如何在python中使用pygatt从BLE设备获取通知？

2019年7月28日 389次阅读

我正在使用
python开发一个
Linux应用程序,它将连接到我的BLE设备并通过通知特性来获取数据.我正在使用
pygatt进行BLE通信.我可以成功连接并绑定到设备并读取/写入特性.即使我可以订阅通知特性,但问题是,我的BLE设备是一个自定义机器,里面有4个计数器,每当计数器的一个数据发生变化时,它就会设置相应的通知标志,因此,使用onDataChanged-像方法我可以从阅读特征中读取计数器的数据.在使用pygatt的Python中,我可以订阅通知特性：

class_name.device.subscribe(uuid.UUID(notify_characteristic),callback=notifyBle)

而notifyBle是：

def notifyBle(self,handle,data):
    read_data = class_name.device.char_read(uuid.UUID(read_characteristic))
    print(read_data)

当我运行程序时,首先我扫描设备并连接到我的设备并与之绑定,然后我发现特征并列出它们.一切都很成功.列出特性后,我写了写特性来清除通知标志,也是成功的.最后我订阅通知特征它是成功的.

完成所有这些过程后,我会在物理上增加设备的计数器(设备上有按钮用于增加计数器).当我按下按钮程序进入notifyBle方法,它给出错误,这是：

Exception in thread Thread-3:
Traceback (most recent call last):
  File "/usr/lib/python3.5/threading.py", line 914, in _bootstrap_inner
    self.run()
  File "/usr/local/lib/python3.5/dist-packages/pygatt/backends/gatttool/gatttool.py", line 137, in run
    event["callback"](event)
  File "/usr/local/lib/python3.5/dist-packages/pygatt/backends/gatttool/gatttool.py", line 479, in _handle_notification_string
    self._connected_device.receive_notification(handle, values)
  File "/usr/local/lib/python3.5/dist-packages/pygatt/device.py", line 226, in receive_notification
    callback(handle, value)
  File "/home/acd/Masaüstü/python_workspace/ble.py", line 54, in notifyBle
    read_data = bleFunctions.dev.char_read(uuid.UUID(bleFunctions.read_characteristic))
  File "/usr/local/lib/python3.5/dist-packages/pygatt/backends/gatttool/device.py", line 17, in wrapper
    return func(self, *args, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/pygatt/backends/gatttool/device.py", line 40, in char_read
    return self._backend.char_read(self, uuid, *args, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/pygatt/backends/gatttool/gatttool.py", line 53, in wrapper
    return func(self, *args, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/pygatt/backends/gatttool/gatttool.py", line 519, in char_read
    self.sendline('char-read-uuid %s' % uuid)
  File "/usr/lib/python3.5/contextlib.py", line 66, in __exit__
    next(self.gen)
  File "/usr/local/lib/python3.5/dist-packages/pygatt/backends/gatttool/gatttool.py", line 180, in event
    self.wait(event, timeout)
  File "/usr/local/lib/python3.5/dist-packages/pygatt/backends/gatttool/gatttool.py", line 154, in wait
    raise NotificationTimeout()
pygatt.exceptions.NotificationTimeout

任何帮助,将不胜感激.

PS：我在Android和Windows UWP中编写了完全相同的程序.使用python,我的目标是在raspberry pi 3上运行它.

PSS：我正在使用带有Ubuntu Mate的raspberry pi 3来在python中开发这个程序.

最佳答案 首先,创建如下的事件类,

class Event:
    def __init__(self):
        self.handlers = set()

    def handle(self, handler):
        self.handlers.add(handler)
        return self

    def unhandle(self, handler):
        try:
            self.handlers.remove(handler)
        except:
            raise ValueError("Handler is not handling this event, so cannot unhandle it.")
        return self

    def fire(self, *args, **kargs):
        for handler in self.handlers:
            handler(*args, **kargs)

    def getHandlerCount(self):
        return len(self.handlers)

    __iadd__ = handle
    __isub__ = unhandle
    __call__ = fire
    __len__  = getHandlerCount

然后,
创建一个ble类

import pygatt
from eventclass import Event

class myBle:
    ADDRESS_TYPE = pygatt.BLEAddressType.random
    read_characteristic = "0000xxxx-0000-1000-8000-00805f9b34fb"
    write_characteristic = "0000xxxx-0000-1000-8000-00805f9b34fb"
    notify_characteristic = "0000xxxxx-0000-1000-8000-00805f9b34fb"
    def __init__(self,device):
        self.device = device
        self.valueChanged = Event()
        self.checkdata = False

    def alert(self):
         self.valueChanged(self.checkdata)

    def write(self,data):
        self.device.write_char(self.write_characteristic,binascii.unhexlify(data))

    def notify(self,handle,data):
        self.checkdata = True

    def read(self):
        if(self.checkdata):
            self.read_data = self.device.char_read(uuid.UUID(self.read_characteristic))
            self.write(bytearray(b'\x10\x00'))
            self.checkdata = False
            return self.read_data
    def discover(self):
        return self.device.discover_characteristics().keys()

当你收到通知时,你会将布尔值设置为true,并且alert方法将通知boolean值被更改.你将听取alert方法

def triggerEvent(checkdata):
   print(str(checkdata))

ble = myBle(device)
ble.valueChanged += triggerEvent
ble.alert()

您可以使用triggerEvent方法调用read方法来获取特征值.

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