Control design of 4×4 matrix keyboard by AT89S51 microcontroller

1. Experimental tasks

As shown in Figure 4.14.2, use the parallel port P1 of AT89S51 to connect to a 4×4 matrix keyboard, use P1.0-P1.3 as the input line, and use P1.4-P1.7 as the output line; it is displayed on the digital tube The "0-F" serial number of each button. The sequence number arrangement of the corresponding keys is shown in Figure 4.14.1

4.14.1

2. Hardware circuit schematic diagram

Figure 4.14.2

3. Hardware wiring on the system board

(1). Connect the P3.0-P3.7 ports in the "SCM System" area to the C1-C4 R1-R4 ports in the "4X4 Matrix Keyboard" area with an 8-core cable;

(2). Connect the P0.0/AD0-P0.7/AD7 ports in the "SCM System" area to any a-h port in the "Four Static Digital Display Module" area with an 8-core cable; Requirement: P0. 0/AD0 corresponds to a, P0.1/AD1 corresponds to b,..., P0.7/AD7 corresponds to h.

4. Programming content

(1). 4×4 matrix keyboard recognition processing

(2). Each key has its row value and column value. The combination of row value and column value is the code that identifies this key. The row lines and column lines of the matrix communicate with the CPU through two parallel interfaces respectively. The status of each button also needs to be changed into digital quantities "0" and "1". One end of the switch (column line) is connected to VCC through a resistor, and the grounding is achieved by outputting the digital "0" through the program. The task of the keyboard handler is to determine whether a key is pressed, determine which key is pressed, and what the key's function is; and also eliminate the jitter when the keys are closed or opened. Among the two parallel ports, one outputs the scan code to dynamically ground the keys line by line, and the other parallel port inputs the key status. The line scan value and the feedback signal jointly form the key code to identify the key. The software looks up the table to find out the key. Function.

5. Block diagram

Figure 4.14.3

6. Assemble source program

KEYBUF EQU 30H

ORG 00H

START： MOV KEYBUF，#2

WAIT：

MOV P3，#0FFH

CLR P3.4

MOV A，P3

ANL A，#0FH

XRL A，#0FH

JZ NOKEY1

LCALL DELY10MS

MOV A，P3

ANL A，#0FH

XRL A，#0FH

JZ NOKEY1

MOV A，P3

ANL A，#0FH

CJNE A，#0EH，NK1

MOV KEYBUF，#0

LJMP DK1

NK1： CJNE A，#0DH，NK2

MOV KEYBUF，#1

LJMP DK1

NK2： CJNE A，#0BH，NK3

MOV KEYBUF，#2

LJMP DK1

NK3： CJNE A，#07H，NK4

MOV KEYBUF，#3

LJMP DK1

NK4：NOP

DK1：

MOV A，KEYBUF

MOV DPTR，#TABLE

MOVC A，@A+DPTR

MOV P0，A

DK1A： MOV A，P3

ANL A，#0FH

XRL A，#0FH

JNZ DK1A

NOKEY1：

MOV P3，#0FFH

CLR P3.5

MOV A，P3

ANL A，#0FH

XRL A，#0FH

JZ NOKEY2

LCALL DELY10MS

MOV A，P3

ANL A，#0FH

XRL A，#0FH

JZ NOKEY2

MOV A，P3

ANL A，#0FH

CJNE A，#0EH，NK5

MOV KEYBUF，#4

LJMP DK2

NK5： CJNE A，#0DH，NK6

MOV KEYBUF，#5

LJMP DK2

NK6： CJNE A，#0BH，NK7

MOV KEYBUF，#6

LJMP DK2

NK7： CJNE A，#07H，NK8

MOV KEYBUF，#7

LJMP DK2

NK8: NOP

DK2：

MOV A，KEYBUF

MOV DPTR，#TABLE

MOVC A，@A+DPTR

MOV P0，A

DK2A：MOV A，P3

ANL A，#0FH

XRL A，#0FH

JNZ DK2A

NOKEY2：

MOV P3，#0FFH

CLR P3.6

MOV A，P3

ANL A，#0FH

XRL A，#0FH

JZ NOKEY3

LCALL DELY10MS

MOV A，P3

ANL A，#0FH

XRL A，#0FH

JZ NOKEY3

MOV A，P3

ANL A，#0FH

CJNE A，#0EH，NK9

MOV KEYBUF，#8

LJMP DK3

NK9： CJNE A，#0DH，NK10

MOV KEYBUF，#9

LJMP DK3

NK10： CJNE A，#0BH，NK11

MOV KEYBUF，#10

LJMP DK3

NK11： CJNE A，#07H，NK12

MOV KEYBUF，#11

LJMP DK3

NK12： NOP

DK3：

MOV A，KEYBUF

MOV DPTR，#TABLE

MOVC A，@A+DPTR

MOV P0，A

DK3A：MOV A，P3

ANL A，#0FH

XRL A，#0FH

JNZ DK3A

NOKEY3：

MOV P3，#0FFH

CLR P3.7

MOV A，P3

ANL A，#0FH

XRL A，#0FH

JZ NOKEY4

LCALL DELY10MS

MOV A，P3

ANL A，#0FH

XRL A，#0FH

JZ NOKEY4

MOV A，P3

ANL A，#0FH

CJNE A，#0EH，NK13

MOV KEYBUF，#12

LJMP DK4

NK13： CJNE A，#0DH，NK14

MOV KEYBUF，#13

LJMP DK4

NK14： CJNE A，#0BH，NK15

MOV KEYBUF，#14

LJMP DK4

NK15： CJNE A，#07H，NK16

MOV KEYBUF，#15

LJMP DK4

NK16： NOP

DK4：

MOV A，KEYBUF

MOV DPTR，#TABLE

MOVC A，@A+DPTR

MOV P0，A

DK4A：MOV A，P3

ANL A，#0FH

XRL A，#0FH

JNZ DK4A

NOKEY4：

LJMP WAIT

DELY10MS：

MOV R6，#10

D1: MOV R7，#248

DJNZ R7，$

DJNZ R6，D1

RIGHT

TABLE： DB 3FH，06H，5BH，4FH，66H，6DH，7DH，07H

DB 7FH，6FH，77H，7CH，39H，5EH，79H，71H

END

7. C language source program

#include

unsigned char code table［］={0x3f，0x06，0x5b，0x4f，

0x66，0x6d，0x7d，0x07，

0x7f，0x6f，0x77，0x7c，

0x39，0x5e，0x79，0x71};

unsigned char temp;

unsigned char key;

unsigned char i，j;

void main（void）

{

while（1）

{

P3=0xff;

P3_4=0;

temp=P3;

temp=temp & 0x0f;

if （temp！=0x0f）

{

for（i=50;i》0;i--）

for（j=200;j》0;j--）;

temp=P3;

temp=temp & 0x0f;

if （temp！=0x0f）

{

temp=P3;

temp=temp & 0x0f;

switch（temp）

{

case 0x0e：

key=7;

break;

case 0x0d：

key=8;

break;

case 0x0b：

key=9;

break;

case 0x07：

key=10;

break;

}

temp=P3;

P1_0=~P1_0;

P0=table［key］;

temp=temp & 0x0f;

while（temp！=0x0f）

{

temp=P3;

temp=temp & 0x0f;

}

}

}

P3=0xff;

P3_5=0;

temp=P3;

temp=temp & 0x0f;

if （temp！=0x0f）

{

for（i=50;i》0;i--）

for（j=200;j》0;j--）;

temp=P3;

temp=temp & 0x0f;

if （temp！=0x0f）

{

temp=P3;

temp=temp & 0x0f;

switch（temp）

{

case 0x0e：

key=4;

break;

case 0x0d：

key=5;

break;

case 0x0b：

key=6;

break;

case 0x07：

key=11;

break;

}

temp=P3;

P1_0=~P1_0;

P0=table［key］;

temp=temp & 0x0f;

while（temp！=0x0f）

{

temp=P3;

temp=temp & 0x0f;

}

}

}

P3=0xff;

P3_6=0;

temp=P3;

temp=temp & 0x0f;

if （temp！=0x0f）

{

for（i=50;i》0;i--）

for（j=200;j》0;j--）;

temp=P3;

temp=temp & 0x0f;

if （temp！=0x0f）

{

temp=P3;

temp=temp & 0x0f;

switch（temp）

{

case 0x0e：

key=1;

break;

case 0x0d：

key=2;

break;

case 0x0b：

key=3;

break;

case 0x07：

key=12;

break;

}

temp=P3;

P1_0=~P1_0;

P0=table［key］;

temp=temp & 0x0f;

while（temp！=0x0f）

{

temp=P3;

temp=temp & 0x0f;

}

}

}

P3=0xff;

P3_7=0;

temp=P3;

temp=temp & 0x0f;

if （temp！=0x0f）

{

for（i=50;i》0;i--）

for（j=200;j》0;j--）;

temp=P3;

temp=temp & 0x0f;

if （temp！=0x0f）

{

temp=P3;

temp=temp & 0x0f;

switch（temp）

{

case 0x0e：

key=0;

break;

case 0x0d：

key=13;

break;

case 0x0b：

key=14;

break;

case 0x07：

key=15;

break;

}

temp=P3;

P1_0=~P1_0;

P0=table［key］;

temp=temp & 0x0f;

while（temp！=0x0f）

{

temp=P3;

temp=temp & 0x0f;

}

}

}

}

}