如何实现BTLE设备（Sensirion SHT41x）的可靠蓝牙连接？

问题背景 #

Windows笔记本与Sensirion SHT41x BTLE设备（距离半米）连接时，仅约1/10的成功率，连接失败时抛出错误：

raise BleakDeviceNotFoundError(
bleak.exc.BleakDeviceNotFoundError: Device with address ... was not found.

已尝试的操作：

• 重新运行脚本
• 开关笔记本蓝牙
• 移除设备电池重启设备

初始测试脚本：

import asyncio
from bleak import BleakClient

address = "..."

async def connect_device():
    async with BleakClient(address) as client:
        connected = await client.is_connected()
        print(f"Connected: {connected}")
        disconnected = await client.disconnect()
        print(f"Disonnected: {disconnected}")

asyncio.run(connect_device())

添加重试逻辑后的脚本仍多数失败：

import time
import asyncio
from bleak import BleakClient
from loguru import logger

async def just_connect(mac):
    async with BleakClient(mac) as client:
        pass
    await asyncio.sleep(2)
    
mac = "C5:5A:42:A4:3C:80"
tries = 10

results = {}
start = time.time()
timeout = 12
for try_ in range(tries):
    try:
        await asyncio.wait_for(just_connect(mac), timeout)
        logger.info(f"try {try_} succeeded")

    except Exception as e:
        logger.info(f"try {try_} failed due to {type(e).__name__}: {e}")

典型失败日志：

2024-06-02 15:25:25.346 | INFO     | __main__:<module>:24 - try 0 failed due to BleakDeviceNotFoundError: Device with address C5:5A:42:A4:3C:80 was not found.
2024-06-02 15:25:35.366 | INFO     | __main__:<module>:24 - try 1 failed due to BleakDeviceNotFoundError: Device with address C5:5A:42:A4:3C:80 was not found.
2024-06-02 15:25:45.377 | INFO     | __main__:<module>:24 - try 2 failed due to BleakDeviceNotFoundError: Device with address C5:5A:42:A4:3C:80 was not found.
2024-06-02 15:25:55.907 | INFO     | __main__:<module>:24 - try 3 failed due to TimeoutError: 
2024-06-02 15:26:05.941 | INFO     | __main__:<module>:24 - try 4 failed due to BleakDeviceNotFoundError: Device with address C5:5A:42:A4:3C:80 was not found.
2024-06-02 15:26:17.953 | INFO     | __main__:<module>:24 - try 5 failed due to TimeoutError: 
2024-06-02 15:26:27.951 | INFO     | __main__:<module>:24 - try 6 failed due to BleakDeviceNotFoundError: Device with address C5:5A:42:A4:3C:80 was not found.
2024-06-02 15:26:39.963 | INFO     | __main__:<module>:24 - try 7 failed due to TimeoutError: 
2024-06-02 15:26:51.971 | INFO     | __main__:<module>:24 - try 8 failed due to TimeoutError: 
2024-06-02 15:27:01.978 | INFO     | __main__:<module>:24 - try 9 failed due to BleakDeviceNotFoundError: Device with address C5:5A:42:A4:3C:80 was not found.

提升连接可靠性的具体方案 #

1. 明确BLE设备地址类型 #

Windows下SHT41x可能使用随机BLE地址，默认Bleak按公共地址查找会导致设备找不到。先扫描确认地址类型：

from bleak import BleakScanner
import asyncio

async def scan_devices():
    devices = await BleakScanner.discover(timeout=5)
    for d in devices:
        print(f"设备名称: {d.name}, 地址: {d.address}, 地址类型: {d.address_type}")

asyncio.run(scan_devices())

然后在连接时指定地址类型：

async def just_connect(mac):
    # 按扫描到的地址类型填写，通常为"random"
    async with BleakClient(mac, address_type="random") as client:
        if client.is_connected:
            logger.info("连接成功")
    await asyncio.sleep(1)

2. 先扫描再连接，避免直接用MAC硬连 #

直接通过MAC连接容易因设备未被扫描到失败，改为先扫描确认设备存在再发起连接：

import asyncio
from bleak import BleakClient, BleakScanner
from loguru import logger

TARGET_MAC = "C5:5A:42:A4:3C:80"

async def scan_and_connect():
    # 延长扫描时间确保捕获设备信号
    scanner = BleakScanner()
    await scanner.start()
    await asyncio.sleep(3)
    devices = scanner.discovered_devices
    await scanner.stop()

    target_device = next((d for d in devices if d.address == TARGET_MAC), None)
    if not target_device:
        logger.error("扫描未找到目标设备")
        return False

    # 使用扫描到的设备对象连接，而非仅MAC
    try:
        async with BleakClient(target_device, timeout=15) as client:
            if client.is_connected:
                logger.info("连接成功")
                return True
    except Exception as e:
        logger.error(f"连接失败: {type(e).__name__}: {e}")
        return False

async def retry_connection(max_tries=5):
    for try_num in range(max_tries):
        success = await scan_and_connect()
        if success:
            return True
        logger.info(f"第{try_num+1}次尝试失败，等待2秒后重试")
        await asyncio.sleep(2)
    return False

asyncio.run(retry_connection())

3. 调整Windows蓝牙栈设置 #

• 更新蓝牙驱动：前往笔记本厂商官网下载最新蓝牙适配器驱动，旧驱动常存在BLE兼容性问题。
• 禁用蓝牙节能：打开设备管理器 → 蓝牙适配器 → 属性 → 电源管理，取消勾选"允许计算机关闭此设备以节约电源"，避免系统休眠蓝牙适配器。
• 减少干扰：暂时关闭笔记本附近其他BLE设备（如耳机、蓝牙鼠标），减少信道冲突。

4. 优化Bleak连接参数 #

• 延长连接超时：Windows下BLE协商耗时更长，设置timeout=15避免过早触发超时。
• 禁用缓存：添加cached=False参数，强制每次重新扫描设备，避免使用过期的设备缓存：

async with BleakClient(target_device, timeout=15, cached=False) as client:
    # ...

5. 检查SHT41x设备配置 #

• 确认设备持续广播：部分BLE传感器会进入低功耗休眠模式停止广播，查看SHT41x文档调整广播间隔，确保设备处于持续可发现状态。
• 重置设备蓝牙：若设备支持，通过官方工具重置蓝牙配置，恢复默认广播参数。

内容的提问来源于stack exchange，提问作者Dr-Nuke