JPH03288919A - System for preventing erroneous output of keyboard when pushing-down multiple keys - Google Patents

Abstract

PURPOSE:To reduce the number of electronic parts and to reduce an area for packaging the electronic parts by executing a check processing for preventing an erroneous output by using an erroneous output key check program when the state of key scan is changed. CONSTITUTION:As a hardware, this keyboard is equipped with a key matrix 1, key scan line decoder 2, one-chip microcomputer 3 for controlling the keyboard, interface circuit 4 and connector 5. In such a case, when the state of the key is changed, according to the erroneous output key check program, the erroneous output is prevented by masking key switch data changed to an ON state with the possibility of the erroneous output. Thus, it is not necessary to mount any diode to each switch, to increase the number of electronic parts and to secure the area for packaging the electronic parts.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for preventing erroneous output when multiple keys are pressed on a keyboard used as an input device for an information processing device.

[Conventional technology]

Conventionally, as a method for preventing erroneous output in this type of keyboard, a switch SWI is used as shown in FIG.

SW3. When SW5 is on, when line X2 is scanned, line Yl is caused by a loop current.

Since key-on data will be output as scan data for Y3, in order to prevent erroneous output that the SW7 key has been pressed, prevent erroneous output by suppressing the current flowing through each switch as shown in Figure 7. It was equipped with a diode D. According to this, each switch SW1 to SW
Since the current direction at 8 is limited to one direction, wraparound due to reverse current (generated at switch SW1 in the example of FIG. 6) is prevented.

[Problem to be solved by the invention]

In the conventional erroneous output prevention method described above, since a diode is mounted on each switch, it is essential to increase the number of components and secure an area for mounting electronic components.

In addition, in keyboards that use membrane switches or integrated rubber contacts, it is structurally difficult to mount a diode near the switch element, so it is necessary to separate the diode mounting area for the erroneous output prevention method away from the switch element.
Another drawback is that it requires a special implementation method.

[Means to solve the problem]

The method for preventing erroneous output when multiple keys are pressed in the keyboard of the present invention is based on an nxm key matrix, inputting data from m input lines of this key matrix, reading scan data from n output lines, and detecting presses. In the keyboard, the processing means determines a key, converts the code, and outputs the code, when the m input lines are sequentially scanned one by one, the processing means calculates the result of the previous scan of the same input line. When a change in is detected, the scan results of other input lines are read out, and the scan result of the one input line indicates the on state of the key, and the scan result of the other input line indicates the on state of the key. The present invention is characterized in that when two or more output lines match, the state change of the key that has turned on this time among the scan results of the one input line is invalidated.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a functional block diagram in one embodiment of the present invention. As hardware, the keyboard includes a key matrix 1, a key scan line decoder 2, a one-chip microcomputer 3 for controlling the keyboard, an interface circuit 4, and a connector 5. On the other hand, FIG. 2 shows the key matrix 1 and switch circuit configuration in FIG. 1.

FIG. 3 is a schematic functional flowchart of the one-chip microcomputer 3 for keyboard control in FIG. 1, and FIG. 4 is a schematic functional flowchart of the erroneous output key check section of FIG.

The one-chip microcomputer 3 for keyboard control sets scan data in the key scan decoder 2, selects the l line of the input X lines, and reads the scan data from the output Y line. If this is the case, the code is converted and outputted to the information processing device (upper device) via the connector 5 in a format specified by the interface circuit 4.As shown in FIG. is not implemented, the scan data may contain incorrect key-on data.

As shown in Figure 3, the keyboard control one-chip microcomputer functions, and when there is a change in the state of the key,
The erroneous output key check program masks key switch data that has been turned on and that may cause erroneous output, thereby preventing erroneous output. This will be explained in detail with reference to FIG.

The one-chip microcomputer 3 has an output line Y1 for each human power line X1 to X16 in its own work area.
A 16 x 8 bit key map that stores the scan result data of ~Y8, an 8 bit scan data area that temporarily stores the current scan result data for one specified input X line, and one specified input X line. It has an 8-bit change data area that stores the position of the output line whose state has changed (from OFF to ON) with respect to the line.

After initialization (step SL), the one-chip microcomputer 3 instructs the key scan line decoder 2 to perform a key scan from the input line X1, and sets the address of the key map to the address where the scan result data of the input line X1 is to be stored. (Step S2). Next, select one input line to be key-scanned (in this case, the lines are in order from X1 to X16, and for the sake of explanation, we will call it Xl), set this input line X1 to a low level, and set the output line Y1 to - Read the scan result data of Y8 (step S3). Next, the output line data for the currently scanned X1 line is compared with the output line data for the previously scanned XI line stored in the key map (step S4). If there is no change, it means that the key has not been operated, so
Check whether all five lines have been scanned (step S5), and if not, send the next line X to the key scan line decoder 2 to scan the next input line.
2, and updates the address of the key map to the address where the scan result data of line X2 is to be stored (step S6).

If there is a change in the scan result in step S4, a check process (step S7) for preventing erroneous output, which is a feature of the present invention, is performed. The details will be explained with reference to FIG.

FIG. 4 is a flowchart showing the function of the erroneous output key check program, and this erroneous output key check program is always executed when a change in the key scan state occurs due to the scan data of one input line.

First, a bit whose state has changed is detected from the previous scan data of the relevant line and the current scan data of the relevant line, and the data end (change bit) is stored in the above-mentioned change data area. Furthermore, the current scan result data is stored in the scan data area mentioned above.

Next, check "1" indicating the key-on state in the data (8 bits) in this scan data area, and check which bit it is on (Step 571
).

Next, the data of the line X1 scanned this time is compared with the scan data of the other lines X2 to X15 currently stored in the key map. For this purpose, first, the current scan data of line X1 and the previous scan data of line X2 are compared (step 572). As a result, it is determined whether the bit is suspected of being looped around (S
73). Here, if such a bit exists, "l" in the scan result data is masked to "0" for the bit (step 576). Next, this process is performed for all input lines and all bits (steps S74, S75, 577).

That is, in the process shown in FIG. 4, all data that has changed to key-on and is suspected of being bypassed is masked to "0" to prevent erroneous output.

Returning to FIG. 3 again, after the key scan result data to be output is determined as described above, it is determined whether or not this data is stable (step S8). If it is not stable due to chattering etc., the manual The scan result at the X line is ignored and the process proceeds to step S5. If it is stable, the scan result data of that input line X1 (
8 bits), it is checked whether or not there is a bit whose state has changed by comparing each bit with the previous scan result (steps S9 and 10). If there is a change, the result is code-converted and output to the host device, and the corresponding bit of the key map is rewritten to a new state (steps 312 to 312).
514).

Next, the detailed operation in FIG. 4 will be explained using a specific numerical example. As explained in the conventional example, in FIG. 6, where wraparound may occur, the switch is set to SWI during scanning at a certain point in time.

Assuming that SW5 is on, the scan result data for input line Xl is '1000', input line X2
The scan result data for is '1000'.

This data is stored in a keymap. At the next scan of input line X1, switches SWI, SW3 . SW
5 is on, the input line X1 at this time
The scan result data for is "1010'".

Here, when compared with the previous data, the change data indicating a state change to on is obtained as "0010" (step 571).
.

Next, scan result data “1” for the current input line
010″' and the scan result data “1000” of the other input line Perform bit-by-bit AND of the previous scan result data for line AND with the received data "1000".

Since "1" remains in the data "1000" obtained by this, there is a possibility that the change data "0010" obtained for the scan of input line X1 this time contains false detection due to wraparound. Therefore, the data of this change cloth is masked and set as change data "0000" (steps S72, S73, 576).

As a result, this process compares the scan result data of input line Xa and other input line When ON is confirmed, the above-mentioned change data is masked, and the ON change data that may be erroneously output is deleted from the scan result data of the input line Xa.

FIG. 5 shows a functional flowchart of an erroneous output key check program in a second embodiment of the present invention. Compared to the first embodiment shown in FIG. 4, this embodiment has the advantage that the program execution speed is shorter because the erroneous output check is performed only on lines where there is a possibility of erroneous output.

〔Effect of the invention〕

As explained above, the present invention has a function of comparing Y1 to Yn lines of the scanned Xa line and other xb lines, and as a result of this comparison, the Y line of the key that is turned on on the scanned Xa line on the xb line matches. The keyboard control program has a function to mask the data of the key that turned on on the scanned Xa line from the scan data when there are 2 keys or more, and a function to output the code using the masked scan data. The addition has the effect of reducing the number of electronic components and the electronic component mounting area.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram of an embodiment of the present invention, FIG. 2 is a switch circuit configuration of key matrix l in FIG.
Figure 3 is a functional flowchart of the firmware of the one-chip microcomputer 3 in Figure 1, Figure 4 is a functional flowchart of the erroneous output key check block in Figure 3, and Figure 5
The figure is a functional flowchart of the erroneous output key check program according to the second embodiment of the present invention, FIG. 6 is a diagram showing a conventional key matrix without measures to prevent erroneous output, and FIG. 7 is a diagram showing a conventional key matrix in which measures to prevent erroneous output have been implemented. FIG. 2 is a diagram showing a conventional key matrix. 1...Key matrix, 2...Key scan line decoder, 3...One-chip microcomputer, 4...Interface circuit, 5...
・Connector for connecting to higher-level equipment. Figure 1

Claims (1)

[Claims] An n×m key matrix, inputting data from m input lines of this key matrix, reading scan data from n output lines, determining the pressed key, and converting the code. In the keyboard, the processing means is configured to scan the m input lines one by one, and when it detects a change in the same input line with respect to the previous scan result, to output another line. Read the scan results of the input line, and match two or more output lines indicating the key on state based on the scan result of the one input line and output lines indicating the key on state based on the scan result of the other input line. A method for preventing erroneous output when multiple keys are pressed in a keyboard, characterized in that, in the case where the input line is scanned, the state change of the key that has turned on this time among the scan results of the one input line is invalidated.