Serial.flush()函数不具备清空缓存区的作用，其主要作用是串口发送数据时等待，
直到串口数据发送完例如下面程序都发送了同一个字符串，各自打印的时间不一致可说明若要清空缓存区请重复读取串口，直到串口数据为空Serial9600local_variate时间1unsigned longmillisSerialprintlnhelloSerialprintlnMINUS1millis1时间1local_variate时间2unsigned longmillisSerialprintlnhelloSerialSerialprintlnMINUS1millis1时间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