为减小体积，自V5.3版本起，新增的"多段格式"的空调协议，
将仅支持以bc7215_ac_init2()函数进行初始化，如使用
bc7215_ac_init()初始化新增多段协议的第一段信息，将返回
"不成功"，建议现有用户尽快参照新版所附建议初始化流程将
初始化流程更新，以保持对新增协议的支持。

* V5.3版之前已有多段协议维持不变，仍可使用
  bc7215_ac_init()初始化第一段，并在
  bc7215_ac_need_extra_sample()得到返回值"4". 即如不
  升级初始化流程而仅升级码库，不会丧失对已有协议的支持，
  新增普通协议亦可支持，仅新增多段协议将受限。


To reduce memory footprint, starting from version V5.3,
newly added "multi-segment" A/C protocols will only
support initialization via the bc7215_ac_init2() function.
If the bc7215_ac_init() is used on the first segment of
a new multi-segment protocol, it will return "unsuccessful."
It is recommended that existing users update their
initialization process as soon as possible to ensure
compatibility with newly added "multi-segment" protocols.
(Please refer to the attached programming flowchart)

Note:
  Legacy multi-segment protocols (those existing prior to
  V5.3) remain unchanged. You can still use bc7215_ac_init()
  to initialize the first segment, and 
  bc7215_ac_need_extra_sample() will continue to return a
  value of "4". In other words, if you only upgrade the
  library without updating the initialization flow, you 
  will not lose support for existing protocols, and added 
  standard protocols will be supported. Only newly added 
  multi-segment protocols will be restricted.
