51单片机超声波测距程序。包含了四位LED显示 蜂鸣器报警程序 应用于以51为核心的 单片机电路 需要配合相应的超声波接收器和发射器-51 single-chip ultrasonic ranging process. Contains four procedures used LED Display Buzzer alarm to the core of the microcontroller circuit 51 with the corresponding need for ultraso