51单片机基础训练项目之会唱歌的单片机。本例使用普通有源蜂鸣器，通过控制单片机输出频率来达到“唱歌”的目的。着重训练初学者对IO管脚的认识。-51 MCU-based training program in the microcontroller will be singing. In this case the use of ordinary active buzzer, by controlling the microcontroller output frequency to achieve the " singing"　objective. Focus on training for beginners to the IO pin awareness.