4X4键盘扫描，由4X4组成16个按键矩阵，设计成16个音的输入， 使按下其中一个键时，经过8位单片机AT89S52的处理后能发出其对应的音符。-4X4 keyboard scanning, composed of 16 keys from the 4X4 matrix, designed to sound input 16, so that pressing one of the key, through the 8-bit microcontroller AT89S52 of treatment can issue the corresponding notes.