蜂鸣器模拟电子琴 蜂鸣器只能发出滴滴响声。本源代码通过控制蜂鸣器的频率配置矩阵键盘实现用蜂鸣器模拟电子琴的功能-Buzzer buzzer can only be issued by bit analog keyboard sounds. Source code configuration by controlling the frequency of the buzzer by buzzer analog matrix keyboard to achieve the function k