JPH0444116A - Wireless coordinate reader - Google Patents

Abstract

PURPOSE:To detect the ON/OFF states of plural switches provided to a coordinate pointing device by providing a phase detecting circuit which detects the phase of a calling-on signal and outputs it as a phase signal and a controller which decides the states of switches of the coordinate pointing device based on the phase signal. CONSTITUTION:A coordinate pointing device 10 is provided near the exciting line and the sense line in a process where the AC signals serving as the exciting signals are successively applied to the energized line groups and at the same time the sense line groups 3 are selected. Thus the calling-on signals are produced on the sense lines. When a switch of the device 10 is pushed, a capacitor is connected in parallel to a resonance circuit via a resistor connected in series to the pushed switch. Then the resonance frequency is changed to a lower level. A phase detecting circuit 8 compares the phase of the calling-on signal induced on the sense line with the phase of the exciting signal to detect the difference between both phases as a phase signal. A control circuit 9 inputs this phase signal to decide the state of switches. Thus the states of switches provided to the device 10 can be decided.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a coordinate reading device that inputs coordinates to an external device such as a computer, and in particular, the present invention relates to a coordinate reading device that inputs coordinates to an external device such as a computer. This relates to a wireless coordinate reading device that does not require

[Summary of the Invention] The present invention sequentially applies an AC signal to a plurality of excitation lines laid on a sense line board, and at the same time sequentially selects a sense line, and a coordinate indicator having a resonant circuit including a coil and a capacitor is installed on the sense line board. In a wireless coordinate reading device that obtains coordinate values from the induced signal induced in the sense line by electromagnetic coupling between the excitation line, coil, and sense line, multiple switches provided on the coordinate indicator can be turned on/off. The object of the present invention is to realize a coordinate reading device that can detect an off state.

For this purpose, in the present invention, a plurality of series circuits of switches and resistors are connected in parallel, and a switch circuit formed by connecting a capacitor in series to one end is connected in parallel to a resonant circuit consisting of a coil and a capacitor. A coordinate reading device is configured by providing a phase detection circuit that constitutes an indicator and detects the phase of a guided signal guided to a sense line, and a control circuit that determines the state of a switch of the coordinate indicator from the detected phase signal. .

The resonant frequency of the resonant circuit changes when the switch of the coordinate indicator is operated, and the state of the switch is detected by detecting that this changes the phase of the induced signal.

[Prior Art] In a coordinate reading device in which electromagnetic coupling between an excitation line and a sense line is mediated by a resonant circuit consisting of a coil and a capacitor provided in a coordinate indicator, the phase of the induction signal induced into the sense line is different from that of the coordinate indicator. It changes depending on the resonant frequency of the device.

In order to change the resonance frequency of the coordinate indicator, for example, a switch 107 and a second capacitor 1 are connected as shown in FIG.
08 series circuit with coil 105 and first capacitor 10
This can be realized by connecting in parallel to a resonant circuit according to No. 6.

The coordinate indicator is constructed as described above, the excitation line 102 and the sense line 103 are arranged perpendicularly to form the sense line plate 101, and an alternating current signal is given as an excitation signal to the excitation line 102, which is guided onto the sense line 103. Observe the induced signal.

The coordinate indicator 104 is placed on the sense line board 101 and the switch 107 is turned on/off. When the switch 107 is off, the induction signal is induced with a certain phase difference from the excitation signal depending on the characteristics of the circuit. When the switch 107 is turned on, the second capacitor 108 is connected in parallel to the resonant circuit, so the resonant frequency changes to a lower side, and the phase of the induced signal is delayed compared to when it is turned off. By detecting this phase delay, the state of the switch can be determined.

[Problems to be Solved by the Invention] However, by connecting a capacitor in parallel to the resonant circuit, there is a problem that the phase cannot be changed subtly.

For example, at a frequency of about 300 kHz and a coil inductance of about 1 mH, the resonant capacitor is about 3 oopr. It depends on the number of switches to be identified and the phase range used, but if you are trying to identify 16 switches in a phase range of about 130 degrees, for example, you will need to use a highly accurate capacitor of several pF or less. There wasn't. This makes manufacturing difficult.

The present invention has been made to solve the above-mentioned problems in the conventional technology. The main purpose is to be a wireless coordinate reading device that does not require a signal line connection between the coordinate reading device and the coordinate indicator, and to detect the on/off status of multiple switches provided on the coordinate indicator. An object of the present invention is to realize a wireless coordinate reading device that can be easily manufactured.

[Means for Solving the Problems] In order to solve the above problems, the present invention includes a sense line board in which a plurality of excitation line groups and a plurality of sense line groups are arranged in an overlapping manner, and a coordinate indicator. In a wireless coordinate reading device that sequentially applies an AC signal to a group of lines, simultaneously selects a group of sense lines one after another, and obtains the coordinate values of the position where the coordinate indicator is placed from the guidance signal guided to the sense line, the coordinate indicator is , a switch circuit having a resonant circuit including a coil and a first capacitor, one or more series circuits of a switch and a resistor connected in parallel, and a second capacitor connected in series to one end. A coordinate indicator connected in parallel to a resonant circuit, which inputs the AC signal given to the excitation line group and the induction signal induced to the sense line, detects the phase of the induction signal, and outputs it as a phase signal. A detection circuit and a control device that controls each part of the coordinate reading device, inputs a phase signal, and determines the state of the switch of the coordinate indicator from the phase signal is provided.

[Function] In the coordinate reading device configured as described above, in the process of sequentially applying an AC signal, which is an excitation signal, to the excitation line group and simultaneously selecting the sense line group, the vicinity of the selected excitation line and sense line is When a coordinate indicator is placed at
An inductive signal is generated on the sense line.

When the coordinate indicator switch is not pressed, the phase of the guidance signal has a certain phase difference from the excitation signal.

When a switch is pressed, a capacitor is connected in parallel to the resonant circuit via a resistor connected in series with the pressed switch, and the resonant frequency changes downward.

The phase detection circuit compares the phase of the induced signal induced into the sense line with the phase of the excitation signal and detects the amount of change as a phase signal, and the control circuit inputs this phase signal to determine the state of the switch. .

[Embodiment] (Configuration of coordinate reading device according to first embodiment) A first embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

First, the configuration will be explained. FIGS. 1, 2, and 3 show configuration diagrams of a coordinate reading device according to the present invention.

In FIG. 1, 1 is a sense line plate on which an excitation line group 2 and a sense line group 3 are laid. The excitation line group 2 and the sense line group 3 form a folded loop and are arranged at regular intervals. In the first embodiment, the excitation line group 2 and the sense line group 3 are arranged orthogonally.

4 is an excitation scanning circuit to which each excitation line of the excitation line group 2 is connected. The excitation scanning circuit 4 is composed of a plurality of electronic switching elements such as analog switches, and is adapted to apply an excitation signal ds supplied from an excitation circuit 6, which will be described later, to one selected excitation line.

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, it is composed of electronic switching elements, and one of the sense lines is selected and connected to an amplification detection circuit 7 and a phase detection circuit 8, which will be described later.

6 is an excitation circuit. An excitation clock dc is inputted from a control circuit 9 to be described later, and this is waveform-shaped and amplified to be output as an excitation signal ds.

Reference numeral 7 denotes an amplification/detection circuit that amplifies and detects the induced signal is induced into the sense line group 3 and outputs an amplitude signal as of the induced signal. This circuit is used to calculate coordinate values.

8 is a phase detection circuit that detects the phase signal ps of the induction signal is. A detailed configuration diagram is shown in FIG.

81 is an amplifier circuit, and 82 is a comparator. The induction signal is is inputted to the amplifier circuit 81 from the sense scanning circuit 5. The output of the comparator 82 is the exclusive OR circuit 83
connected to one input of the

The excitation clock dc is input to the other input of the exclusive OR circuit 83, and the output is connected to an integrating circuit 84 composed of a resistor and a capacitor. In this circuit, the excitation clock dc is used as a reference phase signal, and the phase 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 that detects the phase difference of the induction signal is with respect to the excitation clock dc, and cannot detect a lead or a lag. However, as a design matter, it is conceivable that the guided signal may lead compared to the reference signal and exhibit delayed behavior due to the way the reference signal is taken for phase detection, phase inversion or delay due to the circuit, etc.

In such a case, a circuit for detecting phase lead/lag may be provided. This circuit can be easily realized.

The configuration of the phase detection circuit is not a wooden one for the present invention, and the circuit is not limited to this circuit as long as it detects the phase difference between two signals.

Let's return to Figure 1 and continue the explanation. The control circuit 9 controls each part, inputs and calculates each signal, and determines coordinate values and switch states.

The excitation scanning circuit 4 is provided with a drive address dadrs that instructs the excitation line to be selected, and the sense scanning circuit 5 is provided with a sense address 5ad that instructs the sense line to be selected.
Give rs. In addition, the amplitude signal as is used to calculate the coordinate values, and the phase signal ps is used to determine the state of the switch.
Enter. This control circuit 9 is realized by a microprocessor, and each calculation process is performed by a program.

10 is a coordinate indicator, the circuit diagram of which is shown in FIG.

Coil 11 and first capacitor 12 constitute a resonant circuit. The resonant frequency of this resonant circuit is set around the frequency of the excitation clock dc.

They do not necessarily have to match.

The switch 13a and the resistor 14a are connected in series to form one switch subcircuit. In this embodiment, a normally open switch is used as the switch 13. The details will be described later, but this is to delay the phase by pressing the switch 13. A plurality of switch subcircuits are connected in parallel, and a second capacitor 15 is connected in series to one end to form a switch circuit. This switch circuit is connected in parallel to the resonant circuit.

The resistors in the switch subcircuits are arranged differently so that pressing each switch causes a different amount of phase change. However, it goes without saying that if you want multiple switches to have the same meaning, you can use the same value.

Furthermore, by employing appropriate constants, it is also possible to detect the state when a plurality of switches are pressed simultaneously.

(About the scanning and coordinate calculation operations of the coordinate reading device) Next, the operations will be described. First, the operation of selecting the excitation line group 2 and the sense line group 3 and the coordinate calculation operation will be explained.

The control circuit 9 outputs a drive address dadrs to select one of the excitation lines. As a result, the excitation circuit 6
The output of is connected to a selected excitation line, which generates an alternating magnetic field. While selecting one excitation line, the control circuit 9 outputs the sense address 5adrs to sequentially select the sense line group 3. The selected sense line will be connected to the amplification detection circuit 7 and the phase detection circuit 8. The control circuit 9 repeats this operation. This operation is called "scanning".

When 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 perpendicular to each other. However, when the coordinate indicator 10 is placed on the sense line plate 1, a guidance signal is is induced in each sense line of the sense line group 3 according to the positional relationship between the sense line plate 1 and the coordinate indicator 10. Ru. This is the excitation line, coil 1
1. This is due to the effect of electromagnetic coupling between the three sense lines.

FIG. 4 shows the guidance signal is as a scanning timing diagram. Taking FIG. 1 as an example, the excitation line group 2 is scanned from the top to the bottom of the figure, and the sense line group 3 is scanned from the left to the right of the figure. The position p of the coil 11 is located in the area where the excitation line d2 and the sense line s2 intersect.

Now, when the excitation line dO and the sense line sOM are selected, that is, when the area where they intersect is far away from the position p of the coil 11, the induction signal is
is not observed. The induction signal is increases as the region where the excitation line and the sense line intersect approaches the position p of the coil, and reaches its maximum when the excitation line d2 and the sense line s2 are selected. The guidance signal is has a distribution as shown in the timing diagram of FIG.

The induced signal is is converted into an amplitude signal as by the amplification/detection circuit 7.
, and its magnitude is read by the control circuit 9. The method of calculating the coordinates is not the gist of the present invention, so the details will be omitted, but the control circuit 9 uses the signals ispXisxl, 1sxh, 1sy as shown in the timing diagram of FIG.
The coordinate values of the position where the coordinate indicator 10 is placed are calculated from the amplitude signals of l and 1syh.

(Regarding the operation for determining the switch state) Next, the operation for determining the switch state will be explained.

The control circuit 9 scans the sense line plate 1 as described above. During that time, the induced signal is is input to the phase detection circuit 8 and converted into a phase signal ps.

The operation of the phase detection circuit 8 will be explained with reference to the timing diagram of FIG. In the figure, dc is an excitation clock, ds is an excitation signal, and IS is an induction signal.

If 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 by which the guidance signal is is processed will be explained. First, the guided signal is is amplified by the amplifier circuit 81 in the phase detection circuit 8, and further converted into a square wave by the comparator 82, resulting in a shaped guided signal wave ip. The induced signal shaped wave ip and the excitation clock dc are phase-detected by an exclusive OR circuit 83 to become a detected signal pp. Furthermore, the detection signal pp is converted into a DC signal by an integrating circuit 84 and a phase signal ps
becomes.

When one of the switches of the coordinate indicator 10 is pressed, a capacitor is connected in parallel to the resonant circuit via a resistor connected in series to the pressed switch.

Therefore, the resonant frequency of the resonant circuit changes to the lower side. This effect has an influence in the direction of delaying the phase of the induction signal is. In FIG. 5, the induction signal ish is obtained when one of the switches is pressed, and is shown to be delayed in phase than the induction signal is when the switch is not pressed. This signal is similarly converted into a phase signal psh by the phase detection circuit 8. As is clear 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.

The control circuit 9 converts the phase signal pS into an A/
Convert it to D and import its size. Then, as shown in Fig. 4, the signal is used to calculate the coordinates.
The phase signal ps when p occurs is employed as phase information for determining the switch state.

The timing at which the phase signal ps is adopted is the above signal isp.
The phase detection is not limited to the case where the induced signal is generated, but phase detection is possible as long as the induced signal is generated, so it is sufficient to sample at a specific timing. However, in consideration of S/N, it is preferable to detect the phase of isp, which is the largest induced signal.

As explained above, pressing the switch changes the voltage level of the phase signal ps. The control circuit 9 receives the phase signal ps and compares it with a comparison value for phase determination, thereby determining the state of the switch.

(Coordinate reading device according to second embodiment) Although the coordinate indicator in the first embodiment uses a normally open switch, it can be constructed using a normally closed switch.

FIG. 6 shows a circuit diagram of a second embodiment of the coordinate indicator. Other than that, the configuration of the coordinate reading device is the same as that of the first embodiment, and some operations are different.

If no switch of the coordinate indicator 20 is pressed,
The switches are all closed and the second capacitor 25 is connected in parallel to the resonant circuit through all the resistors connected in series. Capacitor 25 with lowest resistance value
will be connected.

In this state, the induction signal is is induced with a constant phase difference with respect to the excitation signal ds.

When one of the switches is pressed, the resistor connected in series with the pressed switch is disconnected from the resonant circuit, and the resistance value of the switch circuit increases. Therefore, the resonant frequency of the resonant circuit changes to a higher value. This effect affects the direction in which the phase of the induced signal is is advanced.

The change in phase lead is detected by the phase detection circuit 8,
The control circuit makes a switch decision based on the phase signal ps.

(Configuration of coordinate reading device according to third embodiment) The gist of the present invention is to change the frequency of the resonant circuit of the coordinate indicator by operating a switch, and as a result, to change the frequency between the excitation line, coil, and sense line. The purpose of this is to determine the switch state of the coordinate indicator by detecting a change in the phase of the induced signal caused by electromagnetic coupling. Therefore, the arrangement of the excitation lines and sense lines is not limited to the first embodiment.

FIG. 7 is a configuration diagram of the second embodiment. As shown in the figure, in this embodiment, the excitation line group 52 is not orthogonal to the sense line group 3 but is arranged in the same direction. Furthermore, the two overlap in part. The other configurations are similar to the first embodiment.

With the sense line plate 51 configured in this way, the excitation circuit 4
Select one excitation line and give an excitation signal by
When one sense line that overlaps this excitation line is selected at the same time, an induced signal is generated in this sense line due to electromagnetic coupling with the excitation line.

The difference from the first embodiment is that a guidance signal is generated even if the coordinate indicator 10 is not on the sense line plate 51. However, when the coordinate indicator 10 is placed on the sense line plate 51, the coupling becomes stronger and a larger induced signal is generated. Therefore, coordinate values can be determined by observing the amplitude of the guidance signal, and phase signals can also be detected.

Since the induced signal is the sum of the signal coupled through the coil and the signal coupled directly to the excitation line, the phase signal is the first
The reference value is different when compared with the example. but,
While the phase of the signal directly coupled to the excitation line is constant, the phase of the signal coupled via the coil always changes depending on the state of the switch. can be determined.

[Effects of the Invention] As explained above, in the present invention, the coordinate indicator is configured such that when a switch is pressed, the capacitor is connected in parallel to the resonant circuit via the resistor, and the excitation line group and the coordinate indicator The phase of the induced signal due to electromagnetic coupling between the sensor and the sense line group can be changed by operating a switch. In addition, it was possible to realize a wireless coordinate reading device in which this phase change is detected by a phase detection circuit, and the switch state can be determined by a control circuit.

The coordinate indicator was constructed so that the phase change was distributed by resistors. Resistors are more accurate than capacitors,
Moreover, those with a large number of effective digits are easily available, and the phase can be divided in detail. Compared to the past, it has become easier to manufacture.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a first embodiment of a wireless coordinate reading device according to the present invention, FIG. 2 is a block diagram of a phase detection circuit, and FIG.
Figure 4 is a circuit diagram of the coordinate indicator, Figure 4 is a guidance signal generation timing diagram, Figure 5 is a timing diagram of phase detection operation, and Figure 6 is a timing diagram of the phase detection operation.
The figure is a circuit diagram of the second embodiment of the coordinate indicator, and Figure 7 is the circuit diagram of the third embodiment of the coordinate indicator.
FIG. 8 is an explanatory diagram of a conventional switch detection technique. 1.. 2.. 3.. 4.. 5.. 6.. 7.. 8.. 9.. 10.. 11.. 12.. 13. 14.. 15.. Sense line board... Excitation line group...Sense line group...Excitation scanning circuit...Sense scanning circuit...Excitation circuit...Amplification/detection circuit...Phase detection circuit...Control circuit...Coordinate indicator/ ...Coil...First capacitor...Switch...Resistor...Second capacitor or more Trap O Fig. 4 sh

Claims (1)

[Scope of Claims] a. Consisting of a sense line board in which a plurality of excitation line groups and a plurality of sense line groups are arranged one on top of the other, and a coordinate indicator, and at the same time giving alternating current signals to the excitation line groups in sequence, A wireless coordinate reading device that sequentially selects the sense line group and obtains the coordinate value of the position where the coordinate indicator is placed from the guidance signal guided to the sense line, b. It has a resonant circuit with a capacitor of a coordinate indicator connected in parallel to a circuit; d) inputting an alternating current signal given to the excitation line group and a guiding signal induced to the sense line group, detecting the phase of the guiding signal; A phase detection circuit that outputs the signal as a signal; e. A control device that controls each part of the coordinate reading device, inputs the phase signal, and determines the state of the switch of the coordinate indicator from the phase signal. A wireless coordinate reading device featuring: