5x6矩阵键盘实现，基本思想：逐行扫描，列端口设置为上拉输入，先将第一行置低，检测列有没有被拉低的，没有则置低第二行，置高第一行，检测列有没有置低的，以此类推。-5x6 matrix keyboard realization, the basic idea: Progressive scan, the column is set to pull the input port, the first line of the first set low, there has not been pulled out testing, there is no second line is set low, the first line is set high detect the row has not set low, and so on.