LOW ENERGY CORE CONFIGURATION
在武汉疫情期间，难得有空余时间，根据最近更新Bluetooth core spec v5.2，整理一下ble相关知识。
希望能够在上班之前，系统的把ble 相关理论知识梳理一遍。如有偏差，也欢迎专家指证，感谢！
该系列文章以spec为主要来源，会加入一些个人的理解，如有阐述不清的地方，也欢迎您留言交流.
Host part：
| Layer | Required Features |
|---|---|
| L2CAP ([Vol 3] Part A) | If the GAP Peripheral or Central role is supported, L2CAP LE Signaling channel (CID 0x0005) and all mandatory features associated with it |
| GAP ([Vol 3] Part C) | All mandatory features for at least one of the LE GAP roles (Broadcaster, Observer, Peripheral or Central) in sections 9-12 and section 15 |
| ATT ([Vol 3] Part F) | If the GAP Peripheral or Central role is supported, all mandatory features |
| GATT ([Vol 3] Part G) | GATT is mandatory when ATT is supported. When supported,all mandatory features |
| SM ([Vol 3] Part H) | If the GAP Peripheral or Central role is supported, all mandatory features |
Controller part：
| Layer | Required Features |
|---|---|
| PHY ([Vol 6] Part A) | All mandatory features |
| LL ([Vol 6] Part B) | All mandatory features |
上述表格搬运自core spec，该表格所列出的内容是针对纯ble设备，需要区别于br/edr 和ble 共存的设备。
所涉及到的章节，后续会依次展开对spec的研读。