使用Python和bleak庫通知一個藍牙GATT設備，結果不穩定

Question

我嘗試使用 Python 來控制一些 BLE GATT 設備。 我發現 Bleak ( https://bleak.readthedocs.io/en/latest/ ) 這個庫與 GATT 設備通信。

當我使用它時，大多數時候它都運行良好。

但是一旦我嘗試與 BLE GATT 醫療設備進行通信，我發現我無法始終與該設備進行通知。

這是我的代碼，我只是對 Bleak 的 github 示例做了一點改動：( https://github.com/hbldh/bleak/blob/develop/examples/enable_notifications.py )

import asyncio
import logging

from bleak import discover
from bleak import BleakClient

devices_dict = {}
devices_list = []
receive_data = []

#To discover BLE devices nearby 
async def scan():
    dev = await discover()
    for i in range(0,len(dev)):
        #Print the devices discovered
        print("[" + str(i) + "]" + dev[i].address,dev[i].name,dev[i].metadata["uuids"])
        #Put devices information into list
        devices_dict[dev[i].address] = []
        devices_dict[dev[i].address].append(dev[i].name)
        devices_dict[dev[i].address].append(dev[i].metadata["uuids"])
        devices_list.append(dev[i].address)

#An easy notify function, just print the recieve data
def notification_handler(sender, data):
    print(', '.join('{:02x}'.format(x) for x in data))

async def run(address, debug=False):
    log = logging.getLogger(__name__)
    if debug:
        import sys

        log.setLevel(logging.DEBUG)
        h = logging.StreamHandler(sys.stdout)
        h.setLevel(logging.DEBUG)
        log.addHandler(h)

    async with BleakClient(address) as client:
        x = await client.is_connected()
        log.info("Connected: {0}".format(x))

        for service in client.services:
            log.info("[Service] {0}: {1}".format(service.uuid, service.description))
            for char in service.characteristics:
                if "read" in char.properties:
                    try:
                        value = bytes(await client.read_gatt_char(char.uuid))
                    except Exception as e:
                        value = str(e).encode()
                else:
                    value = None
                log.info(
                    "\t[Characteristic] {0}: (Handle: {1}) ({2}) | Name: {3}, Value: {4} ".format(
                        char.uuid,
                        char.handle,
                        ",".join(char.properties),
                        char.description,
                        value,
                    )
                )
                for descriptor in char.descriptors:
                    value = await client.read_gatt_descriptor(descriptor.handle)
                    log.info(
                        "\t\t[Descriptor] {0}: (Handle: {1}) | Value: {2} ".format(
                            descriptor.uuid, descriptor.handle, bytes(value)
                        )
                    )

                #Characteristic uuid
                CHARACTERISTIC_UUID = "put your characteristic uuid"

                await client.start_notify(CHARACTERISTIC_UUID, notification_handler)
                await asyncio.sleep(5.0)
                await client.stop_notify(CHARACTERISTIC_UUID)

if __name__ == "__main__":
    print("Scanning for peripherals...")

    #Build an event loop
    loop = asyncio.get_event_loop()
    #Run the discover event
    loop.run_until_complete(scan())

    #let user chose the device
    index = input('please select device from 0 to ' + str(len(devices_list)) + ":")
    index = int(index)
    address = devices_list[index]
    print("Address is " + address)

    #Run notify event
    loop = asyncio.get_event_loop()
    loop.set_debug(True)
    loop.run_until_complete(run(address, True))

在大多數情況下，此代碼可以像此圖像一樣工作。

但有時（大約25%的比例），這個問題恰好發生：

[0]08:6B:D7:12:F1:33 Nonin3150_502892837['uuid']
[1]1D:BD:4A:69:8B:AB Unknown []
[2]73:15:CD:47:AF:08 Unknown []
[3]40:4E:36:5B:8D:1B HTC BS 1BBDB9 ['uuid']
[4]6B:FB:E5:DD:7F:4E Unknown []
[5]69:A7:87:23:5C:7C Unknown []
please select device from 0 to 6:0
Address is 08:6B:D7:12:F1:33
Traceback (most recent call last):
  File "D:/Bletest/nonin_test.py", line 91, in <module>
    loop.run_until_complete(run(address, True))
  File "C:\Users\rizal\AppData\Local\Programs\Python\Python37\lib\asyncio\base_events.py", line 579, in run_until_complete
    return future.result()
  File "D:/Bletest/nonin_test.py", line 36, in run
    async with BleakClient(address) as client:
  File "C:\Users\rizal\AppData\Local\Programs\Python\Python37\lib\site-packages\bleak\backends\client.py", line 60, in __aenter__
    await self.connect()
  File "C:\Users\rizal\AppData\Local\Programs\Python\Python37\lib\site-packages\bleak\backends\dotnet\client.py", line 154, in connect
    "Device with address {0} was not found.".format(self.address)
bleak.exc.BleakError: Device with address 08:6B:D7:12:F1:33 was not found.

Process finished with exit code 1

我不知道為什么程序可以發現這個設備，但不能通知它。

這是我代碼的問題，還是這個設備的程序流程導致的？

Answer 1

我確實有同樣的問題。 但是，我認為這與Windows中BLE的實現有關。當您在Windows界面中掃描設備時，您有時可以看到設備如何出現和消失。 設備廣告間隔可能太長。

但是，可以通過將其包裝在 try catch 部分中來修復它。

這樣的事情可能對你有用。

    async def connect_to_device(self):
        while True:
            if self.connection_enabled:
                try:
                    await self.client.connect()
                    self.connected = await self.client.is_connected()
                    if self.connected:
                        print("Connected to Device")
                        self.client.set_disconnected_callback(self.on_disconnect)
                        await self.client.start_notify(
                            self.notify_characteristic, self.notify_callback,
                        )
                        while True:
                            if not self.connected:
                                break
                            await asyncio.sleep(1.0)
                    else:
                        print(f"Failed to connect to Device")
                except Exception as e:
                    print(e)
            else:
                await asyncio.sleep(1.0)

您只需要將此任務添加到循環中

asyncio.ensure_future(self.connect_to_device(), loop)

定義客戶

self.client = BleakClient(self.connected_device.address, loop=loop)

並啟用連接

self.connection_enabled = true