JPH0737145Y2 - Touch panel key address detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is a key for detecting an address of a key touched by a finger or the like in a touch panel used as an input device of various data processing devices. The present invention relates to an address detection circuit.

[Conventional technology]

As an input device of a data processing device, for example, there is one having a digital touch panel on the screen of a CRT display device.

In this digital touch panel, for example, a plurality of lines (conductors) made of transparent resistance films are formed in a grid pattern on the mutually facing surfaces of two transparent polyester sheets, and the key matrix is formed at the intersections. There is a configured resistance film type.

Lines lined up in the X direction of this digital touch panel are referred to as "lines in the X direction", and lines lined up in the Y direction are called "Y".
Direction line ".

By the way, in such a digital touch panel, when the front sheet is pushed toward the back sheet in the vicinity of the intersection of the respective lines with a finger or a pen, two lines intersecting at the intersection are conducted, A key address detection circuit that reads the data corresponding to the key address (X, Y coordinates) of the intersection point by a microcomputer inside the device (hereinafter abbreviated as "CPU") and detects the input key address It is used.

That is, all the lines in the X direction are kept at the high level by the power source through the pull-up resistors, and the CPU sends the addresses to selectively set one line in the Y direction of the touch panel to the low level, and the addresses are transmitted. The key address of the touch panel is detected by reading the data of all the lines in the X direction and discriminating the low level lines.

[Problems to be solved by the device]

However, in such a conventional key address detection circuit, when the CPU sets a line in the Y direction of the touch panel to the low level, it is determined that one of the lines in the X direction is at the low level, and then the low level is detected. Even if the line in the Y direction to be changed to the next line is changed to the next line, the line in the X direction that once went to the low level took about 100 μS to rise to the high level by the pull-up power supply (floating Because there is capacity etc.).

Therefore, at least 100 μS or more from when the CPU selects one line in the Y direction to read the data of all lines in the X direction and then selects the next line in the Y direction to read the data of all lines in the X direction. Therefore, it took a considerable time to scan all the lines in the Y direction and finish detecting all the entered key addresses. Therefore, there was a problem in detecting this key address in CPU interrupt processing.

The present invention has been made in view of the above points, and an object thereof is to shorten the detection time of a key address.

[Means for Solving the Problems]

In order to achieve the above object, the present invention has a bidirectional bus transceiver between the output bus of all lines in the X direction of the touch panel and the input bus of the microcomputer in the touch panel key address detection circuit as described above. At the same time, the pull-up resistors that are inserted between the bidirectional bus transceiver and the micro-computer to all the input lines of the micro-computer and the power supply to keep the respective input lines at a high level, and the micro-computer. When the address for selecting the line in the Y direction to be transmitted is changed, a control circuit for switching the data transmission direction from the microcomputer side to the touch panel side for a short time before reading the data from the bidirectional bus transceiver. And are provided.

The data transmission direction of the bidirectional bus transceiver is changed only when the control circuit changes the address to be transmitted immediately after the microcomputer determines that one of the lines in the X direction of the touch panel is at the low level. It is advisable to switch between.

[Action]

According to the key address detection circuit of the touch panel configured as described above, each time the address sent by the microcomputer is changed to switch the line to the low level in the Y direction of the touch panel, the data of the line in the X direction is read. In addition, since the data transmission direction of the bidirectional bus transceiver is switched from the microcomputer side to the touch panel side for a short time, each line in the X direction is connected not only to the pull-up power supply on the touch panel side but also to the input line side of the microcomputer. Since it is also connected to the pull-up power supply, even if it is at low level, it will instantly charge the stray capacitance and rise to high level.

Therefore, it is possible to shorten the line scan interval in the Y direction, check the key addresses of all the lines in a short time, and reliably detect all the input key addresses in a short time. .

Further, the data transmission direction of the bidirectional bus transceiver is switched only when the microcomputer changes the address to be transmitted immediately after determining that one of the X-direction lines of the touch panel is at the low level. It is possible to further reduce the time required to detect all the entered key addresses.

〔Example〕

An embodiment of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a block diagram showing an example of a key address detection circuit of a touch panel embodying the present invention.

First, reference numeral 1 denotes a digital touch panel (hereinafter simply referred to as "touch panel") similar to the above-mentioned conventional example, and is mounted on the screen of a CRT display device provided in a data processing device such as a personal computer.

As the touch panel 1, a 40 × 24 touch panel having 40 lines (X1 to X40) in the X direction and 24 lines (Y1 to Y24) in the Y direction is used.

The key address detection circuit of the touch panel 1 includes a bus buffer 2, a binary counter 3, a decoder 4, a key detector 5, a bidirectional bus transceiver 6, a microcomputer (hereinafter abbreviated as "CPU") 7, pull-up resistor groups 8 and 9, and pull-up resistors. and a use power supply V _cc1, V _cc2.

The output terminal of the decoder 4 and each line in the Y direction of the touch panel 1 are connected by a data bus 11 of 24 lines, and each line in the X direction of the touch panel 1, the input terminal of the key detector 5 and the bidirectional bus. The input terminal of the transceiver 6 and the other end of each resistor, one end of which is connected to the power supply _Vcc1 of the pull-up resistor group 8, are mutually connected by a data bus 12 of 40 lines.

Further, the output terminal and by connexion mutually Debasu 13 by sixteen lines from the other end of each resistor each end to a power source V _cc2 input ports and Puruatsupu resistor group 9 is connected to CPU7 bidirectional bus transceiver 6 It is connected.

And, always keeps the 40 lines of the power supply V _cc1 data bus 12 via a respective Puruatsupu resistance Puruatsupu resistor group 8 to the high level "H", respectively, each Puruatsupu power V _cc2 likewise Puruatsupu resistance group 9 Of the data bus 13 through the resistor
Each of the 16 lines is kept at high level “H”.

The bus buffer 2 inputs the address from the binary counter 3 and the address from the CPU 7, and when the interrupt signal INTKY from the key detector 7 is at high level "H", the address from the binary counter 3 and the interrupt signal INTKY at low level "L". ", The address from the CPU 9 is selected and input to the decoder 4.

The binary counter 3 is an address generator, and in order to scan all the lines in the Y direction of the touch panel 1 at all times,
Corresponding addresses are sequentially generated in order to circulate the 24 lines in the Y direction in order to attain the low level "L".

The decoder 4 decodes and outputs the address from the buffer 2, and selects one of the 24 lines of the data bus 11 (corresponding to each line in the Y direction of the touch panel 1).
Only books are selectively set to low level.

When any key of the touch panel 1 is touched at the time of scanning by the address from the binary counter 3 and any one of the lines in the X direction becomes low level “L”, the key detector 5 detects it and detects the CPU 7 and the bus buffer 2.
Generates an interrupt signal INTKY.

The bidirectional bus transceiver 6 inputs CP to terminals G ₀ and G _1.
When the 2-bit signal XSEL from U7 is "0,0", the output is opened and the data bus 12 on the touch panel 1 side is connected.
The data bus 13 on the CPU 7 side is disconnected.

When the signal XSEL is "0,1", the lines 1 to 16 of the data bus 12 on the touch panel 1 side are connected. When the signal XSEL is "1,0", the lines 17 to
When 32 is “1,1”, the lines 33 to 40 are connected to the 16 lines of the data bus 13 on the CPU 7 side, respectively.

Furthermore, when the signal XCHRG from the CPU7 input to the terminal DIR is always at the high level "H", the data transmission direction is from the data bus 12 on the touch panel 1 side to the data bus 13 on the CPU7 side. When XCHRG becomes low level “L”, the data transmission direction is switched from the bus line 13 on the CPU 7 side to the bus line 12 on the touch panel 1 side.

At this time, all 40 lines of the data bus 12 are connected to the data bus 13 regardless of the type of the data XSEL input to the terminals G ₀ and G _1.
Connected to all 16 lines on the side. For example, the data bus
Twelve lines 1, 17, 33 and line 1 on the data bus 13 side are commonly connected.

The CPU 7 is a 16-bit microcomputer including a CPU, ROM, RAM, I / O, etc. When the interrupt signal INTKY from the key detector 7 becomes low level “L”, it starts interrupt processing and the binary counter 2 Decoder 4 instead
Address to the touch panel 1 X
All the data of 40 lines in the same direction are read through the bidirectional bus transceiver 6 in 16-bit units (however, the last data is 8-bit data), and the address of the low level "L" line is determined.

At this time, the CPU 7 is the terminal of the bidirectional bus transceiver 6.
A signal XSEL (2-bit signal) corresponding to G ₀ and G ₁ is sequentially output at a predetermined timing, and the address to be transmitted is changed, or the touch panel 1 moves in the X direction.
Only when the address to be sent is changed immediately after it is determined that one of the 40 lines is low level "L",
Before reading data from the bidirectional bus transceiver 6, the signal XCHRG output to the terminal DIR of the bidirectional bus transceiver 6 is set to low level “L”.

Next, the operation of this embodiment thus configured will be specifically described with reference to FIG.

At any time, the address from the binary counter 3 is supplied to the decoder 4 via the bus buffer 2 and the decoder 4
Output, the lines in the Y-direction of the touch panel 1 are selectively and sequentially set to low level for scanning.

At this time, the CPU 7 operates the terminals G ₀ and G _{1 of the} bidirectional bus transceiver 6.
"0,0" is given as a signal XSEL to the bidirectional bus transceiver 6, and the output of the bidirectional bus transceiver 6 is in an open state.

In this state, when one of the keys on the touch panel 1 is touched and any of the lines in the X direction becomes low level "L", the key detector 5 detects it and outputs CP.
Outputs interrupt signal INTKY to U7 and bus buffer 2.

When receiving the interrupt signal INTKY, the bus buffer 2 outputs the address from the CPU 7 to the decoder 4 instead of the binary counter 3.

On the other hand, when the CPU 7 receives the interrupt signal INTKY, it starts the interrupt process, sends the address to the bus buffer 2 instead of the binary counter 3, and outputs “0, 0” as the signal XSEL to the terminals G ₀ and G ₁ of the bidirectional bus transceiver 6. 1 "" 1,0 "
"1,1" is output sequentially.

Accordingly, the bidirectional bus transceiver 6 sequentially connects the lines 1 to 16, 17 to 32, and 33 to 40 of the data bus 12 to the data bus 13 sequentially.
Connect to lines 1 to 16 of.

Therefore, the CPU 7 sends the address every time the touch panel 1 is sent.
The data of the 40 lines in the X direction are read in three times via the bidirectional bus transceiver 6 and the address of the line at the low level "L" is determined.

If the CPU 7 discriminates the line at the low level "L", when the address to be transmitted next is changed, the data of the bidirectional bus transceiver 6 is read before the data is read from the bidirectional bus transceiver 6. Set the signal XCHRG output to the direction determination terminal DIR to low level “L” for a short time,
The data transmission direction of the bidirectional bus transceiver 6 is switched to the reverse direction.

And I connexion, through each Puruatsupu resistance and bidirectional bus transceiver 6 of Puruatsupu resistor group 9 from the power source V _cc2, high-level voltage is applied to each line in the X direction Tatsuchipaneru 1.

Therefore, if the touched key is the key switch 10 shown in FIG. 2 of the touch panel 1, for example, even if the corresponding Y line becomes low level, the key switch 10
There If off, from the power source V _cc1 through Puruatsupu resistor R ₁ of Puruatsupu resistance group 8, Puruatsupu resistance Puruatsupu resistor group 9 from the power supply V _cc2 R ₂ and bidirectional bus transceiver 6
Since the electric power is supplied to the X line of the touch panel 1 via each of them, the X line instantly rises to a high level.

Note that this time becomes shorter as the resistance value of each pull-up resistor of the pull-up resistor groups 8 and 9 becomes smaller. Ie power
Since current supplied from the V _cc1, V _cc2 is increased, which reduces the time it takes to much of the stray capacitance of the corresponding line Chiyaji, shorten the time from the low level "L" to rise to high level "H" It becomes possible to do.

For example, it took about 100 μS to start up in the past, but it can be shortened to about 1.8 μS.
The time from selecting a certain Y line to read the X line data and then selecting the next Y line to read the X line data can be shortened to 1/50 of the conventional time. Sukiyan time can be greatly reduced as well.

It is needless to say that the CPU 7 reads the line data in the X direction after the data transmission direction of the bidirectional bus buffer is returned from the data bus 12 side to the data bus 13 side.

After that, the CPU 7 repeats the same processing as described above until the scanning for all the lines in the Y direction of the touch panel 1 is completed, and outputs "0,0" as the signal XSEL to the bidirectional bus transceiver 6 when the scanning is completed. Then, the bidirectional bus transceiver 6 is returned to the output open state, and the key of the touch panel 1 is newly touched to generate the interrupt signal INTKY.
It keeps that state until you type, while you can perform other tasks.

[Effect of device]

As described above, the touch panel key address detection circuit according to the present invention selects the Y-direction line in which the CPU is present, reads the X-direction line data, and then selects the next Y-direction line and selects the X-direction line. The time required to read the data of the line in the direction can be significantly shortened compared to the conventional method, and therefore, scanning of all the lines in the Y direction is completed and the detection of all key addresses input is completed. The time can also be greatly reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of a key address detecting circuit of a touch panel showing an embodiment of the present invention, and FIG. 2 is a block circuit diagram showing a part of FIG. 1 for explaining the operation of this embodiment. 1 ... Touch panel 2 ... Bus buffer 3 ... Binary counter 4 ... Decoder 5 ... Key detector 6 ... Bidirectional bus transceiver 7 ... Micro computer (CPU) 8, 9 ... Pull-up resistor group 10 ... Key switch 11, 12, 13 ... Data bus V _cc1, V _cc2 ... Puruatsupu for power

Claims (2)

[Scope of utility model registration request] 1. A pull-up resistor, which is inserted between all the lines in the X direction of the key matrix by a resistance film of a digital touch panel and a power source, to keep each line at a high level, and an address transmission. Then, all the lines in the Y direction of the key matrix are sequentially set to a low level one line at a time, and the X level is sent every time the address is transmitted.
In a touch panel key address detection circuit including a microcomputer for inputting data of all lines in the direction and discriminating low level lines, an output bus of all lines in the X direction of the touch panel and an input bus of the microcomputer are provided. And a bidirectional bus transceiver inserted between the bidirectional bus transceiver and the microcomputer, and all the input lines of the microcomputer and the power source are respectively inserted to connect the input lines. When the pull-up resistor that keeps high level and the address sent by the microcomputer are changed, the data transmission direction of the bidirectional bus transceiver is changed from the microcomputer computer side to the touch panel side for a short time before reading the data. Having a switching control circuit A touch panel key address detection circuit characterized by: 2. A key address detection circuit for a touch panel according to claim 1, wherein the control circuit sends the signal immediately after the microcomputer determines that one of the lines in the X direction of the touch panel is at a low level. A key address detection circuit for a touch panel, which is a circuit for switching the data transmission direction of the bidirectional bus transceiver from the microcomputer side to the touch panel side only for a short time before changing the address.