JPH0417524B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tablet input device, and more particularly to improvements in the electrode line arrangement and coordinate identification method in a capacitively coupled tablet input device.

[Conventional technology]

Improving functionality and reducing costs are universal themes in product development. In the case of capacitively coupled tablet input devices, one such theme is improving coordinate detection speed and reducing assembly man-hours and number of parts.

[Problem that the invention seeks to solve]

However, it is difficult to solve these two issues simultaneously. For example, Patent Application No. 214301 filed in 1982 and Patent Application No. 113442 filed in 1988 by the applicant.
In order to shorten the scanning time, digit electrode wires for block identification are further placed between the electrode wires for normal coordinate identification. However, with this method, if the required segment spacing is, for example, 6 mm, then regular electrode wires would be placed at 6 mm intervals, and digit electrodes would be placed in between, so the result would be The spacing becomes 3 mm, which is half the segment spacing. As a result, as the spacing becomes narrower, the number of man-hours for pattern creation increases, the difficulty of processing increases, and it becomes necessary to change the electrode line pattern to cope with the decrease in the signal output of the lower electrode due to the increased shielding effect of the upper electrode. etc., leading to an increase in costs.

Therefore, in the present invention, the first and second electrodes are arranged alternately in parallel, the first electrode wires are connected in parallel every m, the second electrode wires are connected in parallel every m+n, and the group electrode wires are connected in parallel. a tablet configured as such, and a pulse application means for applying a scanning pulse to the group electrode line;
current detection means for detecting a charging current flowing through the group electrode wires when the scanning pulse is applied; and electrode wires of the first electrode wire group and the second electrode wire that are closest to the contact position from the timing of the detection pulse. Once the group number is determined, it is determined from the combination which first electrode line and second electrode line the contact position is located between, and the coordinate specifying means specifies the specified coordinates on the tablet. It shall be provided with the following.

[Effect]

That is, if the first electrode wire and the second electrode wire are connected in parallel in different numbers, for example, m
=7, n=-1, the 1st, 8th, 15th, etc. of the first electrode wires belong to the same electrode wire group, while the second electrode wires located next to them belong to the same electrode wire group. 1st, 8th, 15th... For example, 8th is 2
The 15th wire, the 15th wire, the 3rd wire, etc. belong to different electrode wire groups.

Therefore, if each electrode wire group is scanned and the numbers of the first electrode wire group and the second electrode wire group closest to the contact position are determined from the timing of the detection pulse at that time, From the combination, it is possible to determine which first electrode wire and second electrode wire the corresponding contact position is located between.

Furthermore, according to the inventor's research, in a capacitively coupled tablet, when a desired coordinate is indicated with an input pen or a fingertip with the tip of the detection rod grounded, the ground capacitance of the electrode wire passing near the indicated coordinate increases compared to other electrodes. There is a characteristic that the charging current flowing through these electrode lines when scanning becomes larger than the charging current flowing through other electrode lines.

Therefore, in the present invention, by adopting the former type of electrode line connection, the number of required electrode line scans is reduced and speeding up is achieved without increasing the cost, and at the same time, the latter type of detection method is adopted. As a result, the structure of the input pen can be simplified and the cost can be further reduced.

〔Example〕

The details of the present invention will be explained below based on illustrated embodiments. FIG. 1 shows an example of the electrode line arrangement in the X direction.
In the figure, 1 is a first electrode line, and 2 is a second electrode line, and to distinguish them, they are given subscripts A to L from the left. (The electrode wire 2Z will be described later.) In this embodiment, the first electrode wire 1 is three from the left.
Group electrode wires 3, 4, 5, 6 are connected in parallel every other book.
The second electrode wires 2 are connected every second from the left to form group electrode wires 7, 8, and 9.

FIG. 2 shows an example of the block configuration. In the figure 1
Reference numeral 1 designates a tablet substrate on which, in addition to electrode line groups 3 to 9 in the X direction shown in FIG. 1, similar electrode line groups 21 to 27 are also arranged in the Y direction. 12 is an input pen, the detection tip 13 of which is grounded. 14 is a pen switch built into the input pen.

DX1 is a driver and the central processing unit CPU (described later)
According to the address signal supplied from
A scanning pulse is supplied to the group electrode lines 3 to 6 of the electrode line 1. DX2, DY1, DY2 are also drivers, DX
1, each group electrode wire 7-9, 21-24, 25
-27 respectively. Each power input terminal PT of these drivers has a detection resistor RS
A power supply voltage VCC is supplied through the group electrode lines 3-9, 21-2 when the scanning pulse is applied
A detection signal SS is generated across the resistor RS by the charging current flowing through the resistor 7.

AMP is an amplifier that amplifies the detection signal SS. A/D is an analog-to-digital converter that converts the analog value of the amplified detection signal into a digital value. MPX is a multiplexer with each driver DX1,
Switch and supply address signals to DX2, DY1, and DY2.

The central processing unit CPU is, for example, Intel Z8
0, etc., and executes predetermined processing using the random access memory RAM according to a program written in the read-only memory ROM. I.O.
is the input/output port through which the central processing unit
Data is exchanged between the CPU and external circuits. Note that in the following explanation, the names of each block will be omitted.

Details of driver DX1 are shown in FIG. 3. In the figure, 101 is a decoder, which receives the address signal supplied from the CPU via the terminal ADT and multiplexer MPX.
Decode AD. T3 to T7 are field effect transistors, each gate of which is connected to the decoder 10.
1 to the corresponding output terminals D3 to D6, each source to the corresponding X group electrode line 3 to 6, and each drain to the resistor via the terminal PT.
Connected to RS. R3 to R7 are discharge resistors connected between each source and ground.

Note that the structures of drivers DX2, DY, and DY2 are also similar to this driver DX1.

When the input pen 12 comes into contact with the tablet 11, the pen switch 14 operates and the signal PSW is activated.
is supplied to the CPU via IO. In response to the arrival of this signal PSW, the CPU sends a switching signal to MPX.
Supply CH and connect it to DX1 first.
Next, the CPU supplies DX1 via MPX with an address signal AD whose value sequentially changes from 0 to 3 at regular time intervals. DX1 follows this address signal AD and connects group electrode lines 3 to 6 as described above.
Scanning pulses SP3 to SP6 are sequentially supplied to. By applying this scanning pulse SP3 to SP6, each group electrode line 3
A charging current flows through 6, and a signal SS corresponding to the magnitude of the charging current is generated at the resistor RS, which is supplied to the AMP.

An example of the signal SS at this time is shown in FIG. In this figure, the vertical axis represents the pulse height H, the horizontal axis represents the time t, and each signal SS3 to SS6 represents the group electrode line 3.
This is the signal SS detected when the scanning pulses SP3 to SP6 are applied to 6 to 6. And this signal SS
is amplified by the AMP, and converted to a digital value according to each pulse height H by the AD.

The CPU stores this digital value supplied via IO in a predetermined location in RAM. Next, the CPU
Switch MPX and supply address signal AD to DX2. When DX2 applies scanning pulses SP7 to SP9 to each group electrode line 7 to 9 in accordance with address signal AD, signal SS is generated at resistor RS as described above. An example of the detection signal SS at this time is shown in FIG. In this figure, signals SS7 to SS9 indicate signals SS when scanning pulses are applied to group electrode lines 7 to 9, respectively, and these signals SS7 to SS9 are also digitally converted and stored at predetermined locations in the RAM.

Thereafter, scanning pulses are similarly applied to the group electrode lines 21 to 27 formed by the first and second electrode lines in the Y direction, and the digital value of the detection signal SS (not shown) at that time is stored in a predetermined location in the RAM. Ru.

Next, the CPU determines the contact position of the input pen 12 based on the digital value of this detection signal SS.

The procedure for determining the contact position in the X direction will be explained using FIGS. 1, 4, and 5. Note that the contact position in the X direction is expressed by a combination of subscripts of the first electrode wire 1 and the second electrode wire 2. For example, the contact position of the first electrode wire 1 and the second electrode wire 2 is
Between A is expressed as AA.

First, the CPU compares the digital values of the signals SS3 to SS6 detected when the group electrode lines 3 to 6 are scanned by the first electrode line in the X direction, and extracts the signal SS with the maximum value among them. do. In the example of FIG. 4, signal SS4 is extracted. This maximum value signal is SS4
This means that the input pen 12 is in contact with the area Z4 of the group electrode line 4 shown in FIG. Next, the CPU detects the signals detected during scanning of the group electrode lines 7 to 9 by the second electrode line in the X direction.
Extract the largest one and the second one from SS7 to SS9. In the example of FIG. 5, signal SS8 is detected as the largest one, and signal SS7 is detected as the second one. The fact that the largest one is SS8 means that the input pen 12 is in contact with the range Z8 in Figure 1, and the second one is SS8.
Being SS7 means that the group electrode wire
This means that the input pen 12 is in contact with the half Z87 that is closer to the SS7.

Therefore, from this result, the area where the signal SS as shown in FIGS. 4 and 5 can be detected is the above-mentioned Z4.
The area where Z87 and Z87 overlap, that is, area BB, becomes the contact area of the input pen 12 at this time. Note that this area can be specified by previously storing a table as shown in FIG. 6 in the ROM and applying the above determination result to the table. (In Figure 6, the initial letter SS of the signal is omitted.)
For area AA, the maximum signal SS3 when scanning the group electrode line with the first electrode line, the maximum signal SS7 when scanning the group electrode line with the second electrode line, and the second signal SS8 at that time, which is the same as that of area DE. Become. Therefore, in this embodiment, the dummy electrode line 2Z is placed next to the electrode line 1A as shown in FIG. The second signal is SS
9 to distinguish it from the area DE. Note that when the area AA is an unused area, it is not necessary to provide such a dummy electrode 2Z.

The above process is performed using the group electrode line 2 using the Y direction electrode line.
The same process is performed for the signal SS obtained when scanning 1 to 27, and the contact areas AA to LL in the Y direction are specified.

Then, the CPU sends data TD indicating the respective contact areas in the X direction and the Y direction to a data processing device (not shown) or the like via the IO.

〔Effect of the invention〕

As described above, according to the present invention, the detection speed can be improved without complicating the pattern, and since the electrode wires are scanned together, the number of parts for scanning is also reduced. In addition, in the present invention, it is sufficient that the detection tip of the input pen is simply grounded, so the number of parts is reduced in this respect as well. It should be noted that the human body is also imperfectly grounded, and it is also possible to input coordinates on a tablet using a fingertip instead of using an input pen; in this case, the input pen itself becomes unnecessary.

In addition, in this embodiment, the first
The largest signal among the signals when the group electrode line was scanned by the electrode line, the largest signal and the second signal when the group electrode line was scanned by the second electrode line were used; The area can be specified in the same way by using the maximum signal related to the electrode line, the second signal, and the maximum signal related to the group electrode line by the second electrode line.

[Brief explanation of drawings]

The figures show an embodiment of the tablet input device of the present invention, FIG. 1 is a diagram of the arrangement of electrode lines in the X direction, FIG. 2 is a block diagram of the device, and FIG. 3 is the driver of FIG. 2.
A circuit diagram of DX1, FIG. 4 is a waveform diagram showing the output signal when group electrode lines 3 to 6 are scanned, and FIG. 5 is a waveform diagram showing the output signal when group electrode lines 7 to 9 are scanned.
FIG. 6 is a diagram showing a table for specifying contact areas. 1...First electrode line, 2...Second electrode line, 3
~9,21~27... Group electrode wire, 11... Tablet, DX1, DX2, DY1, DY2... Pulse application means, RS... Current detection means, CPU, ROM,
RAM: Coordinate identification means.

Claims (1)

[Claims] 1. A tablet in which first and second electrodes are alternately arranged in parallel, the first electrode wires are connected in parallel every m, and the second electrode wires are connected in parallel every m+n to form a group electrode wire. a pulse applying means for applying a scanning pulse to the group electrode wire; a current detecting means for detecting a charging current flowing through the group electrode wire when the scanning pulse is applied; The numbers of the electrode wire group of the first electrode wire and the electrode wire group of the second electrode wire are determined, and from the combination, it is determined between which first electrode wire and the second electrode wire the contact position is located. A tablet input device characterized by comprising: coordinate specifying means for specifying designated coordinates on the tablet.