这个文件的代码用来解算PPM信号。PPM信号时用一个通道传输多路信息的一种编码方式。本代码将此此“串行”信号解码，为使用PPM信号者提供方便。-This file contains the code that decodes the PPM signal which features　serial　transfer of several signals in one channel. The code is dedicated to the people who needs to use PPM signal in embedded system.