bumble.transport.common.TransportSpecError: unknown transport scheme

[x48x4b]

Hello,
I have a checked working bluetooth dongle.
But the bumble-hci-bridge does not work.
The error is "bumble.transport.common.TransportSpecError: unknown transport scheme".
(See details below.)
Any ideas on how to get that working.
Best regards

---

someuser@somehost:$ hcitool dev
Devices:
hci0 5C:F3:70:8F:D2:1E
someuser@somehost:$ uname -a ; date
Linux renegade03 6.17.4-200.fc42.x86_64 #1 SMP PREEMPT_DYNAMIC Sun Oct 19 18:47:49 UTC 2025 x86_64 GNU/Linux
So 26 Okt 2025 14:19:52 CET
someuser@somehost:$ hcitool dev
Devices:
hci0 5C:F3:70:8F:D2:1E
someuser@somehost:$ bumble-hci-bridge android-netsim , mode=controller usb:0

connecting to HCI...
connected
connecting to HCI...
Traceback (most recent call last):
File "/home/someuser/.local/bin/bumble-hci-bridge", line 8, in
sys.exit(main())
~~~~^^
File "/home/someuser/.local/lib/python3.13/site-packages/bumble/apps/hci_bridge.py", line 105, in main
asyncio.run(async_main())
~~~~~~~~~~~^^^^^^^^^^^^^^
File "/usr/lib64/python3.13/asyncio/runners.py", line 195, in run
return runner.run(main)
~~~~~~~~~~^^^^^^
File "/usr/lib64/python3.13/asyncio/runners.py", line 118, in run
return self._loop.run_until_complete(task)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
File "/usr/lib64/python3.13/asyncio/base_events.py", line 725, in run_until_complete
return future.result()
~~~~~~~~~~~~~^^
File "/home/someuser/.local/lib/python3.13/site-packages/bumble/apps/hci_bridge.py", line 57, in async_main
async with await transport.open_transport(sys.argv[2]) as (
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/someuser/.local/lib/python3.13/site-packages/bumble/transport/init.py", line 101, in open_transport
transport = await _open_transport(scheme, spec)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/someuser/.local/lib/python3.13/site-packages/bumble/transport/init.py", line 203, in _open_transport
raise TransportSpecError('unknown transport scheme')
bumble.transport.common.TransportSpecError: unknown transport scheme
someuser@somehost:~$

[barbibulle]

That's because you have space characters in the first transport name (around the ","). There shouldn't be any spaces.

[x48x4b]

My present conclusion is that "usb.py" does not properly handle the device class attributes of my BT400 (see below from"lsusb").
Do I have to fix "usb.py" myself?

from "lsusb".
...
Bus 004 Device 006: ID 0b05:17cb ASUSTek Computer, Inc. Broadcom BCM20702A0 Bluetooth
Negotiated speed: Full Speed (12Mbps)
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 255 Vendor Specific Class
bDeviceSubClass 1 [unknown]
bDeviceProtocol 1
bMaxPacketSize0 64
idVendor 0x0b05 ASUSTek Computer, Inc.
idProduct 0x17cb Broadcom BCM20702A0 Bluetooth
bcdDevice 1.12
iManufacturer 1 Broadcom Corp
iProduct 2 BCM20702A0
iSerial 3 5CF3708FD21E
bNumConfigurations 1
...

[barbibulle]

The reason usb:0 doesn't work is because this USB dongle doesn't declare itself as a normal USB dongle (doesn't specify the right class). You can still use it, by specifying the USB vendor and product ID explicitly (see the list of acceptable names on the Bumble Transport Names line printed by usb_probe.py. In your case, usb:0B05:17CB would work.

[x48x4b]

Thanks again.
I agree with your analysis.
Also I did the explicit USB vendor and product indication before.
And I just did it again.
But there is still some other problem that makes the bridge terminate (output see below).

---

someuser@somehost:$ someuser@somehost:/.local/lib/python3.13/site-packages/bumble/transport$ date
$ bumble-hci-bridge android-netsim:_:8554,mode=controller usb:0B05:17CB

connecting to HCI...
connected
connecting to HCI...
Traceback (most recent call last):
File "/home/someuser/.local/bin/bumble-hci-bridge", line 8, in
sys.exit(main())
~~~~^^
File "/home/someuser/.local/lib/python3.13/site-packages/bumble/apps/hci_bridge.py", line 105, in main
asyncio.run(async_main())
~~~~~~~~~~~^^^^^^^^^^^^^^
File "/usr/lib64/python3.13/asyncio/runners.py", line 195, in run
return runner.run(main)
~~~~~~~~~~^^^^^^
File "/usr/lib64/python3.13/asyncio/runners.py", line 118, in run
return self._loop.run_until_complete(task)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
File "/usr/lib64/python3.13/asyncio/base_events.py", line 725, in run_until_complete
return future.result()
~~~~~~~~~~~~~^^
File "/home/someuser/.local/lib/python3.13/site-packages/bumble/apps/hci_bridge.py", line 57, in async_main
async with await transport.open_transport(sys.argv[2]) as (
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/someuser/.local/lib/python3.13/site-packages/bumble/transport/init.py", line 101, in open_transport
transport = await _open_transport(scheme, spec)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/someuser/.local/lib/python3.13/site-packages/bumble/transport/init.py", line 173, in _open_transport
return await open_usb_transport(spec)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/someuser/.local/lib/python3.13/site-packages/bumble/transport/usb.py", line 525, in open_usb_transport
raise TransportInitError('no compatible interface found for device')
bumble.transport.common.TransportInitError: no compatible interface found for device

someuser@somehost:~/.local/lib/python3.13/site-packages/bumble/transport$

[x48x4b]

Now, I used the enforced mode.
There is some progress, although I have not achied a real pairing yet (see below).

bumble-hci-bridge android-netsim:_:8554,mode=controller usb:0B05:17CB!

connecting to HCI...
WARNING: All log messages before absl::InitializeLog() is called are written to STDERR
I0000 00:00:1761578081.261857 5471 chttp2_server.cc:712] WARNING: UNKNOWN:Only 1 addresses added out of total 2 resolved {children:[UNKNOWN:Unable to configure socket {children:[UNKNOWN:bind: Address already in use (98)]}]}
connected
connecting to HCI...
connected
16:14:44.831 I bumble.bridge: [CONTROLLER->HOST] HCI_INQUIRY_COMPLETE_EVENT:
status: HCI_SUCCESS
16:15:49.585 I bumble.bridge: [CONTROLLER->HOST] HCI_CONNECTION_REQUEST_EVENT:
bd_addr: 5C:FB:7C:63:21:DF/P
class_of_device: 2360324
link_type: ACL
16:16:04.654 I bumble.bridge: [CONTROLLER->HOST] HCI_CONNECTION_COMPLETE_EVENT:
status: HCI_CONNECTION_TERMINATED_BY_LOCAL_HOST_ERROR
connection_handle: 11
bd_addr: 5C:FB:7C:63:21:DF/P
link_type: ACL
encryption_enabled: 0

[x48x4b]

Conclusion, sofar this does not really work.
The bridge is started, but what happens with the bluetooth stack of the emulator phone?
My guts say: Nothing.

I keep trying.

Start emulator:
./emulator -avd Pixel_2_API_36 -accel auto -gpu auto -packet-streamer-endpoint localhost:8554

Start bridge:
$ bumble-hci-bridge android-netsim:_:8554,mode=controller usb:0B05:17CB!

connecting to HCI...
connected
connecting to HCI...
connected
08:48:33.109 W bumble.transport.android_netsim: Unsupported chip type

What should this mean?