对于单一按键每个按键必须占用一根I/O口线，在按键数量较多时，I/O口线浪费较大，采用矩阵键盘可以解决这个问题-For each key must occupy a single button an I/O port lines, while a larger number keys, I/O port lines wasting large, the use of matrix keyboard can solve this problem