python - 使用 bluez python dbus 接口(interface)连接到蓝牙 LE 设备

Question

我想连接到蓝牙 LE 设备并在 python 中接收来自它的通知。我想使用 Bluez dbus API，但找不到我能理解的示例。 :-)

借助 gatttool，我可以使用以下命令:

gatttool -b C4:8D:EE:C8:D2:D8 --char-write-req -a 0x001d -n 0100 –listen

我如何使用 Bluez 的 dbus API 在 python 中做同样的事情？

Answer 1

使用 BlueZ DBus API 作为 gatt 客户端可能是使用 pydbus 库最简单的方法。 https://pypi.org/project/pydbus/

BlueZ DBus API 文档位于:

https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/doc/adapter-api.txt

https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/doc/device-api.txt

https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/doc/gatt-api.txt

一些有助于您入门的有用信息:

1. bluez 的 Dbus 服务称为“org.bluez”
2. Raspberry Pi 上的蓝牙适配器通常将“/org/bluez/hci0”作为 DBus 对象路径。
3. 设备的 DBus 对象路径是适配器路径加上前缀为“dev_”的 mac 地址，分号替换为下划线。即“DE:82:35:E7:43:BE”会在'/org/bluez/hci0/dev_DE_82_35_E7_43_BE'

我没有你的设备，所以我做了一个例子，使用 BBC micro:bit 来更改它更新温度值(周期)的频率值，然后获取这些温度值的通知。希望它可以很容易地适应您的情况。

此代码假定您已经使用 bluetoothctl 来配对您的设备。在命令行中键入 bluetoothctl devices，如果您的设备在列表中，那么这是一个好兆头。

import pydbus
from gi.repository import GLib

# Setup of device specific values
dev_id = 'DE:82:35:E7:43:BE'
adapter_path = '/org/bluez/hci0'
device_path = f"{adapter_path}/dev_{dev_id.replace(':', '_')}"
temp_reading_uuid = 'e95d9250-251d-470a-a062-fa1922dfa9a8'
temp_period_uuid = 'e95d1b25-251d-470a-a062-fa1922dfa9a8'

# Setup DBus informaton for adapter and remote device
bus = pydbus.SystemBus()
mngr = bus.get('org.bluez', '/')
adapter = bus.get('org.bluez', adapter_path)
device = bus.get('org.bluez', device_path)
# Connect to device (needs to have already been paired via bluetoothctl)
device.Connect()

# Some helper functions
def get_characteristic_path(device_path, uuid):
    """Find DBus path for UUID on a device"""
    mng_objs = mngr.GetManagedObjects()
    for path in mng_objs:
        chr_uuid = mng_objs[path].get('org.bluez.GattCharacteristic1', {}).get('UUID')
        if path.startswith(device_path) and chr_uuid == uuid:
           return path

def as_int(value):
    """Create integer from bytes"""
    return int.from_bytes(value, byteorder='little')

# Get a couple of characteristics on the device we are connected to
temp_reading_path = get_characteristic_path(device._path, temp_reading_uuid)
temp_period_path = get_characteristic_path(device._path, temp_period_uuid)
temp = bus.get('org.bluez', temp_reading_path)
period = bus.get('org.bluez', temp_period_path)
# Read value of characteristics
print(temp.ReadValue({}))
# [0]
print(period.ReadValue({}))
# [232, 3]
print(as_int(period.ReadValue({})))
# 1000

# Write a new value to one of the characteristics
new_value = int(1500).to_bytes(2, byteorder='little')
period.WriteValue(new_value, {})

# Enable eventloop for notifications
def temp_handler(iface, prop_changed, prop_removed):
    """Notify event handler for temperature"""
    if 'Value' in prop_changed:
        print(f"Temp value: {as_int(prop_changed['Value'])} \u00B0C")

mainloop = GLib.MainLoop()
temp.onPropertiesChanged = temp_handler
temp.StartNotify()
try:
    mainloop.run()
except KeyboardInterrupt:
    mainloop.quit()
    temp.StopNotify()
    device.Disconnect()