New understanding of matrix keyboard reverse scanning (interrupt trigger) digital tube-EEWORLD

Collect

1. Circuit diagram

2. Effect diagram
3. Code
4. Summary (digital tube) [page] Code

#include

sbit dm = P2^2; //segment code

sbit wm = P2^3; //bit code

sbit led =P3^7;

unsigned char hc[8];

unsigned char jj=0;

unsigned char DM[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f}; // Display segment code value 0~9

unsigned char WM[]={0xfe,0xfd,0xfb,0xf7,0xef,0xdf,0xbf,0x7f}; //Bit code. Display position

void DelayUs2x(unsigned char t)

{

while(--t);

}

void DelayMs(unsigned char t)

{

while(t--)

{

//About 1mS delay

DelayUs2x(245);

}

void sm()

{

unsigned char ii=0;

while(8!=ii && hc[ii]!=0)

{

P1 = 0; //Eliminating

dm = 1;

dm = 0;

P1 = WM[ii]; //Write bit code

wm = 1;

wm = 0;

P1 = hc[ii]; //Write segment code

dm = 1;

dm = 0;

DelayUs2x(10);

ii++;

}

/*The following function is the essence of reverse scanning*/

unsigned char jpsm() //Matrix keyboard reverse scan

{

unsigned char i=0; //Used to receive key value

P0 = 0x0f; //Detect the lower 4 bits

if(0x0f != P0) //Check if the button is pressed

{

DelayMs(10); //debounce

if(0x0f != P0) // Check if the button is really pressed and not interfered by other factors

{

i = P0; //Assign the lower 4 bits to i

P0 = 0xf0; //Detect the upper 4 bits

DelayUs2x(5); //Slight delay. This statement can be removed

i = i | P0; //Combine the lower 4 bits and the upper 4 bits into a complete key value

while( 0xf0 != P0 ) // Check if the button is released

{

sm();

}

return i; //Return the key value

}

return 0; //If the button is not pressed, return 0

}

unsigned char hcxr(unsigned char i) //key decoding function

{

switch(i)

{

case 0x77:hc[jj]=DM[0];break; //0

case 0x7e:hc[jj]=DM[1];break; //1

case 0xbe:hc[jj]=DM[2];break; //2

case 0xde:hc[jj]=DM[3];break; //3

case 0x7d:hc[jj]=DM[4];break; //4

case 0xbd:hc[jj]=DM[5];break; //5

case 0xdd:hc[jj]=DM[6];break; //6

case 0x7b:hc[jj]=DM[7];break; //7

case 0xbb:hc[jj]=DM[8];break; //8

case 0xdb:hc[jj]=DM[9];break; //9

/*case 0xee: //+

case 0xed: //-

case 0xeb: //*

case 0xe7: ///

case 0xd7: //=

case 0xb7: //.*/

default :return 0;

}

if(jj<7)

{

jj++;

hc[jj]=0;

}

else

jj=0;

}

void csh_wbzd_0() //Initialize external interrupt 0

{

IT0=0; //External interrupt 0 falling edge trigger

EX0=1; //Enable external interrupt 0

EA=1; //Open the general interrupt

}

void wbzd_0() interrupt 0 //External interrupt service function

{

unsigned char i;

i=jpsm(); //Receive key value

hcxr(i); //key value decoding

}

void main()

{

csh_wbzd_0(); //Initialize external interrupt 0

P0=0xf0; //This is very important for interrupt detection

while(1)

{

sm(); //Scan digital tubes in a loop

}

Summary 1. The cache data of the digital tube generally has two places.

1 ) It is declared by ourselves in the microcontroller. 2) There is also data in the latch.

Reference address：New understanding of matrix keyboard reverse scanning (interrupt trigger) digital tube

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