键盘码读取，消抖，回传。--Read keyboard value.-Read keyboard value.

这是一个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-This is a 4* 4 matrix keyboard scan function, using the state machine implemented without delay in order to eliminate shaking, just a timer interrupt function calls in about 10 ~ 12m