完整地实现上层按键扫描函数，按键的短按，长按，连按，释放等等状态的判断均是在此程序中完成。可以更容易的去理解按键的执行流程。便于移植。是完整的单片机程序-Full realization of the upper key scan function, press the button, press, double-click, release, etc. are completed to determine the status of this program. Easier to unders