JP2009032203A - Key scan circuit, electronic apparatus, and key scan method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a key scan circuit, an electronic apparatus and a key scan method, capable of detecting simultaneous depression of three or keys more without a combination limitation. <P>SOLUTION: An identical ON resistance value Rs is provided for each of key switches K111-K155 of a key matrix 101. With reference to an input line voltage value Vtrue stored in advance in a memory 15 and with an input line key switch closed, the voltage value on each input line acquired by setting an output line at a low level is compared with Vtrue, and a key switch on the input line with a voltage value matching Vtrue is judged to be in the closed state. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a key scan circuit having a plurality of operable keys, an electronic apparatus, and a key scan method.

Many small electronic devices such as mobile phones and PDAs (Personal Digital Assistants) that have been widely used in recent years are provided with a plurality of operable keys such as numeric keys.
Such electronic devices are complicated in operation as their functions are improved, and it is difficult to handle all the functions of the electronic device only by using a conventionally provided key alone. . For this reason, it is required to enable more complex operations without increasing the number of keys by detecting simultaneous pressing of a plurality of keys provided in an electronic device.

However, a conventional electronic device having a plurality of operation keys cannot accurately detect three or more simultaneous presses. Hereinafter, a key detection circuit for operation keys of a conventional electronic device will be briefly described.
FIG. 1 is a diagram showing a key scan circuit 200 of a conventional electronic device having a plurality of operation keys.
As shown in FIG. 1, a key scan circuit 200 includes a key matrix 201 composed of a total of 25 keys of 5 × 5, and an arithmetic unit that can detect the on / off state of these keys by scanning the key matrix. 202.

The key matrix 201 has a configuration in which 25 keys of the key switches K200 to K255 are arranged in a matrix.
Lines L21 to L25 are connected to the output port 21 of the arithmetic unit 202, lines I21 to I25 are connected to the input port 22, and pull-up resistors R21 to 25 are connected to the lines I21 to I25, respectively.

  The arithmetic unit 202 detects the open / closed state of the key switches K211 to K255 by sequentially outputting the low level key scan signal S21 to the lines L21 to L25 connected to the output port 21 and scanning the key matrix 201. .

A specific example of key scanning will be briefly described below.
For example, when the key scan signal S21 is output to the line L21 and the key switches K211, K221, K231, K241, and K251 on the line L21 are all open, the lines I21 to I25 connected to the input port 22 are output. All the key sense signals S22 are at a high level.
Here, if the key switch K211 is pressed, a low level key sense signal S22 is input to the input port 22 on the line I21 and a high level key sense signal S22 is input to the other lines I22 to I25. It can be detected that the key switch K211 located at the intersection of the line L21 and the line I21 on the key matrix 201 is closed.

When two key switches, for example, K211 and K221 are closed at the same time, the low-level key sense signal S22 is input to the lines I21 and I22 to the input port 22 of the calculation unit 202. It can be detected that the key switch K211 located at the intersection of the line L21 and the line I21 on the matrix 201 and the key switch K221 located at the line L21 and the line I22 are closed.
In addition, when two key switches, for example, K211 and K212 are closed at the same time, when a key scan signal is output from the output port 21 of the arithmetic unit 202 to the line L21, the input port 22 has a low level on the line I21. When the key sense signal is input and the key scan signal is output from the output port 21 to the line L22, the low-level key sense signal is input to the line I21 to the input port 22. It can be detected that the key switch K211 located at the intersection of the line L21 and the line I21 and the key switch K212 located at the intersection of the line L22 and the line I21 are closed.

Next, for example, consider a case where three keys corresponding to the key switches K211, K212, and K221 are pressed simultaneously.
In this case, when the low level key scan signal S21 is output to the line L21 of the output port 21, the key switches K211 and K221 are closed, so that the input port 22 has the low level and the line I21 and I22. A high level key sense signal S22 is input to I23, I24 and I25.

Next, when the key scan signal S21 is output to the line L22, a short circuit occurs between the key switches K211 and 221 and a low level key sense signal is input to the line I22 of the input port 22. As a result, the key scan circuit 200 erroneously recognizes that the non-closed key switch K222 is closed.
Such a situation may occur when a plurality of key switches on the same output line (any of lines L21 to L25) and key switches on other output lines are closed simultaneously.

That is, in the conventional key scan circuit 200, when three or more keys are simultaneously pressed, the key scan circuit may not accurately detect the key switch closed by the key press.
In order to avoid such a situation, there are techniques disclosed in Patent Documents 1 and 2, for example.
Japanese Patent Laid-Open No. 5-189116 JP 2004-78688 A

Japanese Patent Application Laid-Open No. 2004-228561 discloses a technique that can correctly detect three or more simultaneous pressings by providing a diode in each key switch and blocking a key sense signal of a key switch that is not closed.
Also, in Patent Document 2, by preparing a plurality of key matrices for keys that are supposed to be pressed simultaneously, if there are two or less keys pressed simultaneously in the same key matrix, three or more simultaneous presses are detected. Possible techniques are disclosed.

However, the technique disclosed in Patent Document 1 has a disadvantage that the cost increases because it is necessary to prepare a diode for each key switch. Further, in a small electronic device, there is a disadvantage that it is difficult to secure a space for preparing a diode in the key switch.
In addition, the technique disclosed in Patent Document 2 has a disadvantage that three or more simultaneous presses within the same key matrix cannot be detected. Furthermore, there is a disadvantage that the number of output / input ports of the key scan circuit increases.

  The present invention has been made to solve the above disadvantages, and an object of the present invention is to provide a key scan circuit, an electronic apparatus, and a key scan method capable of detecting three or more simultaneous presses without limitation of combinations. .

  In order to solve the above-described problem, a key scan circuit according to a first aspect of the present invention is a key matrix in which a plurality of key switches corresponding to a plurality of keys are arranged in a matrix, and the key matrix scanned by the key matrix is closed. A calculation unit that detects a key switch; and a power supply unit that supplies power to the key matrix, wherein each of the key switches has an on-resistance value, and the calculation unit includes the plurality of key switches. A voltage measuring unit that measures a voltage value in each of the key switches when any of the key switches is closed; a storage unit that stores in advance a voltage value when any of the plurality of key switches is closed; And the arithmetic unit detects the closed key switch by comparing the voltage value measured by the voltage measuring unit with the voltage value stored in the storage unit.

  An electronic apparatus according to a second aspect of the present invention is an electronic apparatus including an input unit having a plurality of keys, and includes a key scan circuit that detects which one of the plurality of keys is operated. A key matrix in which a plurality of key switches that open and close according to the operation of the plurality of keys are arranged in a matrix, a calculation unit that scans the key matrix and detects the closed key switches, and the key matrix A power supply unit for supplying power, wherein each of the key switches has an on-resistance value, and when the operation unit closes any one of the plurality of key switches, each of the key switches A voltage measuring unit that measures a voltage value in the memory, and a storage unit that stores in advance a voltage value when any of the plurality of key switches is closed, Calculation unit detects a key switch, which is closed by comparing the voltage value by the voltage measuring unit is measured, and a voltage value stored in the storage unit.

  According to a third aspect of the present invention, there is provided a key scanning method, comprising: a key matrix corresponding to a plurality of keys and having a plurality of key switches having on-resistance values arranged in a matrix; and the key switch closed by scanning the key matrix. A key scan method of a key scan circuit having a calculation unit to detect and a power supply unit that supplies power to the key matrix, and when each of the plurality of key switches is closed, A step of measuring a voltage value in the key switch, a step of comparing a voltage value when any of the plurality of key switches stored in advance is closed and the voltage value measured in the step, And a step of detecting a closed key switch based on a result of the process comparison.

  According to the present invention, it is possible to provide a key scan circuit, an electronic device, and a key scan method capable of detecting three or more simultaneous presses without limitation on combinations.

Hereinafter, a portable terminal 1000 will be described as an example of the electronic apparatus of the present invention.
The mobile terminal 1000 of this embodiment is a mobile phone, for example.
FIG. 2 is a diagram illustrating an example of the configuration of the mobile terminal 1000.
As illustrated in FIG. 2, the mobile terminal 1000 includes a communication unit 1, a storage unit 2, a display unit 3, an input unit 4, and a control unit 5.

The communication unit 1 is a wireless communication unit that communicates with a public network and transmits / receives data via a base station (not shown) in FIG. Examples of data transmitted and received by the communication unit 1 include voice data when the mobile terminal 1000 is in a voice call, web page data when web browsing, and the like.
The storage unit 2 is a memory that stores data necessary for various operations of the mobile terminal 1000, and includes, for example, an SRAM (Static Random Access Memory). The data stored in the storage unit 2 includes, for example, a program for executing various operations of the mobile terminal 1000, and a plug-in as a playback program of the present invention for executing a plug-in playback function at the time of web browsing to be described later Program, address book data for voice calls and mail transmission / reception, voice data necessary for executing a voice reading function to be described later, and the like.

  The display unit 3 is a display device for performing display related to various operations of the mobile terminal 1000, and includes, for example, a liquid crystal display (LCD) or an organic EL (electroluminescence) panel. The display unit 3 is, for example, an outgoing / incoming screen for voice calls, a voice call screen for voice calls, a web browser screen for web browsing, a mail creation screen, a mail reception screen, or the like.

The input unit 4 is an input device that accepts various inputs to the mobile terminal 1000, and includes, for example, a cross key or a numeric keypad.
The input unit 4 includes the key scan circuit 100 and detects which key is pressed. Details of the key scan circuit 100 will be described later.

  The control unit 5 is a control device that performs overall control of various configurations of the mobile terminal 1000 and executes various functions of the mobile terminal 1000, and includes, for example, a CPU (Central Processing Unit). The various functions executed by the control unit 5 are, for example, a voice call function, a mail transmission / reception function, and the like. The control unit 5 acquires an input signal (a signal indicating which key of the input unit 4 is pressed) output from the calculation unit 102 of the key scan circuit 100 described later, and controls various functions in accordance with this. .

Hereinafter, the key scan circuit 100 will be described.
FIG. 3 is a diagram illustrating a configuration of the key scan circuit 100.
The key scan circuit 100 includes a key matrix 101, a calculation unit 102, and a power supply voltage (corresponding to the power supply unit of the present invention) VDD that supplies power.

The key matrix 101 is normally open, and has key switches K111 to K155 that are closed when a plurality of keys of the input unit 4 are pressed, and pull-up resistors R11 to 15 (resistance values are uniformly R). .
The key switches K111 to K155 include output lines (corresponding to the first signal line group of the present invention) L11 to L15 connected to an output port of the arithmetic unit 102, which will be described later, and lines I11 to I15 connected to the input port 12. (Corresponding to the second signal line group of the present invention) and pull-up resistors R11-15 are connected to the lines I11-I15, respectively. Further, a power supply voltage VDD is connected to them. The pull-up resistor R is, for example, a resistance of about 100 kΩ to 200 kΩ.
Each of these key switches K111 to K155 has the same predetermined ON resistance value Rs.

The calculation unit 102 includes an output port 11, an input port 12, a voltage measurement unit 13, an A / D conversion unit 14, a storage unit 15, and a control unit 16.
The output port 11 and the input port 12 are ports for output and input of the arithmetic unit 102.
The voltage measurement unit 13 measures analog voltage values of the input lines I11 to I15 connected to the input port 12. Here, the voltage value of any one of the input lines I11 to I15 is the potential of the key switch located at the intersection of the output line being scanned and the input line.
The A / D (Analog / Digital) conversion unit 14 converts the analog voltage values of the input lines I11 to I15 measured by the voltage measurement unit 13 into digital values and outputs the digital values to the control unit 16.
The storage unit 15 stores the voltage value Vtrue of the input lines (lines I11 to I15) corresponding to the number of closed key switches. Details of Vtrue will be described later.

The control unit 16 controls the operation unit 102 overall.
Further, the control unit 16 sequentially outputs the low-level key scan signal S11 to the lines L11 to L15 connected to the output port 11, and as a result, the digital value of the voltage obtained from the A / D conversion unit 14 is used as a basis. Next, the open / close state of the key switches K111 to K155 is determined.

Hereinafter, a specific example of the key scan in the key scan circuit 100 will be described.
First, when one of the plurality of keys of the input unit 4 is pressed, that is, when one switch in the key matrix 101 is closed, for example, only the key switch K111 of the key matrix 101 shown in FIG. 3 is closed. The case will be described.
The control unit 16 first scans the key switches K111 to K151 with the line L11 at a low level. At this time, the voltage value of the line I11 measured by the voltage measuring unit 13 is VDD / (Rs / (R + Rs)) due to the pull-up resistor R11 and the ON resistance Rs of the key switch K111. On the other hand, the voltage value of the lines I12 to I15 is VDD. That is, the voltage value of the input line where the key switch is closed is different from the voltage value of the input line which is not closed. The control unit 16 detects the closed key switch by detecting these differences.

Next, a case where two keys in the key matrix 101 are closed, that is, a case where, for example, the key switches K111 and K121 are closed will be described.
When the control unit 16 scans the key switches K111 to K151 with the line L11 at a low level, the voltage value of the line I11 measured by the voltage measurement unit 13 is equal to VDD / (Rs / (R + Rs)). Similarly, the voltage value of the line I12 is also VDD / (Rs / (R + Rs)). The voltage value of the lines I13 to I15 is VDD. Therefore, since the voltage value of the input line I11 where the key switch K111 is closed and the input line I12 where the key switch K121 is closed differs from the voltage value of the input lines I13 to I15 which are not closed, the key switch K111. And that K121 is closed.

Next, a case where two keys are pressed simultaneously, for example, a case where the key switches K111 and K112 are closed will be described.
When the control unit 16 scans the key switches K111 to K151 with the line L11 at a low level, the voltage value of the line I11 measured by the voltage measurement unit 13 becomes VDD / (Rs / (R + Rs)), and the line I12 The voltage value of .about.I15 is VDD. Similarly, when the scan of K112 to K152 is performed with the line L12 at the low level, the voltage value of the line I11 becomes VDD / (Rs / (R + Rs), and the voltage value of the lines I12 to I15 becomes VDD. It is detected that the switches K111 and K112 are closed.

Next, a case where three keys are pressed simultaneously will be described.
For example, a case where keys corresponding to K111, K121, and K112 are simultaneously pressed, which is similar to the case where erroneous recognition occurs in a conventional key scan circuit, will be described.
First, when the control unit 16 scans the key switches K111 to K151 with the line L11 at a low level, the line I11 and the line I12 become VDD / (Rs / (R + Rs)).

Next, when scanning of the key switches K121 to K125 is performed with the line L12 at a low level, the voltage value of the line I11 becomes VDD * Rs / (R + 3Rs) due to a short circuit between the key switch K111 and the key switch K121. The voltage value of the line I12 is VDD * 3Rs / (R + 3Rs).
FIG. 4 shows an equivalent circuit of the key scan circuit 100 when scanning is performed with the line L12 at the low level when three are simultaneously pressed.
FIG. 4A shows only the components that contribute to the voltage drop among the components of the key matrix 101, and FIG. 4B shows an equivalent circuit thereof.

Here, the control unit 16 sets the voltage value when the key switch is closed in advance, that is, VDD * Rs / (R + 3Rs), the key switch on the line I11 that matches the voltage value Vtrue stored in the storage unit 15. It is determined that K112 is closed, and it is determined that the key switch K122 on the line I12 whose voltage value does not match Vtrue is not closed.
Vtrue is a value that can be taken by the voltage value of the input line calculated in advance and stored in the storage unit 15 when the key switch on the input line is closed. That is, in order to detect three or more simultaneous presses, VDD / (Rs / (R + Rs)) and VDD * Rs / (R + 3Rs) are stored in advance in the storage unit 15 as Vtrue. By referring to this, the control unit 16 can detect a closed key switch even when three or more buttons are simultaneously pressed.

When three or more key switches on the same output line (any of L11 to L15) are closed at the same time, or three or more key switches on the same input line (any of I11 to I15) Since the voltage values of the input lines including the closed key switches are all the same as in the case of the two simultaneous pressing described above, the control unit 16 can easily close the key switches. Can be judged.
As described above, the control unit 16 can detect three or more simultaneous presses.

Next, an operation example at the time of determination by the control unit 16 when any of the key switches is closed will be described with reference to FIG.
FIG. 5 is a flowchart illustrating an operation example of the control unit 16 when any one of the key switches is closed.

Step ST1:
The control unit 16 sets the output lines (L11 to L15) Li (i is any one of 11 to 15) to a low level.
Step ST2:
The control part 16 acquires the voltage value which the voltage measurement part 13 measured from the A / D conversion part 14 as a result of step ST1.

Step ST3:
The control unit 16 excludes the voltage values of the lines I11 to I15 acquired in step ST2 whose voltage value is VDD. This is because the key switch on the input line whose voltage value is VDD is not closed.
Step ST4:
The control unit 16 compares the voltage values of the lines I11 to I15 acquired in step ST2 with the Vtrue in the storage unit 15 and the voltage value.

Step ST5:
In step ST4, the control unit 16 determines that the key switch on the input line of the voltage value that matches Vtrue is closed.
Step ST6:
The control unit 16 sets i = i + 1 and returns to step ST1 until scanning of all output lines is completed.
By doing so, the key scan circuit 100 of the present embodiment can detect three or more simultaneous presses.

  As described above, in the mobile terminal 1000 having the key scan circuit 100 of the present embodiment, the key switches K111 to K155 of the key matrix 101 have the same ON resistance value Rs, and are stored in the storage unit 15 in advance. Further, referring to the voltage value Vtrue of the input line when the key switch on the input line is closed, the voltage value of each input line obtained as a result of setting the output line to the low level is compared with Vtrue, and Vtrue and Since it is detected that the key switch on the input line of the matching voltage value is closed, the key switch closed by the simultaneous pressing can be correctly detected even when three or more simultaneous pressings are performed. Moreover, since the ON resistance provided to each key switch is cheaper than, for example, a diode, the manufacturing cost can be kept relatively low.

  When comparing the voltage values of the input lines with each other, the voltage value of the input line with the key switch closed (eg, VDD * Rs / (R + 3Rs) in the above example) and the input line with the key switch not closed. Voltage value (for example, VDD * 3Rs / (R + 3Rs) in the above-described example) needs to be different from each other to such a degree that it can be compared. Experience has shown that a resistance value of about 20% is sufficient.

The present invention is not limited to the embodiment described above.
That is, when implementing the present invention, various modifications, combinations, sub-combinations, and alternatives may be made with respect to the components of the above-described embodiments within the technical scope of the present invention or an equivalent scope thereof.

In the above-described embodiment, three or less simultaneous presses have been described. However, the key scan circuit of the present invention can detect four or more simultaneous presses. When voltage values of a plurality of types of input lines different from VDD are detected due to a short circuit, this can be dealt with by storing Vtrue in that case in the storage unit 15 in advance.
In the above-described embodiments, the ON resistance values Rs are all set to the same value Rs. However, the present invention is not limited to this, and may be set to different resistance values. In this case, since the voltage value of the input line is uniquely determined by how many key switches are closed, it is easy to store the voltage value Vtrue when the keys are simultaneously pressed in the storage unit 15 in advance. It is possible to detect a key switch that is closed.

  In addition to the portable terminal 1000, the key scan circuit 100 of the above-described embodiment can be applied to a portable electronic device having a plurality of keys such as a PDA.

FIG. 1 is a diagram illustrating a key scan circuit of a conventional electronic device having a plurality of operation keys. FIG. 2 is a diagram illustrating an example of the configuration of the mobile terminal according to the present embodiment. FIG. 3 is a diagram showing the configuration of the key scan circuit of this embodiment. FIG. 4 is a diagram showing an equivalent circuit of the key scan circuit when three keys are simultaneously pressed in the key scan circuit of the present embodiment. FIG. 5 is a flowchart showing an operation example of the control unit when any key switch is closed in the key scan circuit of the present embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1000 ... Portable terminal, 1 ... Communication part, 2 ... Memory | storage part, 3 ... Display part, 4 ... Input part, 5 ... Control part, 100 ... Key scan circuit, 101 ... Key matrix, 102 ... Calculation part, 11 ... Output port , 12 ... input port, 13 ... voltage measurement unit, 14 ... conversion unit, 15 ... storage unit, 16 ... control unit, L11 to L15 ... output line, I11 to I15 ... input line, 200 ... key scan circuit, 201 ... key Matrix, 202 ... operation unit, 21 ... output port, 22 ... input port, S11 ... key scan signal, S21 ... key scan signal, S22 ... key sense signal, R ... resistance value of pull-up resistor, Rs ... key switch K111 ON resistance value of each of 155, L21-25 output lines (first signal line group), I21-25 input lines (second signal line group)

Claims (4)

A key matrix in which a plurality of key switches corresponding to a plurality of keys are arranged in a matrix, and
An arithmetic unit that scans the key matrix and detects the closed key switch;
A power supply unit for supplying power to the key matrix;
Have
Each of the key switches has an on-resistance value,
The computing unit is
A voltage measuring unit that measures a voltage value in each key switch when any of the plurality of key switches is closed;
A storage unit for preliminarily storing a voltage value when any of the plurality of key switches is closed;
Have
The key scanning circuit, wherein the arithmetic unit detects a closed key switch by comparing a voltage value measured by the voltage measuring unit with a voltage value stored in the storage unit. The key matrix is
A plurality of first signal line groups;
A plurality of second signal line groups;
A plurality of key switches arranged at each intersection of the first signal line group and the second signal line group;
Have
The voltage measurement unit measures a voltage value of the key switch by measuring a voltage value of the second signal line group when any one of the first signal line groups becomes a low level. The key scan circuit according to claim 1, wherein: An electronic device including an input unit having a plurality of keys,
A key scanning circuit for detecting which one of the plurality of keys is operated;
The key scan circuit includes:
A key matrix in which a plurality of key switches that open and close in response to operations of the plurality of keys are arranged in a matrix;
An arithmetic unit that scans the key matrix and detects the closed key switch;
A power supply unit for supplying power to the key matrix;
Have
Each of the key switches has an on-resistance value,
The computing unit is
A voltage measuring unit that measures a voltage value in each key switch when any of the plurality of key switches is closed;
A storage unit for preliminarily storing a voltage value when any of the plurality of key switches is closed;
Have
The electronic device is characterized in that the calculation unit detects a closed key switch by comparing the voltage value measured by the voltage measurement unit and the voltage value stored in the storage unit. A key matrix in which a plurality of key switches corresponding to a plurality of keys and having an on-resistance value are arranged in a matrix, an arithmetic unit that scans the key matrix to detect the closed key switches, and the key matrix A key scanning method of a key scanning circuit having a power supply unit for supplying power,
A step of measuring a voltage value at each key switch when any of the plurality of key switches is closed;
Comparing a voltage value when any of the plurality of key switches stored in advance is closed with the voltage value measured in the step;
Detecting a closed key switch according to the comparison result of the step;
A key scanning method characterized by comprising:

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