*键盘被假定为6列有4列的矩阵。然而，第…

代码说明：

* The keyboard is assumed to be a matrix having 4 rows by 6 columns. However, this code works for any * matrix arrangements up to an 8 x 8 matrix. By using from one to three of the column inputs, the driver * can support "SHIFT" keys. These keys are: SHIFT1, SHIFT2 and SHIFT3.