//首先先定义一下这8个变量：
sbit KEY_IN_1 = P2 ^ 4;
sbit KEY_IN_2 = P2 ^ 5;
sbit KEY_IN_3 = P2 ^ 6;
sbit KEY_IN_4 = P2 ^ 7;
sbit KEY_OUT_1 = P2 ^ 3;
sbit KEY_OUT_2 = P2 ^ 2;
sbit KEY_OUT_3 = P2 ^ 1;
sbit KEY_OUT_4 = P2 ^ 0;

//接着给这16个按键给个数值：

const unsigned char KeyCodeMap[4][4] =
{
    //矩阵按键编号到标准键盘键码的映射表
    {0x31, 0x32, 0x33, 0x26}, //数字键1、数字键2、数字键3、向上键
    {0x34, 0x35, 0x36, 0x25}, //数字键4、数字键5、数字键6、向左键
    {0x37, 0x38, 0x39, 0x28}, //数字键7、数字键8、数字键9、向下键
    {0x30, 0x1B, 0x0D, 0x27}  //数字键0、ESC键、  回车键、 向右键
};

//全部矩阵按键的当前状态
unsigned char KeySta[4][4] =
{
    {1, 1, 1, 1},
    {1, 1, 1, 1},
    {1, 1, 1, 1},
    {1, 1, 1, 1}
};

/* 按键动作函数，根据键码执行相应的操作，keycode-按键键码 */
void KeyAction(unsigned char keycode)
{
    if ((keycode >= 0x30) && (keycode <= 0x39)) //输入0-9的数字
    {
        //do something
    }
    else if (keycode == 0x25) //向左键
    {
        //do something
    }
    else if (keycode == 0x26) //向上键
    {
        //do something
    }
    else if (keycode == 0x27) //向右键
    {
        //do something
    }
    else if (keycode == 0x28) //向下键
    {
        //do something
    }
    else if (keycode == 0x0D) //回车键
    {
        //do something
    }
    else if (keycode == 0x1B) //Esc键
    {
        //do something
    }
}

/* 按键驱动函数，检测按键动作，调度相应动作函数，需在主循环中调用 */
void KeyDriver()
{
    unsigned char i, j;
    static unsigned char backup[4][4] =  //按键值备份，保存前一次的值
    {
        {1, 1, 1, 1},
        {1, 1, 1, 1},
        {1, 1, 1, 1},
        {1, 1, 1, 1}
    };

    for (i = 0; i < 4; i++) //循环检测4*4的矩阵按键
    {
        for (j = 0; j < 4; j++)
        {
            if (backup[i][j] != KeySta[i][j]) //检测按键动作
            {
                if (backup[i][j] != 0) //按键按下时执行动作
                {
                    KeyAction(KeyCodeMap[i][j]); //调用按键动作函数
                }

                backup[i][j] = KeySta[i][j]; //刷新前一次的备份值
            }
        }
    }
}

/* 按键扫描函数，需在定时中断中调用，推荐调用间隔1ms */
void KeyScan()
{
    unsigned char i;
    static unsigned char keyout = 0;     //矩阵按键扫描输出索引
    static unsigned char keybuf[4][4] =  //矩阵按键扫描缓冲区
    {
        {0xFF, 0xFF, 0xFF, 0xFF},
        {0xFF, 0xFF, 0xFF, 0xFF},
        {0xFF, 0xFF, 0xFF, 0xFF},
        {0xFF, 0xFF, 0xFF, 0xFF}
    };
    //将一行的4个按键值移入缓冲区
    keybuf[keyout][0] = (keybuf[keyout][0] << 1) | KEY_IN_1;
    keybuf[keyout][1] = (keybuf[keyout][1] << 1) | KEY_IN_2;
    keybuf[keyout][2] = (keybuf[keyout][2] << 1) | KEY_IN_3;
    keybuf[keyout][3] = (keybuf[keyout][3] << 1) | KEY_IN_4;

    //消抖后更新按键状态
    for (i = 0; i < 4; i++) //每行4个按键，所以循环4次
    {
        if ((keybuf[keyout][i] & 0x0F) == 0x00)
        {
            //连续4次扫描值为0，即4*4ms内都是按下状态时，可认为按键已稳定的按下
            KeySta[keyout][i] = 0;
        }
        else if ((keybuf[keyout][i] & 0x0F) == 0x0F)
        {
            //连续4次扫描值为1，即4*4ms内都是弹起状态时，可认为按键已稳定的弹起
            KeySta[keyout][i] = 1;
        }
    }

    //执行下一次的扫描输出
    keyout++;               //输出索引递增
    keyout = keyout & 0x03; //索引值加到4即归零

    switch (keyout)         //根据索引，释放当前输出引脚，拉低下次的输出引脚
    {
        case 0:
            KEY_OUT_4 = 1;
            KEY_OUT_1 = 0;
            break;

        case 1:
            KEY_OUT_1 = 1;
            KEY_OUT_2 = 0;
            break;

        case 2:
            KEY_OUT_2 = 1;
            KEY_OUT_3 = 0;
            break;

        case 3:
            KEY_OUT_3 = 1;
            KEY_OUT_4 = 0;
            break;

        default:
            break;
    }
}

void InterruptTimer0() interrupt 1
{
    KeyScan(); //调用按键扫描函数
}

void main(void)
{
    while (1)
    {
        KeyDriver(); //调用按键驱动函数
    }
}