TWI487279B - Scanning circuit for keyboard and method and electronic device using the same - Google Patents

Description

Keyboard scanning circuit and method and electronic device

The present invention relates to an electronic device, and more particularly to a keyboard scanning circuit and method.

The keyboard is the main human-machine dialogue input device in electronic products such as computers, PDAs (personal digital assistants), and mobile phones. The keyboard scans the keys on the keyboard by an internal matrix scanning circuit to determine the position of the keys. Most existing matrix keyboard scanning circuits use a single-chip I/O port for keyboard scanning. As the functionality of electronic products increases, to complete complex and diverse control functions, the keyboard needs to provide enough keys. Since the increase of the button often leads to an increase in the I/O埠 for keyboard scanning, for example, N*M buttons require N+M I/O埠, which causes the keyboard scanning circuit to take up too much I/O.埠 Resources, which increases the cost of the keyboard.

In view of this, it is necessary to provide a keyboard scanning circuit that implements a multi-button with a small amount of I/O 。.

In addition, it is also necessary to provide a keyboard scanning method and an electronic device using the keyboard scanning circuit.

A keyboard scanning circuit is connected to a controller having a plurality of input and output ports, the keyboard scanning circuit comprising N row lines, M column lines, M-2 single-conducting switch tubes, M-2 first a resistor, and a second resistor, wherein N is a natural number and M is a natural number greater than or equal to 3. The N row lines are electrically connected to the N inputs of the controller. One end of the first one of the M column lines can be electrically connected to the N row lines by N buttons, and the other end is grounded. One end of the Mth column line of the M column line can be electrically connected to the N line lines by N buttons, and is also electrically connected to the first end of the M-2 single-conducting switch tubes, and the other end is electrically connected. Grounded by a second resistor. One of the remaining M-2 column lines of the M column lines can be electrically connected to the N line lines through N buttons, and is also electrically connected to the second ends of the M-2 single-conducting switch tubes respectively. And electrically connected to a power source by M-2 first resistors, and the other end is electrically connected to M-2 outputs of the controller. The one-way switch is turned on when the voltage of the first terminal is lower than the voltage of the second terminal.

A keyboard scanning method applied to a keyboard scanning circuit, which performs scanning of each column by setting the level state of the output port, reads the level state of the input port, and further determines the keyboard button, and includes the following steps:

Reading the initial level state of the N input ports;

Set M-2 outputs to be high level, and read the level state of N input ports again;

Determining whether the N input 有 has a level state change;

If there is a change, record the changed input 埠 and determine that the pressed button is in the first column and is the button corresponding to the changed input ;;

If there is no change, set the ith output M of M-2 output 埠 to low level, and keep the other output 埠 high level, and read the level state of N input 再次 again, where i a natural number between 2 and M-2;

Determining whether the N input 有 has a level state change;

If there is a change, record the changed input 埠 and determine whether the button of the first column is pressed, if not, determine that the pressed button is located in the ith column, and is the button corresponding to the changed input ;;

If there is no change, set M-2 output 埠 to low level, and read the level state of N input 再次 again;

Determining whether the N input 有 has a level state change;

If there is a change, record the changed input 埠 and determine if the button in the first column is pressed. If not, it is determined that the pressed button is in the Mth column and is the button corresponding to the changed input 埠.

An electronic device includes a controller, a plurality of buttons, and a keyboard scanning circuit. The controller includes N input ports and M output ports. The keyboard scanning circuit includes N row lines, M column lines, and M-2 a single-conducting switch, M-2 first resistors, and a second resistor, wherein N is a natural number and M is a natural number greater than or equal to 3; the N row lines and the M column lines are in an array Arranging to form an N*M intersection; the plurality of buttons are disposed on the N*M intersection, one end of which is electrically connected to the corresponding row line, and the other end is electrically connected to the corresponding column line; the N row lines respectively The N inputs of the controller are electrically connected; one end of the first column line of the M column lines is electrically connected to the corresponding row line by a corresponding button, and the other end is grounded; the Mth line of the M column lines One end of the column line is electrically connected to the corresponding row line by corresponding buttons, and is also electrically connected to the first end of the M-2 single-conducting switch tubes, and the other end is grounded by the second resistor; the M columns are in the line One of the remaining M-2 line lines is electrically connected to the corresponding line by the corresponding button, and is also separately connected with M-2. The second end of the switch is electrically connected, and is electrically connected to a power source by M-2 first resistors, and the other end is electrically connected to M-2 outputs of the controller; the single-conducting switch The tube is turned on when its first terminal voltage is less than the second terminal voltage.

The above keyboard scanning circuit realizes scanning N*M keys by using N input ports, which reduces the occupation of the input resources by the keyboard, and realizes scanning of the plurality of keys. At the same time, a scanning method employed by the scanning circuit is used.

Please refer to FIG. 1, which is a circuit diagram of a keyboard scanning circuit 200 of a preferred embodiment. The keyboard scanning circuit 200 can utilize a controller 10, such as N inputs 埠K ₁ ~K _{n of the} single chip microcomputer, M-2 outputs 埠W2~W(m-1), and N*M buttons S _1-1 ~ S _nm is scanned for recognition.

The keyboard scanning circuit 200 includes N row lines L1~Ln, M column lines P1~Pm, M-2 diodes D ₂ ~D _m-1 , M-2 first resistors R2~R(m- 1) and a second resistor Rs, where N is a natural number and M is a natural number greater than or equal to 3. The M column lines are alternately arranged with the N line lines to form N*M intersections. The N*M intersections respectively place the N*M buttons S _1-1 ~S _nm . One end of the N*M buttons S _1-1 ~S _nm is electrically connected to the corresponding row line, and the other end is electrically connected to the corresponding column line. In the present embodiment, the N inputs 1K1~Kn and the M-2 outputs 埠W2~W(m-1) are input/output ports 一 on the controller 10, and the controller 10 can set the input/output 埠W2. The level state of ~W(m-1).

One end of the first column line P1 is connected to the N row lines L1 to Ln by N buttons S _1-1 to Sn _-1 , and the other end is grounded. One end of the Mth column line is connected to the N row lines L1~Ln by N buttons S _1-m ~S _nm , and also with the cathode electrical properties of M-2 diodes D ₂ ~D _m-1 Connected, the other end is grounded by the second resistor Rs. One end of the remaining M-2 column lines P2~P(m-1) is connected to the N line lines L1~Ln by N buttons, and also respectively with M-2 diodes D ₂ ~D The anode of _m-1 is electrically connected, and is electrically connected to a voltage source Vcc by the first resistors R2 R R(m-1). The other ends of the remaining M-2 column lines P2~P(m-1) are electrically connected to the output ports W2~W(m-1).

The resistances of the first resistors R2 R R(m-1) are the same or similar, and are much smaller than the resistance of the second resistor Rs, so that the second resistor Rs and a first resistor divide the output voltage of the voltage source Vcc Thereafter, the voltage on the second resistor Rs can be recognized by the controller 10 as a high level.

The diode D ₂ ~D _m-1 has a one-way conduction characteristic. When at least one of the outputs 埠W2~W(m-1) is at a high level, the two corresponding to the output 埠W2~W(m-1) The polar body D ₂ ~D _{m-1 is} turned on. Since the first resistor R2 R R (m-1) is much smaller than the second resistor Rs, the voltage drop across the second resistor Rs is much larger than the voltage drop across the first resistor R2 R R ( m - 1 ), that is, the controller 10 One end of the M column button S _1-m ~S _nm is identified to be connected to a high level. Therefore, in the process of scanning the first to the M-1th columns, the influence of the Mth column on the input 埠K ₁ ~K _n is excluded.

When the key scan program is executed, the keyboard scan circuit 200 is subjected to column scan by setting the level state of the output 埠W2~W(m-1), and the level state of the input 埠K ₁ to K _n is read at the same time, and it is judged whether or not There is a button press. In order to clearly describe the keyboard scanning program, the following changes in the level state are relative to the initial level states of the inputs 埠K ₁ to K _n . First, the initial level state of the input 埠K ₁ ~K _{n is} read. Then, scan the first column: set the output 埠W2~W(m-1) to the high level state, read the level state of the input 埠K ₁ ~K _n again, and judge whether the input 埠K ₁ ~K _n is The level has changed. If a change occurs, record the changed input and determine that the button is pressed for the first column of buttons and is the button corresponding to the changed input 埠.

If there is no change, scan the second to the M-1th column in turn: set the output 埠W2~W(m-1), the ith output 埠 is low, while keeping the other output 高电平 high level, The level state of the input 埠K ₁ ~K _n is read again. It is judged whether or not the input 埠K ₁ to K _n has a level state change. If there is a change, record the changed input and determine if the button in the first column is pressed. The method of determining whether the button of the first column is pressed is similar to the method of scanning the first column: switching the ith output 埠 to a high level, and reading the state of the input 埠K ₁ ~K _n again, where i is 2 to the natural number in M-1. If the level state of the input 埠K ₁ to K _n changes, it is determined that the button of the first column is pressed, and is a button corresponding to the changed input 埠. If the level state of the input 埠K ₁ ~K _n has not changed, it is judged that the key of the first column is not pressed. If the button of the first column is not pressed, it is determined that the pressed button is located in the ith column and is the button corresponding to the changed input 埠.

If there is no change, scan the Mth column: set the output 埠W2~W(m-1) to the low state, and read the level state of the input 埠K ₁ ~K _n in turn. It is judged whether or not the input 埠K ₁ to K _n has a level state change. If there is a change, record the change input 埠 and judge whether the keys of the first to the M-1th column are pressed. Wherein, the method of determining whether the button of the first column is pressed is the same as described above, and determining whether the button of the second to the M-1th column is pressed and scanning the second to the M-1th column The method is the same: one of the M-2 output ports is set to be low level, and the rest is high level. If the level state of the input 埠K ₁ ~K _{n does} not change, it is judged that it is not the second column to the Mth. - The button of the -1 column is pressed. If the level of the input 埠K ₁ ~K _n changes when the ith output 埠 is low, it is determined that the pressed button is located in the (i+1)th column, and The button corresponding to the changed input 埠. If the determination is not, it is determined that the pressed button is located in the Mth column and is the button corresponding to the changed input port.

In actual operation, since the scanning speed of the controller 10 is very fast, when the Mth column is scanned, the interference from the second column to the M-1th column can be directly excluded. That is, the step of judging whether the keys of the second to the M-1th columns are pressed is omitted, and it is determined that the pressed key is located in the Mth column after the button that is not the first column is excluded.

Please refer to FIG. 2, which is a circuit diagram of a keyboard scanning circuit 201 of a preferred embodiment when N=M=4. The keyboard scanning circuit 201 includes four row lines L1 to L4, four column lines P1 to P4, two diodes D ₂ to D ₃ , two first resistors R2 to R3 and one second resistor Rs. The four column lines are interleaved with the four line lines to form 4*4 intersections. The 4*4 intersections respectively place the 4*4 buttons S _1-1 ~S _4-4 . One end of the 4*4 buttons S _1-1 ~S _4-4 is electrically connected to the corresponding row line, and the other end is electrically connected to the corresponding column line. In the present embodiment, the four inputs 1K1 to K4 and the two outputs 埠W2 to W3 are input/output ports on the controller 10, and the controller 10 can set the level states of the input/output ports 2W2 to W3.

One end of the first column line P1 is connected to the N line lines L1 to L4 by four buttons S _1-1 to S _4-1 , and the other end is grounded. One end of the fourth column line is connected to the N line lines L1 to L4 by four buttons S _1-4 to S _4-4 , and is also electrically connected to the cathodes of the two diodes D ₂ to D ₃ . The other end is grounded by a second resistor Rs. One ends of the remaining M-2 column lines P2 to P3 are respectively connected to the four row lines L1 to L4 by four buttons, and are also electrically connected to the anodes of the two diodes D ₂ to D ₃ respectively. And electrically connected to a voltage source Vcc by the first resistors R2 R R3. The other ends of the remaining two column lines P2 to P3 are electrically connected to the output ports 2W2 to W3.

The resistances of the first resistors R2 R R3 are the same or similar, and are much smaller than the resistance of the second resistor Rs, so that the second resistor Rs and a first resistor divide the output voltage of the voltage source Vcc, and the second resistor The voltage on Rs can be recognized by controller 10 as being high.

When the button scanning program is executed, if the button S _3-3 is pressed, the scanning process is: in order to clearly describe the keyboard scanning program, the following level state changes are relative to the input 埠K ₁ ~K ₄ In terms of the initial level state.

First, the initial level state of the input 埠K ₁ ~K _{4 is} read. Then, scan the first column: set the output 埠W2~W3 to the high level state, read the level state of the input 埠K ₁ ~K ₄ again, and judge whether the input 埠K ₁ ~K ₄ has a level state change.

If the input 埠K ₁ ~K ₄ level state has not changed, scan the second column: set the output 埠W2 to the low level, while keeping the output 埠W3 at the high level, read the input 埠K ₁ ~K again. The level status of ₄ . It is judged whether or not the input 埠K ₁ to K ₄ has a level state change.

If the input 埠K ₁ ~K ₄ level state has not changed, set the output 埠W3 output 埠 to low level, while keeping the output 埠W2 at the high level, read the input 埠K ₁ ~K _{4 again} . Flat state. It is judged whether or not the input 埠K ₁ to K ₄ has a level state change. If the level state of the input 埠K ₃ changes, it is further determined whether the button of the first column is pressed. The method of judging whether the button of the first column is pressed is similar to the method of scanning the first column: switching the output 埠W3 to the high level, and reading the input 埠K ₁ ~K ₄ state again, if the input 埠K ₁ ~ The level state of K ₄ has not changed, and it is judged that the button of the first column is not pressed. If the button of the first column is not pressed, it is determined that the pressed button is in the third column, and the button S _3-3 corresponding to the changed input 埠K ₃ is pressed.

Please refer to FIG. 3, which is a flowchart of a scanning method 300 of the keyboard scanning circuit of FIG. 1. After the scanner is started, the controller 10 starts scanning the inputs 1K ₁ ~K _n .

In step 301, the initial level state of the input 埠K ₁ ~K _n is read. In order to clearly describe the keyboard scanning method 300, the changes in the level states described below are all relative to the initial level state.

In step 302, the output 埠W2~W(m-1) is set to a high level, and the level state of the input 埠K ₁ ~K _n is read again.

In step 303, it is determined whether the input state 埠K ₁ ~K _n has a level state change. If there is no change, step 304 is performed; if there is a change, step 314 is performed.

Step 304, setting the output 埠W2~W(m-1) to the ith state to be the low level, and keeping the other output 埠 state to the high level, and reading the level state of the input 埠K ₁ ~K _n again. . i takes values from 2 to (m-1) in order.

Step 305 determines whether the input state 埠K ₁ ~K _n has a level change. If there is a change, step 306 is performed; if there is no change, step 308 is performed.

Step 306, the i-th output port W2 ~ W (m-1) is switched to the high level, the input port reads the K ~ K _n level state ₁ again.

Step 307, it is determined whether the input state 1K ₁ ~ K _n has a level state change, if there is a change, step 314 is performed; if there is no change, step 315 is performed.

In step 308, the output 埠W2~W(m-1) is set to a low level, and the level state of the input 埠K ₁ ~K _n is read again.

In step 309, it is determined whether the input state 埠K ₁ ~K _n has a level state change. If there is a change, step 310 is performed; if there is no change, the keyboard scan ends.

In step 310, the output 埠W2~W(m-1) is set to a high level, and the level state of the input 埠K ₁ ~K _n is read again.

In step 311, it is determined whether the input state 埠K ₁ ~K _n has a level state change. If there is no change, step 312 is performed; if there is a change, step 314 is performed.

Step 312, the output port sequentially W2 ~ W (m-1) is switched to the high level, the input port reads the K ~ K _n level state ₁ again.

In step 313, it is determined whether the input state 埠K ₁ ~K _n has a level state change. If there is a change, step 315 is performed; if there is no change, step 316 is performed.

In step 314, the change is recorded and the button is determined to be the first column, and the button corresponding to the change 被 is pressed.

In step 315, the change 埠 is recorded and the button is determined to be a low level output 埠 corresponding column, and is a button corresponding to the change 埠.

In step 316, the change is recorded and the button is determined to be the Mth column, and is the button corresponding to the change 埠. This keyboard scan ends.

In other embodiments, steps 312-313 may be omitted, and step 311 needs to be changed to: determine whether the input 埠K ₁ ~K _n has a level state change, if there is no change, perform step 316; if there is a change, perform steps 314.

Please refer to FIG. 4, which is a flowchart of a scanning method 400 of the keyboard scanning circuit of FIG. 2. After the scan program starts, the controller 10 starts to scan the input port K ₁ ~ K _4.

In step 401, the initial level state of the input 埠K ₁ ~K ₄ is read. In order to clearly describe the keyboard scanning method 400, the changes in the level states described below are all relative to the initial level state.

Step 402 sets the output port W2 ~ W3 are high, the input port reads the level state K ₁ ~ K ₄ again.

In step 403, it is determined whether the input state 埠K ₁ ~ K ₄ has a level change. If there is no change, step 404 is performed; if there is a change, step 414 is performed.

In step 404, the ith of the output 埠W2~W3 is set to a low level, and the other output 埠 state is kept at a high level, and the level state of the input 埠K ₁ ~K ₄ is read again. i takes values from 2 to 3 in order.

Step 405 determines whether the input 埠K ₁ ~ K ₄ has a change in the level state. If there is a change, step 406 is performed; if there is no change, step 408 is performed.

Step 406, the i-th output port W2 ~ W3 is switched to the high level, the input port reads the level state K ₁ ~ K ₄ again.

In step 407, it is determined whether the input 埠K ₁ ~ K ₄ has a level change. If there is a change, step 414 is performed; if there is no change, step 415 is performed.

Step 408 sets the output port W2 ~ W3 are low, the input port reads the level state K ₁ ~ K ₄ again.

In step 409, it is determined whether the input state 埠K ₁ ~ K ₄ has a level change. If there is a change, step 410 is performed; if there is no change, the keyboard scan ends.

Step 410 sets the output port W2 ~ W3 are high, the input port reads the level state K ₁ ~ K ₄ again.

In step 411, it is determined whether the input state 埠K ₁ ~ K ₄ has a level change. If there is no change, step 412 is performed; if there is a change, step 414 is performed.

Step 412, the output port sequentially W2 ~ W3 is switched to the high level, the input port reads the level state K ₁ ~ K ₄ again.

In step 413, it is determined whether the input state 埠K ₁ ~ K ₄ has a level change. If there is a change, step 415 is performed; if there is no change, step 416 is performed.

In step 414, the change is recorded and the button is determined to be the first column, and the button corresponding to the change 被 is pressed.

In step 415, the change 埠 is recorded and the button is determined to be a low level output 埠 corresponding column, and is a button corresponding to the change 埠.

At step 416, the change is recorded and the button is determined to be the fourth column and is the button corresponding to the change 埠. This keyboard scan ends.

In summary, the present invention complies with the requirements of the invention patent and submits a patent application according to law. The above descriptions are only preferred embodiments of the present invention, and those skilled in the art will be able to include equivalent modifications or variations in the spirit of the present invention.

200‧‧‧Keyboard scanning circuit

10‧‧‧ Controller

K ₁ ~K _n ‧‧‧Input埠

W2~W(m-1)‧‧‧ Output埠

S _{1 - 1} ~S _{n - m} ‧‧‧ button

L1~Ln‧‧‧ line

P1~Pm‧‧‧ line

D ₂ ~D _{m - 1} ‧‧‧ diode

R2~R(m-1)‧‧‧first resistance

Rs‧‧‧second resistance

Vcc‧‧‧ voltage source

201‧‧‧Keyboard scanning circuit

K ₁ ~K ₄ ‧‧‧Input埠

W2~W3‧‧‧ Output埠

S _{1 - 1} ~S _{4 - 4} ‧‧‧ button

L1~L4‧‧‧ line

P1~P4‧‧‧ column line

D ₂ ~D _{4 - 1} ‧‧‧ Dipole

R2~R3‧‧‧First resistance

1 is a circuit diagram of a keyboard scanning circuit of a preferred embodiment.

2 is a circuit diagram of a keyboard scanning circuit of a preferred embodiment when the input port is 4.

3 is a flow chart of a scanning method of the keyboard scanning circuit of FIG. 1.

4 is a flow chart of a scanning method of the keyboard scanning circuit of FIG. 2.

200‧‧‧Keyboard scanning circuit

10‧‧‧ Controller

K ₁ ~K _n ‧‧‧Input埠

W2~W(m-1)‧‧‧ Output埠

S _1-1 ~S _nm ‧‧‧ button

L1~Ln‧‧‧ line

P1~Pm‧‧‧ line

D ₂ ~D _m-1 ‧‧‧ Diode

R2~R(m-1)‧‧‧first resistance

Rs‧‧‧second resistance

Vcc‧‧‧ voltage source

Claims (10)

A keyboard scanning circuit comprising N input ports, M-2 output ports, N row lines, M column lines, M-2 single-conducting switch tubes, M-2 first resistors, And a second resistor, wherein N is a natural number, and M is a natural number greater than or equal to 3; the N row lines are electrically connected to the N input turns respectively; and the first one of the M column lines is at one end The N terminals are electrically connected to the N row lines, and the other end is grounded. One end of the Mth column line of the M column lines is electrically connected to the N row lines by N buttons, and is also connected with M. - the first end of the two single-conducting switch tubes is electrically connected, and the other end is grounded by a second resistor; one end of the remaining M-2 column lines of the M column lines is by the N buttons and N strips The line is electrically connected, and is also electrically connected to the second end of the M-2 single-conducting switch tubes respectively, and is electrically connected to a power source by the M-2 first resistors, and the other end is connected with M - 2 output electrical connections; the single-conducting switching transistor is turned on when the first terminal voltage is less than the second terminal voltage. The keyboard scanning circuit of claim 1, wherein the one-way switching transistor is a diode, and the diode is used when at least one of the M-2 output ports is at a high level One end of the button connected to the M column is set to a high level. The keyboard scanning circuit of claim 1, wherein the N row lines and the M column lines are in one-to-one correspondence and intersect to form an N*M intersection, and the N*M buttons are placed on the N*M intersections. One end of each button is electrically connected to the corresponding row line, and the other end is electrically connected to the corresponding column line. The keyboard scanning circuit of claim 1, wherein the resistance of the M-2 first resistors is equal and less than the resistance of the second resistor. A keyboard scanning method applied to a keyboard scanning circuit according to claim 1 of the patent application, the keyboard scanning method comprising the following steps:
Reading the initial level state of the N input ports;
Setting the M-2 outputs to be high level, and reading the level state of the N input ports again;
Determining whether the N input 有 has a level state change;
If the level state of the N input ports changes, an input port whose level state changes is recorded, and it is determined that the pressed button is located in the first column, and is a button corresponding to the changed input port;
If the level state of the N input ports does not change, set the ith output M of the M-2 output ports to be low level, and keep the other outputs 高电平 high level, and read the N again. The level state of the input 埠, where i is a natural number between 2 and M-2;
Determining whether the N input 有 has a level state change;
If the level state of the N input ports changes, the input level of the level change state is recorded and it is determined whether the button of the first column is pressed. If not, it is determined that the pressed button is located in the ith column, and a button corresponding to the changed input 埠;
If the level state of the N input ports does not change, set M-2 outputs to be low level, and read the level state of the N input ports again;
Determining whether the N input 有 has a level state change;
If the level state of the N input ports changes, an input port whose level state changes is recorded, and it is determined whether the button of the first column is pressed, and if not, it is determined that the pressed button is located in the Mth column. And it is a button corresponding to the changed input 埠. The keyboard scanning method of claim 5, wherein the step of determining whether the button of the first column is pressed further comprises the following steps:
Set M-2 outputs to be high level, and read the state of the N input ports again;
Determining whether the N input 有 has a level state change;
If the level state of the N input ports does not change, the recording level state changes input, and determines that the pressed button is located in the first column and is a button corresponding to the changed input port;
If the level state of the N input ports changes, it is determined that the keys that are not in the first column are pressed. The keyboard scanning method according to claim 5, wherein when the M-2 outputs are set to a low level, the level state of the N input ports is determined to be changed, and the keys that are not in the first column are determined to be When pressed, it is further determined whether the keys of the second to the M-1th column are pressed, and if not, it is determined that the pressed key is located in the Mth column and is the key corresponding to the changed input 埠. According to the keyboard scanning method described in claim 7, the determining whether the buttons of the second to the M-1th columns are pressed further comprises the following steps:
One of the M-2 output ports is set to a low level in turn, and the rest is a high level. If the levels of the N input ports are both high, it is determined that the buttons are not in the second column to the M-1 column. Was pressed. An electronic device includes a controller, a plurality of buttons, and a keyboard scanning circuit. The controller includes N input ports and M output ports, wherein the keyboard scanning circuit includes N row lines and M column lines. M-2 single-conducting switch tubes, M-2 first resistors, and a second resistor, wherein N is a natural number, M is a natural number greater than or equal to 3; the N row lines and the M columns The lines are arranged in an array to form an N*M intersection; the plurality of buttons are disposed on the N*M intersection, one end of which is electrically connected to the corresponding row line, and the other end is electrically connected to the corresponding column line; the N lines The wires are respectively electrically connected to the N inputs of the controller; one end of the first column line of the M column lines is electrically connected to the corresponding row line by a corresponding button, and the other end is grounded; the M column lines are in the middle One end of the Mth column line is electrically connected to the corresponding row line by the corresponding button, and is also electrically connected to the first end of the M-2 single-conducting switch tubes, and the other end is grounded by the second resistor; One end of the remaining M-2 column lines in the line line is electrically connected to the corresponding line line by corresponding buttons, and is also respectively associated with M - The second ends of the two single-directional switch tubes are electrically connected, and are electrically connected to a power source by M-2 first resistors, and the other end is electrically connected to the M-2 outputs of the controller. The one-way switch is turned on when the first terminal voltage is lower than the second terminal voltage. The electronic device of claim 9, wherein the resistance of the M-2 first resistors is less than the resistance of the second resistor.