How can I make a USB volume knob work?

[robroy]

How can I make this cool knob work?

It was hand made by Charlie Skilbeck in London.

Etsy: Tiny Little USB Volume Knob.

Turning the knob doesn't change the output of mixer(8).

Its FreeBSD 14.0-RELEASE kernel messages:

ugen0.2: <CH Skilbeck Volume Knob> at usbus0
usbhid3 on uhub0
usbhid3: <Volume Knob> on usbus0
hidbus3: <HID bus> on usbhid3
usbhid4 on uhub0
usbhid4: <Volume Knob> on usbus0
hidbus4: <HID bus> on usbhid4
hcons2: <CH Skilbeck Volume Knob Consumer Control> on hidbus4
hkbd0: <CH Skilbeck Volume Knob Keyboard> on hidbus3
kbd3 at hkbd0

And its usbconfig:

# usbconfig list | grep Skilbeck
ugen0.2: <CH Skilbeck Volume Knob> at usbus0, cfg=0 md=HOST spd=LOW (1.5Mbps) pwr=ON (100mA)

 

[cracauer@]

That's a cool device. Does it need software drivers under Windows and macOS?

 

[sidetone]

My guess is with x11/sxhkd with usbhid enabled. If output shows in x11/xev, while turning the knob, you can put that code to a hotkey with sxhkd.

It's good that it shows as an HID device, as usbhid along with the newer drivers are intended to be useful for them all. The instruction would be similar to that of hotkeys on USB HID keyboards.

 

[robroy]

Thank you both!

cracauer@, it worked automatically with macOS Monterey and Windows Server 2022.

sidetone, I'll give x11/sxhkd and x11/xev a try.

 

[cracauer@]

Given that no driver is required by other OSes and the FreeBSD output above I guess that this is another kind of device that is standardized (like class-compliant sound devices). It is probably pretty easy to interface with it. I would mail the freebsd-usb mailing list.