Pen, sensor device, and pen system

A pen is configured to supply an N-bit internal digital value NA to a sensor device, and includes an integrated circuit that acquires a series of the internal digital values NA(s) based on a state OPS of a writing pressure detector. The integrated circuit supplies a first internal digital value NA to the sensor device by transmitting, from an antenna, first transmission data MF including a first standard digital value MS corresponding to the first internal digital value NA. The integrated circuit supplies a second internal digital value NA to the sensor device by transmitting, from the antenna, second transmission data MF that is smaller than N bits and includes an M-bit relative digital value (M<N) corresponding to a relative value between the first internal digital value NA obtained by restoration from the first standard digital value MS and the second internal digital value NA.

BACKGROUND

Technical Field

The present disclosure relates to a pen, a sensor device, and a pen system, and particularly relates to a pen that transmits a digital value, a sensor device that receives the digital value, and a pen system including the pen and the sensor device.

Description of the Related Art

A pen that transmits a digital value toward a sensor device by changing an alternating current (AC) electric field, AC magnetic field, or AC electromagnetic field is known. For example, in Patent Document 1, a pen that transmits a digital value, which represents information on continuous quantity (for example, a writing pressure) corresponding to a continuous operation, toward a sensor device is disclosed.

Furthermore, a display device is known, in which a touch sensor configuring a sensor device is incorporated based on an in-cell system. In a pen system using this kind of display device, signal transmission from a pen to the sensor device is carried out in a display's non-driving period. However, the time length of the display's non-driving period may be too short to transmit a writing pressure value, which is fixed-length data. Thus, the transmission of the writing pressure value may need to be executed in such a manner as to be divided in plural display's non-driving periods, which exist in a dispersed manner in one frame defined by an uplink signal. In Patent Document 2, a pen system that carries out such divided transmission is disclosed.

PRIOR ART DOCUMENT

Patent Documents

Patent Document 2: International Publication Pamphlet No. WO 2018/066100

BRIEF SUMMARY

Technical Problem

In recent years, the size of data transmitted from the pen toward the sensor device has been increasing: a writing pressure value is expressed with 8196 grayscale levels, for example. As a result, particularly in a system in which the communication time is limited within the display's non-driving period as in Patent Document 2, or the like, communication resources that can be used for communication between the pen and the sensor device tend to be insufficient and improvement is needed. In addition, in recent years, the multi-pen system that allows simultaneous use of plural pens has been widespread and communication resources are becoming scarce.

According to one aspect of the present disclosure, a pen, a sensor device, and a pen system are provided that can alleviate insufficiency of communication resources used for communication between a pen and a sensor device.

Technical Solution

A pen according to a first aspect of the present disclosure is a pen that supplies an N-bit internal digital value to a sensor device. The pen includes a writing pressure detector that detects a force applied to a pen tip, an antenna, and an integrated circuit that is connected to the writing pressure detector and the antenna and that acquires a series of the internal digital values based on a state of the writing pressure detector. The series of the internal digital values includes a first internal digital value and a second internal digital value acquired subsequently to the first internal digital value. The integrated circuit supplies the first internal digital value to the sensor device by transmitting, from the antenna, first transmission data including a first standard digital value corresponding to the first internal digital value. The integrated circuit supplies the second internal digital value to the sensor device by transmitting, from the antenna, second transmission data that is smaller than N bits and includes an M-bit relative digital value (M<N) corresponding to a relative value between the first internal digital value, which can be restored from the first standard digital value, and the second internal digital value.

A sensor device according to the first aspect of the present disclosure is a sensor device that receives supply of a series of internal digital values each composed of N bits from a pen configured to acquire the series of internal digital values based on a force applied to a pen tip. The series of internal digital values include a first internal digital value and a second internal digital value acquired subsequently to the first internal digital value. When receiving first transmission data including a first standard digital value corresponding to the first internal digital value from the pen, the sensor device restores the first internal digital value from the first transmission data and stores the first internal digital value in an internal memory. When receiving, from the pen, second transmission data that is smaller than N bits and includes an M-bit relative digital value (M<N) corresponding to a relative value between the first internal digital value, which is restored from the first standard digital value, and the second internal digital value, the sensor device restores the second internal digital value from the second transmission data by using the value stored in the internal memory.

A pen according to a second aspect of the present disclosure is a pen that supplies an N-bit internal digital value to a sensor device. The pen includes an antenna and an integrated circuit that is connected to a user operation tool and the antenna and that acquires a series of the internal digital values. The integrated circuit receives a reference value corresponding to the internal digital value that has been already supplied from the sensor device and supplies a first internal digital value included in the series of the internal digital values to the sensor device by transmitting, from the antenna, transmission data that is smaller than N bits and includes an M-bit relative digital value (M<N) corresponding to a relative value between the first internal digital value and the reference value.

A sensor device according to the second aspect of the present disclosure is a sensor device that receives supply of a series of internal digital values each composed of N bits from a pen configured to acquire the series of internal digital values based on a force applied to a pen tip. The sensor device transmits a reference value to the pen. When receiving, from the pen, transmission data that is smaller than N bits and includes an M-bit relative digital value (M<N) corresponding to a relative value between a first internal digital value included in the series of internal digital values and the reference value, the sensor device restores the first internal digital value from the transmission data by using the reference value.

A pen system according to the present disclosure is a pen system that includes a pen and a device and that outputs an N-bit internal digital value. The pen includes a writing pressure detector that detects a force applied to a pen tip, an antenna, and an integrated circuit that is connected to the writing pressure detector and the antenna and that acquires a series of the internal digital values based on a state of the writing pressure detector. The integrated circuit supplies a first internal digital value included in the series of the internal digital values to the sensor device by transmitting, from the antenna, first transmission data including a standard digital value. The reference digital value is obtained by compressing the first internal digital value using a compression method, in which a quantization step becomes smaller when a value of the internal digital value is smaller. The device is configured to restore the first internal digital value from the first transmission data and to output the first internal digital value.

Advantageous Effect

According to the first aspect of the present disclosure, the N-bit internal digital value can be supplied using the transmission data that is smaller than N bits. Thus, it becomes possible to alleviate insufficiency of communication resources that can be used for communication between the pen and the sensor device.

According to the second aspect of the present disclosure, even when a discrepancy occurs between the internal digital value acquired by the pen and the internal digital value acquired by the sensor device due to a communication error or the like, the error can be eliminated once the reference value is transmitted and received.

According to the pen system in accordance with the present disclosure, it becomes possible to reduce the possibility that the user senses an error that possibly occurs at the time of transmission of the standard digital value.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

FIG.1is a diagram illustrating the system configuration of a pen system1according to a first embodiment of the present disclosure. As illustrated in this diagram, the pen system1according to the present embodiment is configured to have a pen2, a sensor device3, and a host computer4. Among them, the host computer4may be any of various types of computer such as a tablet type computer, a notebook type computer, and a desktop type computer.

The sensor device3is a position detecting device compatible with various systems such as active electrostatic (ES) system, electromagnetic resonance (EMR) system, pressure sensing system, and is configured to have a sensor30, which forms a touch surface3t,and a sensor controller31that is an integrated circuit. Although diagrammatic representation is not made, the sensor30has a configuration in which plural electrodes are disposed in the touch surface3t.The sensor controller31detects the position of the pen2in the touch surface3tby using these electrodes. In addition, the sensor controller31receives, through these electrodes, data transmitted from the pen2by receiving a signal transmitted from the pen2(hereinafter referred to as a “downlink signal DS”).

The case in which the sensor device3is compatible with the active ES system or electromagnetic resonance (EMR) system will be specifically described. In the downlink signal DS, an unmodulated burst signal and a data signal obtained by modulation with various kinds of data are included. The burst signal is a signal used for detection of the position of the pen2in (on) the touch surface3tby the sensor controller31. The sensor controller31determines the electrode by which the burst signal has been received by sequentially scanning the plural electrodes configuring the sensor30, and detects the position of the pen2based on the result thereof. The data signal is a signal including various internal digital values acquired by the pen2(a writing pressure value, a wheel indication value, and so forth acquired by a user operation tool25to be described later). The sensor controller31receives data transmitted from the pen2by using the electrode, which is closest to the position of the pen2in the plural electrodes forming the sensor30, as an antenna and receiving the data signal.

Signal transmission from the sensor controller31to the pen2may also be allowed. Hereinafter, the signal thus transmitted will be referred to as “uplink signal US.” The sensor controller31uses the plural electrodes forming the sensor30as the transmitting antenna and transmits the uplink signal US.

An instruction (or a command) from the sensor controller31to the pen2can be included in the uplink signal US. The pen2determines the transmission timing of the downlink signal DS based on the timing when the uplink signal US is received. In addition, the pen2determines the kind of internal digital value transmitted in the downlink signal DS based on the command included in the uplink signal US.

The sensor controller31supplies the detected position and the received data to the host computer4. The host computer4generates and stores stroke data indicating the trace formed by the pen2based on the series of positions and signals thus supplied, and carries out rendering of the stored stroke data.

In the present embodiment, a description will be made based on the assumption that the uplink signal US and the downlink signal DS are transmitted and received through the sensor30. However, the uplink signal US may be transmitted and received by another communication system (for example, Bluetooth (registered trademark), wireless LAN, or the like).

In one example, the sensor30is incorporated in a display device of the host computer4, which may be a tablet type computer based on the in-cell system. In this case, in order to avoid the influence of noise generated due to pixel driving carried out in the display device, transmission and reception of the uplink signal US and the downlink signal DS may be carried out during the display's non-driving period such as the vertical blanking period or horizontal blanking period of a liquid crystal display device, for example. Because the transmission and reception of the uplink signal US and the downlink signal DS are not carried out during the display's driving period, communication resources that can be used for communication between the pen2and the sensor device3are significantly limited.

Here, between the pen2and the sensor device3having the sensor30incorporated in the display device based on the in-cell system, normally communication is carried out based on frame communication in which plural time slots (=the display's non-driving periods) are included in one frame. In this case, the time slot used for transmission of the uplink signal US is configured separately from the time slot used for transmission of the downlink signal DS, in advance. Therefore, even when a reference value Ref is transmitted by the uplink signal US as described in a fourth embodiment, such uplink transmission does not interfere with the transmission of the downlink signal DS.

The pen2is an electronic pen compatible with the same system as the sensor device3(for example, active electrostatic (ES) system or electromagnetic resonance (EMR) system) and is configured to have a core body20, an antenna22, a writing pressure detector23, a power supply26, and an integrated circuit27.

The core body20is a bar-shaped member disposed in such a manner that its longitudinal direction corresponds with the pan axis direction of the pen2, and its one end forms a pen tip21of the pen2. An electrically-conductive material is applied to the surface of the core body20, which forms the antenna22.

The antenna22is an electrical conductor disposed near the core body20and is electrically connected to the integrated circuit27by a wiring line. The integrated circuit27carries out reception of the above-described uplink signal US and transmission of the downlink signal DS through this antenna22. Signals other than the above-described burst signal may be transmitted and received by using an antenna other than the antenna22(not illustrated, for example, a built-in antenna for Bluetooth (registered trademark)). Furthermore, the antenna22may be separated into an antenna for transmission and an antenna for reception.

The writing pressure detector23is a functional unit that detects a force (a writing pressure) applied to the pen tip21. Specifically, the writing pressure detector23abuts against the rear end part of the core body20and is configured to detect, through this abutting, the force applied to the pen tip21when the user presses the pen tip of the pen2against the touch surface3tor the like. In a specific example, the writing pressure detector23is formed of a variable-capacitance module whose capacitance changes according to the force applied to the pen tip21.

Here, it can be said that the writing pressure detector23is a user operation tool that detects the amount of operation by the user (specifically, a magnitude of the force with which the user presses the touch surface3t), and the pen2can include such user operation tool25besides the writing pressure detector23. For example, the pen2may include a wheel that can be rotated by the user, or a wheel operation tool that detects the amount of rotation of the wheel.

The power supply26is a component for supplying operating power (direct-current voltage) to the integrated circuit27and is formed of an AAAA battery with a cylindrical shape, for example.

The integrated circuit27is a processing unit formed of a circuit group formed on a board that is not illustrated, and is connected to the user operation tool25and the antenna22. If an antenna other than the antenna22is used for reception of the uplink signal US or transmission of the downlink signal DS, the integrated circuit27is connected also to such antenna. The integrated circuit27is responsible for acquiring a series of internal digital values NA(s) each composed of N bits based on a state of the writing pressure detector23(or a state of another user operation tool) and sequentially supplying the internal digital values NA(s) to the sensor device3by using the downlink signal DS. However, when the internal digital values NA(s) are transmitted using the number of bits N as is, there is a possibility that communication resources may become insufficient. Thus, as illustrated inFIG.1, a configuration is made such that the internal digital values NA(s) are transmitted after being converted to transmission data MF that is smaller than N bits. A characteristic of the present embodiment is that the pen2and the sensor device3are configured in such a manner that, although the integrated circuit27transmits the transmission data MF smaller than N bits, the original N-bit internal digital value NA can be restored in the sensor device3and the N-bit internal digital value NA can be provided to the host computer4. This point will be described in detail below.

First,FIG.2is a diagram explaining the principle of the present embodiment. The integrated circuit27is configured to, in transmitting the N-bit internal digital value NA, transmit the transmission data MF of M+1 bits, instead of the internal digital value NA itself. The transmission data MR includes an M-bit (M<N−1) transmission digital value MD, which is either of a standard digital value MS or a relative digital value MR as illustrated inFIG.2, and a one-bit identification flag F indicating the kind of transmission digital value MD.

The standard digital value MS is a value corresponding to the internal digital value NA and, specifically, is formed of an M-bit digital value obtained by compressing the internal digital value NA. This compression is carried out by discarding the least significant N−M bits of the internal digital value NA in the example ofFIG.2. However, it is also possible to obtain the standard digital value MS by another compression method as described later.

The relative digital value MR is an M-bit digital value corresponding to the relative value between the internal digital value NA, which is being supplied, and the internal digital value NA, which has been already supplied to the sensor device3. The internal digital value NA that has been already supplied means the internal digital value NA restored from the transmission digital value MD that has been actually transmitted, and is the same as the internal digital value NA restored by the sensor device3that has received this transmission digital value MD (as long as a communication error to be described later does not exist). The relative value may be the difference between the internal digital value NA , which is being supplied, and the internal digital value NA that has been already supplied to the sensor device3, for example.

As described in detail later, the integrated circuit27is configured to set the standard digital value MS as the transmission digital value MD, in a case where communication has just started and so the internal digital value NA has not been supplied yet, or in a case where the internal digital value NA is what can be restored from the standard digital value MS without an error (for example, in a case where the N−M least significant bits of the internal digital value NA are all 0), or in a case where the relative value cannot be expressed with M bits. The integrated circuit27is configured to set the relative digital value MR as the transmission digital value MD, in a case where the internal digital value NA that has been already supplied exists and the internal digital value NA is not what can be restored from the standard digital value MS without an error (for example, the N−M least significant bits of the internal digital value NA include a bit that is not 0) and the relative value can be expressed with M bits. The case in which the relative value cannot be expressed with M bits corresponds to the case in which the relative value is not in a range of −2M−1+2M−1−1, for example, where a negative digital value is expressed by using a two's complement.

When receiving the transmission data MF smaller than N bits from the pen2, first, the sensor controller31determines which of the standard digital value MS or the relative digital value MR is included in the transmission data MF based on the identification flag F. If it is determined that the transmission data MF includes the standard digital value MS, the internal digital value NA is restored from the transmission digital value MD (=the standard digital value MS) and the restored internal digital value NA is stored in an internal memory, which is not illustrated. In the example ofFIG.2, this restoration is carried out by complementing the N−M least significant bits with a predetermined value (for example, 0). In this case, an error corresponding to up to N−M bits possibly occurs.

On the other hand, when determining that the transmission data MF includes the relative digital value MR, the sensor controller31is configured to restore the internal digital value NA from the transmission digital value MD (=the relative digital value MR) by using the value stored in the internal memory and to store the restored internal digital value NA in the internal memory. If the relative digital value MR is composed of the difference between the internal digital value NA being supplied and the internal digital value NA that has been already supplied to the sensor device3as in the above-described example, this restoration is carried out by adding the value stored in the internal memory and the received relative digital value MR. The internal digital value NA restored from the relative digital value MR is data that does not include an error and maintains an accuracy of N bits, as long as the transmission data MF is not lost due to a communication error or the like.

As above, according to the present embodiment, the N-bit internal digital value NA can be supplied with the transmission data MF smaller than N bits (specifically, with M+1 bits). Furthermore, although a certain level of error possibly occurs when the standard digital value MS is transmitted, this error can be eliminated by the relative digital value MR which immediately follows and, therefore, does not become a substantial problem. In addition, an error attributed to transmission of the standard digital value MS occurs when the relative value is large, i.e., when a change in the internal digital value NA is large. In such a case, even when a certain degree of error exists, the impact on the perception of a human user is limited (as compared with the case in which a change in the internal digital value NA is small). Therefore, according to the present embodiment, it becomes possible to alleviate insufficiency (or shortage) of communication resources that can be used for communication between the pen2and the sensor device3. A specific configuration to supply such internal digital value NA will be described in detail below.

FIG.3is a schematic block diagram illustrating functional blocks of the integrated circuit27. As illustrated inFIG.3, the integrated circuit27is configured to functionally include an internal digital value acquisition circuit100, a transmission digital value acquisition circuit101, a transmission circuit102, and an already-supplied internal digital value holding circuit103.

The internal digital value acquisition circuit100is a functional unit that sequentially converts a state OPS of the writing pressure detector23(or a state of another user operation tool25) to the N-bit internal digital value. The internal digital value acquisition circuit100sequentially supplies a series of internal digital values NA(s) acquired by the conversion to the transmission digital value acquisition circuit101.

The transmission digital value acquisition circuit101is a functional unit that generates the transmission data MF including the transmission digital value MD and the identification flag F based on the internal digital value NA supplied from the internal digital value acquisition circuit100and supplies the transmission data MF to the transmission circuit102. The transmission digital value acquisition circuit101, in response to the internal digital value NA that is newly supplied, determines which of the standard digital value MS or the relative digital value MR is to be set as the next transmission digital value MD to be transmitted based on the internal digital value NA, and generates the transmission data MF including either of the standard digital value MS or the relative digital value MR based on the determination result.

This determination is composed of two determinations. The first determination is a determination of whether or not the internal digital value NA is what can be restored from the standard digital value MS without an error. The transmission digital value acquisition circuit101, which has determined that the internal digital value NA can be restored without an error, acquires the standard digital value MS corresponding to the internal digital value NA and sets the reference digital value MS as the transmission digital value MD to be transmitted next.

The second determination is a determination of whether or not the relative value between an already-supplied internal digital value NS held in the already-supplied internal digital value holding circuit103and the internal digital value NA being supplied can be expressed with M bits, and is carried out in response to determining that the internal digital value NA cannot be restored without an error in the first determination. When determining that the relative value cannot be expressed with M bits, the transmission digital value acquisition circuit101acquires the standard digital value MS corresponding to the internal digital value NA and sets the reference digital value MS as the transmission digital value MD to be transmitted next. On the other hand, when determining that the relative value can be expressed with M bits, the transmission digital value acquisition circuit101acquires the relative value as the relative digital value MR and sets the relative digital value MR as the transmission digital value MD to be transmitted next.

The transmission digital value acquisition circuit101may further carry out, before the first determination, a determination of whether the already-supplied internal digital value holding circuit103holds a value (for example, 0 if the internal digital value NA is the writing pressure) indicating that, after the last pen-up (separation of the pen tip21from the touch surface3t), the standard digital value MS has never been transmitted. If the result of this determination is positive, the transmission digital value acquisition circuit101may set the standard digital value MS as the transmission digital value MD to be transmitted next irrespective of the above-described two determinations. This makes it possible to prevent the situation in which the relative digital value MR is transmitted without the standard digital value MS being transmitted at the time of pen-down (contact of the pen tip21with the touch surface3t).

The already-supplied internal digital value holding circuit103is a functional unit configured to include one or more N-bit registers and is responsible for holding the already-supplied internal digital value NS. The specific held content of the already-supplied internal digital value NS depends on the content of the transmission digital value MD generated by the transmission digital value acquisition circuit101. For example, if the transmission digital value acquisition circuit101sets the standard digital value MS as the transmission digital value MD, the internal digital value NA restored from the standard digital value MS (this internal digital value NA does not necessarily correspond with the internal digital value NA acquired by the internal digital value acquisition circuit100) is set in the already-supplied internal digital value holding circuit103. On the other hand, if the transmission digital value acquisition circuit101sets the relative digital value MR as the transmission digital value MD, the internal digital value NA restored from the relative digital value MR by use of the already-supplied internal digital value NS held in the already-supplied internal digital value holding circuit103is set in the already-supplied internal digital value holding circuit103. In this case, the restored internal digital value NA precisely corresponds with the internal digital value NA acquired by the internal digital value acquisition circuit100. Thus, instead of the restored internal digital value NA, the internal digital value NA acquired by the internal digital value acquisition circuit100may be set in the already-supplied internal digital value holding circuit103.

The acquisition of the internal digital value NA by the internal digital value acquisition circuit100is not always carried out, but carried out only when the internal digital value NA needs to be supplied to the sensor device3(for example, when the pen2is detecting the sensor device3). The operation of the transmission digital value acquisition circuit101is carried out in response to supply of the new internal digital value NA from the internal digital value acquisition circuit100. Therefore, depending on a case, the held content of the already-supplied internal digital value holding circuit103may be not updated for a long time. Thus, the already-supplied internal digital value holding circuit103may be configured to autonomously delete the held content when the held content is not updated over a predetermined time.

The transmission circuit102is a functional unit that transmits, to the sensor device3through the antenna22, the transmission data MF supplied from the transmission digital value acquisition circuit101as part of a data signal which forms the downlink signal DS.

FIG.4is a flowchart illustrating a transmission processing of the internal digital value NA executed by the integrated circuit27. With reference to this diagram, the transmission processing of the internal digital value NA executed by the integrated circuit27will be described more specifically below.

First, the integrated circuit27acquires the N-bit internal digital value NA based on the state OPS (seeFIG.3) of the user operation tool25(step S1). Subsequently, the integrated circuit27determines whether or not the internal digital value NA acquired in step S1is what can be restored from the standard digital value MS without an error (step S3). This processing may be executed after step S5to be described later. As in the example ofFIG.2, when the standard digital value MS is composed of the M most significant bits of the internal digital value NA and the sensor device3is configured to restore the internal digital value NA from the standard digital value MS by complementing the N−M least significant bits with a predetermined value (for example, 0), the result of this determination becomes positive if the N−M least significant bits of the internal digital value NA are all 0, and becomes negative if not so. When determining that the internal digital value NA can be restored without an error in this determination, the integrated circuit27moves the processing to step S6irrespective of the relative value acquired in step S4to be described later. When determining that the internal digital value NA cannot be restored without an error, the integrated circuit27moves the processing to step S4.

In step S4, the integrated circuit27acquires the relative value between the already-supplied internal digital value NS and the internal digital value NA acquired in step S1(step S4). The relative value acquired here is the difference between the already-supplied internal digital value NS and the internal digital value NA acquired in step S1as described above, for example. Then, the integrated circuit27determines whether or not the acquired relative value is a numerical value that can be expressed with M bits (step S5). When determining that the relative value cannot be expressed in this determination, the integrated circuit27moves the processing to step S6. When determining that the relative value can be so expressed, the integrated circuit27moves the processing to step S9.

In step S6, the integrated circuit27acquires the M-bit standard digital value MS by compressing the internal digital value NA (step S6). This compression is processing of extracting the M most significant bits of the internal digital value NA to make the standard digital value MS as described above, for example.

With reference toFIG.5, the compression method of the internal digital value NA will be described in more detail.

FIGS.5A and5Bare each a diagram illustrating one example of the compression method of the internal digital value NA. In these diagrams, examples of N=12 and M=8 are illustrated. Both compression methods are processing of converting a discrete value expressed with a relatively-large number of bits (the internal digital value NA) to a discrete value expressed with a relatively-small number of bits (the standard digital value MS).

The compression method illustrated inFIG.5Ais a method in which 2Nkinds of internal digital values NA(s) that can be expressed with N bits are separated into total 2Mranges (hereinafter, the size of this range will be referred to as “quantization step”) in units of 2N−Mvalues sequentially from the smallest value, and in which the value of the standard digital value MS is allocated to each range. This compression method is a processing of extracting the M most significant bits of the internal digital value NA to make the standard digital value MS. Therefore, when employing the compression method illustrated inFIG.5A, it is preferable that the integrated circuit27be configured to acquire the standard digital value MS using the processing of extracting the M most significant bits of the internal digital value NA. Furthermore, it is preferable for the sensor device3that has received the standard digital value MS to restore the internal digital value NA by complementing the N−M least significant bits with a predetermined value (for example, 0) as described above.

The compression method illustrated inFIG.5Bis the same as the compression method illustrated inFIG.5Ain that 2Nkinds of internal digital values NA(s) are separated into 2Mranges sequentially from the smallest value and the value of the standard digital value MS is allocated to each range. However, the compression method illustrated inFIG.5Bis different from the compression method illustrated inFIG.5Ain that the boundaries of the ranges are adjusted in such a manner that the quantization step becomes smaller when the value of the internal digital value NA is smaller. InFIG.5B, the example is illustrated in which the quantization step when the internal digital value NA is 0 to 5 is set to 1, and the quantization step when the internal digital value NA is 620 to 658 is set to 13, and the quantization step when the internal digital value NA is 2042 to 2133 is set to 23, and the quantization step when the internal digital value NA is 3968 to 4095 is set to 32. Regarding the intermediate internal digital values NA(s) that are not illustrated in the diagram, it is preferable to set the quantization step in such a manner that the quantization step rises in a stepwise manner in association with the rise of the internal digital value NA.

When employing the compression method illustrated inFIG.5B, it is preferable that the integrated circuit27be configured to store, in advance, a table that associates the standard digital value MS with each internal digital value NA and to convert the internal digital value NA to the standard digital value MS by referring to this table. Furthermore, regarding the sensor device3that has received the standard digital value MS, it is preferable that the sensor device3be configured to store, in advance, a table that associates one of the plural values belonging to the corresponding range of the internal digital value NA (for example, median or maximum value) with each standard digital value MS and to restore the internal digital value NA from the standard digital value MS by referring to this table.

Using either the compression method ofFIG.5Aor the compression method ofFIG.5B, the N-bit internal digital value NA is compressed to the M-bit standard digital value MS. However, according to the compression method ofFIG.5B, the compression rate of the standard digital value MS when the internal digital value NA is small can be made low compared with the compression method ofFIG.5A. Such a compression method ofFIG.5Bis particularly advantageous when the internal digital value NA is that which represents the writing pressure value. Specifically, the writing pressure value has a characteristic that the user becomes more sensitive to an error when the value becomes smaller. According to the compression method ofFIG.5B, the compression rate of the standard digital value MS can be made lower when the writing pressure value is smaller (i.e., the internal digital value NA is smaller). Therefore, according to the compression method ofFIG.5B, it becomes possible to reduce the possibility that the user notices an error that possibly occurs at the time of transmission of the standard digital value MS.

Referring back toFIG.4, the integrated circuit27that has acquired the standard digital value MS in step S6sets the acquired standard digital value MS as the transmission digital value MD (step S7). In addition, the integrated circuit27restores the internal digital value NA from the standard digital value MS (step S8). This restoration is carried out by the same method as the restoration carried out by the sensor device3.

The integrated circuit27, when the processing is forwarded to step S9, sets the relative digital value MR that is the relative value expressed with M bits as the transmission digital value MD (step S9). In addition, the integrated circuit27restores the internal digital value NA from the relative digital value MR by using the already-supplied internal digital value NS (step S10). This restoration is also carried out by the same method as the restoration carried out by the sensor device3.

The integrated circuit27that has carried out step S8or step S10subsequently sets the restored internal digital value NA in the already-supplied internal digital value holding circuit103(step S11). Then, the integrated circuit27transmits the transmission data MF, which is obtained by adding the identification flag F according to the value set in the transmission digital value MD to the transmission digital value MD (step S12), and returns to step S1to continue the processing.

FIG.6andFIG.7are diagrams illustrating specific examples of the respective values used in the process of the processing illustrated inFIG.4.FIG.6illustrates a case in which the standard digital value MS is set as the transmission digital value MD (i.e., a case in which step S6inFIG.4is carried out).FIG.7illustrates a case in which the relative digital value MR is set as the transmission digital value MD (i.e., a case in which step S9inFIG.4is carried out). Furthermore,FIG.6andFIG.7illustrate cases in which the compression method illustrated inFIG.5Ais used as the method for acquiring the standard digital value MS from the internal digital value NA.

Referring first toFIG.6, as the transmission digital value MD in this case, the standard digital value MS is set which comprises the M most significant bits of the internal digital value NA. Furthermore, the transmission data MF is composed of the standard digital value MS and the identification flag F having the value indicating the standard digital value MS (the first value, for example, “1”). The already-supplied internal digital value NS after the transmission data MF is transmitted (i.e., what is set in the already-supplied internal digital value holding circuit103in step S11) is the internal digital value NA restored from the standard digital value MS, i.e., the value obtained by adding N−M “0” bits to the least significant side of the standard digital value MS.

Referring next toFIG.7, as the transmission digital value MD in this case, the M-bit relative digital value MR calculated from the internal digital value NA and the already-supplied internal digital value NS is set. Furthermore, the transmission data MF is composed of the relative digital value MR and the identification flag F having the value indicating the relative digital value MR (the second value different from the first value, for example, “0”). The already-supplied internal digital value NS after the transmission data MF is transmitted (i.e., what is set in the already-supplied internal digital value holding circuit103in step S11) is the internal digital value NA restored from the relative digital value MR by using the already-supplied internal digital value NS, i.e., the internal digital value NA itself acquired in step S1.

FIG.8is a flowchart illustrating a reception processing of the internal digital value NA executed by the sensor controller31. With reference to this diagram, the reception processing of the internal digital value NA executed by the sensor controller31will be described in detail below.

First, the sensor controller31receives the transmission data MF through the sensor30, for example (step S20). Then, based on the identification flag F included therein, the sensor controller31determines whether the transmission digital value MD in the transmission data MF is the standard digital value MS or the relative digital value MR (step S21).

When determining that the transmission digital value MD is the standard digital value MS in step S21, the sensor controller31executes processing of restoring the N-bit internal digital value NA from the received M-bit transmission digital value MD (=the standard digital value MS) (step S22). The specific content of this processing is as described with reference toFIGS.5A and5B.

On the other hand, the sensor controller31that has determined that the transmission digital value MD is the relative digital value MR in step S21executes processing of restoring the N-bit internal digital value NA from the received M-bit transmission digital value MD (=the relative digital value MR) by using the value stored in the internal memory previously in step S24to be described later (step S23). This processing is executed as inverse processing of the method used by the pen2to acquire the relative value in step S4inFIG.4(for example, the processing of adding the relative digital value MR to the value stored in the internal memory).

The sensor controller31that has carried out step S22or step S23subsequently outputs the restored N-bit internal digital value NA to the host computer4(seeFIG.1) and stores it in the internal memory (step S24). Thereafter, the sensor controller31returns the processing to step S20and waits for reception of the next transmission data MF. The internal digital value NA stored in the internal memory in step S24is used when step S23is carried out next.

As described above, according to the present embodiment, the N-bit internal digital value NA can be supplied with the transmission data MF smaller than N bits (specifically, with M+1 bits). Thus, it becomes possible to alleviate insufficiency of communication resources that can be used for communication between the pen2and the sensor device3.

Furthermore, according to the present embodiment, the number of bits of the standard digital value MS is also set to M, and therefore it becomes possible to carry out transmission of the transmission data MF by using a fixed-length communication method. In this case, immediately after the standard digital value MS is received, an error is possibly included in the internal digital value NA restored in the sensor device3. However, this error is eliminated by the relative digital value MR which is subsequently transmitted.

Moreover, according to the present embodiment, through acquisition of the standard digital value MS by use of the compression method illustrated inFIG.5B, it becomes possible to reduce the possibility that the user feels or recognizes an error at the time of transmission of the standard digital value MS.

In addition, according to the present embodiment, the standard digital value MS is transmitted instead of the relative digital value MR in a certain case. Therefore, even when an error occurs between the internal digital value NA acquired by the pen2and the internal digital value NA acquired by the sensor device3due to a communication error or the like, the error can be eliminated after transmission and reception of the standard digital value MS. This effect will be described in detail below with reference toFIGS.9A and9B.

FIG.9Ais a diagram illustrating a temporal change in various digital values acquired in each of the pen2and the sensor device3. In this diagram, N=12 and M=7. In the example of this diagram, the standard digital value MS (a value with hatching) is set as the transmission digital value MD at clock times t1and t7and the relative digital value MR (a value without hatching) is set as the transmission digital value MD at clock times t2to t6.

The clock time t1is the clock time when supply of the internal digital value NA from the pen2to the sensor device3has started. At the stage before the clock time t1, the internal digital value NA written last in the last communication between the pen2and the sensor device3is held in the already-supplied internal digital value holding circuit103. The relative value between the internal digital value NA thus held and the internal digital value NA newly acquired is normally a large value like “−200” exemplified inFIG.9A, for example, and therefore the standard digital value MS is transmitted also at the clock time t1. However, after the communication between the pen2and the sensor device3ends, the integrated circuit27may overwrite the held content of the already-supplied internal digital value holding circuit103with a predetermined value. Although the specific value of this predetermined value is not particularly limited, it is preferable to use a value far from values that can be normally taken by the internal digital value NA (for example, the maximum value “4095 (=111111111111)”). This can prevent the relative digital value MR from being transmitted first in the next communication. Furthermore, the reason why the standard digital value MS is transmitted at the clock time t7is that the internal digital value NA “1088 (=010001000000)” corresponds with the value “1088 (=010001000000)” obtained by adding N−M “0” bits to the tail end of the standard digital value MS “34 (=0100010)” obtained from this internal digital value NA and, hence, the determination result of step S3inFIG.4is positive (“YES”).

InFIG.9A, a communication error occurs at the clock times t4and t5and the transmission data MF does not reach the sensor device3. As a result, at the clock times t4to t6, the internal digital value NA acquired by the pen2does not correspond with the internal digital value NA restored in the sensor device3. However, due to the transmission of the standard digital value MS by the pen2at the clock time t7, they return to the corresponding state again. As above, according to the present embodiment, the error that occurs due to a communication error can be eliminated by the standard digital value MS, which is transmitted when the internal digital value NA can be restored from the standard digital value MS without an error.

Next,FIG.9Bis also a diagram illustrating a temporal change in various digital values acquired in each of the pen2and the sensor device3. Also in this diagram, N=12 and M=7. The situation up to the clock time t6in the example of this diagram is the same as inFIG.9A. At the clock times t4to t6, the internal digital value NA acquired by the pen2does not correspond with the internal digital value NA restored in the sensor device3. Thereafter, the internal digital value NA changes significantly at the clock time t7. As a result, the relative value exceeds the range in which the relative value can be expressed with M bits (with M=7, −64 to +63) and thus the pen2transmits the standard digital value MS at the clock time t7. As a result, similarly to the case ofFIG.9A, the internal digital value NA acquired by the pen2corresponds with the internal digital value NA restored in the sensor device3again at the clock time t7. As above, according to the present embodiment, the error that occurs due to a communication error can be eliminated also by the standard digital value MS, which is transmitted when the relative value cannot be expressed with M−1 bits. When the standard digital value MS is thus transmitted, there is a possibility that the internal digital value NA acquired by the pen2does not correspond with the internal digital value NA restored in the sensor device3and thus an error remains. However, as described above, this error is eliminated by the immediately-subsequent relative digital value MR. In addition, the impact of this error on the perception of a human user is limited and therefore this error does not become a significant program.

FIG.10toFIG.13are diagrams illustrating a working example of the present embodiment. Curves illustrated in the upper portions ofFIG.11toFIG.13represent the internal digital value NA (e.g., a writing pressure value) sequentially acquired by the integrated circuit27(seeFIG.3) when a user inputs three strokes A1to A3illustrated inFIG.10by using the pen2. InFIGS.11-13, white circle marks represent that the standard digital value MS is set as the transmission digital value MD at the timing and the specific value of the set standard digital value MS. White triangle marks represent that the relative digital value MR is set as the transmission digital value MD at the timing and the specific value of the set relative digital value MR. Moreover, curves illustrated in the lower portions ofFIG.11toFIG.13represent the error between the original internal digital value NA and the internal digital value NA restored from the transmission digital value MD. Examples where N=10 and M=7 are illustrated inFIG.11andFIG.12, and an example where N=12 and M=7 is illustrated inFIG.13. Furthermore,FIG.12illustrates an example in which the determination result of step S3illustrated inFIG.4is fixed as the negative result (i.e., a case in which, even when the internal digital value NA can be restored from the standard digital value MS without an error, transmission of the standard digital value MS for that reason is not carried out).

Referring first toFIG.11, it is understood that the standard digital value MS is set as the transmission digital value MD at portions in which the internal digital value NA changes significantly, at the start and end of each stroke, whereas the relative digital value MR is set as the transmission digital value MD at portions in which a change in the internal digital value NA is small, mostly in the middle of each stroke. Furthermore, it is understood that, in the middle of each stroke, the state in which the error between the original internal digital value NA and the internal digital value NA restored from the transmission digital value MD is 0 continues including the case in which the standard digital value MS is set as the transmission digital value MD. The case in which the standard digital value MS is set as the transmission digital value MD and the error between the original internal digital value NA and the internal digital value NA restored from the transmission digital value MD becomes 0 is, in short, the case in which the standard digital value MS is set as the transmission digital value MD because the determination result of step S3inFIG.4is positive. Moreover, it is understood that the absolute value of the error between the original internal digital value NA and the internal digital value NA restored from the transmission digital value MD is up to 4.

From the example ofFIG.11, it can be said that, according to the present embodiment, the internal digital value NA can be transmitted from the pen2to the sensor device3in the state in which the error is sufficiently small at least in the case of N=10 and M=7. Therefore, it becomes possible to apply the present embodiment to the pen system1and reduce communication resources used for transmission of the internal digital value NA. Thus, according to the present embodiment, insufficiency of communication resources that can be used for communication between the pen2and the sensor device3can be alleviated.

Referring next toFIG.12, it is understood that a result similar to that when step S3is carried out is obtained even when step S3is skipped. Therefore, in this case, it is not necessarily essential to determine whether or not the internal digital value NA can be restored from the standard digital value MS without an error and to change the processing according to the determination result.

Lastly, referring toFIG.13, in the example of this diagram, the case in which the standard digital value MS is set as the transmission digital value MD is more frequent compared withFIG.11, and the absolute value of the error between the original internal digital value NA and the internal digital value NA restored from the transmission digital value MD is a large value (at most 15) in a wide range. In this case, it is difficult to apply the present embodiment to the pen system1, and insufficiency of communication resource that can be used for communication between the pen2and the sensor device3may not be alleviated by the present embodiment in the case of N=12 and M=7. A further technique may be needed to achieve the desired effect also in the case of N=12 and M=7. In the second and third embodiments to be described below, some examples of such technique will be described.

FIG.14is a diagram explaining the principle of the second embodiment of the present disclosure. The present embodiment is different from the first embodiment in that a medium-accuracy relative digital value MM is used in addition to the relative digital value MR used also in the first embodiment, and is the same as the first embodiment in other respects. In the following, the description will be continued with focus on the difference from the first embodiment.

The integrated circuit27according to the present embodiment is configured to, in transmitting the N-bit internal digital value NA, transmit the transmission data MF with bits smaller than N bits including the transmission digital value MD that is any of the M-bit standard digital value MS, the L-bit (L<M) medium-accuracy relative digital value MM, or the L-bit relative digital value MR, which are illustrated in the diagram, instead of the internal digital value NA itself. An example with L=M−1 is illustrated inFIG.14and the description will be continued using this example in the following. However, it suffices for L to be an integer smaller than M, and L=M−1 does not need to be satisfied.

One identification flag F1is included in the transmission data MF if the transmission digital value MD is the standard digital value MS. On the other hand, two identification flags F1and F2are included in the transmission data if the transmission digital value MD is the medium-accuracy relative digital value MM or the relative digital value MR. The identification flag F1is one-bit data that becomes a first value (for example, “1”) if the transmission digital value is the standard digital value MS, and becomes a second value (for example, “0”) different from the first value if the transmission digital value is not the standard digital value MS. The identification flag F2is one-bit data that becomes a third value (for example, “1”) if the transmission digital value is the medium-accuracy relative digital value MM, and becomes a fourth value (for example, “0”) different from the third value if the transmission digital value is the relative digital value MR.

The relative digital value MR according to the present embodiment is composed of the relative value expressed with L bits, when the relative value described in the first embodiment is what can be expressed with L bits. The medium-accuracy relative digital value MM is composed of the L most significant bits of the relative value expressed with L+K bits, when the relative value described in the first embodiment is what can be expressed with L+K bits (1≤K≤N−M). The medium-accuracy relative digital value MM may be obtained by compressing the internal digital value NA by the same compression method as the compression method illustrated inFIG.5B.

FIG.15is a flowchart illustrating a transmission processing of the internal digital value NA executed by the integrated circuit27according to the present embodiment. With reference toFIG.15, the transmission processing of the internal digital value NA executed by the integrated circuit27according to the present embodiment will be described in detail below. The processing flow ofFIG.15replaces a portion ofFIG.4.

After acquiring the relative value between the already-supplied internal digital value NS and the internal digital value NA by carrying out step S4ofFIG.4, the integrated circuit27according to the present embodiment determines whether or not the acquired relative value can be expressed with L bits (step S30). When determining that the relative value cannot be so expressed, the integrated circuit27moves the processing to step S33. When determining that the relative value can be expressed, the integrated circuit27moves the processing to step S31.

In step S31, the integrated circuit27sets the relative digital value MR, which is the relative value expressed with L bits, as the transmission digital value MD (step S31) and moves the processing to step S10ofFIG.4.

On the other hand, in step S33, the integrated circuit27determines whether or not the relative value acquired in step S4can be expressed with L+K bits (step S33). When determining that the relative value cannot be so expressed, the integrated circuit27moves the processing to step S6ofFIG.4. When determining that the relative value can be expressed, the integrated circuit27moves the processing to step S34.

In step S34, the integrated circuit27sets the medium-accuracy relative digital value MM, which is the L most significant bits of the relative value expressed with L+K bits, as the transmission digital value MD (step S34). Then, the integrated circuit27restores the internal digital value NA from the medium-accuracy relative digital value MM by using the already-supplied internal digital value NS (step S35) and thereafter moves the processing to step S11ofFIG.4. The restoration processing is carried out by the same method as the restoration carried out by the sensor device3in steps S8and S10illustrated inFIG.4.

FIG.16is a flowchart illustrating a reception processing of the internal digital value NA executed by the sensor controller31according to the present embodiment. With reference to this diagram, the reception processing of the internal digital value NA executed by the sensor controller31according to the present embodiment will be described in detail below. The processing flow ofFIG.16replaces a portion ofFIG.8.

After receiving the transmission data MF by carrying out step S20ofFIG.8, the sensor controller31according to the present embodiment determines whether or not the transmission digital value MD in the transmission data MF is the standard digital value MS based on the identification flag F1included in the transmission data MF (step S40).

When determining that the transmission digital value MD is the standard digital value MS in step S40, the sensor controller31moves the processing to step S22inFIG.8(i.e., the step of restoring the internal digital value NA from the standard digital value MS). On the other hand, when determining that the transmission digital value MD is not the standard digital value MS in step S40, the sensor controller31further determines whether the transmission digital value MD in the transmission data MF is the relative digital value MR or the medium-accuracy relative digital value MM based on the identification flag F2included in the received transmission data MF (step S41).

The sensor controller31, when determining that the transmission digital value MD is the relative digital value MR in step S41, executes processing of restoring the N-bit internal digital value NA from the received L-bit transmission digital value MD (=the relative digital value MR) by using the value previously stored in the internal memory in step S24ofFIG.8(step S42). This processing is executed as inverse processing of the method used by the pen2to acquire the relative value in step S4ofFIG.4.

On the other hand, the sensor controller31, which has determined that the transmission digital value MD is the medium-accuracy relative digital value MM in step S41, executes processing of restoring the N-bit internal digital value NA from the received L-bit transmission digital value MD (=the medium-accuracy relative digital value MM) by using the value previously stored in the internal memory in step S24ofFIG.8(step S43). This processing is executed by first adding K “0” bits to the least significant side of the transmission digital value MD to acquire a digital value of L+K bits and executing, on this digital value, inverse processing of the method used by the pen2to acquire the relative value in step S4ofFIG.4.

The sensor controller31that has carried out step S42or step S43moves the processing to step S24ofFIG.8(the step of outputting the restored N-bit internal digital value NA and storing it in the internal memory).

FIG.17is a diagram illustrating a working example of the present embodiment. The meanings of the curve, white circle marks, and white triangle marks in the upper portion of this diagram and the curve in the lower portion of this diagram are the same as those inFIG.11toFIG.13. Black square marks illustrated in the upper portion ofFIG.17represent that the medium-accuracy relative digital value MM is set as the transmission digital value MD at the timing and the specific value of the set medium-accuracy relative digital value MM. InFIG.17, an example where N=12 and M=8 is illustrated as withFIG.13. L=M−1=7 is satisfied.

As is understood fromFIG.17, in the present working example, the medium-accuracy relative digital value MM is set as the transmission digital value MD at places at which a change in the internal digital value NA is at a medium degree. As a result, the range in which the error (discrepancy) between the original internal digital value NA and the internal digital value NA restored from the transmission digital value MD becomes large is small compared with the example ofFIG.13. As a result, in the present embodiment, there are fewer issues associated with actually using the pen system1as compared with the first embodiment. Therefore, according to the present embodiment, insufficiency of communication resources that can be used for communication between the pen2and the sensor device3can be alleviated also in the case where N=12 and M=8.

Although the example in which one kind of medium-accuracy relative digital value MM is used is described in the present embodiment, plural kinds of medium-accuracy relative digital value MM may be used. For example, an medium-accuracy relative digital value that comprises the L most significant bits of a relative value expressed with L+K1 bits (1≤K1≤N−M) and an medium-accuracy relative digital value that comprises the L most significant bits of a relative value expressed with L+K2 bits (1≤K2≤N−M and K2>K1) may be used. In this case, the identification flag may be one to identify whether the number of kinds of medium-accuracy relative digital value increases or decreases, for example.

Furthermore, the magnitude of the value represented by one bit of the medium-accuracy relative digital value MM (i.e., a value of K) may be changed adaptively according to the relative value or the amount of a change in the relative value. In this case, the identification flag may be what represents the change ratio of the magnitude of the value represented by one bit of the medium-accuracy relative digital value MM (i.e., a ratio between K before the change and K after the change).

In the present embodiment, the example is described in which the one-bit identification flag is added to the standard digital value MS and the two-bit identification flag is added to the relative digital value MR and the medium-accuracy relative digital value MM. However, the one-bit identification flag may be added to one of the relative digital value MR and the medium-accuracy relative digital value MM, and the two-bit identification flag may be added to the other of the relative digital value MR and the medium-accuracy relative digital value MM, and the standard digital value MS. This makes it possible to set the number of bits of one of the relative digital value MR and the medium-accuracy relative digital value MM to M bits and to set the other of the relative digital value MR and the medium-accuracy relative digital value MM, and the standard digital value MS, to L bits. In short, how many bits of the flag are assigned to which type of writing pressure expression (e.g., the standard digital value MS, the medium-accuracy relative digital value MM, or the relative digital value MR, and so forth) can be arbitrarily set.

FIG.18is a flowchart illustrating a transmission processing of the internal digital value NA executed by the integrated circuit27according to the third embodiment of the present disclosure. The processing flow ofFIG.18replaces a portion ofFIG.4. The present embodiment is different from the first embodiment in that a relative value between a predicted value P of the internal digital value NA and the internal digital value NA is used, instead of the relative value between the already-supplied internal digital value NS and the internal digital value NA, and is the same as the first embodiment in other respects. In the following, the description will be continued with focus on the difference from the first embodiment.

The already-supplied internal digital value holding circuit103of the integrated circuit27according to the present embodiment is configured to store a defined number of the internal digital values NA(s) (as set in step S11). Furthermore, as illustrated inFIG.18, after the negative determination in step S3, the integrated circuit27according to the present embodiment executes processing of acquiring the predicted value P of the internal digital value NA from the stored defined number of the internal digital values NA(s) based on a predetermined prediction rule (step S50). This processing can be executed based on an interpolation curve of the defined number of the internal digital values NA(s), for example. As one example, an example based on an interpolation curve of two (the defined number=2) of the internal digital values NA(s) will be described in detail. First, the interpolation curve of the two previous internal digital values NA(s) is obtained. The interpolation curve in this case is a straight line, and NA(n)=−10n+1080 is obtained as the interpolation curve if the two previous internal digital values NA(s) are “1100” and “1090,” for example. For example, NA(n) may represent the n-th internal digital value NA in a series, and n is a numerical value that becomes −2 for the internal digital value NA before last (two times before), −1 for the internal digital value NA of the last time (one time before), and 0 for the internal digital value NA of the present time. By substituting n=0 in the interpolation curve thus obtained, the predicted value P can be obtained as “1080.”

The integrated circuit27, which has carried out step S50, executes processing of acquiring the relative value between the predicted value P and the internal digital value NA acquired in step S1instead of step S4ofFIG.4(step S51). The relative value acquired here is the difference between the predicted value P and the internal digital value NA acquired in step S1, for example. Thereafter, the integrated circuit27moves the processing to step S5and executes the processing described with reference toFIG.4.

Next,FIG.19is a flowchart illustrating a reception processing of the internal digital value NA executed by the sensor controller31according to the present embodiment. The processing flow ofFIG.19replaces a portion ofFIG.8.

The sensor controller31according to the present embodiment is configured to store a defined number of the internal digital values NA(s) (as stored in step S24) in the internal memory. As illustrated inFIG.19, when determining that the transmission digital value MD in the transmission data MF is the relative digital value MR in step S21, the sensor controller31according to the present embodiment executes processing of acquiring the predicted value P of the internal digital value NA from the stored determined number of the internal digital values NA(s) based on the predetermined prediction rule (step S60). This processing is executed by the same method as in step S50ofFIG.18.

The sensor controller31, which has carried out step S60, executes, instead of step S23ofFIG.8, processing of restoring the N-bit internal digital value NA from the received M-bit transmission digital value MD (=the relative digital value MR) by using the predicted value P (step S61). This processing is executed as inverse processing of the method used by the pen2to acquire the relative value in step S51ofFIG.8(for example, the processing of adding the relative digital value MR to the predicted value P). Thereafter, the sensor controller31moves the processing to step S24and executes the processing described with reference toFIG.8.

FIG.20is a diagram illustrating a working example of the present embodiment. The meanings of the curve, white circle marks, and white triangle marks in the upper portion of this diagram and the curve in the lower portion of this diagram are the same as those inFIG.11toFIG.13andFIG.17. InFIG.20, an example in which N=12 and M=7 is illustrated as withFIG.13andFIG.17.

As is understood fromFIG.20, in the present working example, the range in which the error (difference) between the original internal digital value NA and the internal digital value NA restored from the transmission digital value MD becomes large is small compared with the examples ofFIG.13andFIG.17. As a result, in the present embodiment, there are fewer issues associated with actually using the pen system1than in the second embodiment. Therefore, also by the present embodiment, insufficiency of communication resources that can be used for communication between the pen2and the sensor device3can be alleviated also in the case where N=12 and M=7.

FIG.21is a diagram illustrating a temporal change in various digital values acquired in each of the pen2and the sensor device3according to the fourth embodiment of the present disclosure. As illustrated in this diagram, the present embodiment is different from the first embodiment in that the reference value Ref is supplied from the sensor device3to the pen2, and the already-supplied internal digital value NS is updated based on this reference value Ref, and is the same as the first embodiment in other respects. In the following, the description will be continued with focus on the difference from the first embodiment.

As illustrated inFIG.21, the sensor controller31according to the present embodiment is configured to employ the internal digital value NA stored in the internal memory (a value stored in step S24) as the reference value Ref, and to transmit the reference value Ref toward the pen2via the uplink signal US at an arbitrary timing. For example, the arbitrary timing may be immediately after detection of the pen2by the sensor controller31or may be a timing after the elapse of a predetermined time period from the last reception of the transmission data MF from the sensor controller31. Alternatively, the arbitrary timing may be a timing decided based on a random number, or may be a timing that periodically occurs, or may be a combination of two or more of these timings. After transmitting the reference value Ref, the sensor controller31skips step S24until transmitting the next reference value Ref or until receiving the standard digital value MS. As a result, the reference value Ref continues to be stored in the internal memory of the sensor controller31, and processing of restoring the N-bit internal digital value NA from the received transmission digital value MD of M−1 bits (=the relative digital value MR) by using the reference value Ref is executed in step S23ofFIG.8.

FIG.22is a schematic block diagram illustrating functional blocks of the integrated circuit27according to the present embodiment. As illustrated in this diagram, the integrated circuit27according to the present embodiment is configured to functionally include a reception circuit104, additionally. The reception circuit104is a functional unit that receives the uplink signal US through the antenna22and extracts the reference value Ref from the received uplink signal US to set the reference value Ref in the already-supplied internal digital value holding circuit103.

The integrated circuit27according to the present embodiment carries out operation of supplying the internal digital value NA to the sensor device3according to the value held in the already-supplied internal digital value holding circuit103. Specifically, until the reference value Ref is set in the already-supplied internal digital value holding circuit103, the integrated circuit27executes the same processing as the first embodiment as illustrated inFIG.21. However, once the reference value Ref is set in the already-supplied internal digital value holding circuit103, afterward, step S11ofFIG.4is skipped as long as the processing is executed through step S10ofFIG.4. As a result, while the relative digital value MR continues to be set as the transmission digital value MD, the already-supplied internal digital value NS continues to be the reference value Ref and, in step S4ofFIG.4, the relative value between the reference value Ref and the internal digital value NA acquired in step S1is acquired.

Due to the execution of the above processing by the pen2and the sensor device3, generation of the relative value and restoration of the internal digital value NA are carried out based on the reference value Ref after the reference value Ref is transferred as illustrated inFIG.21. This processing is particularly effective when a communication error has occurred as in the example illustrated inFIG.21. Specifically, even when an error (discrepancy) occurs between the internal digital value NA acquired by the pen2and the internal digital value NA acquired by the sensor device3due to a communication error, the error (discrepancy) can be eliminated after transmission and reception of the reference value Ref.

As described above, according to the present embodiment, even when an error (discrepancy) occurs between the digital value acquired by the pen and the digital value acquired by the sensor device due to a communication error or the like, the error can be eliminated after transmission and reception of the reference value.

In the present embodiment, the example is described in which, once the reference value Ref is set in the already-supplied internal digital value holding circuit103, afterward step S11ofFIG.4is skipped as long as the processing of the integrated circuit27is executed through step S10ofFIG.4. However, the skipping of step S11may be limited to one time of skipping immediately after the reference value Ref is set in the already-supplied internal digital value holding circuit103. In this case, at the clock time t6inFIG.21, for example,1030is set as the already-supplied internal digital value NS after transmission. In this case also, the same effect as the present embodiment can be achieved.

FIG.23is a flowchart illustrating processing executed by the integrated circuit27according to a fifth embodiment of the present disclosure. The present embodiment is different from the first embodiment in that the integrated circuit27can operate in two operation modes, and the sensor device3can switch the operation mode of the integrated circuit27, and is the same as the first embodiment in other respects. In the following, the description will be continued with focus on the difference from the first embodiment.

The integrated circuit27according to the present embodiment is configured to operate in either a relative digital value use mode, in which operation is carried out as inFIG.4, and a constant standard digital value use mode, in which the steps S3to S5ofFIG.4are skipped and the processing of step S6and the subsequent steps is always executed after step S1. Switching between them is carried out by using a command included in the uplink signal US from the sensor device3.

The operation of the integrated circuit27will be described. As illustrated inFIG.23, first the integrated circuit27receives the uplink signal US (step S70). Then, the integrated circuit27determines whether or not a command indicating the operation mode is included therein (step S71). If the command is not included, the integrated circuit27keeps the current operation mode and returns the processing to step S70. If the command is included, the integrated circuit27further determines which of the relative digital value use mode or the constant standard digital value use mode is indicated. If the relative digital value use mode is indicated, the integrated circuit27enters the relative digital value use mode (step S72). If the constant standard digital value use mode is indicated, the integrated circuit27enters the constant standard digital value use mode (step S73). Thereafter, the integrated circuit27returns the processing to step S70.

According to the present embodiment, the pen2can send the standard digital value MS according to a command from the sensor device3when the sensor device3needs the standard digital value MS. Therefore, for example, when an error occurs between the internal digital value NA acquired by the pen2and the internal digital value NA acquired by the sensor device3due to the occurrence of a communication error, the error can be immediately eliminated.

Although preferred embodiments of the present disclosure are described above, it is obvious that the present disclosure is not limited to such embodiments and the present disclosure can be implemented in various modes without departing from the scope of the present disclosure.

For example, in the above-described respective embodiments, the examples are described in which the internal digital value acquisition circuit100converts the state of the user operation tool25(including the writing pressure detector23) to the N-bit internal digital value. However, the internal digital value acquisition circuit100may acquire the N-bit internal digital value from a factor or element other than the state of the user operation tool. For example, data transmitted from the pen2to implement setting of the sensor device3or the host computer4may be acquired as the N-bit internal digital value. This data can be supplied also based on M-bit transmission data (M<N). Thus, it becomes possible to further alleviate insufficiency of communication resources that can be used for communication between the pen2and the sensor device3.

In the above-described respective embodiments, determination of whether or not to transmit the standard digital value MS is carried out on the side of the pen2. However, this determination may be carried out also in the sensor controller31, and the sensor controller31may cause the electronic pen2to transmit the standard digital value MS by using a command transmitted in the uplink signal US when the sensor controller31determines to cause the pen2to transmit the standard digital value MS. In this case, it is preferable for the sensor controller31to determine to cause the pen2to transmit the standard digital value MS if the standard digital value MS has never been received after detection of the pen2, or when the standard digital value MS has not been received over a predetermined time, or the like. Furthermore, after causing the pen2to transmit the standard digital value MS, the sensor controller31may cause the transmission of the standard digital value MS to continue a predetermined number of times. This continuous transmission may be implemented through transmission of a command from the sensor controller31in every transmission, or may be implemented by configuring the pen2to autonomously transmit the standard digital value MS a predetermined number of times after having received a command requesting the transmission of the standard digital value MS.

DESCRIPTION OF REFERENCE SYMBOLS

23Writing pressure detector

24Wheel user operation tool

25User operation tool

100Internal digital value acquisition circuit

101Transmission digital value acquisition circuit

103Already-supplied internal digital value holding circuit

DS Downlink signal

MD Transmission digital value

MF Transmission data

MM Medium-accuracy relative digital value

MR Relative digital value

MS Standard digital value

NA Internal digital value

OPS State

P Predicted value

Ref Reference value

US Uplink signal