超声波测距系统软件设计采用模块化设计，由主程序、发射子程序、查蟓接收子程序、定时子程序、显示子程序等模块组成。该系统的主程序处于键控循环工作方式，当按下测量键时，主程序开始调用发射子程序、查询接收子程序、定时子程序，并把测量结果用显示子程序在液晶屏上显示出来。 由于液晶要使用同一P3口，所以必须使用位操作，否则将导致LCD不能正常显示。在系统还可以加入温度传感器来监测环境温度，可进行温度被偿。为了增强系统的可靠性，应在软硬件上采用抗干扰措施。-Ultrasonic ranging system design uses modular software design, by the main program, launched Subroutine, Subroutine search蟓receive regular subroutine, subroutines, such as display modules. The main program of the system at work keying cycle, when the press measurement key, the main program to launch the beginning of subroutine calls, inquiries receive subroutine, time subroutine, and the measurement results show the subroutines used in liquid crystal display screen . As the LCD I want to use the same P3, it is necessary to use bit operation, or they will not lead to the normal LCD display. Also can be added in the system temperature sensor to monitor ambient temperature, the temperature can be outstanding. In order to enhance the reliability of the system hardware and software should be used in anti-jamming measures.