特点：

按键在松手后有效,灵敏度高,消耗资源少,运行效率高

独立键盘为:K01=P2^4;K02=P2^5;K03=P2^6;K04=P2^7;

矩阵键盘为:行(上到下)_P2.3_P2.2_P2.1_P2.0

           列(左到右)_P2.7_P2.6_P2.5_P2.4

提供的操作函数：

//独立键盘.无按键动作时其返回值num_key=0,否则返回按键号num_key

extern unsigned char keyboard_self();

//矩阵键盘.无按键动作时其返回值num_key=0,否则返回按键号num_key****检测高四位

extern unsigned char keyboard_matrix();

****************************************/

先看独立键盘（和矩阵键盘的算法一样）

-----------------------------------------------------------------------

#include

#include

//独立键盘.无按键动作时其返回值num_key=0,否则返回按键号num_key

extern unsigned char keyboard_self()

{

        unsigned char num_key=0;//按键号

        unsigned char temp=0;//用于读取P2线上按键值

        static unsigned char temp_code=0;//保存按键值

        static unsigned char num_check=0;//低电平有效次数

        static unsigned char key_flag=0;//按键有效标识

        temp=P2&0xF0;//读取P2线数据

        if(temp!=0xF0)//低电平判断

        {

                num_check++;

                if(num_check==10)//连续10次(10ms)低电平有效,则认为按键有效

                {

                        key_flag=1;//使能按键有效标识

                        temp_code=temp;//保存按键值

                }

        }

        else//松手时判断

        {

                num_check=0;

                if(key_flag==1)//按键有效

                {

                        key_flag=0;

                        switch(temp_code)//读取按键号

                        {

                                case 0xE0: num_key=1;

                                           break;

                                case 0xD0: num_key=2;

                                           break;

                                case 0xB0: num_key=3;

                                           break;

                                case 0x70: num_key=4;

                                           break;

                        }

                }

        }

        return(num_key);

}

现在是矩阵键盘的

-----------------------------------------------------------------------

#include

#include  

//矩阵键盘.无按键动作时其返回值num_key=0,否则返回按键号num_key****检测高四位

extern unsigned char keyboard_matrix()

{

        unsigned char num_key=0;//按键号

        unsigned char temp=0;//读取P2口线数据

        static unsigned char temp_code=0;//用于保存按键值

        static unsigned char temp_circle=0xFE;//保存P2线上的循环扫描值

        static unsigned char num_check=0;//低电平计数

        static unsigned char key_flag=0;//按键有效标识

        P2=temp_circle;//0xFX

        temp=P2;//读取P2口线数据

        if(temp!=temp_circle)//有按键动作

        {

                num_check++;//低电平计数|逢低电平加1

                if(num_check==10)//连续10次(10ms)低电平有效

                {

                        key_flag=1;//按键有效标识置1

                        temp_code=temp;//保存按键值

                }

        }

        else//松手OR无按键动作,此时应该改变扫描线

        {

                num_check=0;

                if(key_flag==1)//按键有效判断

                {

                        key_flag=0;

                        switch(temp_code)//读取按键号

                        {

                                //P2^0线

                                case 0xEE: num_key=1;

                                           break;

                                case 0xDE: num_key=2;

                                           break;

                                case 0xBE: num_key=3;

                                           break;

                                case 0x7E: num_key=4;

                                           break;

                                //P2^1线

                                case 0xED: num_key=5;

                                           break;

                                case 0xDD: num_key=6;

                                           break;

                                case 0xBD: num_key=7;

                                           break;

                                case 0x7D: num_key=8;

                                           break;

                                //P2^2线

                                case 0xEB: num_key=9;

                                           break;

                                case 0xDB: num_key=10;

                                           break;

                                case 0xBB: num_key=11;

                                           break;

                                case 0x7B: num_key=12;

                                           break;

                                //P2^3线

                                case 0xE7: num_key=13;

                                           break;

                                case 0xD7: num_key=14;

                                           break;

                                case 0xB7: num_key=15;

                                           break;

                                case 0x77: num_key=16;

                                           break;

                        }

                }

                temp_circle=_crol_(temp_circle,1);//改变扫描线

                if(temp_circle==0xEF)

                {

                        temp_circle=0xFE;

                }

        }

        return(num_key);//返回按键号

}

/*************************************************************************

未按键时,扫描线一直变化。

长按键时,扫描线不变化,使得该行按键变成了独立按键,这样的扫描效率极高。

如当按下P2.0线上的某个键时,程序将扫描到这个键,而后扫描线不变化,

当键盘程序连续10次进入时检测到10次按键有效,直到松手后扫描线才变化