矩阵键盘的模块原理图：

功能：按下矩阵按键，在LCD上显示对应的数值。
采用模块化编程，在此只给出MatrixKey.c 和 main.c 两部分代码

#include <REGX52.H>
#include "Delay.h"

/*
	矩阵键盘读取键码
	按下不放，会停留在此函数，松开时返回数值，不按返回零
*/
unsigned char Matrixkey()
{
	unsigned char KeyNum = 0;
	
	P1 = 0xFF;
	P1_3 = 0;
	if(P1_7 == 0) {Delay(20); while(P1_7 == 0); Delay(20); KeyNum = 1;}
	if(P1_6 == 0) {Delay(20); while(P1_6 == 0); Delay(20); KeyNum = 5;}
	if(P1_5 == 0) {Delay(20); while(P1_5 == 0); Delay(20); KeyNum = 9;}
	if(P1_4 == 0) {Delay(20); while(P1_4 == 0); Delay(20); KeyNum = 13;}
	
	P1 = 0xFF;
	P1_2 = 0;
	if(P1_7 == 0) {Delay(20); while(P1_7 == 0); Delay(20); KeyNum = 2;}
	if(P1_6 == 0) {Delay(20); while(P1_6 == 0); Delay(20); KeyNum = 6;}
	if(P1_5 == 0) {Delay(20); while(P1_5 == 0); Delay(20); KeyNum = 10;}
	if(P1_4 == 0) {Delay(20); while(P1_4 == 0); Delay(20); KeyNum = 14;}
	
	P1 = 0xFF;
	P1_1 = 0;
	if(P1_7 == 0) {Delay(20); while(P1_7 == 0); Delay(20); KeyNum = 3;}
	if(P1_6 == 0) {Delay(20); while(P1_6 == 0); Delay(20); KeyNum = 7;}
	if(P1_5 == 0) {Delay(20); while(P1_5 == 0); Delay(20); KeyNum = 11;}
	if(P1_4 == 0) {Delay(20); while(P1_4 == 0); Delay(20); KeyNum = 15;}
	
	P1 = 0xFF;
	P1_0 = 0;
	if(P1_7 == 0) {Delay(20); while(P1_7 == 0); Delay(20); KeyNum = 4;}
	if(P1_6 == 0) {Delay(20); while(P1_6 == 0); Delay(20); KeyNum = 8;}
	if(P1_5 == 0) {Delay(20); while(P1_5 == 0); Delay(20); KeyNum = 12;}
	if(P1_4 == 0) {Delay(20); while(P1_4 == 0); Delay(20); KeyNum = 16;}
	
	return KeyNum;
}

这里要注意必须先判断KeyNum是否为0，否则while不断循环会不断显示0，导致看不到按下按钮显示的数字

#include <REGX52.H>
#include "Delay.h"
#include "LCD1602.h"
#include "MatrixKey.h"

unsigned char KeyNum;

void main()
{
	LCD_Init();
	LCD_ShowString(1, 1, "HelloWorld");
	
	while(1)
	{
		KeyNum = MatrixKey();
		if(KeyNum) LCD_ShowNum(2, 1, KeyNum, 2);
	}
}

要利用写好的矩阵键盘来制作一个密码锁，只需要调用MatrixKey文件来直接使用即可，以下是一个简单的密码锁，还有一些bug，不过可以满足基本需求

#include <REGX52.H>
#include "Delay.h"
#include "LCD1602.h"
#include "MatrixKey.h"

unsigned char KeyNum;
unsigned int Password, Count;

void main()
{
	LCD_Init();
	LCD_ShowString(1, 1, "PassWord");
	
	while(1)
	{
		KeyNum = MatrixKey();
		if(KeyNum)
		{
			if(KeyNum <= 10) //数字
			{
				if(Count < 4)
				{
					Password *= 10;
					Password += (KeyNum % 10);
					Count ++; //输入次数，最多为4
				}
				LCD_ShowNum(2, 1, Password, 4); //更新显示
			}
			if(KeyNum == 11) //确认键
			{
				if(Password == 1234) //如果等于正确密码
				{
					LCD_ShowString(1, 14, "OK"); //密码正确
					Password = 0;
					Count = 0;
					LCD_ShowNum(2, 1, Password, 4); //更新显示
				}
				else
				{
					LCD_ShowString(1, 14, "ERR"); //密码错误
					Password = 0;
					Count = 0;
					LCD_ShowNum(2, 1, Password, 4); //更新显示
				}
			}
			if(KeyNum == 12) //取消键
			{
				Password = 0;
				Count = 0;
				LCD_ShowNum(2, 1, Password, 4); //更新显示
			}
		}
	}
}