JP2002062977A - Communication system and coordinate reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a communication system capable of shortening the time required for discrimination of information and a coordinate reader using the communication system. SOLUTION: In this system, n-kinds of modulation period Tm1-Tmn differed every attribute such as color of a pen are selected, and a signal with carrying wave periods T1 and T2 repeatedly switched every modulation period is transmitted from the pen to a writing panel. The modulation period Tm1 is optional, and the modulation period Tmn is selected according to the following numerical equation 1: Tmn=(1+df/10).Tmn-1+2.TX/(1-df/100) (wherein TX is T1 or T2, and the modulation periods Tm1 to Tmn might be fluctuated within the range of (1-df/100).Tmp to (1+df/100).Tmp as an allowable error).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a communication system and a coordinate reading apparatus using the communication system.

[0002]

2. Description of the Related Art A coordinate reading apparatus shown in FIG. FIG. 20A is an explanatory diagram illustrating a configuration of a conventional coordinate reading device. The coordinate reading device shown in FIG. 20A has sense coils (conductors) X1 to Xm for detecting the X coordinate and Y1 to Y for detecting the Y coordinate.
coordinate input sheet 91 having n sense coils (conductors)
And a scanning circuit 92 for sequentially scanning the sense coils of the coordinate input sheet 91, and a detection circuit 90 for detecting an induction signal generated in the sense coils and calculating the position coordinates.

A coil 191 for generating an alternating magnetic field
(Writing means) 190 having a coordinate input sheet 91
, An induction signal 97 is induced in the sense coil near the pen 190 in contact with the alternating magnetic field generated from the coil 191, and the induction signal 97 is generated.
Is input to the detection circuit 90. The induction signal 97 input to the detection circuit 90 is amplified by the amplifier 93 and subjected to, for example, amplitude detection by the detection circuit 94. Next, A / D
The conversion circuit 95 measures the amplitude of the detected induction signal and outputs the measured value to the CPU 96. And CP
U96 detects the pen 190 based on the input digital value.
Is calculated. For example, a calculation method of referring to a position coordinate table in which digital values and position coordinates are associated with each other and selecting position coordinates corresponding to the digital values is used.

When a plurality of types of pens are used in the coordinate reading apparatus as described above, attribute information indicating attributes such as the type of the pen is transmitted from the pen using a code string, and the attribute information is input to the coordinate input device. One that recognizes on the sheet side is known (JP-A-5-233127). FIG. 20B is an explanatory diagram illustrating a code string transmitted from the pen.

The code G is a 2 bit start bit, 7 bit attribute information bits indicating pen attribute information, and 1
It is composed of a total of 10 stop bits, and is superimposed on the alternating magnetic field from the pen in accordance with the operation clock F and output. And the coordinate input sheet side,
The code string superimposed on the signal generated in the sense coil by the alternating magnetic field transmitted from the pen is read to recognize the attribute information of the pen.

[0006]

However, the above-mentioned conventional coordinate reading apparatus (Japanese Patent Laid-Open No. 5-233127) recognizes pen attribute information unless a plurality of cycles from a start bit to a stop bit are received. Can not do.

Further, unless the operation clock of the pen and the operation clock of the coordinate input sheet are synchronized, the attribute information of the pen cannot be recognized. Furthermore, when detection is started by the sense coil from the middle of the start bit to the stop bit, the control waits until the next start bit is transmitted, and unless the start bit to the stop bit are received again, the attribute information of the pen is transmitted. I can't recognize.

That is, the conventional coordinate reading apparatus has a problem that it takes time to recognize the attribute information of the pen. Therefore, the present invention has been made to solve the above-described problem, and has as its object to realize a communication system capable of reducing the time required for identifying information and a coordinate reading device using the communication system. Aim.

[0009]

Means for Solving the Problems, Functions and Effects of the Invention
In order to achieve the above object, the communication system according to claim 1 or 2 provides n types (where n is an integer satisfying n ≧ 2) of n types of different modulation periods Tm ₁ to Tm ₁ . Tm _n are preselected, 2 value period is the n types of modulation period Tm ₁ to Tm from the binary a signal switched alternately one to switch from one again switched to the other to the other a transmitting means for frequency-modulating the carrier with a signal selected from _n and transmitting a signal in which the carrier periods T ₁ and T ₂ are switched in accordance with the binary value; and receives the signal, demodulates the received signal to detect the modulation period Tm ₁ to Tm _n, based on the detected modulation period Tm ₁ to Tm _n, the information indicated by the transmitted signal Recognition And receiving means for identifying the information.

[0010] In this communication system, n kinds of information is not associated with the n different modulation period Tm ₁ to Tm _n, signal any n types of signals representing each information having a fixed period Becomes Therefore, it is possible to recognize which of the n types of information by detecting only one cycle of the signal. Therefore, as before,
The time required for identifying information can be reduced as compared with the case of identifying information indicated by using a plurality of cycles from a start bit to a stop bit.

[0011] Also, only slightly different signal periods,
Information can be identified. For example, information can be identified only by a difference of at least one cycle of the system clock of the receiving device used in this communication system. Therefore, it is possible to transmit very many types of information and to identify the information in a short time.

Further, since the signal is frequency-modulated and transmitted, even if the amplitude of the carrier wave changes, the period indicating information is not affected. Can be. Still further, claim 1
, The modulation periods Tm _{1 to} Tm ₁
For m _n, the modulation period Tm ₁ is arbitrarily selected, the modulation period Tm _n are selected on the basis of the equation 1 (see claim 1). In the communication system according to claim 2, the modulation period Tm ₁ to Tm _n is as ± df% modulation frequency margin, (1-df / 100) · Tm p
~ (1 + df / 100) · Tm p ( Here, p is an integer of 1 to n) assuming that may vary in the range of, for modulation period Tm ₁ to Tm _n, the modulation period Tm ₁
Is arbitrarily selected, the modulation period Tm _n are selected on the basis of the equation 2 (see claim 2).

[0013] Thus the equation 1 or based on Equation 2 selects the modulation period Tm ₁ to Tm _n, even when the detection value of each modulation period Tm ₁ to Tm _n is varies somewhat, some modulation period the other modulation cycle is erroneous it is not possible to determine, moreover, can be allocated efficiently modulation period Tm ₁ to Tm _n so as not wasting away between the modulation period and the modulation period adjacent numerically.

[0014] To explain in more detail, when detecting the modulation period Tm ₁ to Tm _n demodulates the received signal, T ₁
Detecting a timing of changing to T ₁ from the timing or T ₂ changes to T ₂ from but relates this time, an error occurs between the timing of actually detected the true timing. Then, is this error caused, the detection value of each modulation period Tm ₁ to Tm _n may fluctuate within the numerical range of each. Therefore, if two numerically adjacent modulation periods are set too close to each other, an upper limit and a lower limit of each numerical range will overlap, and if a detected value that overlaps the two is obtained, either If it is determined that one of the modulation periods is used, there is a possibility that an erroneous determination may be made. Meanwhile, in order to avoid such erroneous determination, setting the two modulation periods adjacent to numerically excess away, although overlapping numerical ranges are overcome, since the numerical range which can not be utilized occurs, the modulation period Tm ₁ ~ T
The numerical range necessary for allocating all _mn is unnecessarily expanded, and the efficiency of allocation is reduced. In contrast, when selecting the modulation period Tm ₁ to Tm _n based on the formula 1 or 2, do not overlap the numerical range of the modulation period adjacent each other and between numbers adjacent range is not unnecessarily leave With this setting, the erroneous determination as described above can be prevented, and the efficiency of modulation period allocation can be improved.

In particular, the communication system according to claim 2
The modulation period Tm₁~ Tm_nBut modulation frequency merge
(1-df / 100) · Tm_p~
(1 + df / 100) · Tm_p(However, p is an integer of 1 to n
Number).
The modulation period is assigned taking this variation into account.
For example, due to individual differences in electronic components and usage environment,
And the modulation period Tm₁~ Tm _nBut the above modulation frequency merge
Even if it can vary within the range of ± df%,
The numerical ranges of the modulation periods that do not overlap and do not overlap
It is set so that there is no useless separation between matching numerical ranges
Will be.

Next, a coordinate reading apparatus according to a third or fourth aspect of the present invention provides a coordinate reading apparatus comprising: a main body having a coordinate input sheet in which a plurality of conducting wires magnetically coupleable with an alternating magnetic field are laid below a writing surface; Writing means for generating a magnetic field, wherein the coordinate reading device reads the position coordinates of the writing means on the writing surface based on a signal generated on the conductive wire, wherein n types (where n is n N types of different modulation periods Tm associated with attribute information of ≧ 2)
₁ to Tm _n are preselected, said writing means includes a coil for generating an alternating magnetic field having a predetermined period, the binary A signal binary switches alternately again switched from one to the other the signal is either the period from one to switch to the other is selected from among the n types of modulation period Tm ₁ to Tm _n, an alternating magnetic field generated from the coil and frequency modulation, corresponding to the binary and a transmitting means for transmitting the carrier wave period T _1, T ₂ is switched signal Te, the body demodulates the signal generated in the conductor by detecting the modulation period Tm ₁ to Tm _n, the detection was based on the modulation period Tm ₁ to Tm _n, and a receiving means for recognizing attribute information indicated by the signal transmitted from said writing means.

[0017] In this coordinate reading device, n type of attribute information to be transmitted from the writing means to the body, have associated with n different modulation period Tm ₁ to Tm _n, n kinds of signals representing each attribute information Are signals having a constant period. Therefore, the main body can recognize which of the n types of information is the information from the writing means only by detecting one cycle of the signal. Therefore,
It is possible to reduce the time required to identify the attribute information as compared with the related art that identifies attribute information indicated by using a plurality of cycles from a start bit to a stop bit.

Further, attribute information is transmitted by frequency-modulating an alternating magnetic field generated from a coil of the writing means,
By demodulating the signal generated on the conductor laid on the coordinate input sheet, the modulation period of the signal transmitted from the writing means is detected, and the attribute information is identified based on the detected modulation period. Even when the strength of the attribute changes, the period indicating the information is not affected, so that the attribute information can be transmitted and received accurately.

[0019] Further, in the communication system according to claim 3, the modulation period Tm ₁ to Tm _n, the modulation period Tm ₁ is arbitrarily selected, the modulation period Tm _n is the equation 3 (see claim 3) Is selected based on In the communication system according to claim 4, the modulation period Tm ₁ to Tm _n is as ± df% modulation frequency margin, (1-df / 100) · Tm p ~ (1 + df / 1
00) · Tm _p (where p is an integer of 1 to n) on the assumption that the modulation period Tm p may fluctuate.
About ₁ to Tm _n, the modulation period Tm ₁ is arbitrarily selected, the modulation period Tm _n are selected on the basis of the above equation 4 (see claim 4).

[0020] Thus the equation 3 or on the basis of Equation 4 selects the modulation period Tm ₁ to Tm _n, even when the detection value of each modulation period Tm ₁ to Tm _n is varies somewhat, some modulation period the other modulation cycle is erroneous it is not possible to determine, moreover, can be allocated efficiently modulation period Tm ₁ to Tm _n so as not wasting away between the modulation period and the modulation period adjacent numerically.

[0021] To explain in more detail, when detecting the modulation period Tm ₁ to Tm _n demodulates the received signal, T ₁
Detecting a timing of changing to T ₁ from the timing or T ₂ changes to T ₂ from but relates this time, an error occurs between the timing of actually detected the true timing. Then, is this error caused, the detection value of each modulation period Tm ₁ to Tm _n may fluctuate within the numerical range of each. Therefore, if two numerically adjacent modulation periods are set too close to each other, an upper limit and a lower limit of each numerical range will overlap, and if a detected value that overlaps the two is obtained, either If it is determined that one of the modulation periods is used, there is a possibility that an erroneous determination may be made. Meanwhile, in order to avoid such erroneous determination, setting the two modulation periods adjacent to numerically excess away, although overlapping numerical ranges are overcome, since the numerical range which can not be utilized occurs, the modulation period Tm ₁ ~ T
The numerical range necessary for allocating all _mn is unnecessarily expanded, and the efficiency of allocation is reduced. In contrast, when selecting the modulation period Tm ₁ to Tm _n based on the equation 3 or Equation 4, without overlapping numerical range of the modulation period adjacent each other and between numbers adjacent range is not unnecessarily leave With this setting, the erroneous determination as described above can be prevented, and the efficiency of modulation period allocation can be improved.

In particular, the communication system according to claim 4
The modulation period Tm₁~ Tm_nBut modulation frequency merge
(1-df / 100) · Tm_p~
(1 + df / 100) · Tm_p(However, p is an integer of 1 to n
Number).
The modulation period is assigned taking this variation into account.
For example, due to individual differences in electronic components and usage environment,
And the modulation period Tm₁~ Tm _nBut the above modulation frequency merge
Even if it can vary within the range of ± df%,
The numerical ranges of the modulation periods that do not overlap and do not overlap
It is set so that there is no useless separation between matching numerical ranges
Will be.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A first embodiment of a communication system according to the present invention and a coordinate reading apparatus using the communication system will be described below with reference to the drawings.

In the first embodiment, a so-called electronic blackboard, which electrically reads handwritten characters and figures drawn on a coordinate input sheet, will be described as an example of a coordinate reading apparatus according to the present invention. As a communication system according to the present invention, a communication system that performs communication between a pen provided on an electronic blackboard and a writing panel will be described as an example. [Main Configuration] First, the main configuration of the electronic blackboard according to the first embodiment will be described with reference to FIGS.

FIG. 1 is an external perspective view showing the main structure of the electronic blackboard, and FIG. 2 shows a state in which a personal computer (hereinafter abbreviated as PC) and a printer are connected to the electronic blackboard shown in FIG. FIG. The electronic blackboard 1 includes a writing panel 10, a pen 60 for writing on the writing surface 21a, and an eraser 40 for erasing the written locus and data indicating the locus. The writing panel 10 includes a frame 11 having a frame shape, and the frame 11 includes a writing panel main body 20.
Is incorporated. At the lower end of the entire surface of the frame 11, a plate-like base 12 is attached along the lower end so as to project to the front. A recess 12 a having a semicircular cross section for accommodating the pen 60 is formed on the upper surface of the table 12.
On the right side of the concave portion 12a, a flat portion 12b for placing the eraser 40 and the like is formed.

On the front right side of the frame 11, an operation unit 30
Is provided. The operation unit 30 includes a speaker 31 for reproducing sounds such as an operation sound and a warning sound, and a seven-segment page number storing data indicating the contents written on the writing surface 21a (hereinafter abbreviated as writing data). A page number display LED 32 displayed by an LED, a page return button 33 for returning one page each time the button is pressed, a page forward button 34 for sending one page each time the button is pressed, and one page each time the stored writing data is pressed. Delete button 35 for writing the stored writing data to the printer 200
Printer output button 36 pressed to output to (FIG. 2)
, A PC output button 37 pressed to output the stored writing data to the PC 100 (FIG. 2), a dead battery notification LED 39 for reporting that the battery of the pen 60 is dead, and the electronic blackboard 1 to start or stop. And a power button 38 to be pressed.

A battery case 14 for accommodating four C-size batteries 14a serving as a power source of the electronic blackboard 1 is provided at a lower portion of the front surface of the frame 11, and a lid 14b is opened and closed on the front surface of the battery case 14. Mounted as possible. On the right side of the battery case 14, a volume control knob 13c for controlling the volume of the speaker 31 is provided, and on the right side, connectors 13b and 13a are provided. As shown in FIG. 2, the plug 13 of the connection cable 201 connected to the printer 200 is connected to the connector 13b, and the PC 13 is connected to the connector 13a.
The plug 102 of the connection cable 101 connected to 00 is connected.

That is, writing data indicating the contents written on the writing surface 21a of the electronic blackboard 1 is output to the PC 100,
The electronic blackboard 1 is monitored by the monitor 110 provided in the C100.
You can see the contents written in. Further, it is also possible to output handwriting data to the printer 200 and print the contents handwritten on the electronic blackboard 1 on the printing paper 203.

Metal fittings 15, 15 for hanging the electronic blackboard 1 on a wall are provided at both ends at the upper end of the rear surface of the frame 11.
Is installed. In the first embodiment, the writing surface 2
The height H1 of 1a is 900 mm and the width W1 is 600 m
m. Further, the frame 11 and the base 12 are made of a synthetic resin such as polypropylene so as to be lightweight.
The total weight of the electronic blackboard 1 is 10 kg or less. Further, the eraser 40 includes a coil for generating an alternating magnetic field, a transmission circuit, a battery, and the like. [Configuration of Network] Next, the configuration of a network when data is communicated between the electronic whiteboard 1 and another electronic whiteboard 1 will be described with reference to FIG.

Here, a case where communication is performed between a plurality of rooms equipped with the electronic whiteboard 1 in a company or between companies is described as an example. Room 3 in company 2
Electronic blackboard 1 and PC 100 connected to electronic blackboard 1
And a LAN board 103 connected to the PC 100. The room 4 includes an electronic blackboard 1, a PC 100 connected to the electronic blackboard 1, and a modem 108 connected to the PC 100. Have been. Each room 3
LAN board 103 provided for LAN cable 1
04 is connected to the HUB 105. Also, HU
B105 is connected to the server 106,
06 can be connected to another company 5 via the Internet 300. The modem 108 provided in the room 4 can be connected to another company 5 from the telephone line 109 via the public switched telephone network 301.

Although not shown, other companies 5 include:
Electronic blackboard 1 communicable via PC as in company 2
Is provided. Here, the flow of data in the network will be described. The writing data stored in the electronic blackboard 1 provided in a certain room 3 is transmitted from the PC 100 to the PC 100 in the designated room 3 via the LAN board 103 and the HUB 105. Then, the person who has received the data displays the received data on a monitor 110 provided in the PC 100 (FIG. 2), or prints the received data on a sheet 203 by a printer 200 connected to the PC 100. (FIG. 2), the contents of the received data can be seen.

Also, the handwritten data may be, for example, TIFF
(Tag Image File Format) format and attach it to an e-mail as an image file.
6 to another company 5 via the Internet 300. Thus, the other company 5 becomes the company 2
By decoding the image file attached to the e-mail sent from the company, the contents of the handwritten data can be viewed. [Structure of Writing Panel Body 20] Next, the writing panel body 2
The structure of 0 will be described with reference to FIG.

FIG. 4 is an explanatory view showing each constituent member of the writing panel main body 20. The writing panel body 20 includes the writing surface 2
A writing sheet 21 having 1a, a plate-shaped panel 22,
Frame-shaped mounting panel 24 on which sense coil 23 is laid
And a plate-shaped back panel 25 are sequentially laminated.

In this embodiment, the writing sheet 21 is formed of a PET (polyethylene terephthalate) film having a thickness of 0.1 mm, and the panel 22 is made of acrylic resin and ABS (acrylonitrile-butadiene-styrene). (Polymer), PC (polycarbonate), etc., to a thickness of 3.0 mm. The mounting panel 24 is formed of a foamed resin material such as styrene foam to have a thickness of 40 mm, and the back panel 25 is formed of a conductive material such as aluminum to have a thickness of 1.0 mm. Furthermore, the entire thickness of the frame 11 that holds each end of the writing panel body 20 is 5
0 mm. [Configuration of Sense Coil 23] Next, the configuration of the sense coil 23 will be described with reference to FIG.

FIG. 5A shows the sense coil 2 shown in FIG.
FIG. 5 is an explanatory view showing the configuration of FIG.
FIG. 5B is an explanatory diagram showing the width and the overlapping pitch of the sense coils 23 shown in FIG. In the following description, among the sense coils 23, the sense coils arranged in the X-axis direction are referred to as X coils, and the sense coils arranged in the Y-axis direction are referred to as Y coils.

As shown in FIG. 5A, in the X-axis direction,
There are m X coils X1 to Xm for detecting the X coordinate of the (X, Y) coordinates of the pen 60 and the eraser 40. In the Y-axis direction, Y1 to Y1 for detecting the Y coordinate are arranged.
The n Y coils of Yn are arranged orthogonally to the X coils. The X coil and the Y coil are each formed in a substantially rectangular shape, and the length of the long side of the rectangular portion is P2
X, P2Y.

As shown in FIG. 5B, the X coils are each formed to have a width (the length of the short side of the rectangular portion) P1, and adjacent X coils are overlapped at a pitch of P1 / 2. Have been. Each Y coil is also formed to have a width P1, and adjacent Y coils are respectively overlapped at a pitch of P1 / 2. Also, each terminal 23a of the X coil
Are connected to the X coil switching circuit 50a, and each terminal 23b of the Y coil is connected to the Y coil switching circuit 50b (FIG. 9).

In the first embodiment, P1 = 50 mm, P2X = 680 mm, and P2Y = 980 mm
It is. Also, m = 22 and n = 33. Further, both the X coil and the Y coil are formed of a 0.35 mm diameter copper wire having an insulating coating layer (for example, an enamel layer) on the surface.

In FIG. 5 (A), the sides of each coil are drawn so as not to overlap in order to make the arrangement of the coils easy to understand. The short sides of each of the Y coils Y1, Y2, Y3,... The terminals 23a and 23b are
The interval is configured to be the minimum. [Position coordinate table] Next, the pen 60 on the writing surface 21a
A position coordinate table for detecting the position coordinates of the position will be described with reference to FIGS.

FIG. 6A is an explanatory view showing a part of the X coils X1 to X3, and FIG. 6B is a diagram showing the voltages generated in the X coils X1 to X3 shown in FIG. FIG. 6C is a graph showing a relationship with distance, and FIG.
It is a graph which shows the voltage difference between mutually adjacent sense coils of coils X1-X3. FIG. 7A is an explanatory diagram showing the position coordinate table as a graph, FIG. 7B is an explanatory diagram of the position coordinate table, and FIG. 7C is a storage of detected values detected from each X coil. It is explanatory drawing which shows a state.

In FIG. 6, the center lines of the X coils X1, X2 and X3 are C1, C2 and C3, respectively.
1, X2, and X3 are represented by ex1, ex, respectively.
2, ex3. As shown in FIG.
1 to ex3 are the center C1 to C3 of the sense coil, respectively.
, And has a monomodal property which becomes smaller as approaching the end in the longitudinal direction. Each coil has a P1 / 2 such that its own null point, that is, the point at which each of the voltages ex1 to ex3 becomes 0, is outside the center of the adjacent coil.
Layered.

As shown in FIG. 6C, the X coil X
The voltage difference between mutually adjacent sense coils 1 to X3 is
A graph having a maximum value on each of the centers C1 to C3 of the sense coil, and being zero at an intermediate point between the center of the sense coil and a long side portion of the sense coil, that is, an intermediate point of a portion where the adjacent sense coils overlap. Become.

For example, in FIG. 6C, (ex1-
ex2), the right half of the graph (the part shown by the solid line)
The distance from the center C1 of the X coil X1 to the midpoint Q2 of the portion where the X coil X2 is superimposed (1/2 of the superimposition pitch,
That is, the relationship between (P1 / 4) and (ex1-ex2) is shown. Now, if the pen 60 exists at the point Q2, (ex
If 1−ex2) is detected, the distance ΔX1 from the center C1 to the point Q2 can be detected, so that the X coordinate of the point Q2 can be obtained.

In this embodiment, the coil width P1 is 50 m
m, P1 / 4 = 12.5 mm. For example, when a portion (the portion drawn by a solid line) showing the characteristic of (ex1-ex2) in FIG. 6C is converted into 8-bit digital data, a graph shown in FIG. 7A is obtained. When this graph is converted into a table format, a position coordinate table 58a shown in FIG. 7B is obtained. The position coordinate table 58a is stored in the ROM 58 (FIG. 9) or the like, and
0 is used for calculating the position coordinates.

Next, the main configuration of the pen 60 will be described with reference to FIG. FIG. 8A is an explanatory diagram showing the internal structure of the pen 60, and FIG. 8B is an explanatory diagram showing the electrical configuration of the pen 60 shown in FIG. 8A. [Internal Structure of Pen 60] The pen 60 is provided with a cylindrical body 61a and a lid 61c detachably attached to the rear end of the body 61a. Inside the body portion 61a, a coil L1, an ink cartridge 63 that can be taken out in a direction indicated by an arrow F2, a pen tip 62 inserted into the ink cartridge 63, and an oscillation for generating an alternating magnetic field from the coil L1. A circuit board 69 on which circuits and the like are mounted and a battery 70 for supplying power to the circuit board 69 are provided.

A push-button switch 67 is provided between the ink cartridge 63 and the circuit board 69 to supply and cut off power to the oscillation circuit and the like. The switch 67 connects the pen tip 62 to the writing surface 21.
a (FIG. 1), and turns on when the ink cartridge 63 moves in the direction shown by the arrow F1, and turns off when it returns in the direction shown by the arrow F2. That is, when the pen 60 is writing on the writing surface 21a, an alternating magnetic field is generated from the coil L1. [Electrical Configuration of Pen 60] As shown in FIG. 8B, the circuit mounted on the circuit board 69 includes a CR oscillation circuit 69e in which a different modulation cycle is set for each pen attribute such as ink color. An LC oscillation circuit 69c that oscillates a carrier wave that carries a signal oscillated from the CR oscillation circuit 69e;
fSK (Frequency)
Shift Keying) FSK circuit 69d that modulates
It is composed of The oscillation frequency of the carrier is determined by the inductance L1 and the capacitors C1, C2, and C3 constituting the LC oscillation circuit 69c.
The capacitor C5 and the resistor R constituting the oscillation circuit 69e
2, determined by R3. The frequency shift of the carrier oscillation frequency is determined by the capacitance of the capacitor C4 of the FSK circuit 69d.

The relationship between the attribute of the pen 60 and the modulation period Tm is set as shown in FIG. 10A for explaining the relationship. The eraser 40 also has a built-in coil, and calculates the erasure range of the eraser 40 based on the signal generated in the sense coil by the alternating magnetic field generated from the coil. Identify.

When the switch 67 is turned on, the power of the battery 70 is supplied to each circuit, and the output of the integrated circuit IC3 of the CR oscillation circuit 69e is output to the MOS F of the FSK circuit 69d.
The gate of the ET is switched, and the carrier wave oscillated from the LC oscillation circuit 69c is frequency-modulated by the signal oscillated from the CR oscillation circuit 69e.

In the first embodiment, the center frequency of the carrier is 405 kHz, and the frequency shift is ± 15 kHz. That is, the frequency of the carrier is f ₁ = 390 kHz.
It switches to z or f ₂ = 420 kHz, and in terms of carrier period, T ₁ = 1/390 ms or T ₂ = 1/42
It switches to 0 ms.

Here, the six types of attributes shown in FIG.
Modulation period Tm associated with information ₁~ Tm₆Is the following
This is the value determined as described above. First, the modulation period Tm
Depends on the usage environment (temperature conditions, etc.) of the pen 60 and individual differences.
May vary slightly. Specifically, this first
In the pen 60 of the embodiment, the modulation frequency margin
± 8%, modulation period Tm₁~ Tm₆Respectively
(1-8 / 100) · Tm_p~ (1 + 8/100) · T
m_p(Where p is an integer of 1 to 6).
The modulation cycle fluctuation within this range is not allowed.
Treat as tolerable. The modulation period Tm is
Wave period T₁From the carrier cycle T_TwoDepending on the interval between
Detected. Given these, the modulation period Tm₁Is
Although it is arbitrarily selected, in the first embodiment, Tm
₁= 0.1ms (= modulation frequency 10kHz)
I have. And the modulation period Tm_Two~ Tm₆Is the following equation 5.
Is calculated based on

[0051]

(Equation 5)

Such a modulation period Tm₁~ Tm₆The set
The reason is as follows. In the first embodiment,
The received signal is demodulated and the modulation period Tm₁~ Tm₆Detect
The carrier wave period T₁From the carrier cycle T_TwoChange to
Timing is detected.
Between the true timing and the actually detected timing.
An error occurs between them. And this error causes
And each modulation period Tm₁~ Tm₆Is the upper and lower limit ± T₁
Fluctuates within the range. Therefore, two numerically adjacent
Modulation period (eg, T₁And T_Two, T_TwoAnd T_ThreeEtc.)
When set close to excessive, the upper limit of each numerical range
Side and lower side overlap, and it becomes the overlap
If a detection value is obtained, the
If this is determined, there is a risk of misjudgment. On the other hand,
In order to avoid erroneous judgments, two numerically adjacent modulation
If the periods are set too far apart, the overlapping of
Although it disappears, a numerical range that can not be used occurs,
Modulation period Tm₁~ Tm ₆Necessary to allocate everything
The numerical range is unnecessarily expanded, and the allocation efficiency is reduced.
On the other hand, the modulation period Tm₁~ T
m₆Is selected, the numerical ranges of adjacent modulation periods
Do not overlap with each other, and there is a wasteful separation between adjacent numerical ranges.
Is set so that misjudgment as described above can be prevented.
In this case, the efficiency of the modulation period allocation is improved.

Further, when the modulation frequency margin is ± 8%, the modulation periods Tm _{1 to} Tm ₆ are (1/8/10
_{0) · Tm p ~ (1} + 8/100) · Tm p ( Here, p
Is an integer of 1 to 6).
Since the modulation periods Tm _{1 to} Tm ₆ are assigned in consideration of this variation, the modulation periods Tm _{1 to} Tm ₆ are set to the modulation frequency margin ± due to, for example, individual differences in electronic components and the use environment. Even if it fluctuates within the range represented by 8%, the numerical ranges of adjacent modulation periods do not overlap each other,
In addition, it is set so that adjacent numerical ranges are not unnecessarily separated.

By the way, when the modulation frequency margin is so small that it can be ignored, that is, when the modulation frequency margin can be regarded as ± 0%, the above equation (5) is used.
Alternatively, the modulation periods Tm _{2 to} Tm ₆ may be determined using the following Expression 6.

[0055]

(Equation 6)

In this case, the range between adjacent numerical ranges is set densely without waste. As described above, the modulation period T
m ₁ to Tm ₆ result of setting the, Tmin _p to Tmax _p each modulation period Tm _p are, each shown in FIG. 10 (A)
, But these ranges do not overlap with each other. The count value Cnorm _p which are also shown in FIG. _{10 (A), Cmin p,} Cmax p , respectively Tm _p, Tmin _p, is a value corresponding to Tmax _p, these will be described later [Determination of Pen Attributes Will be described. [Main electrical configuration and control contents of electronic blackboard 1]
The main electrical configuration and control contents of the electronic blackboard 1 will be described with reference to FIGS. 9, 10B and 11. FIG.

FIG. 9 is an explanatory diagram showing the electrical configuration of the electronic blackboard 1 by blocks, and FIG.
FIG. 11 is an explanatory diagram showing signals at points B and C. FIG. 11 is a flowchart showing main control contents executed by the CPU 56 shown in FIG. When detecting that the power button 38 (FIG. 1) has been turned ON (step (hereinafter abbreviated as S) 100), the CPU 56 provided in the control device 50 shown in FIG.
Yes), the control program and the position coordinate table 58a (FIG. 7B) stored in the ROM 58 are stored in the RAM 59.
Initial settings such as loading to the work area of (S
200), and executes coordinate reading / pen information detection processing (S).
300). [Coordinate Reading Process] Here, the coordinate reading process will be described with reference to the flowchart of FIG.

The CPU 56 outputs a coil selection signal A (FIG. 10B) for sequentially selecting the X coils X1 to Xm to the X coil switching circuit 50a via the input / output circuit (I / O) 53. The X coils X1 to Xm are scanned (S302). Subsequently, a signal generated by magnetic coupling between the alternating magnetic field generated from the coil L1 of the pen 60 and one of the X coils is amplified by the amplifier 50c (FIG. 9), and the amplified signal (FIG. 10B) is obtained. An unnecessary band is filtered by a band-pass filter (BPF) 50 d, and the amplitude is detected by an amplitude detection circuit 51. Subsequently, the amplitude-detected signal (FIG. 10B) is A / D
The signal is converted into a digital signal corresponding to the amplitude, that is, the voltage value by the conversion circuit 52,
56 is input.

Subsequently, the CPU 56 determines that the pen 60 has been detected (S304: Yes), scans the X coils X1 to Xm, and sets the voltage values e1 to em indicated by the input digital signals in FIG. 7C. As shown in (3), it is sequentially stored in the voltage value storage area 59a of the RAM 59 in association with the coil number of the X coil (S306). Then CP
U56 calculates the X coordinate of pen 60 based on each voltage value stored in voltage value storage area 59a by the following procedure (S308).

First, the maximum voltage value emax is selected from the voltage values e1 to em stored in the voltage value storage area 59a, and the coil number of the X coil that generated the voltage value emax (hereinafter referred to as max). ) Is stored in the RAM 59. For example, as shown in FIG.
And as shown in FIG. 6B, X coils X1 and X
Suppose that voltage values e1, e2, and e3 are generated from X2 and X3, respectively, the maximum voltage value e2 is selected and the voltage value e2 is selected.
The coil number 2 of the X coil that generated
Store it in AM59.

Then, the CPU 56 determines the larger one of the voltage values emax ± 1 on both sides of emax, and determines the coil number (hereinafter referred to as ma) of the X coil that generated the determined voltage value.
x2) is stored in the RAM 59. In the example shown in FIG. 6, the larger e3 of the voltage values e3 and e1 on both sides of e2 is determined, and the coil number 3 of the X coil that generated the e3 is stored in the RAM 59 as max2.

Subsequently, the CPU 56 compares the coil numbers max and max2 stored in the RAM 59 to determine whether the coil number max2 exists in the + direction or the − direction of the X axis from the coil number max. If max2 ≧ max, the variable SIDE is set to 1
And if max2 <max, the variable SID
Set E to -1. In the example shown in FIG. 6, since max = 2 and max2 = 3, max2> max, and the variable SIDE is set to 1.

Subsequently, the CPU 56

[0064]

(Equation 7)

Is calculated, and the position coordinates closest to the calculated DIFF are read out from the position coordinate table 58a stored in the ROM 58, and set as OFFSET.
Subsequently, the CPU 56

[0066]

(Equation 8)

Is calculated to obtain an X coordinate X1. here,
(P1 / 2) × max is the X of the center of the coil number max.
Indicates coordinates. In the example shown in FIG.
(P1 / 2) × 2 + (e2-e3) × 1 and the position Q
The X coordinate of the X-axis is + from the center line C2 of the X coil X2.
A distance corresponding to (e2-e3) in the direction, for example, ΔX2
The coordinates are far apart.

Then, the CPU 56 scans each Y coil (S310), and stores the voltage value detected from each Y coil in the voltage value storage area for the Y coil of the RAM 59 (S312). Subsequently, the CPU 56 proceeds to S30.
The Y coordinate of the pen 60 is calculated using the same method as the calculation of the X coordinate in 8 (S314). [Determination of Pen Attribute] Next, the electrical configuration and control for the CPU 56 to determine the pen attribute will be described with reference to FIGS.

FIG. 13 is an explanatory diagram showing an electrical configuration of the FSK demodulation circuit 55 (FIG. 9), and FIG. 14 is an FSK demodulation circuit 55 shown in FIG.
FIG. 9 is an explanatory diagram showing signal waveforms appearing at various parts of the SK demodulation circuit 55. FIG. 15A shows an output signal of a CR oscillation circuit 69e (hereinafter, referred to as a CR signal) and an LC oscillation circuit 69c.
FIG. 14 is an explanatory diagram showing a relationship between an output signal (hereinafter, referred to as a carrier signal), an output signal of a limiter circuit (hereinafter, referred to as a limiter output signal), and a count value of a count circuit 55a (FIG. 13). FIG. 15B is an explanatory diagram showing how the count value stored in the shift register 55b (FIG. 13) shifts.

FIG. 17 is a flowchart showing the flow of processing (pen attribute detection processing 1) from the count circuit 55a to the comparator 55f constituting the FSK demodulation circuit 55. FIG. 18 is a flowchart showing the processing of the counter 55g (pen attribute detection processing 2). 3) is a flow chart showing the flow of FIG.

The carrier signal shown in FIG. 15A has, for example, a center frequency of 405 kHz as described above.
And the frequency shift is ± 15 kHz, but in FIG. 15A, the frequency shift is exaggerated for the sake of easy understanding. First, features of the FSK demodulation circuit 55 for detecting pen attributes will be described with reference to FIG.

In the example shown in FIG. 15A, the carrier signal is modulated to a high frequency (eg, 420 kHz) during the low level of the CR signal, and is modulated to a low frequency (eg, 390 kHz) during the high level. Have been.
Therefore, assuming that the period of the limiter output signal while the CR signal is at a low level is TB, the period of the limiter output signal while the CR signal is at a high level is TC longer than TB.

Therefore, the count value k of one cycle of the limiter output signal by the count circuit 55a increases when the CR signal changes from low level to high level,
Decreases when changing from high level to low level.
That is, by detecting the timing at which the count value k by the count circuit 55a changes, the timing of the change (rising or falling timing) of the CR signal can be detected. Since the time from the change of the count value k to the next change corresponds to a half cycle of the CR signal, if one cycle of the change time of the count value k is measured, the cycle of the CR signal can be obtained. Can be obtained, so that the pen attribute can be detected.

Here, the operation of each component of the FSK demodulation circuit 55 will be briefly described. The count circuit 55a measures the count value k, shift register 55b, first weighted average circuit 55c, and second weighted average circuit 55d. , Subtractor 55e
The comparator 55f detects a change timing of the count value k, and the counter 55g measures a cycle in which the count value k changes. Then, the CPU 56 sets the counter 5
The pen attribute is determined based on the added value output from 5g (S318).

Next, the operation of the FSK demodulation circuit 55 will be described in detail. The signal output from the bandpass filter 50d is converted by the limiter circuit 54 into a square wave limiter output signal shown in FIG.
5 is output. Then, the FSK demodulation circuit 55 detects a change (rising) of the limiter output signal (FIG. 17).
S10: Yes), the counting of the cycle of the limiter output signal is started using the system clock (CLK) (S1).
2) When the next change (rising) of the limiter output signal is detected (S14: Yes), the count value k is output to the shift register 55b (S16), and the count value k is reset (S18).

That is, the count circuit 55a measures the length TB or TC of one cycle of the limiter output signal. In this embodiment, the shift register 55b has the structure shown in FIG.
As shown in (5), the count value k for one cycle of the limiter output signal is stored for five cycles of k1 to k5, and the oldest count value k is discarded every time the newest count value k is fetched, and each count value k is Shift one by one.

The first weighted averaging circuit 55c calculates a value of 2 from the latest count value stored in the shift register 55b.
A weighted average value up to a new count value is calculated first, and the weighted average value (hereinafter, referred to as a first weighted average value) is output to the subtractor 55e. The second weighted average circuit 55d
Calculates the weighted average value from the oldest count value stored in the shift register 55b to the second oldest count value, and outputs the weighted average value (hereinafter, referred to as a second weighted average value) to the subtractor 55e. Output.

As described above, since the count values counted in time apart are weighted and averaged by the weighted averaging circuit, even if a certain count value is affected by noise, the influence can be reduced. The subtractor 55e calculates a difference Δm between the first weighted average value and the second weighted average value, and outputs the difference Δm to the comparator 55f (S2 in FIG. 17).
0).

For example, in FIG. 15A, a first weighted average circuit 55c calculates a weighted average value of count values k4 to k5, and a second weighted average circuit 55d calculates count values k1 to k1.
When the weighted average value of k2 is calculated, since the count values k4 and k5 are obtained by counting the period TC longer than the period TB of the limiter output signal, the first weighted average value is larger than the second weighted average value. Become.

Therefore, if it is detected that the first weighted average value is larger than the second weighted average value, it is possible to detect a change point of the period of the CR signal. Incidentally, a change point of the period of the CR signal can be similarly detected by using a sum instead of the average value. That is, if the period of the change point of the period of the CR signal is detected, the period of the CR signal can be detected, so that the attribute information of the pen 60 can be recognized.

The first weighted average circuit 55c and the second
The weighted averaging circuit 55d outputs the carrier frequency (LC
The determination is made based on the ratio between the oscillation frequency of the oscillation circuit 69c) and the modulation frequency, and the complexity of the circuit. The count value held by the shift register 55b, that is, the number of periods of the limiter output signal is determined by the ratio of the system clock frequency to the frequency of the carrier wave, and the system clock frequency is set to a value that can sufficiently discriminate the change in the frequency. I do.

The comparator 55f calculates the difference Δm [Δm =
(First weighted average value) − (second weighted average value)] and a preset threshold value m1 to determine whether or not the difference Δm is equal to or greater than the threshold value m1 (FIG. 17 S22),
If it is determined that the difference Δm is equal to or larger than the threshold value m1 (S2
2: Yes), the threshold determination output is changed from low level to high level (S24).

That is, it is determined that the cycle of the limiter output signal has changed (the rising edge of the CR signal has been detected). For example, the count value of the shorter cycle TB of the limiter signal shown in FIG. 15A by the count circuit 55a is 39, the count value of the cycle TC is 42, and the threshold value m1 is 2
Then, since the count values k1 to k3 are all 39, the second weighted average value = (k1 + k2) / 2 = 39. Further, since both the count values k4 and k5 are 42, the first weighted average value = (k4 + k5) / 2 = 42, and the difference Δm = 42−39 = 3.

Therefore, since (difference Δm = 3)> (threshold value m1 = 2), the threshold value judgment output changes from low level to high level (S24). This high level state is maintained until the comparator 55f determines that the absolute value of the difference Δm is equal to or larger than the threshold value m1.

When the operation range of the first weighted averaging circuit 55c and the second weighted averaging circuit 55d reaches a portion passing through the edge of the CR signal, the period of the limiter output signal becomes constant. Calculate the weighted average value of the count values of the same period, the subtraction value by the subtractor 55e becomes 0, and the threshold value judgment output remains in the high level state.

On the other hand, when the counter 55g detects that the threshold value judgment output has changed from the low level to the high level (S30 in FIG. 18: Yes), the time during which the judgment output is at the high level, that is, the judgment output Is counted using the system clock (CLK) (S3).
2).

The comparator 55f again determines the difference Δm
Is greater than or equal to the threshold value m1 (S2 in FIG. 17).
2: Yes), the threshold determination output is changed from the high level to the low level (S24). That is, it is determined that the period of the limiter output signal has changed (the falling edge of the CR signal has been detected).

As a result, the counter 55g detects that the threshold value judgment output has changed from the high level to the low level (S34: Yes), and outputs the count value to the CPU 56 (S36). Subsequently, the counter 55g resets the count value (S38), counts the time during which the threshold determination output is at the low level, that is, the next one cycle of the threshold determination output, and outputs it to the CPU 56 again ( S
32).

Then, the CPU 56 reads the count value.
(S316 in FIG. 12), based on the read count value.
Then, the pen attribute is determined (S318). In particular,
The count value is ideally the count value shown in FIG.
Value Cnorm₁~ Cnorm₆One of the values
However, in actuality, errors are included.
Und value Cnorm_pCount value for any of
Cmin_p~ Cmax _pIf the value falls within the range of
Und value Cnorm_pJudge pen attributes as having obtained
I do. For example, when the count value is in the range of 980 to 1173,
If it is within the box, the pen whose count value should be 1077
Attribute, and the pen attribute is, as shown in FIG.
It is determined to be "Black Pen". Also, CP
U56 associates the pen attributes with the XY coordinates in the RAM 5
9 is stored. Writing data stored in this way
Is output, for example, to the printer 200 (FIG. 2),
Printed. In addition, the data is output to the PC 100 and the monitor 11
0 (FIG. 2) is displayed in black.

That is, the writing data can be reproduced according to the attribute of the pen 60. Here, as shown in FIG.
The frequency switching timing of the carrier signal by the CR signal may be k2 <k3 <k4. At this time, k3
And k4 become very close values, then (k3 + k4)-(k
0 + k1) exceeds the threshold value m1, and (k4 + k5) −
Before (k1 + k2) is obtained, the threshold output changes and an error occurs. The modulation period is set based on the above equation 5 so that erroneous detection due to this error does not occur.

Returning now to the description of FIG.
56 is a page return button 33, a page forward button 34
When the erase button 35 is pressed, page processing such as returning, sending, or erasing the stored handwritten data in page units is performed (S400). Furthermore, CP
U56 includes various buttons provided on the operation unit 30 (FIG. 1)
The switching signal generated by the operation of I / F circuit 5
7 (FIG. 9), the page storing the position coordinate data stored in the RAM 59 is sent or returned in page units, or page processing such as erasing the position coordinate data in page units is executed. (S40
0). Further, the CPU 56 executes a data output process of converting the position coordinate data of the target page from the position coordinate data stored in the RAM 59 into an appropriate format and outputting the converted data to the PC 100 or the printer 200 (FIG. 2) ( S500).

Further, the CPU 56 operates the audio circuit 31a based on a switching signal generated when various buttons are pressed, and generates an operation sound such as "P" or "P" from the speaker 31. Is executed (S600). Further, the CPU 56 calculates the wiping locus of the eraser 40 based on the voltage generated in the X coil and the Y coil by the alternating magnetic field generated from the coil built in the eraser 40, and stores the calculated position coordinate data in the wiping locus in the RAM 59. An eraser process for deleting from (FIG. 9) is executed (S700).

As described above, the electronic blackboard 1 of the first embodiment
Is used, the pen signal is transmitted from the pen 60 to the writing panel main body 20 at a cycle corresponding to the attribute of the pen 60, and the C signal is transmitted.
Since the attribute of the pen 60 can be recognized by measuring one cycle of the R signal, it is more necessary to recognize the attribute of the pen 60 than to transmit a code string in a plurality of cycles as in the related art. Time can be reduced.

For example, when the modulation frequency of the CR oscillation circuit 69e is 5 kHz, one cycle of the CR signal, that is, the time required for recognizing the pen attribute is at least 1/5, 0
00 = 200 (μs). Further, in the conventional coordinate reading apparatus shown in FIG.
kHz, 20 to transmit one bit.
0 (μs) is required, and since a total of 10 bits are transmitted, the time required to transmit the code string indicating the pen attribute is 2
00 (μs) × 10 = 2,000 (μs).

That is, if the electronic whiteboard 1 of the first embodiment is used, the time required for recognizing the pen attribute can be reduced to 200 / 2,000 = 1/10 of the related art. Further, since the pen attribute can be recognized based on the measurement result of the period of the CR signal, it is not necessary to synchronize the operation clock on the pen side and the operation clock on the coordinate input sheet side as in the related art. Since it is not necessary to provide a frequency divider or the like that generates, the circuit configuration of the pen 60 can be simplified.

Further, since the CR signal can be repeatedly transmitted in a single cycle, even if the CR signal is scanned in the middle of one cycle, the next one cycle is measured.
Because pen attributes can be recognized, as in the past,
Since it is not necessary to wait until the next start bit is transmitted and receive a plurality of cycles from the start bit to the stop bit, it is possible to reduce the time required for pen attribute recognition.

Further, since the carrier wave by the LC oscillation circuit 69c is frequency-modulated by the CR signal, even if the amplitude of the carrier wave changes, the period of the CR signal does not change. The pen attributes do not change. For example, even when the voltage of the battery 70 built in the pen 60 decreases and the intensity of the alternating magnetic field generated from the coil L1 decreases, the attribute information of the pen 60 can be transmitted accurately.

In the first embodiment, six types of pen attributes (four types of pen colors and two types of pen attributes) are used as pen attributes.
Type of eraser size), but it goes without saying that other pen attributes may be set. For example, several types of thicknesses may be set with a pen of the same color, or more types may be set. A color may be set. Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG.

The electronic blackboard of the second embodiment scans every other X coil and every Y coil,
XY coordinates can be read at high speed. FIG. 19 is a flowchart showing the flow of the coordinate reading process executed by the CPU 56 provided in the electronic whiteboard of the second embodiment. In the second embodiment, the processes executed by the CPU 56 other than the coordinate reading process and other configurations are the same as those of the electronic blackboard of the first embodiment described above. Only the flow of the reading process will be described. Further, the same reference numerals are used for the same configuration as the electronic blackboard of the first embodiment.

The CPU 56 scans every other X coil (S330), and detects the pen 60 (S33).
2: Yes), the voltage values of the respective X coils are sequentially stored in the voltage value storage area 59a of the RAM 59 (S334).
Subsequently, the CPU 56 sets the maximum voltage value emax among the voltage values e1 to em stored in the voltage value storage area 59a.
Is detected (S336), and the X coils (Xi-1) and (Xi +) on both sides of the X coil Xi are detected.
1) is scanned (S338).

That is, since every other X coil is scanned, the X coil (Xi−
Since one of 1) and (Xi + 1) may have a higher voltage value than the X coil Xi, the X coils (Xi-1) and (Xi + 1) on both sides of the X coil Xi are scanned.

Subsequently, the CPU 56 sets the X coil (Xi-
1), the X coil having the maximum voltage among the three X coils of Xi and (Xi + 1) is obtained, and the coil number (hereinafter referred to as max) of the X coil is stored in the RAM 59 (S
340). Subsequently, the CPU 56 selects the larger one of the voltage values of the X coils on both sides of the max, and stores the coil number (hereinafter, referred to as max2) of the X coil that generated the selected voltage value in the RAM 59.

Subsequently, the CPU 56 compares the coil numbers max and max2 stored in the RAM 59 to determine whether the coil number max2 exists in the + direction or the − direction of the X axis from the coil number max. If max2 ≧ max, the variable SIDE is set to 1
And if max2 <max, the variable SID
Set E to -1.

Subsequently, the CPU 56 calculates DIFF using Expression 7 described in the first embodiment, reads the position coordinates closest to the calculated DIFF from the position coordinate table 58a stored in the ROM 58, and Is OFFSET. Subsequently, the CPU 56 calculates the expression 8
Is used to determine the X coordinate X1.

Then, the CPU 56 scans every other Y coil, and calculates the Y coordinate Y1 by the same method (S332 to S344) as the X coordinate calculation described above. For example, in the case where there are 22 X coils, if every other X coil is scanned, the number of scans in S330 is 22/2 = 11, and the number of scans in S338 is 2, so the total number of scans is Is 11 times + 2 times = 13 times.

Therefore, since 13 scans can be performed instead of 22 scans, 9 scans (= 22 scans−13 scans) are performed.
Times) scan time can be reduced. As described above, when the electronic blackboard of the second embodiment is used, the time required for recognizing pen attributes can be reduced, and the scan time of the sense coil 23 can be reduced, so that the speed can be further increased. Can be realized.

Furthermore, in each of the above-described embodiments, the case where the communication system according to the present invention is applied to an electronic blackboard has been described as an example. However, for example, the communication system can be applied to a security device. For example, a pen 60 may be attached to the output of a sensor attached to a monitoring location such as an entrance or a window of a building.
A transmitting device having the same function as that described above is installed, and a receiving device is provided in a management room or the like. In this case, the CR provided in the transmitting device
The cycle of the oscillation circuit is set to a different cycle for each sensor. Then, when a certain sensor is turned on, a transmitting device connected to the sensor operates to transmit a signal to the receiving device. Subsequently, the receiving device demodulates the transmitted signal by the demodulation means described in each of the above-described embodiments, and identifies which sensor has transmitted the signal.

Therefore, since the sensors can be identified only by slightly changing the period of the CR oscillation circuit, a very large number of sensors can be mounted. Note that the pen 60 corresponds to the writing means of the present invention, and
Corresponds to a conductor, and the mounting panel 24 corresponds to a coordinate input sheet. Further, the electrical configuration of the pen 60 shown in FIG. 8B functions as a transmitting unit of the present invention, and the electrical configuration of the electronic whiteboard 1 shown in FIG. 9 functions as a receiving unit.

[Brief description of the drawings]

FIG. 1 is an external perspective explanatory view showing a main configuration of an electronic blackboard according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a state where a PC and a printer are connected to the electronic whiteboard shown in FIG. 1;

FIG. 3 is an explanatory diagram showing a block diagram of a network configuration when data communication is performed between the electronic whiteboard 1 and another electronic whiteboard 1;

FIG. 4 is an explanatory view showing each component of the writing panel main body 20;

5 (A) is an explanatory view showing a configuration of the sense coil 23 shown in FIG. 5 with a part thereof omitted, and FIG. 5 (B) is a width of the sense coil 23 shown in FIG. 5 (A). It is explanatory drawing which shows an overlap pitch.

6 (A) is an explanatory view showing a part of X coils X1 to X3, and FIG. 6 (B) is a diagram showing voltages and width directions generated in X coils X1 to X3 shown in FIG. 6 (A). 6 (C) is a graph showing a voltage difference between mutually adjacent sense coils of the X coils X1 to X3 shown in FIG. 6 (A).

7A is an explanatory diagram showing a position coordinate table as a graph, FIG. 7B is an explanatory diagram of the position coordinate table, and FIG. 7C is a diagram illustrating the position coordinate table detected from each X coil. FIG. 4 is an explanatory diagram showing a storage state of a voltage value.

8A is an explanatory diagram showing an internal structure of a pen 60, and FIG. 8B is an explanatory diagram showing an electrical configuration of the pen 60 shown in FIG. 8A.

FIG. 9 is an explanatory diagram showing the electrical configuration of the electronic blackboard 1 by blocks.

10A is an explanatory diagram illustrating a relationship between an attribute of a pen 60 and a modulation frequency fm, and FIG. 10B is a diagram illustrating FIG.
FIG. 4 is an explanatory diagram showing signals at points A, B, and C in FIG.

11 is a flowchart showing main control contents executed by a CPU 56 shown in FIG.

FIG. 12 is a flowchart illustrating a flow of a coordinate reading process according to the first embodiment.

13 is an explanatory diagram illustrating an electrical configuration of an FSK demodulation circuit 55 (FIG. 9).

FIG. 14 is an explanatory diagram showing signal waveforms appearing at various parts of the FSK demodulation circuit 55.

FIG. 15A shows a CR signal, a carrier signal, a limiter output signal, and a count circuit 55a (FIG. 1).
FIG. 15B is an explanatory diagram showing the relationship with the count value according to 3), and FIG. 15B is an explanatory diagram showing how the count value stored in the shift register 55b (FIG. 13) shifts.

FIG. 16 shows a relationship between a CR signal, a carrier signal, a limiter output signal, and a count value, where the count value is k2 <k.
FIG. 9 is an explanatory diagram showing a case where 3 <k4.

FIG. 17 is a flowchart showing a flow of processing (pen attribute detection processing) from a count circuit 55a to a comparator 55f included in the FSK demodulation circuit 55.

FIG. 18 is a flowchart illustrating a flow of processing of a counter 55g.

FIG. 19 is a flowchart illustrating a flow of a coordinate reading process according to the second embodiment.

FIG. 20A is an explanatory diagram showing a configuration of a conventional coordinate reading device, and FIG. 20B is an explanatory diagram showing a code string transmitted from a pen.

[Explanation of symbols]

1 ... electronic blackboard, 10 ... writing panel, 11 ...
Frame, 12 ... stand, 14 ... battery case,
Reference numeral 20: writing panel body, 21: writing sheet, 2
2 Panel, 23 Sense coil, 24
Mounting panel, 25: back panel, 30: operation unit, 31: speaker, 32: page number display LE
D, 33 ... Page return button, 34 ... Page forward button, 35 ... Delete button, 36 ... Printer output button, 37 ... PC output button, 38 ... Power button, 39 ..LED for battery exhaustion notification, 40 ..
.Eraser, 50 ... Control device, 50a ... X coil switching circuit, 50b ... Y coil switching circuit, 50
c: amplifier, 50d: band-pass filter, 5
1 ... amplitude detection circuit, 52 ... A / D conversion circuit, 5
3 ... I / O circuit, 54 ... Limiter circuit, 55
..FSK demodulation circuits, 55a ... count circuits, 55
b: shift register, 55c: first weighted average circuit, 55d: second weighted average circuit, 55e: subtractor, 55f: comparator, 55g: counter, 56 ... CPU, 57 ... I / F circuit, 58
..ROM, 58a... Position coordinate table, 59 ..
RAM, 59a: voltage value storage area, 60:
Pen, 61a ... body part, 62 ... pen point, 63
..Ink cartridges, 67, switches, 69
..Circuit board, 69c ... LC oscillator circuit, 69d
・ FSK circuit, 69e ・ ・ ・ CR oscillation circuit, 70 ・ ・ ・
battery.

Claims (4)

[Claims] 1. N different types of modulation periods Tm _{1 to} Tm associated with n types of information (where n is an integer satisfying n ≧ 2).
_mn are selected in advance, and the signal is a signal in which two values are alternately switched, and the period from when the two values are switched from one to the other until it is switched from one to the other again is the n kinds of modulation periods Tm _{1 to} Tm. _The carrier is frequency-modulated by a signal selected from _n , and the carrier periods T ₁ and T ₂ corresponding to the binary values.
Transmitting means for transmitting a signal is switched, to receive a signal transmitted by said transmitting means, said detecting a modulation period Tm ₁ to Tm _n demodulates the received signal, the modulation period Tm ₁ that the detected based on the ~Tm _n,
It is provided with a receiving means for recognizing information indicated by the transmitted signal, for the modulation period Tm ₁ to Tm _n, the modulation period T
communication system m ₁ is arbitrarily selected, wherein the modulation period Tm _n are selected based on Equation 1 below. (Equation 1) (However, T _x is the modulation period Tm ₁ to Tm _n, when detecting an interval change point from T ₁ to T ₂ are detected at intervals of changing point from T _1, T ₂ to T ₁ In case T ₂ ) 2. N kinds of different modulation periods Tm _{1 to} Tm associated with n kinds of information (where n is an integer satisfying n ≧ 2).
_mn are selected in advance, and the signal is a signal in which two values are alternately switched, and the period from when the two values are switched from one to the other until it is switched from one to the other again is the n kinds of modulation periods Tm _{1 to} Tm. _The carrier is frequency-modulated by a signal selected from _n , and the carrier periods T ₁ and T ₂ corresponding to the binary values.
Transmitting means for transmitting a signal is switched, to receive a signal transmitted by said transmitting means, said detecting a modulation period Tm ₁ to Tm _n demodulates the received signal, the modulation period Tm ₁ that the detected based on the ~Tm _n,
Be provided with a receiving means for recognizing information indicated by the transmitted signal, the modulation period Tm ₁ to Tm _n is as ± df% modulation frequency margin, (1-df / 100) · Tm p ~ (1
+ Df / 100) · Tm _p (where p is an integer of 1 to n)
The modulation period Tm _{1 to} Tm _n may be varied within the range of
communication system m ₁ is arbitrarily selected, wherein the modulation period Tm _n are selected based on Equation 2 below. (Equation 2) (However, T _x is the modulation period Tm ₁ to Tm _n, when detecting an interval change point from T ₁ to T ₂ are detected at intervals of changing point from T _1, T ₂ to T ₁ In case T ₂ ) 3. A signal generator comprising: a main body having a coordinate input sheet in which a plurality of conductors magnetically coupleable with an alternating magnetic field are laid below a writing surface; and a writing means for generating the alternating magnetic field; A coordinate reading device that reads the position coordinates of the writing means on the writing surface based on the n types of n different (n is an integer satisfying n ≧ 2) attribute information that the writing means has modulation period Tm ₁ to Tm _n are preselected, said writing means, switching a coil for generating an alternating magnetic field having a predetermined period, the binary a signal binary switches alternately from one to the other The period from switching from one to the other again is the n types of modulation periods Tm _{1 to} Tm.
transmitting means for frequency-modulating an alternating magnetic field generated from the coil by a signal selected from _n , and transmitting a signal in which carrier periods T ₁ and T ₂ are switched in accordance with the binary value. and, the body demodulates the signal generated in the conductor by detecting the modulation period Tm ₁ to Tm _n, based on the detected modulation period Tm ₁ to Tm _n, transmitted from said writing means a receiving means for recognizing attribute information indicated by the signal, for the modulation period Tm ₁ to Tm _n, the modulation period T
m ₁ is arbitrarily selected, the coordinate reading device, characterized in that the modulation period Tm _n are selected based on the following equation 3. (Equation 3) (However, T _x is the modulation period Tm ₁ to Tm _n, when detecting an interval change point from T ₁ to T ₂ are detected at intervals of changing point from T _1, T ₂ to T ₁ In case T ₂ ) 4. A signal generator comprising: a main body having a coordinate input sheet in which a plurality of conductors magnetically coupleable with an alternating magnetic field are laid below a writing surface; and writing means for generating the alternating magnetic field; A coordinate reading device that reads the position coordinates of the writing means on the writing surface based on the n types of n different (n is an integer satisfying n ≧ 2) attribute information that the writing means has modulation period Tm ₁ to Tm _n are preselected, said writing means, switching a coil for generating an alternating magnetic field having a predetermined period, the binary a signal binary switches alternately from one to the other The period from switching from one to the other again is the n types of modulation periods Tm _{1 to} Tm.
transmitting means for frequency-modulating an alternating magnetic field generated from the coil by a signal selected from _n , and transmitting a signal in which carrier periods T ₁ and T ₂ are switched in accordance with the binary value. and, the body demodulates the signal generated in the conductor by detecting the modulation period Tm ₁ to Tm _n, based on the detected modulation period Tm ₁ to Tm _n, transmitted from said writing means a receiving means for recognizing attribute information indicated by the signal, the modulation period Tm ₁ to Tm _n is as ± df% modulation frequency margin, (1-df / 100) · Tm p ~ (1
+ Df / 100) · Tm _p (where p is an integer of 1 to n)
The modulation period Tm _{1 to} Tm _n may be varied within the range of
communication system m ₁ is arbitrarily selected, wherein the modulation period Tm _n are selected on the basis of the following equation 4. (Equation 4) (However, T _x is the modulation period Tm ₁ to Tm _n, when detecting an interval change point from T ₁ to T ₂ are detected at intervals of changing point from T _1, T ₂ to T ₁ T _{2 in the} case)