key.c

4*4矩阵键盘扫描函数,用状态机实现,不用延时以消抖,只需在一个定时10~12ms左右的中断函数里调用,从而节省了单片机时间

//针对avr单片机编写,当然也可能移植到其他环境


#define KEY_PORT   PORTC
#define KEY_PIN		PINC
#define NO_KEY    255   //4x4键盘
#define KEY_MASK   0x07		//00000111

//在中断函数里调用,应该是10ms左右一次中断.因为这是消抖所需时间.

char read_keyboard()
{
    static char key_state = 0;
    static char key_value, key_line;
    char key_return = NO_KEY;
    unsigned char i;
    switch(key_state)
    {
        case 0:
            key_line = 0x08;      //0b0000 1000;
            for(i=1;i<=4;i++)    //按键扫描
            {
                KEY_PORT = ~key_line;   //输出行线电平
                KEY_PORT = ~key_line;   //输出两次
                //delay_nms(2);
                key_value = KEY_MASK & KEY_PIN;  //读列电平
                if(key_value == KEY_MASK)
                {
                    key_line <<= 1;   //没有按键,继续扫描
                    //delay_nms(2);
                }
                else
                {
                    key_state++;  //有键按下,停止扫描
                    break;    //转消抖确认状态
                }

            }
            break;
        case 1:
            {
                switch((key_value | key_line)) //与状态0相同,确认按键
                {
                    case 0x0e:              //0b00001110:
                        key_return = K4_3;
                        break;
                    case 0x0d:              //0b00001101:
                        key_return = K4_2;
                        break;
                    case 0x0b:              //0b00001011:
                        key_return = K4_1;
                        break;

                    case 0x16:              //0b00010110:
                        key_return = K3_3;
                        break;
                    case 0x15:              //0b00010101:
                        key_return = K3_2;
                        break;
                    case 0x13:              //0b00010011:
                        key_return = K3_1;
                        break;

                    case 0x26:              //0b00100110:
                        key_return = K2_3;
                        break;
                    case 0x25:              //0b00100101:
                        key_return = K2_2;
                        break;
                    case 0x23:              //0b00100011:
                        key_return = K2_1;
                        break;

                    case 0x46:              //0b01000110:
                        key_return = K1_3;
                        break;
                    case 0x45:              //0b01000101:
                        key_return = K1_2;
                        break;
                    case 0x43:              //0b01000011:
                        key_return = K1_1;
                        break;
				
                }
                key_state++;     //转入按键释放状态
            }
            break;
        case 2:
            KEY_PORT = 0x07;      //行线全部输出低电平
            KEY_PORT = 0x07;
            if((KEY_MASK & KEY_PIN) == KEY_MASK)
            {
                key_state = 0;   //列线全部为高电平,返回状态0
            }
            break;
    }
    return(key_return);
}