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On Sat, 2025-08-23 at 09:11 +0100, Henry Bremridge via list wrote:
>
> But "Just works"
Thanks Henry and Sebastian,
I suspect "Just works" is the norm for any supported Bluetooth adaptor
till you start messing around with poorly supported devices, and newer
features, and have to start digging around.
Latest attempt a Bluetooth 5.4 adaptor Hakimonoe BT542, which under the
hood is an RTL8761bu.
This was curious as when I plugged it into my Debian box "hciconfig -a"
reported "0xa" which is Bluetooth 5.1.
Perplexed I plugged it into a Windows laptop, definitely 5.1
Then after a few minutes Windows 11 updated its driver, and it reported
5.4
So I "borrowed" the firmware from the Windows driver:
rtl8761b_mp_chip_bt40_fw_asic_rom_patch_new.dat
And overwrote the "/usr/lib/firmware/rtl_bt/rtl8761bu_fw.bin" and now
when my Linux box loads the USB device it is advertised as BT 5.4
I noted also this new firmware is smaller than the previous firmware by
a few bytes. I have no idea if the 6 byte content of the config file
should also be modified?
hexdump rtl8761bu_config.bin
0000000 ab55 8723 0000
0000006
I'm suitably cynical that maybe most of the work is being done in the
Windows driver rather than in the USB dongle, but hard to know. It
fails in the same way as earlier model USB dongles but the failure is
deep in the heart of trying to establish a Bluetooth Low Energy
connection, so I suspect this is a failing in Bluez rather than in the
Bluetooth support, but hard to know without a bit more Bluetooth know-
how.
Up until Debian Trixie old devices worked and new devices didn't (with
a TP-Link 5.1 USB adaptor). Trixie seemed to improve the working with
newer devices, but never tried anything with Bluetooth Low Energy, let
alone stuff Windows doesn't even attempt.
Capabilities claimed by bluetoothctl for the the Hakimonoe 5.4 adaptor
with new firmware look slightly more extensive and relevant for what I
am trying, so superficially it looks promising. I suspect next up is
the Bluetooth for Linux Developers Study Guide so I can master
establishing the state of my Bluetooth devices to see why it is going
wrong.
$ bluetoothctl
>list
# To get the controller list
> show 8C:68:8B:A1:2D:F8
Controller 8C:68:8B:A1:2D:F8 (public)
Manufacturer: 0x005d (93)
Version: 0x0d (13)
Name: rodney
Alias: rodney
Class: 0x007c0104 (8126724)
Powered: yes
PowerState: on
Discoverable: no
DiscoverableTimeout: 0x000000b4 (180)
Pairable: yes
UUID: Message Notification Se.. (00001133-0000-1000-8000-
00805f9b34fb)
UUID: Vendor specific (185f3df4-3268-4e3f-9fca-
d4d5059915bd)
UUID: A/V Remote Control (0000110e-0000-1000-8000-
00805f9b34fb)
UUID: Vendor specific (03b80e5a-ede8-4b33-a751-
6ce34ec4c700)
UUID: Audio Stream Control (0000184e-0000-1000-8000-
00805f9b34fb)
UUID: Volume Offset Control (00001845-0000-1000-8000-
00805f9b34fb)
UUID: Message Access Server (00001132-0000-1000-8000-
00805f9b34fb)
UUID: PnP Information (00001200-0000-1000-8000-
00805f9b34fb)
UUID: IrMC Sync (00001104-0000-1000-8000-
00805f9b34fb)
UUID: Volume Control (00001844-0000-1000-8000-
00805f9b34fb)
UUID: Vendor specific (00005005-0000-1000-8000-
0002ee000001)
UUID: Phonebook Access Client (0000112e-0000-1000-8000-
00805f9b34fb)
UUID: Microphone Control (0000184d-0000-1000-8000-
00805f9b34fb)
UUID: Audio Input Control (00001843-0000-1000-8000-
00805f9b34fb)
UUID: A/V Remote Control Target (0000110c-0000-1000-8000-
00805f9b34fb)
UUID: Generic Attribute Profile (00001801-0000-1000-8000-
00805f9b34fb)
UUID: Phonebook Access Server (0000112f-0000-1000-8000-
00805f9b34fb)
UUID: Device Information (0000180a-0000-1000-8000-
00805f9b34fb)
UUID: Audio Sink (0000110b-0000-1000-8000-
00805f9b34fb)
UUID: Generic Access Profile (00001800-0000-1000-8000-
00805f9b34fb)
UUID: OBEX Object Push (00001105-0000-1000-8000-
00805f9b34fb)
UUID: Handsfree Audio Gateway (0000111f-0000-1000-8000-
00805f9b34fb)
UUID: Audio Source (0000110a-0000-1000-8000-
00805f9b34fb)
UUID: Published Audio Capabil.. (00001850-0000-1000-8000-
00805f9b34fb)
UUID: SIM Access (0000112d-0000-1000-8000-
00805f9b34fb)
UUID: OBEX File Transfer (00001106-0000-1000-8000-
00805f9b34fb)
UUID: Broadcast Audio Scan (0000184f-0000-1000-8000-
00805f9b34fb)
UUID: Handsfree (0000111e-0000-1000-8000-
00805f9b34fb)
Modalias: usb:v1D6Bp0246d0553
Discovering: no
Roles: central
Roles: peripheral
Roles: central-peripheral
ExperimentalFeatures: BlueZ Experimental Simu.. (671b10b5-42c0-
4696-9227-eb28d1b049d6)
ExperimentalFeatures: BlueZ Experimental LL p.. (15c0a148-c273-
11ea-b3de-0242ac130004)
ExperimentalFeatures: BlueZ Experimental ISO... (6fbaf188-05e0-
496a-9885-d6ddfdb4e03e)
Advertising Features:
ActiveInstances: 0x00 (0)
SupportedInstances: 0x04 (4)
SupportedIncludes: tx-power
SupportedIncludes: appearance
SupportedIncludes: local-name
SupportedSecondaryChannels: 1M
SupportedSecondaryChannels: 2M
SupportedSecondaryChannels: Coded
SupportedCapabilities.MinTxPower: 0xffffffed (-19)
SupportedCapabilities.MaxTxPower: 0x0017 (23)
SupportedCapabilities.MaxAdvLen: 0xfb (251)
SupportedCapabilities.MaxScnRspLen: 0xfb (251)
SupportedFeatures: CanSetTxPower
SupportedFeatures: HardwareOffload
Advertisement Monitor Features:
SupportedMonitorTypes: or_patterns
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