[4.1 串口协议](4.1%E4%B8%B2%E5%8F%A3%E5%8D%8F%E8%AE%AE.md) [4.2 重要接口说明](4.2%E9%87%8D%E8%A6%81%E6%8E%A5%E5%8F%A3%E8%AF%B4%E6%98%8E.md) [4.3 架构调整](4.3%E6%9E%B6%E6%9E%84%E8%B0%83%E6%95%B4.md) [4.4 应用](4.4%E5%BA%94%E7%94%A8.md)