JP2001255983A - Key matrix device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a key matrix device, capable of detecting the depression of much more key switches than in conventionally, using the same number of terminals by adding a simple hardware circuit. SOLUTION: When a pulse signal is inputted from one line, signals corresponding to a key state are outputted from all the other lines, and while the pulse signal input and output are switched successively, the key state is scanned in each line so that the depression of key switches K00-K55 can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a key matrix device which outputs a signal for detecting a key switch position to a computer or the like in response to a pulse input supplied from a computer or the like when a key is pressed.

[0002]

2. Description of the Related Art Conventionally, a key matrix device has been used for a computer or the like to detect the state of a large number of key switches with a small number of terminals.

FIG. 4 is a circuit diagram showing a configuration of a conventional standard key matrix device. In this configuration example of the key matrix device, a computer or the like can detect the state of 16 key switches with eight terminals including four output terminals and four input terminals. In FIG. 4, an output terminal of a computer or the like is connected to lines Po0 to Po3, and an input terminal is connected to lines Pi0 to Pi3.

FIG. 5 is an example of a time chart waveform diagram in the key scan operation when the key switch K06 is pressed in the circuit diagram of FIG. The computer or the like sequentially outputs L-level pulses having different phases to the output terminals Po0 to Po3. When the key switch is not pressed, the input terminals pi0 to Pi3 go to the H level because they are pulled up by the resistors R0 to R3. On the other hand, when the key switch is pressed, the output terminals Po0 to P0
When any of o3 is at the L level, the input terminals Pi0 to Pi3 whose key switches are short-circuited are at the L level. The computer or the like has output terminals Po0 to P
Pressing of the key switch can be detected by the signal to o3 and the signal input from the input terminals Pi0 to Pi3.

In order to prevent short-circuiting between terminals of a computer or the like which outputs an opposite level due to simultaneous pressing of a plurality of key switches, the computer is configured to be in an L level or a high impedance state. , H level output is not performed.

The circuit example shown in FIG. 4 is an L-active key matrix device in which an L level signal is input from one of the lines Po0 to Po3 and an L level is output from the other line Pi0 to Pi3 when a key switch is pressed. However, an H active type structure in which an H level signal is input and an H level is output when a key switch is pressed is also used as a standard. In this case, the resistors R0 to R3 are connected in a pull-down connection, and a computer or the like outputs an H level to the lines Po0 to Po3 or sets a high impedance state.

In the circuit example shown in FIG. 4, the key matrix has a total of eight lines. However, in an actual system, the number of input terminals and the number of output terminals are required in accordance with the required number of keys. If the number of input terminals is n and the number of output terminals is m, the number of keys that can be detected is n * m.

However, since the number of terminals of a computer or the like is structurally limited or the cost of the wiring cable is required to be reduced, the object is to detect many key switches with a smaller number of lines. 6 and 7 have also been devised.

FIG. 6 is a circuit diagram showing a configuration of a key matrix device using input / output terminals and diodes of a computer or the like. In this circuit example, the state of 32 key switches (K00 to K31) can be detected by adding eight diodes (D0 to D7) using eight input / output terminals (Pio0 to Pio7) of a computer or the like. 4, the number of key switches that can be detected with the same number of terminals is doubled.

In the circuit example of FIG. 6, a computer or the like firstly operates as in the case of the circuit example of FIG.
An L-pulse scan signal is supplied to o0 to Pio3, a voltage level output from the input / output terminals Pio4 to Pio7 is input, and pressing of the key switches K00 to K15 is detected.
After that, the input and output are switched, and the input / output terminal Pio4
To Pio7 to input the voltage levels output from the input / output terminals Pio0 to Pio3, thereby detecting the depression of the key switches K16 to K31. By limiting the current flowing direction to one direction by the diodes D0 to D7, each of the key matrix groups (a set of key switches K00 to K15 and a key switch K16 to
K31).

The circuit example of FIG. 6 is similar to the circuit example of FIG.
There are an active type and an H active type, and the number of detectable key switches can be changed by changing the number of input / output terminals. If the number of input / output terminals is n + m, the required number of diodes is 2 * n or 2 * m,
The number of key switches that can be detected is 2 * (n * m).

FIG. 7 is a circuit diagram showing a configuration of a key matrix device using input / output terminals of a computer or the like. In this circuit example, by using eight input / output terminals Pio0 to Pio7 of a computer or the like,
The state of 28 key switches (K00 to K27) can be detected, and the number of key switches that can be detected with the same number of terminals can be increased as compared with the circuit example of FIG. As compared with the circuit example of FIG. 6, the number of key switches that can be detected is small, but no diode is required.

FIG. 8 is an example of a time chart waveform diagram in the key scan operation when the key switch K10 is pressed in the circuit diagram of FIG. Input / output terminals of a computer or the like are connected to lines Pio0 to Pio7, respectively. The computer or the like first outputs the L level from the line Pio0 and inputs from the lines Pio1 to Pio7. If no key switch is pressed, the line pi
o1 to Pio7 are at the H level because they are pulled up by the resistors R1 to R7.

On the other hand, when the key switch is depressed, the lines Pio1 to Pi where the key switch is short-circuited
o7 becomes L level. Next, the line Pio0 is in the high impedance state, the line Pio1 is output at the L level, and input is performed from the lines Pio2 to Pio7.

In the following, the L level output is sequentially performed on the lines Pio2 to Pio6 and the input is performed from the lines Pio3 to Pio7, so that the input and output are switched at the same terminal. Can be detected.

The circuit example of FIG. 7 is also similar to the circuit example of FIG.
There are an active type and an H active type, and the number of detectable key switches can be changed by changing the number of input / output terminals. Assuming that the number of input / output terminals is n, the number of key switches that can be detected is (n * (n-1)) / 2.

FIG. 9 is an explanatory diagram of the number relationship between the elements in which the number of input / output terminals, the number of key switches that can be detected, and the number of necessary diodes in the above circuit example are summarized in a list. In an actual product, an optimal key matrix device is selected in consideration of the terminal structure of a computer or the like, the number of input / output terminals, the number of required key switches, the cost of a diode, and the like.

[0018]

However, in the conventional key matrix device, in order to solve the problems of limiting the number of terminals of a computer or the like and increasing the cost of a wiring cable, a larger number of key switches are required with a smaller number of terminals than in the prior art. Circuits that perform press detection have been studied.However, the number of key switches is limited due to the limitation of the number of terminals of a computer or the like, and it is difficult to cope with the increase of key switches. There was a problem that the cost increased due to the increase.

The present invention solves the above-mentioned conventional problems. By adding a simple hardware circuit, it is possible to detect the pressing of more key switches with the same number of terminals as in the prior art. And a key matrix device capable of responding to the limitation of the number of terminals, etc., and suppressing an increase in cost due to an increase in the number of wiring cables.

[0020]

In order to solve the above-mentioned problems, a key matrix device according to the present invention comprises a plurality of lines connected to input / output terminals of a computer or the like, and each line has a matrix with other lines. The key switch is formed and short-circuited between the lines, and the diode is configured to transmit a signal only in one direction during key scanning. When a pulse signal is input from one of the lines, the key is switched from all other lines. A signal corresponding to the state is output, and the key state is scanned by sequentially switching the input and output of the pulse signal on each line, thereby detecting the press of the key switch.

As described above, with the addition of a simple hardware circuit, it is possible to detect the depression of a larger number of key switches with the same number of terminals as in the prior art, and to cope with the limitation of the number of terminals of a computer or the like. In addition to this, it is possible to suppress an increase in cost due to an increase in distribution cables.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a key matrix device according to a first aspect of the present invention, a matrix is formed by a plurality of lines connected to input / output terminals of a computer or the like and other lines, and each intersection of the matrix is formed. And a diode for transmitting a signal in only one direction at the time of key scanning for detecting the state of the key switch, and a pulse signal is input from one of the lines. A signal corresponding to the key state is output from all the other lines when it is performed, and each line performs a key scan for detecting the state of the key switch while sequentially switching between pulse signal input and output. .

According to this configuration, when a pulse signal is input from one of the lines, a signal corresponding to the key state is output from all the other lines, and each line switches between the pulse signal input and output sequentially. By scanning the key state, the press of the key switch is detected.

Hereinafter, a key matrix device according to an embodiment of the present invention will be specifically described with reference to the drawings. FIG. 1 is a circuit diagram showing an example of the configuration of the key matrix device of the present embodiment, FIG. 2 is an example of a time chart waveform diagram showing a key scan operation in the circuit diagram of the present embodiment, and FIG. FIG. 4 is a diagram illustrating the relationship among the number of input / output terminals, the number of key switches that can be detected, and the number of required diodes in the circuit diagram of FIG.

In FIG. 1, Pio0-Pio7 are lines connecting input / output terminals of a computer or the like, and K00-K
55 is a key switch, R0 to R7 are resistors, and D0 to D7 are diodes. Also, in FIG.
io7 is a signal waveform on a line connecting input / output terminals of a computer or the like.

The operation of the key matrix device configured as described above will be described below. As shown in the circuit example of FIG. 1, eight input / output terminals of a computer or the like are connected to lines Pio0 to Pio7. FIG. 2 is an example of a key scan waveform when the key switch K11 is pressed in the circuit example of FIG.

The computer or the like first sets the line Pio0
To the line Pio1 to Pi
Input from o7. When line Pio0 is at L level,
The vertical lines of the key switches K00 to K06 go to the L level through the diode D0. Key switch K00-K
06 is not pressed, the lines Pio1 to Pio
7 goes high because it is pulled up by the resistors R1 to R7. When any one of the key switches K00 to K06 is pressed, the lines Pio1 to Pio7 where the key switches are short-circuited are set to the L level. Computers and the like are connected to the lines Pio1 to Pio7.
By inputting more signals, the key switches K00 to K00
The state of K06 can be detected.

Next, the line Pio0 is in a high impedance state, an L-level output is output to the line Pio1, and an input is performed from the lines Pio0, Pio2 to Pio7. Also in this case, the key switch K07 is passed through the diode D1 in the same manner as when the line Pio0 is at the L level.
To K13 become L level, and the line Pio
0, the pressing of the key switches K07 to K13 can be detected at the signal levels of Pio2 to Pio7.

In the following, the L level output is sequentially performed on the lines Pio2 to Pio6, and signals are input from all seven lines other than the lines, whereby the key switches K00 to K
It is possible to detect the pressing of 55 key switch states of 55.

In this example, scanning is performed sequentially from Pio0, but the scanning order can be set arbitrarily. The circuit example of FIG. 1 is an L-active key matrix device in which an L-level signal is input to an arbitrary line and an L-level signal is output from another line when a key switch is pressed. Similarly to the above, an H active type structure in which an H level signal is input and an H level is output when a key switch is depressed, can be employed. In this case, the resistors R0 to R7 are configured to be pulled down, and the computer or the like uses the line Pio
An H-level output is performed for 0 to Pio7 or a high impedance state is set.

The number of lines can be arbitrarily configured as in the conventional circuit example. If the number of lines is n, the addition of n diodes will detect the pressing of n * (n-1) key switches. It can be performed.

The circuit example of this embodiment is an improvement of the conventional example shown in FIG. In the example of FIG. 7, the terminal that output when scanning was performed using the input / output terminal could not be used for input, and the terminal was not effectively utilized. this is,
This is because, when the matrix is combined with all the lines, pressing the key switch short-circuits the two lines, so that there are two key switches having the same scan result, and it cannot be determined.

For example, the key switch K00 and the key switch K07 are both key switches for short-circuiting the line Pio0 and the line Pio1, and even if any key switch is pressed, the same signal is output and it is indistinguishable. When either or both of the key switches K00 and K07 are pressed, the line Pio1 goes low when the line Pio0 outputs L, and the line Pio0 goes low when the line Pio1 outputs L. Becomes

In this embodiment, the diodes D0 to D0
D7 is necessary to distinguish two key switches that short-circuit between two lines. In the above-described example, when the key switch K00 is pressed by the diode D0, when the L level signal is input from the line Pio0, the line Pio1 is at the L level, but when the L level signal is input from the line Pio1. Since the diode D0 is reverse-biased, the line Pio0 goes high.

Conversely, when the key switch K07 is depressed, when the L level signal is input from the line Pio1 by the diode D1, the line Pio0 is at the L level, but the L level signal is input from the line Pio0. At this time, since the diode D1 is reverse-biased, the line Pi
o1 becomes H level. Since a signal opposite to the key switch K00 is output to the lines Pio0 to Pio1, it can be distinguished from the key switch K00.

As described above, in the conventional circuit example shown in FIG. 7, the two keys cannot be distinguished from each other, and there is a terminal which is not used by the scan signal. Since there is no terminal, unused terminals can be eliminated, and the number of key switches that can be detected can be doubled as compared with the circuit example of FIG.

FIG. 3 is a table summarizing the relationship between the number of input / output terminals, the number of key switches that can be detected, and the number of necessary diodes in the circuit of this embodiment.

[0038]

As described above, according to the present invention, a plurality of lines connected to input / output terminals of a computer or the like, and each line forms a matrix with other lines, and a key for short-circuiting between the lines. With the configuration of the switch and the diode for transmitting a signal only in one direction at the time of key scanning, when a pulse signal is input from one of the lines, a signal corresponding to the key state is output from all other lines,
By scanning the key state while the pulse signal input and output of each line are sequentially switched, the press of the key switch can be detected.

Therefore, by adding a simple hardware circuit, it is possible to detect the depression of a larger number of key switches with the same number of terminals as in the prior art, and to cope with the limitation of the number of terminals of a computer or the like. At the same time, an increase in cost due to an increase in the number of wiring cables can be suppressed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a key matrix device according to an embodiment of the present invention.

FIG. 2 is a time chart waveform diagram showing a key scan operation in the embodiment.

FIG. 3 is a diagram illustrating the relationship among the number of input / output terminals, the number of key switches, and the number of diodes in the embodiment.

FIG. 4 is a circuit diagram 1 showing a configuration of a conventional key matrix device.

FIG. 5 is a time chart waveform diagram showing a key scan operation in the conventional example (circuit diagram 1).

FIG. 6 is a circuit diagram 2 showing a configuration of a conventional key matrix device.

FIG. 7 is a circuit diagram 3 showing a configuration of a conventional key matrix device.

FIG. 8 is a time chart waveform diagram showing a key scan operation in the conventional example (circuit diagram 3).

FIG. 9 is a diagram illustrating the relationship among the number of input / output terminals, the number of key switches, and the number of diodes in each conventional example.

[Explanation of symbols]

 Pi0-Pi7 input terminal Po0-Po7 output terminal Pio0-Pio7 input / output terminal K00-K55 Key switch R0-R7 Resistance D0-D7 Diode

Claims (1)

[Claims] 1. A matrix is formed by a plurality of lines connected to input / output terminals of a computer or the like and other lines,
A key switch disposed at each intersection of the matrix for short-circuiting between the lines, and a diode for transmitting a signal in only one direction during key scanning for detecting the state of the key switch; When a pulse signal is input from the other, a signal corresponding to the key state is output from all the other lines, and the pulse signal input and output of each line are sequentially switched, and the key is used for detecting the state of the key switch. A key matrix device configured to scan.