说明：  LCM二级菜单的程序编写,这是一个项目实例，对菜单编写有很好的借鉴作用。希望对单片机开发项目做人机界面的有帮助。
(LCM secondary menu programming, this is an instance of a project, the menu written a very good reference. Microcontroller development projects HCI.)