JPH077322B2 - Keyboard device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a scan type keyboard device.

[Technical background of the invention and its problems]

In the scan type keyboard, there are 2 key lockout and N key rollover as modes for capturing data. The latter is, for example, a new buffer (where N key codes are stored) that stores the key code when both are turned on after scanning twice with an interval of 5 milliseconds. The key code is compared with the contents of the old buffer in which the key code is stored to determine whether the key is pressed or released. That is, it allows multiple keystrokes and is suitable for relatively skilled operators.

The key matrix of this type of keyboard device is constructed as shown in FIG. The operation is shown as a timing chart in FIG. That is, the key matrix is scanned by the control unit (not shown).
The scanning signals shown as 11-SCAN14 are supplied and the return line from the key matrix is RETU
It is read by the control unit via a return reading circuit (not shown) at the timing indicated by RN11 to 14 reading timing.

Now temporarily switch the S106 / S107 / S111 key switches to N at the same time.
When in the state, they are read at times T ₁₂ and T ₁₃ , respectively.

Here, the operation of the circuit (see FIG. 2) in the case where there is no current sneak prevention diode shown as D _{1 to} D ₁₆
The following is a description based on the timing chart shown in the figure. That is, under the control of the control unit, the scanning signals shown in SCAN1 to SCAN4 are supplied to the key matrix, and the return line from the key matrix passes through the return reading circuit at the timing shown in RETURN1 to 4 reading timing. Read by the control unit. now,
If the S6, S7, and S11 key switches are in the N state at the same time, S6 and S7 can be correctly read at the time of T ₂ by SCAN2, RETURN2, and RETURN3. However, at the time of T ₃ , SCAN 3 and RETURN 2 and RETURN 3 cause the second
Due to the current flowing through the path shown in the figure, at the same time as S11, S10 is read as if it is N although it is not N.

Therefore, a keyboard device capable of multiple keystrokes requires a current sneak prevention diode corresponding to each key switch, which has potential drawbacks such as an increased number of parts and an increased price.

[Object of the Invention]

The present invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to provide a keyboard device capable of multiple keystrokes at low cost, which does not include a current sneak prevention diode corresponding to each key forming a matrix. .

[Outline of Invention]

According to the present invention, in order to realize the above-mentioned keyboard device, each return line is read at a different time in response to scanning of a key matrix, and the level of the return line is analog-input and AD converted. Is compared with the value registered in advance as the return level of each key switch, and the key input is enabled only when it is within the valid range. Multiple keys can be typed without a wraparound prevention diode.
This makes it possible to provide a keyboard device that is inexpensive and has a small number of circuit components.

Example of Invention

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a control unit. The control unit 1 is composed of a microprocessor, etc.
The analog-digital (A-D) converted data in the return signal reading circuit 4 in the case of the state is stored. Reference numeral 2 is a scan drive circuit. Scan driving circuit 2 is key matrix 3 for supplying a scanning signal to the key matrix 3 has its details are shown in Figure 2.

Reference numeral 4 is a reading circuit for reading a return signal from the key matrix. In the conventional example, the return signal was digitally read, but in the present invention, it has an AD conversion function. A bus line 5 connects the control unit to the scan drive circuit and the return signal reading circuit to transmit data and control signals.

In the key matrix 3 shown in FIG. 2, S1 to S16 form a key matrix, for example, a rubber contact type key switch, and R1 to R4 are pull-up resistors that suppress the current supplied to the key matrix. . Further, SCAN1 to SCAN4 are scanning signals, and RETURN1 to RETURN4 are return signals.

FIG. 3 is a timing chart showing the operation of the embodiment of the present invention, and the symbols and reference numerals shown in the figure match those of FIG.

The operation of the embodiment of the present invention will be described below with reference to the timing chart of FIG.

First, under the control of the control unit 1, S is set in the key matrix 3.
The scanning signals shown in CAN1 to SCAN4 are supplied, and the return line from the key matrix 3 is RET.
It is read by the control unit 1 via the return reading circuit 4 at the timing shown in reading URN1 to reading RETURN4. That is, the states of all the key switches are read at different timings, and now assume that the S6, S7, and S11 key switches are in the N state at the same time. The voltage levels of the return signals are read by the return signal reading circuit 4 at the times of T ₁₂₂ , T _132, and T ₁₃₃ , respectively.
When the -D converted data is sent to the control unit 1, the control unit 1 compares it with the voltage value of each switch at the time of N in advance, and when it is determined that the return signal is caused by the wraparound and is not apparent. Accept it as a valid keystroke.

Note that an apparent S10 detection signal is generated in the RETURN2 line at the time of T _{123 due} to the current flowing in the path. However, at this time, in the RETURN2 line, the switches S6 ・ S7 ・ S11
A voltage drop occurs due to the resistance of the switch, and its value is different from that when switch S10 is actually N.
The control unit 1 recognizes that it is an apparent return signal due to wraparound by comparing with the voltage value of the switch S10 at the time of N, and does not accept it.

The present invention is not limited to the keyboard device, but can be applied to all detection methods of switches arranged in a matrix.

〔The invention's effect〕

As described above, according to the present invention, it is not necessary to provide a key switch that constitutes a key matrix and a corresponding current sneak prevention diode, so that the keyboard device is inexpensive and has a small number of circuit components and is capable of multiple keystrokes. Can be provided.

[Brief description of drawings]

1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing the internal structure of the key matrix shown in FIG. 1, and FIG.
FIG. 4 is a timing chart showing the operation of the embodiment of the present invention, FIG. 4 is a diagram showing the internal structure of a conventional key matrix, and FIGS. 5 and 6 are operation timing charts of the conventional example. 1 ... Control unit, 2 ... Scan drive circuit, 3 ... Key matrix, 4 ... Return signal reading circuit.

Claims (1)

[Claims] 1. A plurality of keys having a plurality of scan lines, a plurality of return lines, and a resistance component, and electrically connecting / disconnecting both lines at an intersection of the scan line and the return line. A switch unit, means for applying a voltage to the scan line at different times, connected to the return line to detect whether the voltage of each return line is at a predetermined level, and the voltage of the return line is A detection means for validating the input key at a predetermined level is provided, and if the voltage of the return line is not at a predetermined level, the current sneak-prevention diode is not necessary because it is erroneously detected by the sneak current of multiple keystrokes Keyboard device characterized by.