JPH0535396A - Wireless coordinate reader - Google Patents

Abstract

PURPOSE:To exactly detect the state of the switch in a coordinate indicator in a wireless coordinate reader which detects the switch state from the phase of an induction signal. CONSTITUTION:When a coordinate indicator 10 is placed on a sense line plate 1, and an alternating current signal is added to an exiting line group 2, an induction signal (is) is generated at a sense line group 3. The coordinate indicator 10 has a resonance circuit which resonates to the alternating current, and a resonance frequency is changed by operating a control circuit. A phase detecting circuit 8 inputs the induction signal (is), and detects a phase signal (ps). A control circuit 9 inputs the phase signal (ps), and detects the switch state by comparing it with a stored learning phase value. Moreover, when a learning area on the sense plate 1 is indicated, the new learning phase value is searched from the phase signal (ps) and the learning phase value, and stored.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate reader for inputting coordinates to an external device such as a computer, and more particularly to a wireless coordinate reader which does not require a signal line to connect between the main body of the coordinate reader and the coordinate indicator. The present invention relates to a technique for detecting the state of a switch provided in a coordinate indicator in a device.

[0002]

2. Description of the Related Art There is known a wireless coordinate reader for generating an alternating magnetic field from a sense line plate, coupling the coordinate indicator with the alternating magnetic field, and detecting an inductive signal by the sense line plate to obtain a coordinate value. In this type of coordinate reading device, a switch or the like is provided on the coordinate indicator, and the resonance frequency is changed by operating the switch to detect the state of the switch from the phase of the induction signal induced to the sense line plate. The coordinate reading device can be configured as follows.

In order to change the resonance frequency of the coordinate indicator, a series circuit of a switch 907 and a second capacitor 908 is connected in parallel with a resonance circuit of a coil 905 and a first capacitor 906 as shown in FIG. It can be realized. The coordinate indicator is configured as described above, the excitation line 902 and the sense line 903 are arranged orthogonally to form the sense line plate 901, and an AC signal is applied to the excitation line 902 as an excitation signal to induce on the sense line 903. Observe the induced signal.

The coordinate indicator 904 is attached to the sense line plate 901.
The switch 907 is put on and turned on / off. When the switch 907 is off, the induction signal and the excitation signal have a constant phase difference due to the effect of electromagnetic coupling and the characteristics of the circuit. When the switch 907 is turned on, the second capacitor 908 is connected in parallel to the resonance circuit, so that the resonance frequency changes to the lower side and the phase of the induction signal is delayed as compared with the case where it is off. The state of the switch can be determined by detecting this phase delay.

Specifically, the induction signal and the excitation signal are input to a phase detection circuit, the phase delay is converted into a voltage value, and this value is input to a microprocessor or the like, and compared with a threshold value. The switch status is being determined.

[0006]

As described above, the phase information of the inductive signal is used to detect the switch. However, in a circuit system having such a resonance circuit, it is difficult to strictly manage the phase. It's not that easy. For example, in the coordinate indicator, it is necessary to adjust the resonance frequency to a constant value, and therefore it is common to adjust the resonance circuit by providing a trimmer capacitor. However, the adjustment involves variations, and it is impossible to make all the coordinate indicators have the same characteristics. Further, even if the characteristics are adjusted to be the same at a certain point in time, the characteristics may gradually change during use.

Another cause of the fluctuation of the phase is the fluctuation of the phase characteristic due to the temperature of the coordinate indicator and the main body of the coordinate reading device. This variation is also quite large and cannot be ignored in the operating temperature range, for example, in the range of 5 ° C to 35 ° C. When the resonance frequency of the coordinate indicator or the phase characteristic of the circuit fluctuates, the phase of the induction signal also fluctuates, and the phase when the switch of the coordinate indicator is operated also differs, resulting in the problem that the switch is erroneously detected.

The present invention has been made to solve the above-mentioned problems in the prior art. Its main purpose is a wireless coordinate reader that does not require a signal line connection between the main body of the coordinate reader and the coordinate indicator,
It is an object of the present invention to realize a wireless coordinate reading device capable of accurately detecting the on / off state of a switch provided in a coordinate indicator.

More specifically, when the phase characteristic of the coordinate indicator or the main body of the coordinate reading device changes, the wireless coordinate reading device can accurately detect the state of the switch by learning the phase characteristic. Is to be realized.

[0010]

In order to solve the above-mentioned problems, the present invention provides a resonance circuit including a coil and a capacitor,
A coordinate indicator, which is configured to change the resonance frequency by operating the operating circuit without connecting the operating circuit, generates an alternating magnetic field and is coupled with the coordinate indicator by the alternating magnetic field to generate an induction signal. By detecting the sense line plate, the phase detection circuit that detects the phase signal of the induction signal based on the phase of the AC magnetic field, and inputting the phase signal and comparing the stored learning phase value with the phase signal. When the operation state of the operation circuit of the coordinate indicator is obtained and the coordinate indicator indicates a specific area set on the sense line plate, the phase signal is input, and this phase signal and the learned phase value stored A new learning phase value is obtained from the above, and a control circuit configured to store the learning phase value is provided to configure the wireless coordinate reading device.

[0011]

In the coordinate reading device thus constructed, when the coordinate indicator is placed on the sense line plate, an induction signal is generated on the sense line plate. When the operation circuit of the coordinate indicator is operated, the resonance frequency of the resonance circuit changes, so that the phase of the inductive signal changes with the operation.

The induction signal induced in the sense line plate is input to the phase detection circuit and detected as a phase signal. The control circuit inputs this phase signal and compares it with the learned phase value stored in itself to determine the operation state. On the other hand, even when a specific area set on the sense line is indicated by the coordinate indicator and the operation circuit of the coordinate indicator is operated to maintain the state, the sense line plate has a phase corresponding to the operation state. An induction signal is generated.

This inductive signal is input to the phase detection circuit in the same manner as described above, and the phase signal is detected. The control circuit calculates a new learning phase value by calculating this phase signal and the learning phase value stored therein, and stores it again.
This learned phase value is used to determine the operation state of the coordinate indicator as described above. In this way, the phase characteristics of the coordinate indicator and the main body of the coordinate reading device in the operated state are learned, so that the switch can be accurately identified even if those phase characteristics change.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS.
It will be explained based on. First, the configuration will be described. Figure 1
In the figure, 1 is a sense line plate, and an excitation line group 2
And the sense line group 3 is laid. Excitation line group 2
And the sense line group 3 form a folded loop, and they are arranged at equal intervals in the same group. In the first embodiment, the excitation line group 2 and the sense line group 3 are arranged orthogonal to each other.

As shown in FIG. 2, a learning area 20 is set in a part of the area of the sense line plate 1, and is identified by a control circuit 9 which will be described later. In the case of the present embodiment, the learning area is divided into areas according to the possible states of the switches provided in the coordinate indicator described later. The position of the learning area is arbitrary. An excitation scanning circuit 4 is connected to each excitation line of the excitation line group 2. The excitation scanning circuit 4 is composed of a plurality of electronic switching elements such as analog switches, and applies an excitation signal ds supplied from an excitation circuit 6 described later to one selected excitation line.

Reference numeral 5 is a sense scanning circuit, to which each sense line of the sense line group 3 is connected. Like the excitation scanning circuit 4, this circuit is also composed of electronic switch elements, and one of the sense lines is selected and connected to the amplification detection circuit 7 and the phase detection circuit 8 which will be described later. 6 is an exciting circuit. An excitation clock dc is input from a control circuit 9 described later, the waveform is shaped and amplified, and the excitation signal ds is input.
Output as.

Reference numeral 7 is an amplification detection circuit for amplifying and detecting the induction signal is induced in the sense line group 3 and outputting the amplitude signal as of the induction signal. 8 is the phase signal ps of the induction signal is
Is a phase detection circuit for detecting A detailed configuration diagram is shown in FIG. In FIG. 3, reference numeral 81 is an amplifier circuit, and 82 is a comparator. The induction signal is is input from the sense scanning circuit 5 to the amplifier circuit 81. The output of the comparator 82 is connected to one input of the exclusive OR circuit 83. The excitation clock dc is input to the other input of the exclusive OR circuit 83, and the output is connected to the integration circuit 84 including a resistor and a capacitor. In this circuit, the excitation clock dc is used as a reference phase signal, and the phase signal of the induction signal is is detected as a voltage signal charged in the integrating circuit 84.

The configuration of the phase detection circuit 8 shown in this embodiment is a circuit for detecting the phase difference of the induction signal is with respect to the excitation clock dc, and neither advance nor delay can be detected. However, as design choices, there is flexibility in how to take the reference signal for phase detection, circuit characteristics, etc., and depending on the design, the inductive signal shows the behavior of leading and lagging compared to the reference signal. Can also be considered. In such a case, a circuit for detecting the lead or lag of the phase may be provided. This circuit can be easily implemented.

The structure of the phase detection circuit is not essential to the present invention, and the point is that the circuit is only required to detect the phase difference between two signals, and is not limited to this circuit. Return to FIG. 1 again to continue the explanation. The control circuit 9 controls each unit, inputs each signal and performs an arithmetic operation, and obtains the coordinate value and the state of the switch. The excitation scanning circuit 4 is provided with a drive address dadrs which designates an excitation line to be selected, and the sense scanning circuit 5 is provided with a sense address sadrs which designates a sense line to be selected. Further, the amplitude signal as and the phase signal ps are input to calculate the coordinate value and the switch state. The control circuit 9 is realized by a microprocessor, and each arithmetic processing is performed by a program.

Reference numeral 10 is a coordinate indicator, and a circuit diagram of one embodiment is shown in FIG. In FIG. 4, the coil 11 and the first capacitor 12 form a resonance circuit. The resonance frequency of this resonance circuit is set around the frequency of the excitation clock dc. It does not necessarily have to match. Switch 13
a and the second capacitor 14a are connected in series to form one switch circuit. In this embodiment, a normally open switch is used as the switch 13. Although the details will be described later, this is for pushing the switch 13 to shift the resonance frequency. A plurality of switch circuits are connected in parallel and are connected in parallel to the resonance circuit. In addition,
The number of switches is a design choice.

The second capacitor of the switch circuit has a different value so that the amount of change in phase is different by pressing each switch. However, it goes without saying that the same value may be used when giving the same meaning to a plurality of switches. Further, by adopting an appropriate constant, it becomes possible to detect the state when a plurality of switches are simultaneously pressed.

Next, the operation will be described. The control circuit 9 controls the coordinate reading device, and performs the process of the flowchart shown in FIG. First, the operation of selecting the excitation line group 2 and the sense line group 3 will be described. Control circuit 9
Outputs the drive address dadrs and selects one of the excitation lines (step 1). As a result, the output of the exciting circuit 6 is connected to the selected exciting line, and this exciting line generates an alternating magnetic field. While the control circuit 9 is selecting one excitation line, the sense address sadr
s is output to sequentially select the sense line group 3 (step 2). The selected sense line is the amplification detection circuit 7
And is connected to the phase detection circuit 8.

In the flowchart of FIG. 5, the sense line group 3 is sequentially selected after the excitation line group 2 is determined, but this order may be reversed. In that case, the order of step 4 and step 5 in FIG. 5 is reversed. If the coordinate indicator 10 is not on the sense line plate 1, no signal is induced to the selected excitation line because the excitation line group 2 and the sense line group 3 are orthogonal to each other. When the coordinate indicator 10 is placed on the sense line plate 1, an induction signal is according to the positional relationship between the sense line plate 1 and the coordinate indicator 10 is induced in each sense line of the sense line group 3. This is the excitation line, coil 1
This is because of the effect of electromagnetic coupling between the three sense lines.

FIG. 6 shows the induction signal is as a scanning timing chart. The example shown in FIG. 6 shows a case where the excitation line group 2 shown in FIG. 1 is scanned from the upper part to the lower part of the drawing, and the sense line group 3 is scanned from the left to the right part of the drawing. In FIG. 1, the position p of the coil 11 is in the region where the excitation line d2 and the sense line s2 intersect. Now, when the excitation line d0 and the sense line s0 are selected, that is, when the intersecting region between them is far from the position p of the coil 11, the induction signal is is not observed. The induction signal is increases as the area where the excitation line and the sense line intersect approaches the position p of the coil, and becomes maximum when the excitation line d2 and the sense line s2 are selected. Thus, the induction signal is has a distribution as shown in the timing chart of FIG.

The induction signal is is converted into an amplitude signal as by the amplification detection circuit 7 and into a phase signal ps by the phase detection circuit 8. The operation of the phase detection circuit 8 will be described later. The magnitudes of these signals are read by the control circuit 9 (step 3). The input of the control circuit 9 is an A / D conversion circuit, and these signals are read as digital amounts.

The control circuit 9 repeats the above processing for a range in which an induction signal necessary for calculating coordinate information is obtained, for example, for five exciting lines and five sense lines (steps 4 and 5). This operation is called "scan". The scanning range is not limited to five. When one scan is completed, the control circuit 9 calculates the coordinate value.
Although the method of calculating the coordinates is not the main point of the present invention, a detailed description thereof will be omitted. Calculate the coordinate value of the position.

Next, the operation of the phase detection circuit 8 will be described. The control circuit 9 scans the sense line plate 1 as described above. Meanwhile, the induction signal is is input to the phase detection circuit 8 and converted into the phase signal ps. The operation of the phase detection circuit 8 will be described with reference to the timing chart of FIG. In the figure, dc is an excitation clock, ds is an excitation signal, and is is an induction signal. When no switch of the coordinate indicator 10 is pressed, the induction signal is is induced with a constant phase difference with respect to the excitation signal ds.

The process of processing the inductive signal is will be described. First, the induction signal is is transmitted to the amplification circuit 8 in the phase detection circuit 8.
The signal is amplified by 1, and further converted into a square wave by the comparator 82 to become the induced signal shaping wave ip. The induction signal shaping wave ip and the excitation clock dc are exclusive OR circuit 8
The phase detection is performed by 3 to obtain a detection signal pp. Further, the detection signal pp is converted into a DC signal by the integrating circuit 84 and becomes a phase signal ps.

When one of the switches of the coordinate indicator 10 is pressed, the capacitor connected in series with the pressed switch is connected in parallel with the resonance circuit. Therefore, the resonance frequency of the resonance circuit changes to the lower side. This change is the induction signal is
Affect the direction of delaying the phase of. In FIG.
The induction signal ish is obtained when one of the switches is pressed, and indicates that the phase is behind that of the induction signal is when the switch is not pressed. Similarly, this signal is converted by the phase detection circuit 8 into the induced signal shaping wave iph, the detection signal pph, and the phase signal psh. As is apparent from the operation of the circuit, the magnitude of the phase signal psh is larger than that of the phase signal ps, and it can be seen that a change in phase can be detected.

Next, the operation of determining the switch state and the operation of learning the phase will be described again with reference to the flowchart of FIG. The control circuit 9 selects the phase signal of the induction signal isp used to calculate the coordinate value, for example, as the switch detection phase signal from the phase signals ps of the induction signal input during the scanning (step 6). ) (Hereinafter, the sign of the switch detection phase signal is psw). At this time, the timing for selecting the switch detection phase signal psw is not limited to the case where the signal isp is generated, but the induction signal induced to the sense line having a specific positional relationship with the position where the coordinate indicator is placed. Should be adopted. However, considering S / N, it is preferable to adopt isp, which is the largest induction signal.

On the other hand, the control circuit 9 obtains the position where the coordinate indicator 10 is placed as the original function of the coordinate reading device. Then, based on the obtained coordinate values, it is determined whether or not the position is within the learning area 20 (step 7). Since this determination process is a simple comparison of the magnitudes of the numerical values, the description is omitted. If it is determined by this determination that the region is within the learning area 20, the process branches to step 9, and if not, the process branches to step 8.

Step 8 is a process for judging the switch state. This processing is performed by comparing the switch detection phase signal psw with a threshold value stored in the control circuit 9 itself. FIG. 8 shows a detailed flowchart of an example of the process of determining the switch state. This judgment is a simple numerical comparison. In the example of the processing shown in FIG. 8, there are three possible switch states, namely, switch off, switch 1 on, and switch 2 on.
Switch detection phase signal ps in each switch state
w is psw0 <psw1 <psw2. T
h10 indicates a threshold value for identifying the switch 1 and the switch-off state, and Th21 indicates a threshold value for identifying the switch 2 and the switch 1 state. In the following description, it is assumed that the switches can be in the above three states.

Consider, for example, a case where the switch 1 is now operated and the switch detection phase signal psw1 is observed. This value is first compared with the threshold Th21 in step 81. From the relationship of the above phase and the relationship with the threshold value, psw1 <Th21, and the determination at step 81 is no. Then, in step 82, the threshold value Th
Compared with 10. In this case, psw1> Th10, so the determination is yes, and the process branches to step 83 to determine that switch 1 is on.

The determination process described here is simplified for the purpose of explanation, and the number of switches to be determined,
The order of determination, the magnitude relationship of determination, and the like are not limited to this description. The process of determining the switch state from step 6 to step 8 has been described above, but the order of the steps is not essential and is not limited to this order. Only the learning region must be determined before the switch state is determined, and the context is defined for this. For example, after the learning region is determined (step 7), the switch detection phase signal is selected (step 6). Then, the same function is obtained even if the switch state determination (step 8) is performed in this order. The process flow can be designed with some degree of freedom.

Next, in step 7, the coordinate indicator 1
A process of determining the position designated by 0 within the learning region 20 and learning the phase in step 9 will be described. A detailed flowchart of an example of this processing is shown in FIG.
Shown in. First, the control circuit 9 identifies which area of the area associated with each switch in the learning area 20 the designated position is (step 91). Subsequently, the learning phase value for the switch state corresponding to the identified area is selected from its own storage device, and a new learning phase value is obtained by the following [Equation 1] together with the detected switch detection phase signal pswn.

[0036]

[Equation 1]

The process of updating the learning phase value is performed for a plurality of scans. The learning phase value calculation process (step 9) is called every time the process of the flowchart of FIG. 5 is repeated, and this process is performed for a predetermined number of times of learning. During this time, the determination in step 93 is no.
Therefore, step 94 is not performed. When the determined number of learning is completed, the determination in step 93 becomes yes,
Based on the learning phase value obtained by the above process, the threshold value is obtained by [Equation 2] (step 9).
4).

[0038]

[Equation 2]

[Equation 1] is to obtain a new learning phase value by taking the weighted average of the learning phase value obtained up to the previous scanning and the switch detection phase signal observed in the current scanning. I mean. The weighting coefficient w is a parameter that defines the speed at which the learning phase follows the observed phase, and is a value selected in consideration of the scanning speed, the phase fluctuation speed, and the like.

[Equation 2] means that an intermediate value of the learned phase values of the respective switches is obtained based on the learned phase value learned and used as the threshold value. Specifically, it is performed as follows. For example, assume that the state of the switch 1 is learned. The operator presses the switch 1 of the coordinate indicator 10 and "SW1 ON" in the learning area 20 shown in FIG.
The area indicated by is indicated and the state is retained.

During this time, the control circuit selects the switch detection phase signal psw1 for each scan in step 92 and performs the operation of the above [Formula 1] together with the stored learning phase value lpsw1 to obtain a new learning phase value lpsw1. Ask. This process is repeated as many times as necessary for learning. Then, after the learning is completed, in step 94, the threshold value is obtained based on the new learning phase value.

The "number of times required for learning" is a constant that can be determined by experiment, but may be an appropriate value if not extremely reduced. It is about a dozen or more times. In our company, the scanning cycle is 5 msec, and learning is performed in this cycle. Even if it is performed 100 times, the processing time is 0.
It is 1 sec and has no significant effect on operation. The above processing is performed for all switch states.

By the way, the timing of threshold calculation is
It is not limited to the case of the above description, so some explanation will be added. For example, step 93 may be omitted in the flowchart of FIG. 9, and the threshold value may be obtained each time learning is performed. But,
The threshold value need only be calculated based on the finally learned phase, so it does not make sense to calculate it during learning. The result is similar to the case where the flow of FIG. 9 is unchanged, but the flow of FIG. 9 is more rational in order to improve the processing speed of the entire coordinate reading device.

In order to further rationalize the processing, the threshold value may be obtained after learning of all switch states is completed. However, in this case, the operator has some operational restrictions. How to operate may be designed in consideration of ease of operation and the like. In the first embodiment, the learning area 20 is provided so as to be associated with each switch. However, the same function can be realized by setting this as one area and associating with each switch by time division. Another embodiment relating to this learning area will be briefly described below.

As shown in FIG. 10, the learning area 21 is set in the sense line plate 1 as one area. It is not divided as in the first embodiment. Although the entire operation of the control circuit 9 is the same as that of the flowchart of FIG. 5, the learning phase value calculation process (step 9) is different. Therefore, a schematic flowchart of an example of this process is shown in FIG. 11 and described.

The control circuit 9 sequentially learns about each switch state. The example shown in FIG. 11 shows that the switch-off state is first learned (step 95), and then the switch 1 state (step 96) and the switch 2 state (step 97) are learned in this order. ing. The learning in each switch state is performed for a plurality of scans as in the first embodiment. In order to carry out learning a plurality of times, a control process for that purpose is necessary.
Since the purpose of the flowchart is to conceptually show each switch state in time division, detailed flow is omitted. The level of explanation is different from that of the flowchart of the first embodiment shown in FIG.

In this way, the state of the switch to be learned is changed at the timing of the coordinate reader itself by time division. Therefore, since it is necessary to notify the operator of which state is currently being learned, some kind of display means is required. Also, some delay may be required because the operator must change the state of the switches during the learning period of each switch. These may be designed in consideration of ease of operation.

In the first and second embodiments of the learning area, the learning processing is performed in the same state as the normal switch detection processing, but the learning processing is performed under a specific mode. You may be allowed to do only. For example, a mode called "learning mode" is provided so that this mode can be entered only by a specific operation. Then, the processing described in the above embodiment is performed only in the learning mode. In order to enter the learning mode, for example, a mode changing area may be provided in a part of the reading area of the coordinate reading device, or a mechanical switch may be provided. As for this method, it is recommended to adopt an appropriate method in consideration of ease of use.

Since the present invention relates to a wireless coordinate reader for detecting the switch state of the coordinate indicator based on the phase of the guide signal, the principle of detecting the guide signal is the same as that of the coordinate reader described in the first embodiment. It is not limited. Also, the circuit of the coordinate indicator for changing the phase is not limited to the circuit described in the first embodiment.

FIG. 12 is a block diagram of the second embodiment relating to the main body of the coordinate reading device. In this configuration, the excitation line group 1
02 is not orthogonal to the sense line group 3 and is arranged in the same direction. Furthermore, both of them are partially overlapped. The other structure is similar to that of the first embodiment. In the sense line plate 101 configured in this way, when one exciting line is selected by the exciting circuit 4 and an exciting signal is given, and at the same time, one sense line overlapping with this exciting line is selected, this sense line is selected. Generates an induction signal due to electromagnetic coupling with the excitation line.

The difference from the first embodiment is that an induction signal is generated even if the coordinate indicator 10 is not on the sense line plate 101. However, when the coordinate indicator 10 is placed on the sense line plate 101, the coupling becomes stronger and a large inductive signal is generated. Therefore, the coordinate value can be obtained by observing the amplitude of the induction signal, and the phase signal can also be detected.

Since the induction signal is the sum of the signal coupled via the coil and the signal coupled directly to the excitation line, the phase signal has a value different from that of the first embodiment. However, while the phase of the signal directly coupled to the excitation line is constant, the phase of the signal coupled through the coil still changes depending on the state of the switch, so that the phase signal is changed from the phase signal as in the first embodiment. The switch status can be determined. The operation of determining the switch state and the operation of learning the phase are the same as in the first embodiment.

Although not shown in the figure, the same operation can be carried out in a coordinate reading device which intermittently performs excitation and detects a coordinate value and a switch state by an induction signal detected while the excitation is stopped. Various circuits are possible for the coordinate indicator circuit. 13 and 1
4 and 15 are circuit diagrams of second, third and fourth embodiments relating to the coordinate indicator.

In the coordinate indicator according to the second embodiment of FIG. 13, a resistor is connected in series with each switch circuit.
In the coordinate indicator according to the third embodiment of FIG. 14, one end of the series circuit of the switch and the resistor is commonly connected to the second capacitor, and this circuit is connected in parallel to the resonance circuit. Any circuit can be realized so as to have the same function as that of the first embodiment.

Although the coordinate indicator in the first embodiment uses the normally open switch, it can also be constructed by using the normally closed switch. Figure 1
FIG. 5 shows a circuit diagram of the fourth embodiment. The switches 413a, 413b, ... Of the circuit 410 of the coordinate indicator are all normally closed type switches. When none of these switches are pressed, each switch is closed and all second capacitors 414 are connected in parallel with the resonant circuit. In this state, the induction signal is
Induces with a constant phase difference with respect to the excitation signal ds.

When one of the switches is pressed, the second capacitor connected in series with the pressed switch is disconnected from the resonance circuit, and the resonance frequency of the resonance circuit changes to the higher side. This change affects the direction in which the phase of the induction signal is is advanced. The change in the advance of the phase is detected by the phase detection circuit 8, and the control circuit 9 determines the switch similarly to the operation described in the first embodiment.

It is also possible to combine a normally open switch and a normally closed switch so as to judge the switch in both the phase advance and delay regions.

[0058]

As described above, according to the present invention, a coordinate indicator whose resonance frequency is changed by operating a switch, and a sense line plate which is coupled with the coordinate indicator to detect an induction signal, A phase detection circuit configured to detect a phase of an induction signal induced on the sense line plate and a control circuit, and stored as a phase signal in a coordinate reading device that detects the switch state of the coordinate indicator from the phase signal of the induction signal. The learned phase value detected at this time and the stored learning phase are determined by comparing the learned phase value with the determined learning phase value and indicating the learning area provided on the sense line plate by the coordinate indicator. The control circuit is configured to obtain a new learning phase value from the value and store it.

Therefore, even if the phase characteristic of the coordinate indicator or the main body of the coordinate reading device changes, this characteristic can be learned, so that the threshold value for judging the switch state can be adjusted to the characteristic, and it is accurate. It was possible to realize a wireless coordinate reader capable of detecting the state of the switch.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of a wireless coordinate reading device according to the present invention.

FIG. 2 is an explanatory diagram of an embodiment of a learning area used in the wireless coordinate reading device according to the present invention.

FIG. 3 is a configuration diagram of a phase detection circuit in the first embodiment.

FIG. 4 is a circuit diagram of a coordinate indicator in the first embodiment.

FIG. 5 is a flowchart of processing of a control circuit in the first embodiment.

FIG. 6 is a timing chart of generation of an induction signal in the first embodiment.

FIG. 7 is a timing chart of a phase detection operation in the first embodiment.

FIG. 8 is a flowchart of switch state determination in the first embodiment.

FIG. 9 is a flowchart of learning phase value calculation in the first embodiment.

FIG. 10 is an explanatory diagram of another embodiment of a learning area.

FIG. 11 is a flowchart of learning phase value calculation in FIG.

FIG. 12 is a configuration diagram of a second embodiment relating to the coordinate reading device main body.

FIG. 13 is a circuit diagram of a second embodiment relating to a coordinate indicator.

FIG. 14 is a circuit diagram of a third embodiment relating to a coordinate indicator.

FIG. 15 is a circuit diagram of a fourth embodiment relating to a coordinate indicator.

FIG. 16 is an explanatory diagram of a conventional switch detection technique.

[Explanation of symbols]

1 sense line board 2 Excitation line group 3 sense line group 4 Excitation scanning circuit 5 Sense scanning circuit 6 Excitation circuit 7 Amplification detection circuit 8 Phase detection circuit 9 Control circuit 10 coordinate indicator

Claims (3)

[Claims] 1. A. A coordinate indicator that is formed by connecting a resonance circuit including a coil and a capacitor and an operating circuit, and that is configured to change the resonance frequency by operating the operating circuit. B. A sense line plate for generating an alternating magnetic field and coupled with the coordinate indicator by the alternating magnetic field to detect an inductive signal; c. A phase detection circuit that detects a phase signal of the induction signal based on the phase of the alternating magnetic field; d. The operation state of the operation circuit of the coordinate indicator is obtained by inputting the phase signal and comparing the stored learned phase value with the stored phase signal, and is set on the sense line plate by the coordinate indicator. When the designated specific area is designated, the phase signal is input, a new learning phase value is obtained from the phase signal and the stored learning phase value, and the learning phase value is stored. A wireless coordinate reading device comprising: a circuit. 2. The sense line plate has a structure in which a plurality of excitation line groups and a plurality of sense line groups are overlapped with each other, and the sense line plate is coupled with the coordinate indicator by an alternating magnetic field generated by the excitation line groups, The wireless coordinate reader according to claim 1, wherein is a sense line plate adapted to generate an induction signal. 3. The coordinate indicator comprises a resonance circuit formed by a coil and a first capacitor, and one or more switch circuits connected to each other. The coordinate instruction is such that the resonance frequency is changed by operating the switch. The wireless coordinate reader according to claim 1, wherein the wireless coordinate reader is a reading device.