采用定时器进行频率控制，把乐曲按照可行的数据格式控制定时器的频率及时长，播放音乐，通过GPIO开关实现对音乐的播放速度进行设置，音曲可以由串口传送。 -Frequency control using the timer, the music data format in accordance with a viable frequency control timer length in time, play music, music playback speed is set to achi