（5） Matrix key

In this chapter, we mainly write the contents of matrix keyboard , The principle of matrix keyboard is basically similar to that of independent keys , Just a little introduction to the whole principle , In this chapter, we press one of the matrix keys , Then output the corresponding key value on the nixie tube .

1. About keys

You can see the contents of the previous buttons .

2. Hardware

First, my matrix keyboard is shown below , We first put P1 Interfaces are divided into two groups ,P0 To P3 Group together ,P4 To the plate into a group .

We can start by giving P1^0 A low level , And then to P1^1 To P1^7 High level , Then we test P1^4 To P1^7 The level state of , If a key is pressed , Then you can detect P1^4 To P1^7 On a certain GPIO The pin becomes low , We can detect that the button is pressed .

3 Software

This chapter mainly uses the contents of the previous nixie tube and matrix keys in this chapter , The procedure is as follows ：

#include "reg52.h"
#include "key.h"
extern int key_val;
void key_scan(){
	int temp;

	P1 = 0xfe;
	temp = P1;
	temp &= 0xf0;
	if(temp != 0xf0){
		delay(10);
		P1= 0xfe;
		temp = P1;
		temp &= 0xf0;
		if(temp != 0xf0){
			switch(temp){
				case 0x70:
					key_val = 3;
					break;
				case 0xb0:
					key_val = 7;
					break;
				case 0xd0:
					key_val = 11;
					break;
				case 0xe0:
					key_val = 15;
					break;
			}
		}
		while(temp != 0xf0){
			temp = P1;
			temp &= 0xf0;
		}
	}
	P1 = 0xfd;
	temp = P1;
	temp &= 0xf0;
	if(temp != 0xf0){
		delay(10);
		P1 = 0xfd;
		temp = P1;
		temp &= 0xf0;
		if(temp != 0xf0){
			switch(temp){
				case 0x70:
					key_val = 2;
					break;
				case 0xb0:
					key_val = 6;
					break;
				case 0xd0:
					key_val = 10;
					break;
				case 0xe0:
					key_val = 14;
					break;
			}
		}
		while(temp != 0xf0){
			temp = P1;
			temp &= 0xf0;
		}
	}
	P1 = 0xfb;
	temp = P1;
	temp &= 0xf0;
	if(temp != 0xf0){
		delay(10);
		P1 = 0xfb;
		temp = P1;
		temp &= 0xf0;
		if(temp != 0xf0){
			switch(temp){
				case 0x70:
					key_val = 1;
					break;
				case 0xb0:
					key_val = 5;
					break;
				case 0xd0:
					key_val = 9;
					break;
				case 0xe0:
					key_val = 13;
					break;
			}
		}
		while(temp != 0xf0){
			temp = P1;
			temp &= 0xf0;
		}
	}
	P1 = 0xf7;
	temp = P1;
	temp &= 0xf0;
	if(temp != 0xf0){
		delay(10);
		P1 = 0xf7;
		temp = P1;
		temp &= 0xf0;
		if(temp != 0xf0){
			switch(temp){
				case 0x70:
					key_val = 0;
					break;
				case 0xb0:
					key_val = 4;
					break;
				case 0xd0:
					key_val = 8;
					break;
				case 0xe0:
					key_val = 12;
					break;
			}
		}
		while(temp != 0xf0){
			temp = P1;
			temp &= 0xf0;
		}
	}
}

The main function to be called is as follows ：

#include "reg52.h"
#include "key.h"

sbit LSA = P2^2;
sbit LSB = P2^3;
sbit LSC = P2^4;
int key_val = 0;
unsigned char smgduan[17]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,
					0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71};// Show 0~F Value 

void delay(int xms){
	int i;
	int j;
	for(i = 0;i < xms;i++){
		for(j = 0; j < 100;j++){
			;
		}
	}
}

void main(){
	LSA = 0; LSB = 0;LSC = 0;
	while(1){
		key_scan();
		P0 = smgduan[key_val];
		delay(10);
	}
}

The contents of the header file are as follows ：

#ifndef _KEY_H_
#define _KEY_H_

extern int key_val;
void key_scan();
void delay(int xms);

#endif