这是一个蜂鸣器奏乐程序，通过PWM控制，先把乐谱转换成代码，再根据频率高低、时长发声。此程序是PWM很好的应用。-This is a buzzer play music program, through the PWM control, first convert the music code, according to the frequency level of the sound when the hair. This program is a good application of PW