【从零开始】手写BLE协议栈（3-2）实验：03_phy_connect_ind

3-2 动手实验：编译运行 03_phy_connect_ind

本篇是第 3 章的配套实验，将 3-1 中讲解的 CONNECT_IND 解析与连接参数校验完整跑通。

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一、概述

03_phy_connect_ind 在广播状态下等待 Central 发送 CONNECT_IND 包，收到后解析并打印全部 12 个连接参数字段。本 Demo 仅解析参数，不进入连接状态，解析完成后重新回到广播。

通过本实验，你将验证：

• CONNECT_IND 的 22 字节 LLData 能被正确拆解
• 各参数字段（AA, CRC Init, WinSize, WinOffset, Interval, Latency, Timeout, Hop, SCA, Channel Map）的实际值
• T0（CONNECT_IND 结束时刻的 RTC ticks）被正确记录

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二、编译与烧录

west build -b nrf52dk/nrf52832 .\write-BLE-stack-from-scratch\03_phy_connect_ind\ -p
west flash

编译产物：

Memory region         Used Size  Region Size  %age Used
           FLASH:       96340 B       512 KB     18.38%
             RAM:       18816 B        64 KB     28.71%

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三、串口日志（启动阶段）

*** Booting Zephyr OS build v4.3.0-4808-ga5d4626b8c16 ***

===================================================
  BLE PHY CONNECT_IND Demo
  解析连接请求中的 12 个参数字段
===================================================
Device: ConnInd  Addr: A6:55:44:33:22:11

HFCLK started
RTC0 started (32768 Hz)
SW_SWITCH_TIMER (TIMER1) configured: 1MHz, 16-bit
PPI configured: CH14 END→CLEAR, CH15 CC[0]→RXEN, CH16 CC[1]→TXEN
[STATE] Entering ADVERTISING state
Radio configured: BLE 1M (ADV mode)
[ADV] events: 1 (waiting for connection...)
[ADV] events: 2 (waiting for connection...)
...

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四、运行测试

使用 bumble_connect.py 发送 CONNECT_IND：

.\write-BLE-stack-from-scratch\tools\venv\Scripts\python.exe `
  .\write-BLE-stack-from-scratch\tools\bumble_connect.py `
  --transport usb:2FE3:000B `
  --target A6:55:44:33:22:11 `
  --duration 5

Bumble 侧输出：

Connecting to A6:55:44:33:22:11...
  Sending CONNECT_IND with:
    interval = 40 (50.00ms)
    latency  = 0
    timeout  = 200 (2000ms)

  ★ BLE CONNECTION ESTABLISHED #1
  ...
  ✖ DISCONNECTED
  Reason  : 0x3E - Failed to Establish Connection

断开原因 0x3E 是预期的 — Demo 只解析 CONNECT_IND，不回复任何数据 PDU，Central 等不到响应就超时了。

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五、CONNECT_IND 解析结果（串口日志）

========== CONNECT_IND Received ==========
  Peer:       F0:F1:F2:F3:F4:F5
  AA:         0x2917789E
  CRC Init:   0x6BE11B
  WinSize:    1 (x1.25ms = 1250 us)
  WinOffset:  0 (x1.25ms = 0 us)
  Interval:   40 (x1.25ms = 50000 us)
  Latency:    0
  Timeout:    200 (x10ms = 2000 ms)
  Hop:        8
  SCA:        5 (50 ppm)
  Chan Count: 37 / 37
  T0 (RTC0):  544242 ticks
==========================================

[STATE] CONNECT_IND parsed. (Not entering connection state in this demo)
[STATE] Returning to advertising...

字段对照

字段	字节	解析值	含义
AA	4B	0x2917789E	数据通道接入地址（随机生成）
CRC Init	3B	0x6BE11B	数据通道 CRC 初始值
WinSize	1B	1	发送窗口大小 = 1.25 ms
WinOffset	2B	0	发送窗口偏移 = 0 ms
Interval	2B	40	连接间隔 = 50 ms
Latency	2B	0	从机延迟 = 0（不跳过）
Timeout	2B	200	超时 = 2000 ms
Hop	5-bit	8	跳频增量（5~16）
SCA	3-bit	5	主机时钟精度 = 50 ppm
ChM	5B	37/37	37 个数据通道全部启用

📸 截图占位：Wireshark 抓包显示 CONNECT_IND 包的字节级解析

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六、关键概念图

CONNECT_IND 22 字节布局

字节偏移  长度   字段          值（示例）
[0..3]   4B    AA            0x2917789E
[4..6]   3B    CRCInit       0x6BE11B
[7]      1B    WinSize       1
[8..9]   2B    WinOffset     0
[10..11] 2B    Interval      40
[12..13] 2B    Latency       0
[14..15] 2B    Timeout       200
[16..20] 5B    ChM           0x1FFFFFFFFF (37ch all on)
[21]     1B    Hop(5b)+SCA(3b)  Hop=8, SCA=5

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本系列教程同款硬件：👇
芯片： nRF 52832 开发板
工具： nRF 52840 BLE Dongle 蓝牙嗅探器
工具： 逻辑分析仪
工具： BPA low energy 蓝牙分析仪