JPH0651895A - Switch input detector - Google Patents

Abstract

PURPOSE:To reduce the influence of noise caused by a key scan signal. CONSTITUTION:While no switch on a key matrix is pressed, an output signal from the output port of a signal output part 16 is completely set at a low level. When any switch is pressed and any input port of a signal input part (a) is turned to the low level, the key scan signal is outputted from the signal output part 16 by an operation processing part 20. When it is detected which switch is turned on in response to the key scan signal, the operation processing part 20 stops outputting the key scan signal and outputs a normal signal from the signal output part 16 for judging the OFF of the switch.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switch input detecting device, and more particularly to a switch input detecting device for detecting opening / closing of switches arranged in a matrix structure.

[0002]

2. Description of the Related Art In conventional switch input detection of this type, (a) a signal output section always outputs temporally different pulses (hereinafter referred to as "key scan signal") for each row of a key matrix to input a signal. Method to detect which switch is closed or opened by the appearance or disappearance of a pulse synchronized with the key scan signal in
(b) The key scan signal is not output when all the switches are open, and if any switch is detected to be closed by some method, the key scan signal is output until all the switches are opened. , There was a way to detect when each switch was opened.

[0003]

Since such a key scan signal is repeatedly output at an arbitrary cycle, if there is an amplifier circuit in the vicinity of this key matrix, this key scan signal becomes a very troublesome noise source. turn into. In the above-mentioned conventional technique, the key scan signal which is the noise source is always output in the method (a),
Also, in the method (b), the output is output as long as one of the switches is closed. Therefore, the influence of noise due to the key scan signal is not small in any of the conventional methods.

Therefore, a main object of the present invention is to provide a switch input detection device which can reduce the influence of noise caused by a key scan signal.

[0005]

According to the present invention, a key matrix in which one of the contacts of each of a plurality of switches is wired in each row and the other of the contacts is wired in each column, and each key matrix is wired in each row. A signal output means for outputting a detection signal for detecting the opening / closing operation of each switch, and a signal input means wired for each column of the key matrix and receiving a signal output from the key matrix by opening / closing the switch. In the switch input detection device, the signal output means outputs a pulse that is temporally different for each row, and the signal input means detects which of the plurality of switches is closed by the coincidence of the timing of the input signal and the pulse After detecting that one of the switches is closed, the signal output section detects that the closed switch is in the open state instead of the pulse. Characterized in that so as to output a constant signal, a switch input detection device.

[0006]

When none of the switches on the key matrix is pressed, for example, the signal output means outputs a low level signal for each row, and the signal input means receives a high level signal from each column. Leave. Then, a key scan signal is output from the signal output unit when any switch is pressed. Then, when a pulse corresponding to the pulse of the key scan signal is input to the signal input means to detect which switch is closed, the signal output unit stops the output of the key scan signal and the closed switch is opened. It outputs a steady signal to detect the. This minimizes the time required to output the key scan signal that is a noise source.

[0007]

According to the present invention, the time during which the key scan signal that is a noise source is output is shortened, so that the influence of noise due to the key scan signal can be greatly reduced. The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a switch input detecting device 10 of this embodiment is used for a tape reproducing device, and switches 12a to 12i are arranged in 3 rows and 3 columns, and one of respective contacts is provided. Is wired for each row and the other is wired for each column. Each one contact of the switches 12a, 12b and 12c in the first row is connected to the output port O1 of the signal output unit 16 via the diode D1. Further, each one contact of the switches 12d, 12e and 12f of the second row is connected to the output port O2 of the signal output unit 16 via the diode D2. And the third
Each one-side contact of the switches 12g, 12h, and 12i of the row is connected to the output port O3 of the signal output unit 16 via the diode D3. On the other hand, the switches 12a,
The other contacts of 12d and 12g are connected to the input port I1 of the signal input unit 18 and also connected to the constant voltage source (+ B) via the resistor R1. Also, switch 12
The other contacts of b, 12e and 12h are the signal input unit 18
Input port I2 and a constant voltage source (+ B) via a resistor R2. The other contacts of the switches 12c, 12f and 12i are connected to the input port I3 of the signal input unit 18 and the resistor R3.
Is connected to a constant voltage source (+ B) via.

The signal output unit 16 and the signal input unit 18 are
Each is connected to the arithmetic processing unit 20, and the arithmetic processing unit 20
Controls the output operation of the detection signal from the signal output unit 16 for detecting that any of the switches 12a to 12i is opened or closed, and from the signal input unit 18, any of the switches 12a to 12i is Which of the switches 12a to 12i is opened or closed is detected based on the state of the signal input to the signal input unit 18 by being opened or closed.

When none of the switches are pressed, FIG.
As shown in, all output signals of the output ports O1, O2 and O3 are at low level, and the input ports I1, I2
And all the input signals of I3 are at high level. For example, if the switch 12g functioning as a tape reproducing switch is pressed at the time t1 shown in FIG. 2, only the input port I1 connected to the contact of the switch 12g responds to the output signal of the output port O3 to attain the low level. Becomes At this point, the arithmetic processing unit 20
The pressed switches are the switches 12a, 12d and 12
It cannot be determined which is g.

Therefore, next, the key scan signal is output from each of the output ports O1, O2 and O3 of the signal output section 16. Then, the time t3 of the first cycle of the key scan signal
When the low level signal is output from the output port O3 at the time t4 of the second cycle, the low level signal is input to the input port I1, and the output port O3 is output.
When the low level signal is output from 1 and O2, the low level signal is not input to the input port I1. Therefore, the arithmetic processing unit 20 determines that the switch 12g is reliably pressed.

At that time, that is, at time t4, the arithmetic processing unit 20 stops the output of the key scan signal from the signal output unit 16, and outputs only the output of the output port O3 to which the switch 12g is connected to the low level. The output of the output ports O1 and O2 is fixed to the high level. That is, the signal output unit 16 includes the switch 1
After detecting that 2g is closed, a steady signal that does not become a noise source is output instead of the key scan signal.

In this way, when it is determined that the switch 12g is pressed, the arithmetic processing unit 20 is switched to the switch 12g.
Is a tape playback switch, the tape playback unit 2
2 is controlled to reproduce the tape, and the reproduced sound is amplified by the amplifier 24 and output from the speaker 26. next,
At the time t5 shown in FIG. 2, the switch 1 that has been pressed.
When 2g is separated, the contact of the switch 12g opens and the input signal of the input port I1 becomes high level. The high-level signal input to the input port I1 is processed by the arithmetic processing unit 20.
Detects and detects that the closed switch 12g is opened. Then, at this time, the output signals of the output ports O1 to O3 and the input signals of the input ports I1 to I3 are returned to the initial state.

The operation of the arithmetic processing unit 20 of the switch input detection device 10 is performed based on the flow chart shown in FIG. First, in step S1, all output signals from the output ports of the signal output unit 16 are set to low level. Then, in step S3, the signal input unit 18
It is determined whether any one of the input signals input to each input port of has become low level. In step S3, when the low level signal is not input to any of the input ports, the process waits until the low level signal is input.

When it is determined in step S3 that the low level signal is input to any of the input ports, the process proceeds to step S5, and the key scan signal is output from each output port of the signal output section 16. Then, the process proceeds to step S7, and it is determined whether or not it has been determined which switch has been turned on by the input signal from any one of the input ports of the signal input unit in response to the key scan signal. If it is not determined in step S7 which switch has been turned on, the process returns to step S5 and the key scan signal for the second cycle is output.

When it is determined in step S7 which switch is turned on, the process proceeds to step S9,
It outputs a steady signal that can determine that the switch has been turned off by stopping the key scan signal. And step S1
Proceed to 1 to determine if the switch has been turned off.
If the switch is not turned off in step S11, the process stands by. When the switch is turned off in step S11, the process returns to step S1 and the processes of steps S1 to S11 are repeated until the power is turned off.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a timing diagram showing the operation of the embodiment shown in FIG.

3 is a flowchart showing the operation of the arithmetic processing unit shown in FIG.

[Explanation of symbols]

 10 ... Switch input detection device 12a-12i ... Switch 14 ... Key matrix 16 ... Signal output part 18 ... Signal input part 20 ... Arithmetic processing part

Claims (1)

[Claims] 1. A key matrix in which one of the contacts of each of a plurality of switches is wired in each row and the other of the contacts is wired in each column, and each switch is opened / closed by being wired in each row of the key matrix. Signal output means for outputting a detection signal for detecting an operation, and signal input means wired for each column of the key matrix to receive a signal output from the key matrix by opening / closing the switch, A switch input detection device that outputs a pulse that differs temporally for each row from the signal output means, and that the signal input means detects which of the plurality of switches is closed by coincidence of the timing of the input signal and the pulse. In the case where the closed switch is opened in place of the pulse from the signal output unit after detecting that one of the switches is closed, A switch input detection device, which is configured to output a steady signal for detecting that the switch input state is reached.