用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）-The buzzer is driven with a fixed frequency square wave, a total of 16 kinds of tone sounds of different tones at the same time, buzzer, LED light to binary digital indicator, the tone