51 MCU Experiment 7: Matrix Buttons

The circuit diagram of the development board matrix button module is as follows:

The circuit diagram of the digital tube module of the development board is as follows:

Matrix key scanning principle:

Method 1: Line-by-line scanning: We can scan the matrix keyboard line by line by outputting low level in turn through the upper four bits. When the data received by the lower four bits are not all 1, it means that a key is pressed. Then, we can determine which key is pressed by which bit of the received data is 0.

Method 2: Row and column scanning: We can output low level by all the high four bits and high level by the low four bits. When the low four bits of the received data are not all high level, it means that a key has been pressed. Then, we can judge which column has been pressed by the received data value. Then, we can judge which row has been pressed by the high four bits and low four bits. Then, we can judge which row has been pressed by the received high four bits. In this way, we can determine which key has been pressed.

In this program, the matrix buttons are scanned using row and column scanning!

In this program, the matrix buttons are scanned using row and column scanning!

Program purpose: Assign values ​​of 0, 1, ..., 15 to the 16 buttons in the matrix respectively. When pressed, the label will be displayed on the first digital tube.

Notice:

The value represents the key pressed. To find out the row and column relationship between the keys, only a one-dimensional value is needed to determine the position of the key without finding the row/column numbers separately.

Waiting for the key release statement: while() is different from the while() in the independent key experiment program, so pay attention to the difference!

New tips: Before programming, you can assign new variable names to registers such as IO ports in time to facilitate program modification and other operations, increasing program readability!

#include

#define uc unsigned char

#define dig P0

#define key P1

sbit lsa=P2^2;

sbit lsb=P2^3;

sbit lsc=P2^4;

int value; 

uc code x[16]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,

0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71};

void delay(uc x)

{

uc i,j;

for(i=1;i<=x;i++)

for(j=1;j<=110;j++);

}

void keypros()

{

uc a=0;

key=0x0f;

if(key!=0x0f)

{

delay(10);

if(key!=0x0f)

{

key=0x0f;

switch(key)

{

case(0x07): value=0;break;

case(0x0b): value=1;break;

case(0x0d): value=2;break;

case(0x0e): value=3;break;

}

key=0xf0;

switch(key)

{

case(0x70): value=value; break;

case(0xb0): value=value+4; break;

case(0xd0): value=value+8; break;

case(0xe0): value=value+12; break;

}

}

while((key!=0xf0)&&(a<50))

{

a++;

delay(10);

}

        /*while(key!=0xf0);*/

}

}

void main()

{

lsa=lsb=lsc=0;

while(1)

{

keypros();

dig=x[value];

}

}