Active pen and position detection device

Abstract

To prevent drawing by pen input from being stopped due to failure in receiving an uplink signal.SOLUTION: An active pen communicates with a sensor controller. The active pen includes: an electrode and a coil; a transmitting circuit that transmits a downlink signal to the sensor controller by giving a change to a potential of the electrode; and a receiving circuit that receives an uplink signal transmitted by the sensor controller by detecting an induced current generated in the coil.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to an active pen, a sensor controller, and a position detection device, and more particularly to an active pen and a sensor controller that communicate bidirectionally with each other, and a position detection device including such a sensor controller. [Background technology]

[0002] An active pen that is configured to receive an uplink signal from a sensor controller and transmit a downlink signal to the sensor controller is known. Patent Document 1 discloses an example of this type of active pen. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6059410 Summary of the Invention [Problem to be solved by the invention]

[0004] As described in Patent Document 1, the active pen is configured to transmit a downlink signal using a time slot determined based on the reception timing of the uplink signal as a reference time. Therefore, in order for the active pen to transmit a downlink signal, it must be able to receive an uplink signal.

[0005] However, noise, such as that in a signal for driving pixels in a display, can be superimposed on the uplink signal, causing the active pen to fail to receive the uplink signal. This causes the active pen to be unable to transmit a downlink signal, which stops drawing by pen input, and so an improvement was needed.

[0006] Therefore, one object of the present invention is to provide an active pen and sensor controller that can prevent drawing by pen input from being stopped due to failure to receive an uplink signal. [Means for solving the problem]

[0007] An active pen according to a first aspect of the present invention is an active pen that communicates with a sensor controller using a series of time slots that are determined using the reception timing of an uplink signal as a reference time, and determines whether or not the uplink signal has been received, and if it determines that the uplink signal has been received, transmits the first downlink signal using the time within the series of time slots, while if it determines that the uplink signal has not been received, transmits a second downlink signal consisting of a repetition of unit signals, the time of which is shorter than the time length of each of the series of time slots, using both the time within the series of time slots and the time outside the series of time slots.

[0008] A sensor controller according to a first aspect of the present invention is a sensor controller that communicates with an active pen according to the first aspect of the present invention, and determines whether a signal detected in one of the series of time slots includes a gap, and if it is determined that a gap is included, demodulates the detected signal as the first downlink signal, while if it is determined that a gap is not included, demodulates the detected signal as the second downlink signal.

[0009] An active pen according to a second aspect of the present invention is an active pen that communicates with a sensor controller and includes an electrode and a coil, a transmitting circuit that transmits a downlink signal to the sensor controller by changing the potential of the electrode, and a receiving circuit that receives an uplink signal transmitted by the sensor controller by detecting an induced current generated in the coil.

[0010] A position detection device according to a second aspect of the present invention is a position detection device that detects the position of an active pen within a touch surface, and includes one or more loop coils arranged within the touch surface, a plurality of sensor electrodes arranged within the touch surface, and a sensor controller that transmits an uplink signal to the active pen by supplying an uplink signal to each of the one or more loop coils, and receives a downlink signal transmitted by the active pen by detecting changes in the potential of each of the plurality of sensor electrodes. Effect of the Invention

[0011] According to the first aspect of the present invention, even if the active pen fails to receive an uplink signal and the time position of the time slot becomes unknown, the active pen can continue to transmit a downlink signal, thereby preventing drawing by pen input from being stopped due to failure to receive an uplink signal.

[0012] According to the second aspect of the present invention, an uplink signal can be transmitted using an electromagnetic induction method, which is less susceptible to noise than an electrostatic coupling method, thereby preventing drawing using pen input from being stopped due to failure to receive the uplink signal. [Brief description of the drawings]

[0013] [Figure 1] 1 is a diagram showing a configuration of a position detection system 1 according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view of the sensor 30a shown in FIG. [Diagram 3] 2 is a state transition diagram of the processing circuit 26d shown in FIG. [Figure 4] 2 is a diagram illustrating the operation of the active pen 2 and the sensor controller 31. FIG. [Diagram 5] 2 is a diagram illustrating the operation of the active pen 2 and the sensor controller 31. FIG. [Figure 6]6A is a diagram showing the configuration of the downlink signal DSb shown in FIG. 5 , (b) and (c) are diagrams showing the configurations of the chip signal TIP and the ring signal RING when the downlink signal DSb is modulated by DBPSK, and (d) and (e) are diagrams showing the configurations of the chip signal TIP and the ring signal RING when the downlink signal DSb is modulated by DQPSK. [Figure 7] 2 is a process flow diagram showing a process performed by a processing circuit 26d shown in FIG. [Figure 8] 2 is a process flow diagram showing a process performed by a sensor controller 31 shown in FIG. 1. [Figure 9] 2 is a process flow diagram showing a process performed by a sensor controller 31 shown in FIG. 1. [Figure 10] FIG. 1 is a diagram showing a configuration of a position detection system 1 according to a second embodiment of the present invention. [Figure 11] FIG. 11 is a plan view of the sensor 30b shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0015] 1 is a diagram showing the configuration of a position detection system 1 according to an embodiment of the present invention. As shown in the figure, the position detection system 1 includes an active pen 2 and an electronic device 3 which is a position detection device that detects the active pen 2.

[0016] The electronic device 3 is a computer having a touch surface 3a, such as a tablet computer or a digitizer. The electronic device 3 includes a sensor 30a disposed directly below the touch surface 3a, a sensor controller 31 connected to the sensor 30a, a display 32 disposed overlapping the sensor 30a, and a host processor 33 that controls each part of the electronic device 3 including these components.

[0017] The host processor 33 is a central processing unit of the electronic device 3, and is configured to read and execute various programs from a memory (not shown). The programs thus executed include the operating system of the electronic device 3 and various applications including a drawing application. Among these, the drawing application is a program for executing a process of generating digital ink based on the position and data supplied from the sensor controller 31 and storing it in a memory in the electronic device 3, and a process of rendering the generated digital ink, generating a video signal showing the result, and supplying it to the display 32. The display 32 is a device that displays the video signal supplied from the host processor 33, and is configured, for example, by a liquid crystal display or an organic EL display.

[0018] The sensor controller 31 is an integrated circuit having a function of deriving the position of the active pen 2 on the touch surface 3a by bidirectionally communicating with the active pen 2 via the sensor 30a, acquiring data from the active pen 2, and supplying the derived position and acquired data to the host processor 33 each time. In this embodiment, communication between the sensor controller 31 and the active pen 2 in both directions is performed by electrostatic coupling type communication via electrostatic capacitance formed between electrodes on the electronic device 3 side (sensor electrodes 30x and 30y described later) and electrodes on the active pen 2 side (pen tip electrode 21 and ring electrode 22 described later). Hereinafter, a signal transmitted from the sensor controller 31 to the active pen 2 is referred to as an uplink signal US, and a signal transmitted from the active pen 2 to the sensor controller 31 is referred to as a downlink signal DS.

[0019] FIG. 2 is a plan view of the sensor 30a. As shown in the figure, the sensor 30a includes a plurality of sensor electrodes 30x and 30y arranged in the touch surface 3a. The plurality of sensor electrodes 30x are conductors extending in the illustrated y direction, and are arranged in parallel at equal intervals in the illustrated x direction. The plurality of sensor electrodes 30y are conductors extending in the illustrated x direction, and are arranged in parallel at equal intervals in the illustrated y direction. The sensor controller 31 transmits an uplink signal US to the active pen 2 by changing the potential of one of the plurality of sensor electrodes 30x and the plurality of sensor electrodes 30y. The sensor controller 31 also receives a downlink signal DS transmitted by the active pen 2 by detecting a change in the potential of each of the plurality of sensor electrodes 30x and 30y.

[0020] Here, the electronic device 3 is a so-called "in-cell type" position detection device, and one of the multiple sensor electrodes 30x and multiple sensor electrodes 30y constituting the sensor 30a also serves as a common electrode (electrode for supplying a ground potential to each pixel in common) of the display 32. Therefore, the sensor controller 31 cannot transmit the uplink signal US or receive the downlink signal DS using the sensor 30a at the timing for driving the pixels in the display 32. Therefore, the sensor controller 31 is configured to obtain the timing for driving the pixels in the display 32 from the host processor 33, transmit the uplink signal US at a constant period determined by the pixel drive period, set a plurality of time slots corresponding to the pixel drive intervals as the transmission interval of the uplink signal US, and receive the downlink signal DS from the active pen 2 using the time in each time slot.

[0021] The uplink signal US is a signal modulated by a command indicating an instruction to the active pen 2, and is composed of a pulse wave (rectangular wave) in which each transmission bit is spread by a predetermined chip sequence (spread code). The chip length of the predetermined chip sequence (=pulse period of the uplink signal US) is, for example, 1 μsec or 2 μsec, and the edge period (rising period or falling period) is, for example, 10 nsec.

[0022] On the other hand, the downlink signal DS is a position signal for causing the sensor controller 31 to detect the position of the active pen 2, or a data signal modulated by data instructed to be transmitted by the uplink signal US (such as a pen pressure value and switch information, described below). However, transmission of a position signal is not essential, and the sensor controller 31 can also detect the position of the active pen 2 from a data signal. The specific configuration of the downlink signal DS differs depending on whether or not an uplink signal US has been received immediately before. In the following, a downlink signal DS transmitted when an uplink signal US has been received immediately before is referred to as a downlink signal DSa (first downlink signal), and a downlink signal DS transmitted when an uplink signal US has not been received immediately before is referred to as a downlink signal DSb (second downlink signal).

[0023] The downlink signal DSa is a signal that is divided and transmitted for each of a series of time slots set by the sensor controller 31. The active pen 2 determines the time positions of the series of time slots using the reception timing of the immediately preceding uplink signal US as a reference time, and transmits the downlink signal DSa using the time within each determined time slot.

[0024] Here, the active pen 2 is configured to place the pen pressure value four times in the downlink signal DSa transmitted during one transmission cycle UpIntv. The most recent pen pressure value supplied from the pressure sensor 23 at the time of transmitting the pen pressure value is used as the placed pen pressure value. This allows the pen pressure value to be transmitted with high time resolution, enabling the host processor 33 to perform more realistic drawing.

[0025] The downlink signal DSb is a signal consisting of repeated unit signals each having a time length shorter than the time length of a time slot. The specific configuration of the downlink signal DSb will be described later, but each unit signal is a data signal modulated by predetermined data.

[0026] The active pen 2, which has failed to receive the immediately preceding uplink signal US, cannot determine the time position of the series of time slots, and as a result, the downlink signal DSb is transmitted using both the time within the series of time slots and the time outside the series of time slots. As a result, the sensor controller 31 cannot receive a part of the downlink signal DSb (the part transmitted at a time outside the series of time slots), but by setting the time length of the unit signal as described above, it becomes possible to receive at least one unit signal. Therefore, even if the active pen 2 has lost the time position of the series of time slots, it becomes possible to transmit the downlink signal DS from the active pen 2 to the sensor controller 31.

[0027] Physically, the downlink signals DSa and DSb are each composed of a signal based on a pulse wave (rectangular wave) or a sine wave. In the case of a pulse wave, the downlink signals DSa and DSb are signals having a pulse period and an edge period that are significantly longer than those of the uplink signal US. To give a specific example, the pulse period is, for example, 4 μsec to 40 μsec, and the edge period is, for example, 100 nsec to 5 μsec. On the other hand, in the case of a sine wave, the frequency of the downlink signals DSa and DSb is, for example, 1.8 MHz. As a modulation method for a carrier wave that is a pulse wave or a sine wave, it is preferable to use DQPSK (Differential Quadrature Phase-Shift Keying) or DBPSK (Differential Binary Phase-Shift Keying). Which modulation method is used is determined in advance by a standard.

[0028] Returning to FIG. 1, the active pen 2 is configured to have a core body 20, a pen tip electrode 21 (first electrode), a ring electrode 22 (second electrode), a pressure sensor 23, a side switch 24, a battery 25, an integrated circuit 26, and a stop filter 27. The core body 20 is a member that constitutes the pen shaft of the active pen 2. The tip of the core body 20 constitutes the pen tip of the active pen 2, and the end abuts against the pressure sensor 23. The pen tip electrode 21 and the ring electrode 22 are conductors provided at different positions, the pen tip electrode 21 is disposed at the pen tip of the active pen 2, and the ring electrode 22 is disposed at a position closer to the center of the active pen 2 than the pen tip electrode 21 so as to surround the core body 20.

[0029] The pressure sensor 23 is a sensor that detects the pressure applied to the tip of the core body 20. The pressure detected by the pressure sensor 23 is supplied to the integrated circuit 26 as, for example, a 12-bit writing pressure value. The side switch 24 is a push button switch provided on the surface of the active pen 2, and is configured to be turned on and off by the user. The operational state (on / off state) of the side switch 24 is supplied to the integrated circuit 26 as, for example, 2-bit switch information. The battery 25 serves to supply the power necessary for the integrated circuit 26 to operate.

[0030] The integrated circuit 26 is an integrated circuit configured by various circuits including a boost circuit 26a, a transmission circuit 26b, a reception circuit 26c, and a processing circuit 26d. The transmission circuit 26b is connected to the pen tip electrode 21, and plays a role of transmitting a downlink signal DS by changing the potential of the pen tip electrode 21 using the boost circuit 26a. The reception circuit 26c is connected to the ring electrode 22, and plays a role of receiving an uplink signal US by detecting a change in the potential of the ring electrode 22.

[0031] The processing circuit 26d is a circuit that executes processing according to the uplink signal US received by the receiving circuit 26c. This processing includes a process of determining the time positions of a series of time slots using the reception timing of the uplink signal US as a reference time, a process of generating a downlink signal DS in response to a command from the sensor controller 31 and having the transmitting circuit 26b transmit it, and a process of having the receiving circuit 26c receive the next uplink signal US.

[0032] 3 is a state transition diagram of the processing circuit 26d. As shown in the figure, the processing circuit 26d is configured to operate in any one of a discovery mode, a normal mode, and a self-running mode. The initial state is the discovery mode, and the processing circuit 26d that has entered the discovery mode causes the receiving circuit 26c to perform a detection operation of the uplink signal US continuously or intermittently (step S1).

[0033] If an uplink signal US is detected as a result of the detection operation in step S1, the processing circuit 26d enters the normal mode (step S2). Then, the time positions of a series of time slots are determined using the reception timing of the uplink signal US as a reference time, and the transmission circuit 26b transmits the downlink signal DSa using the time in the series of time slots (step S10). When the reception timing of the next uplink signal US arrives (step S11), the reception circuit 26c performs the detection operation of the next uplink signal US (step S12). As a result, when the next uplink signal US is detected (step S13), the time positions of a series of time slots are determined again using the reception timing of the uplink signal US as a reference time, and the process of step S10 is repeated.

[0034] On the other hand, if the uplink signal is not detected as a result of the detection operation in step S12, the processing circuit 26d enters the free-running mode (step S14). In the free-running mode, the processing circuit 26d generates the downlink signal DSb and causes the transmission circuit 26b to transmit it, and in parallel with this, causes the reception circuit 26c to perform the detection operation of the uplink signal US (step S20). This parallel processing is realized by the stop filter 27 shown in FIG. 1, and the details will be described later. If the uplink signal US is detected in step S20, the processing circuit 26d returns to the normal mode (step S21). Then, the time positions of the series of time slots are determined again with the reception timing of the uplink signal US as the reference time, and the processing of step S10 is repeated. On the other hand, if the state in which the uplink signal US is not detected continues for a predetermined time, the processing circuit 26d returns to the discovery mode and continues the processing (step S22). In this case, the transmission of the downlink signal DSb is stopped.

[0035] Returning to FIG. 1, the stop filter 27 is a filter circuit inserted between the ring electrode 22 and the integrated circuit 26 to simultaneously detect the uplink signal US using the ring electrode 22 and transmit the downlink signal DSb from the pen tip electrode 21. To explain in detail, the voltage increase caused by the boost circuit 26a used to transmit the downlink signal DSb reaches 18 to 20V, so that the change in the potential of the pen tip electrode 21 accompanying the transmission of the downlink signal DSb also affects the receiving circuit 26c. As a result, the downlink signal DSb is superimposed on the potential of the uplink signal US detected by the receiving circuit 26c, making it difficult to detect the uplink signal US simultaneously with the transmission of the downlink signal DSb. When the active pen 2 is in a hover state (a state in which the pen tip is separated from the touch surface 3a) and the ring electrode 22 is far from the sensor 30a, the reception strength of the uplink signal US becomes weak, making it even more difficult to detect the uplink signal US. The stop filter 27 serves to prevent the change in potential of the pen tip electrode 21 accompanying the transmission of the downlink signal DSb from affecting the potential of the uplink signal US detected by the receiving circuit 26c in the integrated circuit 26, thereby enabling the detection of the uplink signal US using the ring electrode 22 and the transmission of the downlink signal DSb from the pen tip electrode 21 to be performed simultaneously.

[0036] As a specific configuration of the stop filter 27, various configurations may be adopted. For example, if the downlink signal DSb is composed of a signal based on a sine wave, the stop filter 27 may be composed of a band-stop filter (notch filter) that blocks a specific frequency band including the frequency of the downlink signal DSb. If the downlink signal DS is composed of a pulse wave, the stop filter 27 may be composed of a high-pass filter configured to pass the pulse wave that constitutes the uplink signal US while blocking the pulse wave that constitutes the downlink signal DSb. In addition, a mute circuit for muting the edge of the downlink signal DSb may be provided in the subsequent stage of this high-pass filter, or the stop filter 27 may be configured by a combination of a gain circuit and a differential circuit, or a combination of a FIR (Finite Impulse Response) filter, a subtractor, and a feedback circuit, thereby removing the downlink signal DSb from the signal arriving at the ring electrode 22.

[0037] 4 and 5 are diagrams for explaining the operation of the active pen 2 and the sensor controller 31. Hereinafter, the operation of the active pen 2 and the sensor controller 31 according to this embodiment will be explained in more detail with reference to these diagrams.

[0038] The horizontal axis in Fig. 4 and Fig. 5 is the time axis. First, referring to Fig. 4, the active pen 2 that has entered the discovery mode continuously or intermittently performs an operation of detecting the uplink signal US that has arrived at the ring electrode 22. Meanwhile, the sensor controller 31 transmits the uplink signal US at a constant period UpIntv determined by the driving period of the pixels in the display 32, sets a series of time slots TS, each of which corresponds to the driving interval of the pixels in the display 32, as the transmission interval of the uplink signal US, and performs an operation of detecting the downlink signal DS in each time slot TS.

[0039] The active pen 2 that successfully receives the uplink signal US at time t1 enters normal mode, determines the time position of the series of time slots TS using the reception timing of the uplink signal US as the reference time, obtains the command transmitted by the sensor controller 31 by demodulating the received uplink signal US, and generates a downlink signal DSa according to the obtained command. The generated downlink signal DSa is then transmitted using the time within each determined time slot TS. The sensor controller 31, which receives the downlink signal DS using only the time within the series of time slots TS, can receive the downlink signal DSa thus transmitted without any problems.

[0040] 5, the active pen 2 detects that it has failed to receive the uplink signal US by detecting that it has not received the uplink signal US at time t2 when the uplink signal US should have been received. The active pen 2 then enters a free-running mode and generates a downlink signal DSb consisting of a repetition of unit signals each having a time length shorter than the time length of each time slot TS. The active pen 2 then transmits the generated downlink signal DSb using both the time within the series of time slots TS and the time outside the series of time slots TS. The sensor controller 31 receives the downlink signal DS using only the time within the series of time slots TS, but since the downlink signal DSb is composed of a repetition of unit signals each having a time length shorter than the predetermined time length of each time slot TS as described above, at least one unit signal can be received.

[0041] Thereafter, the active pen 2, which has successfully received the uplink signal US at time t3, returns to the normal mode. The operations of the active pen 2 and the sensor controller 31 in the normal mode are as described above. Thereafter, the active pen 2 similarly changes its operation mode depending on whether it has successfully or unsuccessfully received the uplink signal US, thereby changing the configuration of the downlink signal DS to be transmitted. Therefore, the active pen 2 according to this embodiment prevents drawing by pen input from being stopped due to failure to receive the uplink signal US.

[0042] 6(a) is a diagram showing the configuration of the downlink signal DSb. As shown in the figure, the downlink signal DSb has a configuration in which chip signals TIP (first signal) and ring signals RING (second signal) are alternately arranged by eight each during the transmission period UpIntv of the uplink signal US. If the time length of each chip signal TIP and ring signal RING is T1, then UpIntv=16×T1.

[0043] 6(b) and 6(c) are diagrams showing the configurations of the chip signal TIP and the ring signal RING when the downlink signal DSb is modulated by DBPSK. Also, 6(d) and 6(e) are diagrams showing the configurations of the chip signal TIP and the ring signal RING when the downlink signal DSb is modulated by DQPSK. As shown in these figures, the chip signal TIP is composed of a repetition of unit signal U1, and the ring signal RING is composed of a repetition of unit signal U2. Also, in the chip signal TIP, a gap GA of two symbols (time when no signal is transmitted) is provided between two unit signals U1 adjacent in time, and in the ring signal RING, a gap GA of three symbols is provided between two unit signals U2 adjacent in time.

[0044] As shown in Fig. 6(b) to Fig. 6(e), both unit signals U1 and U2 are signals including one symbol's worth of start bit SB and six bits' worth of data. The number of data symbols is six symbols for both unit signals U1 and U2 when the downlink signal DSb is modulated by DBPSK, and three symbols when the downlink signal DSb is modulated by DQPSK. The contents of the data differ between unit signals U1 and U2, and the data in unit signal U1 includes two bits of switch information SW indicating the operation state (on / off state) of side switch 24 shown in Fig. 1, and the most significant three bits of data P of the 12-bit writing pressure value indicating the pressure detected by pressure sensor 23 shown in Fig. 1. U On the other hand, the data in the unit signal U2 is composed of the upper 8 bits to the most significant 3 bits of the 12-bit pen pressure value indicating the pressure detected by the pressure sensor 23 shown in FIG. U ) excluding 5 bits of data P L and a 1-bit checksum CS.

[0045] Here, the relationship between the time length of the time slot and the time length of the unit signals U1 and U2 will be explained with a specific example. First, as a first example, focusing on the case where the modulation of the downlink signal DSb is performed by DBPSK, assuming that one symbol is composed of two waves (two periods of the carrier wave), both the unit signals U1 and U2 have a time length of 7×2 waves=14 waves. In addition, the frequency of the carrier wave is, for example, 114 kHz, and the minimum time length of one time slot defined by the standard of the active pen 2 when the modulation of the downlink signal DSb is performed by DBPSK is 175 μsec, so that the time length of the time slot is expressed in the number of carrier waves, 175 μsec / (1 / 114 kHz)=19.95 waves. Therefore, according to the configuration of the unit signals U1 and U2 shown in FIG. 6(b) and FIG. 6(c), it can be said that the time length of the unit signals U1 and U2 is shorter than the time length of the time slot.

[0046] Next, as a second example, let us focus on the case where the downlink signal DSb is modulated by DQPSK, and assume that one symbol is composed of two waves (two periods of carrier waves), then both unit signals U1 and U2 have a time length of 4×2 waves=8 waves. In addition, the frequency of the carrier wave is, for example, 114 kHz, and the minimum time length of one time slot defined by the standard of the active pen 2 when the downlink signal DSb is modulated by DQPSK is 105 μsec, so that the time length of the time slot is expressed in terms of the number of carrier waves, which is 105 μsec / (1 / 114 kHz)=11.97 waves. Therefore, it can be said that the time length of the unit signals U1 and U2 shown in Figures 6(d) and 6(e) can also be made shorter than the time length of the time slot.

[0047] 6(a) again, the writing pressure value, which is partially allocated to each of the tip signal TIP and the ring signal RING, is updated four times during the transmission period UpIntv. Specifically, as shown in the figure, a new writing pressure value P 1 ~P 4 are sequentially supplied, and a part of each is placed in the tip signal TIP and the ring signal RING. This makes it possible to transmit the pen pressure value with a time resolution as high as that of the downlink signal DSa even when transmitting the downlink signal DSb.

[0048] FIG. 7 is a process flow diagram showing the process performed by the processing circuit 26d shown in FIG. 1. As shown in the figure, the processing circuit 26d first enters a discovery mode (step S100). Then, the processing circuit 26d causes the receiving circuit 26c to execute an operation of detecting an uplink signal US (step S101), and as a result, determines whether or not the uplink signal US has been received (step S102). If the processing circuit 26d determines that the uplink signal US has not been received, it repeats the process from step S101. On the other hand, if the processing circuit 26d determines that the uplink signal US has been received, it enters a normal mode (step S103) and determines a transmission / reception schedule for the downlink signal DS and the uplink signal US, using the reception timing of the received uplink signal US as a reference time (step S104). The transmission / reception schedule thus determined includes the time positions of a series of time slots used to transmit the downlink signal DS and the time position of the timing of the next detection operation of the uplink signal US.

[0049] Next, the processing circuit 26d generates a downlink signal DSa in each time slot according to the command in the uplink signal US, and causes the transmitting circuit 26b to transmit the signal using the time in the series of time slots determined in step S104 (step S105). The processing circuit 26d further causes the receiving circuit 26c to perform a detection operation for the next uplink signal US according to the transmission / reception schedule determined in step S104 (step S106).

[0050] Next, the processing circuit 26d judges whether or not the uplink signal US has been received as a result of step S106 (step S107). If the processing circuit 26d judges that the uplink signal US has been received, the processing circuit 26d returns to step S104 and repeats the process. On the other hand, if the processing circuit 26d judges that the uplink signal US has not been received, the processing circuit 26d enters the self-running mode (step S108).

[0051] The processing circuit 26d that has entered the free-running mode causes the transmission circuit 26b to transmit the downlink signal DSb (step S109) while continuing the detection operation of the uplink signal US by the reception circuit 26c. As described above, the transmission circuit 26b transmits the downlink signal DSb using both the time within the series of time slots TS and the time outside the series of time slots TS.

[0052] The processing circuit 26d that has executed step S109 determines whether or not the uplink signal US has been received (step S110). As a result, if the processing circuit 26d determines that the uplink signal US has not been received, it further determines whether or not a predetermined time has elapsed since entering the self-running mode (step S111), and if not, returns to step S109 to continue the processing for transmission and reception. On the other hand, if the processing circuit 26d determines that the uplink signal US has been received in step S110, it moves the processing to step S103, returns to the normal mode, and continues the processing. Also, if the processing circuit 26d determines that the time has elapsed in step S111, it moves the processing to step S103, returns to the discovery mode, and continues the processing.

[0053] 8 and 9 are process flow diagrams showing the process performed by the sensor controller 31. As shown in the figures, the sensor controller 31 first determines a transmission / reception schedule for the uplink signal US and the downlink signal DS (step S120). This determination is performed based on information on the driving period of the pixels of the display 32 acquired from the host processor 33 shown in FIG. 1. The determined transmission / reception schedule includes the initial transmission timing and transmission period of the uplink signal US (period UpIntv shown in FIG. 4, etc.), and the time positions of a series of time slots used to receive the downlink signal DS.

[0054] Next, the sensor controller 31 transmits the uplink signal US in accordance with the transmission / reception schedule determined in step S120 (step S121), and sets a first flag indicating whether the type of the downlink signal DS has been determined to a value (=False) indicating that the type has not been determined (step S122).

[0055] Next, the sensor controller 31 executes the processes of steps S124 to S137 in each time slot determined in step S120 (step S123). More specifically, the sensor controller 31 first executes the detection operation of the downlink signal DS by detecting the change in the potential of each of the plurality of sensor electrodes 30x, 30y shown in FIG. 2 (step S124). Then, it is determined whether the downlink signal DS has been detected (step S125), and if it is determined that the downlink signal DS has been detected, it detects the position of the active pen 2 based on the detection result (step S126). On the other hand, if it is determined that the signal has not been detected, it waits until the next time slot and repeats the processes from step S124.

[0056] After completing step S126, the sensor controller 31 judges the value of the first flag (step S127), and if it is True, the process proceeds to step S128, and if it is False, the process proceeds to step S130. In step S128, the sensor controller 31 judges the value of the second flag indicating the type of downlink signal DS to be transmitted (step S127), and if it is the value indicating the downlink signal DSa (=True), the process proceeds to step S132, and if it is the value indicating the downlink signal DSb (=False), the process proceeds to step S134.

[0057] In step S130, the sensor controller 31 determines whether or not the gap GA shown in Fig. 6(b) to Fig. 6(e) is included in the detected downlink signal DS (step S130). If it is determined that the gap GA is not included, the sensor controller 31 sets the first flag to True and the second flag to True (step S131), and demodulates the received signal as the downlink signal DSa (step S132).

[0058] On the other hand, if the sensor controller 31 determines in step S130 that the gap is included, it sets the first flag to True and the second flag to False (step S133), and then determines the length of the detected gap GA (step S134). If it determines that the gap is two symbols long, it demodulates the received signal as a unit signal U1 (step S135). On the other hand, if it determines that the gap is three symbols long, it demodulates the received signal as a unit signal U2 (step S136). When performing the demodulation process in step S135 or step S136, the sensor controller 31 may obtain the reception timing of the unit signals U1 and U2 based on the position of the gap GA.

[0059] After completing any one of steps S132, S135, and S136, the sensor controller 31 supplies the position detected in step S126 and the data obtained as a result of the demodulation in step S132, S135, or S136 to the host processor 33 (step S137). Then, the sensor controller 31 waits until the next time slot and repeats the process from step S124. After completing the process for all time slots, the sensor controller 31 returns to step S121 and transmits the uplink signal US.

[0060] As described above, according to the position detection system 1 of this embodiment, even if the active pen 2 fails to receive the uplink signal US and the time position of the time slot becomes unknown, the active pen 2 can continue to transmit the downlink signal DS, thereby preventing drawing by pen input from being stopped due to failure to receive the uplink signal US.

[0061] Furthermore, since the pen pressure values, each of which is partially placed in the tip signal TIP and the ring signal RING, are updated four times during the transmission period UpIntv, even when the active pen 2 transmits a downlink signal DSb, it is possible to transmit the pen pressure value from the active pen 2 to the sensor controller 31 with a time resolution as high as when the active pen 2 transmits a downlink signal DSa.

[0062] FIG. 10 is a diagram showing a configuration of a position detection system 1 according to a second embodiment of the present invention. As shown in the figure, the position detection system 1 according to this embodiment differs from the position detection system 1 according to the first embodiment in that the uplink signal US is transmitted and received by electromagnetic induction instead of electrostatic coupling. In terms of specific configuration, the position detection system 1 according to this embodiment differs from the position detection system 1 according to the first embodiment in that the active pen 2 has a coil 28 instead of the ring electrode 22 and the stop filter 27, and the electronic device 3 has a sensor 30b instead of the sensor 30a. Since the position detection system 1 according to the first embodiment is otherwise similar to the position detection system 1 according to the first embodiment, the following description will focus on the differences.

[0063] FIG. 11 is a plan view of the sensor 30b. The sensor electrodes 30x and 30y shown in the figure are the same as those of the sensor 30a described in the first embodiment. The sensor 30b is characterized in that it has one or more loop coils 30r in addition to the sensor electrodes 30x and 30y. The sensor controller 31 transmits the uplink signal US to the active pen 2 by supplying the uplink signal US to each of the one or more loop coils 30r. That is, the sensor controller 31 according to this embodiment transmits the uplink signal US by the magnetic field generated from each loop coil 30r.

[0064] Here, the specific arrangement of the one or more loop coils 30r may be determined so that the active pen 2 can receive the uplink signal US no matter where it is located on the touch surface 3a. For example, as shown in Fig. 11, the touch surface 3a may be divided into a 2 x 2 matrix, and four loop coils 30r may be used, each extending along the edge of each of the regions.

[0065] Returning to Fig. 10, the receiving circuit 26c according to this embodiment detects the uplink signal US transmitted by the sensor controller 31 using one or more loop coils 30r by detecting the induced current generated in the coil 28. That is, the active pen 2 according to this embodiment detects the uplink signal US by detecting the magnetic field generated from each loop coil 30r using the coil 28.

[0066] As described above, according to the position detection system 1 of this embodiment, the uplink signal US can be transmitted by the electromagnetic induction method, which is less susceptible to noise than the electrostatic coupling method, and therefore it is possible to prevent drawing by pen input from being stopped due to failure to receive the uplink signal US.

[0067] According to the position detection system 1 of this embodiment, the possibility that the active pen 2 fails to receive the uplink signal US can be significantly reduced, so there is little need to use the downlink signal DSb described in the first embodiment, and therefore it is sufficient to use only the downlink signal DSa. However, it goes without saying that the position detection system 1 of this embodiment may also use the downlink signal DSb in the same manner as the first embodiment.

[0068] 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.

[0069] For example, in each of the above embodiments, the length of the gap GA in the chip signal TIP is two symbols, and the length of the gap GA in the ring signal RING is three symbols, but it is sufficient that the lengths of the gap GA are different between the chip signal TIP and the ring signal RING, and the specific length of the gap GA is not limited to two symbols or three symbols.

[0070] In addition, in each of the above embodiments, an example has been described in which the pen pressure value is transmitted four times within one transmission period UpIntv of the uplink signal US, but the number of times the pen pressure value is transmitted is not limited to four times, and the pen pressure value may be transmitted only once, or may be transmitted two or more times.

[0071] In addition, in each of the above embodiments, an example in which the present invention is applied to an in-cell type position detection device has been described, but the present invention can also be suitably applied to an on-cell type or out-cell type position detection device. In this case, if the sensor controller 31 can obtain information on the driving cycle of the pixels of the display 32 from the host processor 33, the sensor controller 31 may use the information to determine the transmission and reception schedule of the uplink signal US and the downlink signal DS in the same manner as in the above embodiments, and if the sensor controller 31 cannot obtain information on the driving cycle of the pixels of the display 32 from the host processor 33, the sensor controller 31 may obtain the information by measuring noise generated from the display 32, and may use the obtained information to determine the transmission and reception schedule of the uplink signal US and the downlink signal DS in the same manner as in the above embodiments. [Explanation of symbols]

[0072] 1 Position Detection System 2 Active Pen 3 Electronic equipment 3a Touch Surface 20 core body 21 Pen tip electrode 22 Ring Electrode 23 Pressure Sensor 24 Side Switch 25 Battery 26 Integrated Circuits 26a Boost circuit 26b Transmitting circuit 26c Receiver circuit 26d Processing circuit 27 Stop Filter 28 Coil 30a, 30b Sensor 30r loop coil 30x, 30y sensor electrodes 31 Sensor Controller 32 Display 33 Host Processor CS Checksum DS, DSa, DSb downlink signals GA Gap P L 5 bits of data obtained by excluding the most significant 3 bits from the most significant 8 bits of the 12-bit pen pressure value P U The upper 3 bits of the 12-bit pen pressure value RING Ring signal SB Start bit SW Switch information TIP Tip signal TS Time Slot U1,U2 unit signal UpIntv Transmission period of uplink signal US US uplink signal

Claims

1. An active pen that communicates with a sensor controller, An electrode and a coil; a transmission circuit that transmits a downlink signal to the sensor controller by changing the potential of the electrode; a receiving circuit for receiving an uplink signal transmitted by the sensor controller by detecting an induced current generated in the coil; Includes an active pen.

2. The communication device is configured to communicate with the sensor controller using a series of time slots determined based on a reference time of a reception timing of the most recently received uplink signal, determining whether the uplink signal has been received at a timing determined based on a reception timing of the previously received uplink signal as a reference time; if it is determined that the uplink signal has been received, transmitting a first downlink signal using a time within the series of time slots; when it is determined that the uplink signal has not been received, transmitting a second downlink signal consisting of repetitions of unit signals having a time length shorter than a time length of each of the series of time slots, using both the time within the series of time slots and the time outside the series of time slots; The active pen of claim 1 .

3. The second downlink signal includes a first signal and a second signal including gaps of different lengths between two of the unit signals that are adjacent in time. The active pen of claim 2 .

4. a pressure sensor that detects pressure applied to a pen tip to obtain a pen pressure value having a first number of bits; the first downlink signal includes a signal modulated by the pen pressure value; the unit signal constituting the first signal includes a signal modulated by a part of a predetermined number of upper bits of the writing pressure value, the unit signal constituting the second signal includes a signal modulated by the remaining part of the upper predetermined number of bits of the writing pressure value; The active pen according to claim 3 .

5. The writing pressure value, a portion of which is disposed in each of the first signal and the second signal, is updated two or more times during one transmission period of the uplink signal. The active pen according to claim 4 .

6. A position detection device for detecting a position of an active pen on a touch surface, comprising: one or more loop coils disposed within the touch surface; a plurality of sensor electrodes disposed within the touch surface; a sensor controller that transmits an uplink signal to the active pen by supplying an uplink signal to each of the one or more loop coils, and receives a downlink signal transmitted by the active pen by detecting a change in potential of each of the plurality of sensor electrodes; A position detection device comprising:

7. The active pen is configured to communicate with the sensor controller using a series of time slots determined based on a reference time of the reception timing of the most recently received uplink signal; and determining whether the uplink signal has been received at a timing determined based on a reception timing of the previously received uplink signal as a reference time; if it is determined that the uplink signal has been received, transmitting a first downlink signal using a time within the series of time slots; when it is determined that the uplink signal has not been received, a second downlink signal consisting of repetitions of unit signals having a time length shorter than a time length of each of the series of time slots is transmitted using both the time within the series of time slots and the time outside the series of time slots; The sensor controller includes: determining whether the detected signal in one of the series of time slots includes a gap, which is a time during which no signal is being transmitted by the active pen; If it is determined that the detected signal does not include the first downlink signal, demodulating the detected signal as the first downlink signal; If it is determined that the detected signal is included, demodulating the detected signal as the second downlink signal. The position detection device according to claim 6.

8. the second downlink signal includes a first signal and a second signal including gaps of different lengths between two of the unit signals that are adjacent in time, When the sensor controller determines that the gap is included in the detected signal in one of the series of time slots, the sensor controller demodulates the detected signal as either the first signal or the second signal based on a length of the included gap. The position detection device according to claim 7.

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