensor electrodes arranged on a touch surface and a pen tip electrode of the stylus; the second communication method is a communication method performed via capacitive coupling between an electrode different from the group of sensor electrodes and the pen tip electrode; The sensor controller according to claim 5 .

8. a receiving unit configured to detect both an uplink signal transmitted in a first setting and an uplink signal transmitted in a second setting different from the first setting; A stylus comprising:

9. The receiving unit alternately receives an uplink signal transmitted in the first setting and an uplink signal transmitted in the second setting.

9. A stylus as claimed in claim 8.

10. The receiver selects one of the first setting and the second setting based on a result of communication with the sensor controller performed using a second communication method different from a first communication method used to transmit the uplink signal, and performs a receiving operation of the uplink signal transmitted in the selected one of the settings.

9. A stylus as claimed in claim 8.

11. the first communication method is a communication method performed via capacitive coupling between a sensor electrode group arranged within a touch surface and connected to the sensor controller and a pen tip electrode of the stylus; The second communication method is a communication method that does not involve capacitive coupling.

11. A stylus as claimed in claim 10.

12. the first communication method is a communication method performed via capacitive coupling between a sensor electrode group arranged within a touch surface and connected to the sensor controller and a pen tip electrode of the stylus; the second communication method is a communication method performed via capacitive coupling between an electrode different from the group of sensor electrodes and the pen tip electrode; 11. A stylus as claimed in claim 10.

13. Transmitting a first uplink signal in a first manner; determining whether the stylus fails to detect the first uplink signal; transmitting a second uplink signal in a second scheme different from the first scheme when the stylus determines that it has failed to detect the first uplink signal; Sensor controller.

14. determining that the stylus has failed to detect the first uplink signal when a special downlink signal is received after transmitting the first uplink signal; The sensor controller of claim 13.

15. the special downlink signal is a signal including information indicating that the stylus has entered a free-running mode; The sensor controller of claim 14.

16. The first scheme and the second scheme are schemes in which the frequency of an uplink signal or the chip length of a spreading code constituting an uplink signal is different from each other. The sensor controller of claim 13.

17. The first method and the second method are methods in which the types or chip lengths of spreading codes constituting an uplink signal are different from each other. The sensor controller of claim 13.

18. The first method and the second method are methods in which electrodes used for transmitting an uplink signal are different from each other. The sensor controller of claim 13.

Images