基于STC15w202s单片机的超声波测距、数码管显示距离程序。增加两个按键，同时按下进入调整阈值，当距离高于或者低于阈值，相应管脚输出高。-Based STC15w202s microcontroller Ultrasonic Ranging, digital display the program. Add two buttons, press enter to adjust the threshold, when the distance above or below the thres