固定频率的方波驱动蜂鸣器，共16种音调；在蜂鸣器 发出不同音调的同时，LED发光以二进制数字形式指示 当前音调的编号（1~16）-Fixed-frequency square wave drive buzzer, a total of 16 tones the buzzer sounded a different tone at the same time, LED light-emitting binary digital form, indicate the current t