JPH051486B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for determining which key switch has been operated in a keyboard matrix that uses a microcomputer or the like and is equipped with a plurality of key switches.

Conventional Structure and Problems Conventionally, a scanning method is often used as a method for determining which key switch has been operated in a keyboard matrix having a plurality of key switches. This is because the keyboard is scanned in a time-sharing manner, requiring fewer parts and input/output ports.

A conventional scanning method will be explained below.

FIG. 1 shows the configuration of a keyboard matrix for key switch identification using a conventional scanning method. For ease of explanation, a microcomputer equipped with an input port and an output port is used as a control means, and A 2×2 keyboard matrix was used.

In FIG. 1, numerals 1, 2, 3, and 4 are key switches arranged in a matrix. 5 and 6 are strobe lines, which connect the output port 13a of the microcomputer 13 to the backflow prevention diodes 9 and 1.
Connected via 0. Data lines 7 and 8 are connected to the input port 13b of the microcomputer 13. Resistors 11 and 12 pull down the data lines 7 and 8, respectively, and set the potential of the data lines to a low level when the keyboard is not pressed.

A microcomputer 13 includes an output port 13a, an input port 13b, an arithmetic control section 13c, and a storage section 13d, and operates as a control means to determine the operated key switch.

Regarding the conventional keyboard matrix configured as described above, its operation and key switch discrimination method will be explained below.

Assume that key switch 1 is pressed and the other key switches are not pressed. In this case, the stroke line 5 and the data line 7 are connected by the key switch 1.

First, the microcomputer 13 outputs from the output port 13a such that the strobe line 5 is at a high level and the strobe line 6 is at a low level.
Then, data line 7 becomes high level because it is connected to strobe line 5, and data line 8 remains at low level. Microcomputer 13
At this point, the data on the data lines 7 and 8 are inputted from the input port 13b and stored in the storage section 13d.

Next, the microcomputer 13 outputs an output from the output port 13a so that the strobe line 5 becomes a low level and the strobe line 6 becomes a high level.
At this time, even if key switch 1 is pressed, data lines 7 and 8 are both at low level. At this point, the microcomputer 13 inputs the data on the data lines 7 and 8 through the input port 13b, compares it with previously stored input data, and performs calculations in the calculation control section 13c, thereby pressing the key switch 1. It is determined that

This can be determined from the fact that the timing and contents of the data appearing on the data lines 7 and 8 differ depending on the key switch pressed.

This is shown in FIG. Figure 2 shows strobe signals S 5 and S 6 appearing on strobe lines ₅ and ₆ and data D ₇ and D ₈ when each key switch is pressed.
This is a timing chart showing the timing. FIGS. 2b to 2f show when the key switch is pressed and when keys switches 1 to 4 are pressed, respectively. From this timing chart, it can be seen that the timings are different when no key switch is pressed and when each key switch is pressed individually.

Next, the necessity of the backflow prevention diodes 9 and 10 will be explained.

Strobe line 5 is high level, strobe line 6
is at low level, for example, key switch 1
and 3 are pressed at the same time, diode 9,
10, the high level output signal of the output port 13a would be transmitted from the strobe line 5 to the key switch 1.
→Data line 7 →Key switch 3 →Strobe line 6
It goes around to the other output port 13a through this route. If this happens, the power supply and ground of output buffers such as complementary MOS integrated circuits (C-MOS ICs) will be shorted, and the output port may be destroyed, or output buffers such as those with built-in current control resistors may Although the output buffer is not destroyed, the strobe signal is shunted, making it impossible to maintain a sufficiently high level as a strobe signal.

Therefore, in the conventional key switch discrimination method using the scanning method, a backflow prevention diode is required, and as the number of key switches increases and the number of strobe lines increases, diodes corresponding to the number of strobe lines are required, resulting in an increase in cost. It was hot. Furthermore, the time required to scan the keyboard matrix also increases as the number of strobe lines increases, since strobe signals must be output in sequence in time.

Purpose of the Invention The present invention solves the above-mentioned conventional problems. It does not require a backflow prevention diode, does not increase costs, and can be operated in a short judgment time even when the number of key switches increases. It is an object of the present invention to provide a key switch discrimination method that can discriminate between key switches.

Structure of the Invention The present invention provides a keyboard matrix that includes a first input/output port forming a plurality of row direction lines, a second input/output port forming a plurality of column direction lines,
The first input/output port is set to an output mode to output a strobe signal to all the row direction lines, and the second input/output port is set to an input mode to output a strobe signal to the column direction lines. The data on the line is taken in as first input data, the second input/output port is set to output mode, a strobe signal is output to all the column direction lines, and the first input/output port is inputted. mode, the data on the row direction line is taken in as second input data, and the operated key switch is determined from the first input data and second input data. It is possible to realize a method that eliminates the need for a backflow prevention diode, which was required in the method, and does not require an increase in the time required to determine which key switch has been operated even if the number of key switches increases.

DESCRIPTION OF THE EMBODIMENTS FIG. 3 shows the configuration of a keyboard matrix for key switch identification in an embodiment of the present invention, and for ease of explanation, a microcomputer equipped with an input/output port is used as the control means. In addition, a 2×2 keyboard matrix was used.

In Figure 3, 14, 15, 15, 16, 1
Reference numeral 7 indicates key switches arranged in a matrix. Row direction lines 18 and 19 are connected to the first input/output port 26a of the microcomputer 26, and are pulled down by resistors 22 and 23. 2
0 and 21 are column direction lines connected to the second input/output port 26b of the microcomputer 26, and are pulled down by resistors 24 and 25.

Reference numeral 26 denotes a microcomputer, which includes a first input/output port 26a, a second input/output port 26b, an arithmetic control section 26c, and a storage section 26d, and operates as a control means to determine which key switch is operated. Do the following.

The operation of the keyboard matrix configured as described above and the key switch discrimination method will be explained below.

Assume that the key switch 14 is pressed and the other key switches are not pressed. In this case, the row direction line 18 and the column direction line 20 are connected by the key switch 14.

First, the microcomputer 26 sets the first input/output port 26a to the output mode and sets the second input/output port 26b to the input mode. Next, all the first input/output ports 26a are set to high level, and the row direction lines 18 and 19 are set to high level, and then input data is taken in from the second input/output port 26b. At this time, the row direction line 18 and the column direction line 20 are in a connected state, so the column direction line 20 is at a high level, and the column direction line 21 is at a high level.
Since it is at a low level, this is stored in the storage section 26d as the first input data.

Next, the microcomputer 26 sets the first input/output port 26a to the input mode and sets the second input/output port 26b to the output mode. Then, after setting all the second input/output ports 26b to high level and setting the column direction lines 20 and 21 to high level, input data is taken in from the first input/output port 26a. At this time, the row direction line 18 and column direction line 20 are in a connected state, so the row direction line 18 is at a high level and the row direction line 19 is at a low level, which is taken in as second input data.

By comparing this second input data with the previously stored first input data and performing a calculation in the calculation control section 26c, it is determined that the key switch 14 is pressed.

FIG. 4 shows the case where the key switch is not pressed and the key switches 14, 15, 16, and 1, respectively.
For the case where 7 is pressed, row direction lines 18, 19
and the timing chart for the column direction lines 20 and 21 at that level. x ₁₈ , x ₁₉ and y ₂₀ , y ₂₁
are the levels of the row direction lines and column direction lines 20 and 21, respectively.

FIGS. 4a to 4e show the state when the key switch is not pressed and when the key switches 14 to 17 are pressed, respectively. Taking the case where the key switch 14 is pressed as an example, at t ₁ the row direction lines 18 and 19 become high level, in this case the column direction line 20 becomes high level, and the column direction line 21 becomes high level.
is a low level. At t ₂ the column direction line 20,
21 becomes high level, in this case row direction line 18
is at a high level, and the row direction line 19 is at a low level.

It can be seen from FIG. 4 that the timing is different when no key switch is pressed and when each key switch is pressed. Therefore, it is possible to determine which key switch was operated.

As explained above, the first input/output port 26
a to the output mode, and the second input/output port 26b
There are two steps: setting the input/output port 26b to the input mode and reading the first input data, and setting the second input/output port 26b to the output mode and setting the first input/output port 26a to the input mode and reading the second input data. You can identify the key switch by following these steps. This is true even when the number of key switches increases, and the determination time does not increase as the number of key switches increases.

Furthermore, even if keyswitches 14 and 16 are pressed at the same time, for example, each input/output port is always at a high level in output mode, so the signal shunt as explained in the conventional example does not occur, and the backflow prevention diode is activated. Not necessary.

In this embodiment, each direction line is pulled down by a resistor, but this can be omitted if the microcomputer has a structure in which the input/output port is internally pulled down when the input/output port is in the input mode.

It goes without saying that the high level and low level logic in this embodiment may be reversed.

Effects of the Invention The present invention provides a first input/output port that constitutes a plurality of row direction lines in a keyboard matrix;
The first input/output port is set to output mode and outputs a strobe signal to all the row direction lines, and the second input/output port is provided with a second input/output port that configures a plurality of column direction lines and a plurality of key switches. Set the output port to input mode and take in the data on the column direction line as the first input data, set the second input/output port to output mode and output a strobe signal to all column direction lines, Set the first input/output port to input mode, import the data on the row direction line, and
By using a method of determining the operated key switch from the first input data and the second input data, the backflow prevention diode required in the conventional scanning method is unnecessary, and the configuration can be simplified. It can be simplified and costs can be reduced. Also, since the keyboard data can be read in two steps, the time required to determine the key switch is short. This becomes more effective as the number of key switches increases.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a keyboard matrix for key switch discrimination using a conventional scanning method, FIG. 2 is a timing chart of a conventional scanning method, and FIG. 3 is a keyboard for key switch discrimination according to an embodiment of the present invention. FIG. 4 is a schematic configuration diagram of a matrix and a timing chart in an embodiment of the present invention. 1, 2, 3, 4... key switch, 5, 6...
Strobe line, 7, 8... Data line, 9, 10...
...Backflow prevention diode, 11, 12...Pull-down resistor, 13...Microcomputer, 14,
15, 16, 17... key switch, 18, 19
... Row direction line, 20, 21 ... Column direction line, 22,
23, 24, 25...Pull-down resistor, 26...
microcomputer.

Claims (1)

[Claims] 1. A first input/output port connected to the plurality of row direction lines of a keyboard matrix comprising a keyboard having a plurality of keys and row direction lines and column direction lines connected to each of the keys; , of a central processing unit having a second input/output port connected to the plurality of column direction lines, the first input/output port is set to output mode and all the row direction lines are connected to the central processing unit. outputs a strobe signal, sets the second input/output port to input mode, inputs the data on the column direction line to the central processing unit as first input data, and then outputs the second input/output port to the central processing unit. The port is set to output mode to output strobe signals from the central processing unit to all the column direction lines, and the first input/output port is set to input mode to input the data on the row direction lines to the central processing unit. 1. A method for determining a key switch, characterized in that the key switch is input into a device as second input data, and the operated key is determined from the first input data and the second input data.