如何读取传入的 BLE 数据？ [树莓派]

Question

我为 IOS 开发了一个程序，现在它需要通过 BLE 与 Raspberry Pi 通信。 我能够将 BLE 数据发送到特征，并且可以从bluetoothctl终端看到数据。 我试图创建一个 Python 程序，以便它可以读取传入的 BLE 数据，但我无法做到。 我搜索并找到pexpect但我无法从终端读取数据（很难检测到更改并读取最后一行）。 我搜索并找到了 python dbus，但我从未经历过。 有没有人可以帮助我？

• IOS 应用程序自动配对。

• IOS 应用程序集通知树莓派

• 树莓派

  • 服务：0xffff
  • 特征：0xbbbb 读、写、通知

Answer 1

我只是不确定bluetoothctl中的功能是否打算与 Python 之类的编程语言进行交互。

D-Bus API 记录在： https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/doc是开发人员期望人们访问数据的方式。

我接受使用这些 D-Bus API 有一个学习曲线，并且对于创建 BLE 外设来说，这有点重要，特别是如果这是您第一次使用 D-Bus。

bluetoothctl在幕后所做的是在 D-Bus 上创建一个“应用程序”，它会告诉您路径是什么。 在您发布的示例中，它是/org/bluez/app/service0/chrc0 。

问题是没有简单的方法来获取写入此特征的数据，因为它不会以其他客户端可以获取数据的方式发布到 D-Bus。

您可以使用以下命令在命令行上监控所有 BlueZ D-Bus 活动：

$ sudo busctl monitor org.bluez
Monitoring bus message stream.
‣ Type=method_call  Endian=l  Flags=0  Version=1  Priority=0 Cookie=104
  Sender=:1.1742  Destination=:1.1744  Path=/org/bluez/app/service0/chrc0  Interface=org.bluez.GattCharacteristic1  Member=WriteValue
  UniqueName=:1.1742
  MESSAGE "aya{sv}" {
          ARRAY "y" {
                  BYTE 68;
                  BYTE 105;
                  BYTE 114;
                  BYTE 101;
                  BYTE 107;
          };
          ARRAY "{sv}" {
                  DICT_ENTRY "sv" {
                          STRING "device";
                          VARIANT "o" {
                                  OBJECT_PATH "/org/bluez/hci0/dev_6C_40_BE_46_E5_5A";
                          };
                  };
                  DICT_ENTRY "sv" {
                          STRING "link";
                          VARIANT "s" {
                                  STRING "LE";
                          };
                  };
                  DICT_ENTRY "sv" {
                          STRING "mtu";
                          VARIANT "q" {
                                  UINT16 517;
                          };
                  };
          };
  };
         -       -          

如果您提取发送的字节，那么这就是您的价值

>>> value = [68, 105, 114, 101, 107]
>>> bytes(value)
b'Direk'

但是，这看起来需要做很多工作，而且非常 hacky。

BlueZ 项目在其源存储库中包含一个 Python 示例广告：

https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/test/example-advertisement

BLE 外围设备示例：

https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/test/example-gatt-server

下面我做了一个将这两者都放入一个文件的示例。 我还尝试将您不必更改的“样板”代码和特定于您的应用程序的代码分开。

每次您的 iOS 应用程序将数据（字符串）写入外设时，都会调用 function my_write_callback(txt) 。

import dbus
import dbus.exceptions
import dbus.mainloop.glib
import dbus.service

from gi.repository import GLib

# BlueZ D-Bus interfaces
BLUEZ_SERVICE_NAME = "org.bluez"
GATT_MANAGER_IFACE = "org.bluez.GattManager1"
DBUS_OM_IFACE = "org.freedesktop.DBus.ObjectManager"
DBUS_PROP_IFACE = "org.freedesktop.DBus.Properties"

GATT_SERVICE_IFACE = "org.bluez.GattService1"
GATT_CHRC_IFACE = "org.bluez.GattCharacteristic1"
GATT_DESC_IFACE = "org.bluez.GattDescriptor1"
LE_ADVERTISING_MANAGER_IFACE = 'org.bluez.LEAdvertisingManager1'
LE_ADVERTISEMENT_IFACE = 'org.bluez.LEAdvertisement1'

# Test UUIDs
TEST_SERVICE = "0000ffff-beef-c0c0-c0de-c0ffeefacade"
TEST_CHARACTERISTIC = "0000bbbb-beef-c0c0-c0de-c0ffeefacade"


# Boiler plate start
class InvalidArgsException(dbus.exceptions.DBusException):
    _dbus_error_name = 'org.freedesktop.DBus.Error.InvalidArgs'


class NotSupportedException(dbus.exceptions.DBusException):
    _dbus_error_name = 'org.bluez.Error.NotSupported'


class NotPermittedException(dbus.exceptions.DBusException):
    _dbus_error_name = 'org.bluez.Error.NotPermitted'


class InvalidValueLengthException(dbus.exceptions.DBusException):
    _dbus_error_name = 'org.bluez.Error.InvalidValueLength'


class FailedException(dbus.exceptions.DBusException):
    _dbus_error_name = 'org.bluez.Error.Failed'


def register_app_cb():
    print("GATT application registered")


def register_app_error_cb(error):
    print("Failed to register application: " + str(error))
    mainloop.quit()


def register_ad_cb():
    print('Advertisement registered')


def register_ad_error_cb(error):
    print('Failed to register advertisement: ' + str(error))
    mainloop.quit()


class Advertisement(dbus.service.Object):
    PATH_BASE = '/org/bluez/example/advertisement'

    def __init__(self, bus, index, advertising_type):
        self.path = self.PATH_BASE + str(index)
        self.bus = bus
        self.ad_type = advertising_type
        self.service_uuids = None
        self.manufacturer_data = None
        self.solicit_uuids = None
        self.service_data = None
        self.local_name = None
        self.include_tx_power = False
        self.data = None
        dbus.service.Object.__init__(self, bus, self.path)

    def get_properties(self):
        properties = dict()
        properties['Type'] = self.ad_type
        if self.service_uuids is not None:
            properties['ServiceUUIDs'] = dbus.Array(self.service_uuids,
                                                    signature='s')
        if self.solicit_uuids is not None:
            properties['SolicitUUIDs'] = dbus.Array(self.solicit_uuids,
                                                    signature='s')
        if self.manufacturer_data is not None:
            properties['ManufacturerData'] = dbus.Dictionary(
                self.manufacturer_data, signature='qv')
        if self.service_data is not None:
            properties['ServiceData'] = dbus.Dictionary(self.service_data,
                                                        signature='sv')
        if self.local_name is not None:
            properties['LocalName'] = dbus.String(self.local_name)
        if self.include_tx_power:
            properties['Includes'] = dbus.Array(["tx-power"], signature='s')

        if self.data is not None:
            properties['Data'] = dbus.Dictionary(
                self.data, signature='yv')
        return {LE_ADVERTISEMENT_IFACE: properties}

    def get_path(self):
        return dbus.ObjectPath(self.path)

    def add_service_uuid(self, uuid):
        if not self.service_uuids:
            self.service_uuids = []
        self.service_uuids.append(uuid)

    def add_solicit_uuid(self, uuid):
        if not self.solicit_uuids:
            self.solicit_uuids = []
        self.solicit_uuids.append(uuid)

    def add_manufacturer_data(self, manuf_code, data):
        if not self.manufacturer_data:
            self.manufacturer_data = dbus.Dictionary({}, signature='qv')
        self.manufacturer_data[manuf_code] = dbus.Array(data, signature='y')

    def add_service_data(self, uuid, data):
        if not self.service_data:
            self.service_data = dbus.Dictionary({}, signature='sv')
        self.service_data[uuid] = dbus.Array(data, signature='y')

    def add_local_name(self, name):
        if not self.local_name:
            self.local_name = ""
        self.local_name = dbus.String(name)

    def add_data(self, ad_type, data):
        if not self.data:
            self.data = dbus.Dictionary({}, signature='yv')
        self.data[ad_type] = dbus.Array(data, signature='y')

    @dbus.service.method(DBUS_PROP_IFACE,
                         in_signature='s',
                         out_signature='a{sv}')
    def GetAll(self, interface):
        print('GetAll')
        if interface != LE_ADVERTISEMENT_IFACE:
            raise InvalidArgsException()
        print('returning props')
        return self.get_properties()[LE_ADVERTISEMENT_IFACE]

    @dbus.service.method(LE_ADVERTISEMENT_IFACE,
                         in_signature='',
                         out_signature='')
    def Release(self):
        print('%s: Released!' % self.path)


class Service(dbus.service.Object):
    """
    org.bluez.GattService1 interface implementation
    """

    PATH_BASE = "/org/bluez/app/service"

    def __init__(self, bus, index, uuid, primary):
        self.path = self.PATH_BASE + str(index)
        self.bus = bus
        self.uuid = uuid
        self.primary = primary
        self.characteristics = []
        dbus.service.Object.__init__(self, bus, self.path)

    def get_properties(self):
        return {
            GATT_SERVICE_IFACE: {
                "UUID": self.uuid,
                "Primary": self.primary,
                "Characteristics": dbus.Array(
                    self.get_characteristic_paths(), signature="o"
                ),
            }
        }

    def get_path(self):
        return dbus.ObjectPath(self.path)

    def add_characteristic(self, characteristic):
        self.characteristics.append(characteristic)

    def get_characteristic_paths(self):
        result = []
        for chrc in self.characteristics:
            result.append(chrc.get_path())
        return result

    def get_characteristics(self):
        return self.characteristics

    @dbus.service.method(DBUS_PROP_IFACE, in_signature="s", out_signature="a{sv}")
    def GetAll(self, interface):
        if interface != GATT_SERVICE_IFACE:
            raise InvalidArgsException()

        return self.get_properties()[GATT_SERVICE_IFACE]


class Characteristic(dbus.service.Object):
    """
    org.bluez.GattCharacteristic1 interface implementation
    """

    def __init__(self, bus, index, uuid, flags, service):
        self.path = service.path + "/chrc" + str(index)
        self.bus = bus
        self.uuid = uuid
        self.service = service
        self.flags = flags
        self.descriptors = []
        dbus.service.Object.__init__(self, bus, self.path)

    def get_properties(self):
        return {
            GATT_CHRC_IFACE: {
                "Service": self.service.get_path(),
                "UUID": self.uuid,
                "Flags": self.flags,
                "Descriptors": dbus.Array(self.get_descriptor_paths(), signature="o"),
            }
        }

    def get_path(self):
        return dbus.ObjectPath(self.path)

    def add_descriptor(self, descriptor):
        self.descriptors.append(descriptor)

    def get_descriptor_paths(self):
        result = []
        for desc in self.descriptors:
            result.append(desc.get_path())
        return result

    def get_descriptors(self):
        return self.descriptors

    @dbus.service.method(DBUS_PROP_IFACE, in_signature="s", out_signature="a{sv}")
    def GetAll(self, interface):
        if interface != GATT_CHRC_IFACE:
            raise InvalidArgsException()

        return self.get_properties()[GATT_CHRC_IFACE]

    @dbus.service.method(GATT_CHRC_IFACE, in_signature="a{sv}", out_signature="ay")
    def ReadValue(self, options):
        print("Default ReadValue called, returning error")
        raise NotSupportedException()

    @dbus.service.method(GATT_CHRC_IFACE, in_signature="aya{sv}")
    def WriteValue(self, value, options):
        print("Default WriteValue called, returning error")
        raise NotSupportedException()

    @dbus.service.method(GATT_CHRC_IFACE)
    def StartNotify(self):
        print("Default StartNotify called, returning error")
        raise NotSupportedException()

    @dbus.service.method(GATT_CHRC_IFACE)
    def StopNotify(self):
        print("Default StopNotify called, returning error")
        raise NotSupportedException()

    @dbus.service.signal(DBUS_PROP_IFACE, signature="sa{sv}as")
    def PropertiesChanged(self, interface, changed, invalidated):
        pass


def find_adapter(bus, iface):
    remote_om = dbus.Interface(bus.get_object(BLUEZ_SERVICE_NAME, '/'),
                               DBUS_OM_IFACE)
    objects = remote_om.GetManagedObjects()

    for o, props in objects.items():
        if iface in props:
            return o

    return None

# Boiler plate end


class TestService(Service):
    """
    Test service that provides a characteristic
    """

    def __init__(self, bus, index):
        Service.__init__(self, bus, index, TEST_SERVICE, True)
        self.add_characteristic(TestCharacteristic(bus, 0, self))


class TestCharacteristic(Characteristic):
    """
    Test characteristic. Allows writing arbitrary bytes to its value
    """

    def __init__(self, bus, index, service):
        Characteristic.__init__(
            self, bus, index, TEST_CHARACTERISTIC, ["write"], service
        )
        self.value = ""

    def WriteValue(self, value, options):
        print(f"TestCharacteristic Write: {value}")
        txt = bytes(value).decode('utf8')
        print(f"As text: {txt}")
        self.value = txt
        my_write_callback(txt)


class TestAdvertisement(Advertisement):

    def __init__(self, bus, index):
        Advertisement.__init__(self, bus, index, 'peripheral')
        self.add_local_name('My Test Peripheral')
        self.include_tx_power = True


class Application(dbus.service.Object):
    """
    org.bluez.GattApplication1 interface implementation
    """

    def __init__(self, bus):
        self.path = "/"
        self.services = []
        dbus.service.Object.__init__(self, bus, self.path)
        self.add_service(TestService(bus, 0))

    def get_path(self):
        return dbus.ObjectPath(self.path)

    def add_service(self, service):
        self.services.append(service)

    @dbus.service.method(DBUS_OM_IFACE, out_signature="a{oa{sa{sv}}}")
    def GetManagedObjects(self):
        response = {}
        print("GetManagedObjects")

        for service in self.services:
            response[service.get_path()] = service.get_properties()
            chrcs = service.get_characteristics()
            for chrc in chrcs:
                response[chrc.get_path()] = chrc.get_properties()
                descs = chrc.get_descriptors()
                for desc in descs:
                    response[desc.get_path()] = desc.get_properties()

        return response


def my_write_callback(txt):
    print(f"This is where I can use the <<{txt}>> value")


def main():
    global mainloop

    dbus.mainloop.glib.DBusGMainLoop(set_as_default=True)

    bus = dbus.SystemBus()

    adapter = find_adapter(bus, LE_ADVERTISING_MANAGER_IFACE)
    if not adapter:
        print("Adapter not found")
        return

    service_manager = dbus.Interface(
        bus.get_object(BLUEZ_SERVICE_NAME, adapter), GATT_MANAGER_IFACE
    )

    app = Application(bus)

    test_advertisement = TestAdvertisement(bus, 0)

    ad_manager = dbus.Interface(bus.get_object(BLUEZ_SERVICE_NAME, adapter),
                                LE_ADVERTISING_MANAGER_IFACE)

    ad_manager.RegisterAdvertisement(test_advertisement.get_path(), {},
                                     reply_handler=register_ad_cb,
                                     error_handler=register_ad_error_cb)
    mainloop = GLib.MainLoop()

    print("Registering GATT application...")

    service_manager.RegisterApplication(
        app.get_path(),
        {},
        reply_handler=register_app_cb,
        error_handler=register_app_error_cb,
    )

    mainloop.run()


if __name__ == "__main__":
    main()

我更改了外围设备中使用的 UUID，因为自定义服务和特性需要超出为蓝牙 SIG 保留的范围。 更多信息请访问： https://novelbits.io/uuid-for-custom-services-and-characteristics/

希望这足以让您提升 BlueZ 的 D-Bus 学习曲线。