JPH07104908A - Switch information transmission means in coordinate input device - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To reliably and easily transmit switch information of the input pen in the coordinate input device. [Structure] Different waveforms such as a sine wave and a rectangular wave and signal generators 5 and 6 capable of frequency switching are arranged inside the input pen 2, and a switch information detection circuit 12 on the receiving side is provided with a waveform and frequency discriminating means. Deploy. [Effect] Since the frequency is switched using a sine wave, a rectangular wave, or the like for the carrier wave from the input pen applied to the tablet electrode wire, the switch information can be easily discriminated on the receiving side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate input device using a wireless input pen, and more particularly to a means for transmitting switch information of the input pen.

[0002]

2. Description of the Related Art Heretofore, transmission of switch information of an input pen of a capacitive coupling type coordinate input device using a wireless input pen has been performed by transmitting an alternating signal inside the input pen when a signal is applied from the input pen to a tablet. The rectangular wave oscillating frequency of the generator is varied and applied to the tablet electrode wire from the conductive shaft covered at the tip. Since the X-axis and Y-axis electrode lines of the tablet form a distribution constant equivalently, the rectangular wave is integrated and becomes close to a sine wave. The sine wave detected from each electrode wire is amplified and shaped into a rectangular wave, and then the frequency is determined by counting the number of rectangular waves for a predetermined period by the microprocessor to determine the switch information. It was

As another method, a sine wave detected from each electrode wire is amplified, FM demodulated and converted into a DC signal, which is then compared with a reference voltage of a comparator and A / D converted by a microprocessor. It was judged as switch information. At this time, the rectangular wave oscillator of the alternating signal generator inside the input pen is often used because the circuits of FIGS. 4, 5 and 6 have a small number of parts and are low cost, and switch information is transmitted by a switch. When it was turned on, the frequency was varied by the combined capacity of the capacitors connected in parallel.

[0004]

In the conventional alternating signal generator of the wireless type input pen, as shown in FIGS. 4 and 5, the capacitor 2 for charging and discharging the oscillator is used as the information of the pen switch.
The frequency was changed by increasing the value of the combined capacitance of 5 and 26. However, the wireless input pen requires a battery to be used as the power supply for the oscillator, and the power supply voltage supplied to the oscillator gradually drops due to the capacity life of the battery. Is not good. That is, the frequency is changed by the fluctuation of the power supply voltage, and the fluctuation of the frequency appears as a large error with respect to the reference voltage of the microprocessor or the comparator for judging the switch information on the receiving side, and it becomes difficult to transmit the switch information. Sometimes.

In order to solve the above problem, there is a method of stabilizing the power supply voltage supplied to the input pen internal oscillator by a regulator or the like. However, the mounting area of the pen internal board is increased and the power supply required for using the regulator is provided. An increase in the number of batteries to secure the voltage becomes a problem.

As another method, a circuit in which the frequency is not influenced by the power supply voltage is considered as shown in FIG.
If the variable range of the frequency is narrow and the basic frequency of the ceramic oscillator varies, as in the characteristics of, the frequencies of different circuits will not be crossed even if different circuits are used. In some cases, it may be difficult to transmit switch information as in the circuits of FIGS. 4 and 5 (point a). As a result, it is sometimes difficult to transmit the four pieces of switch information as a mouse function because the frequency stability with respect to the switch information is not good in a circuit that only changes the frequency.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and it is an X-axis and a Y-axis.
In a coordinate input device having a tablet having a plurality of electrode lines arranged along an axis coordinate axis and a wireless input pen capacitively coupled to each electrode line of the tablet, a rectangular wave is formed inside the input pen. The present invention proposes a switch information transmitting means in a coordinate input device having an alternating signal generator capable of switching different waveforms and frequencies and a switch information detecting circuit of the tablet, which has a waveform and frequency discriminating means.

[0008]

In the present invention, since the frequency is switched by using a sine wave or a rectangular wave for the carrier wave from the input pen applied to the tablet electrode wire, it becomes easy to determine the switch information on the receiving side.

[0009]

The present invention will be described with reference to the accompanying drawings. Figure 1
Shows an electrical block diagram of a coordinate input device to which the present invention is applied. Reference numeral 1 is a transmitting means, and reference numeral 2 is an input pen incorporating the transmitting means 1. Reference numeral 3 is a receiving means, and reference numeral 4 is a tablet connected to the receiving means 3.
The transmitting means 1 has a rectangular wave generator 5 and a sine wave generator 6, each of which is switched by a switch 7. The switch 8 is a switch for changing the frequency of the rectangular wave generator 5 or the sine wave generator 6. The rectangular wave and sine wave carrier signals generated from the transmitting means 1 are applied from the input pen 2 to the X-axis side electrode wire 9 and the Y-axis side electrode wire 10 of the tablet 4.

The signal receiving means 3 is a signal receiving tablet 4
The X-axis side electrode line 9 and the Y-axis side electrode line 10 are sequentially switched and connected to the position information detection circuit 11 and the switch information detection circuit 12 via switches 13 and 14, respectively. At this time, the operations of the X-axis side electrode wire 9 and the Y-axis side electrode wire 10 are controlled by the tablet controller 15. Further, in the position information detection circuit 11, the filter-16, the amplifier 17, the detector 1
8 is connected to an analog-digital converter (not shown) included in the control circuit 23. The switch information detection circuit 12 is connected to the filter-19, the amplifier 20, and the waveform shaper 21, and is connected to a counter (not shown) included in the control circuit 23. The waveform shaper 22 connected from the amplifier 17 is also connected to the counter of the control circuit 23.

Next, the actual operation will be described. The transmitting means 1 inside the input pen 2 has switches 7 and 8, and switch information is determined by a combination of these two switches. When both the switches 7 and 8 are turned off in the initial state, a constant frequency f (see FIG.
The rectangular wave of A) is sequentially applied to the X-axis side electrode wire 9 and the Y-axis side electrode wire 10 of the tablet 4. The signal detected by the receiving means 3 is transmitted to the filter-19 via the switch 14. The signal input to the filter-19 has a waveform as shown in FIG. 2B due to the distributed constant circuit formed by the tablet electrode lines. Here, when a rectangular wave is expanded into a Fourier series, 4c / π {sinxt + (sin3xt / 3) + (si
n5xt / 5) + ...} (FIG. 3), it is necessary to detect a harmonic wave other than the fundamental wave in order to detect a rectangular wave. (Because sinx, which is the fundamental wave, is targeted for the detection of the sine wave.) Also, if we simply consider the distributed constant circuit of the tablet electrode line, we find that it is a collection of integrator circuits. The greater the attenuation of the amplitude, the greater. Considering this with the above equation, the amplitude of the first harmonic of the second term is larger than that of the other frequency components, and therefore it is considered that the attenuation amount at the tablet electrode wire is the smallest and detection is possible.

For the above-mentioned reason, the filter 19 has a rectangular wave
A bandpass filter (hereinafter referred to as BPF) that resonates at the first harmonic, which has a doubled cycle. The signal that has passed through the filter 19 is amplified by the amplifier 20, and then the waveform shaper 2
The frequency is determined by the counter of the control circuit 23 from the number of the rectangular waves by making the rectangular wave again at 1 (frequency 3f in FIG. 2C). This determines whether the switches 7 and 8 of the input pen 2 are off.

Next, when the switch 7 of the input pen 2 is off and the switch 8 is on, the capacitor 24 is connected to the rectangular wave generator 5, so that the input pen 2 is slightly lower than when the switches 7 and 8 are off. A rectangular wave of frequency (f-Δf) is output as a carrier (FIG. 2A). The detected signal is processed in the same manner as the above-described flow, and the frequency of the shaped rectangular wave becomes {3 (f-Δf)}, and the control circuit 23 determines the number of rectangular waves.
Determine the frequency with the counter. This determines whether the switch 7 of the input pen 2 is off and the switch 8 is on.
Further, since the filter 16 is a BPF having a wide frequency band, it can pass waveforms of frequencies 3f and 3 (f-Δf).

Next, when the switch 7 of the input pen 2 is on and the switch 8 is off, the input pen 2 uses the sine wave of the frequency f as a carrier wave (FIG. 2A), the electrode wire 9 on the X-axis side of the tablet 4,
A signal is applied to the Y-axis side electrode wire 10. The signal detected by the receiving means 3 is transmitted through the switch 13 to the position information detection circuit 1
The waveform shaping device 22 connected to the filter 16 and the amplifier 17 of No. 1 forms a rectangular wave of frequency f (FIG. 2C), and the frequency of the rectangular wave is determined by the counter of the control circuit 23. This determines whether the switch 7 of the input pen 2 is on and the switch 8 is off. Since position information detection is not the subject of the present invention, detailed description thereof will be omitted. The filter-16 is a BPF that resonates around the frequency f.

Next, when the switches 7 and 8 of the input pen 2 are turned on, the input pen 2 has a frequency (f-Δ) slightly lower than the frequency f.
The sine wave of f) is output as a carrier (FIG. 2A). The detected signal is processed and shaped in the same manner as the above-described flow, and the frequency of the shaped rectangular wave becomes f-Δf, and the frequency of the counter of the control circuit 23 is determined from the number of the rectangular waves. This determines whether the switches 7 and 8 of the input pen 2 are on. The carrier wave is not limited to a rectangular wave and a sine wave as long as it can be detected.

[0016]

According to the present invention, since the frequency is switched using the sine wave and the rectangular wave as the carrier wave from the input pen applied to the tablet electrode wire, it is easy to determine the switch information on the receiving side.

[Brief description of drawings]

FIG. 1 is an electrical block configuration diagram of a coordinate input device to which the present invention is applied.

FIG. 2 Waveform diagram of transmission, reception and detection signals

[Fig. 3] Waveform diagrams for forming a rectangular wave

FIG. 4 Conventional first oscillator circuit

FIG. 5 Second conventional oscillator circuit

FIG. 6 Conventional third oscillator circuit

[Fig. 7] Frequency fluctuation characteristic diagram

[Explanation of symbols]

 1 transmitting means 2 input pen 3 receiving means 4 tablet 5 rectangular wave generator 6 sine wave generator 7 switch 8 switch 9 X-axis side electrode wire 10 Y-axis side electrode wire 11 position information detection circuit 12 switch information detection circuit 13 switch 14 Switch 15 Tablet control 16 Filter-17 Amplifier 18 Detector 19 Filter-20 Amplifier 21 Waveform shaper 22 Waveform shaper 23 Control circuit 24 Capacitor 25 Capacitor 25 Capacitor 26 Capacitor

Claims (1)

[Claims] 1. A coordinate input device having a tablet having a plurality of electrode lines arranged along X-axis and Y-axis coordinate axes, and a wireless input pen capacitively coupled to each electrode line of the tablet. In the coordinate input device, the input pen has an alternating signal generator capable of switching between different waveforms such as a rectangular wave and a frequency, and the switch information detection circuit of the tablet has waveform and frequency discriminating means. Switch information transmission means.