函数：滑动均值滤波--analog signals

优点：可重用，代码量小，数据实时无间断

缺点：边沿平滑，不适合突变检测

要求：使用前，必须先初始化

案例：sum的初值为基准值；buff[]不能大于sum-Function: sliding mean filter- analog signals advantages: reusability, a small amount of code and data in real time without interruption Disadvantages: the edge is smooth, not suitable for mutation detection: before use, you must first initialize the case: the initial value of the sum of the reference value　 buff [] is not greater than the sum