Reversing Sound Blaster X7 Control for fun and Linux support

The Sound Blaster X7 is a DAC (Digital Analog Converter) and amplifier. It allows several inputs to be mixed together toward a single output. Its configuration is maintained directly on the device and can be controlled by either a mobile device over Bluetooth or from a Windows machine over USB. When using my work laptop, I can't change the X7 volume or output. This is an issue when you need to jump into a quick call as you can't switch over to headset easily.

Since control over Bluetooth works well from the Android application, it is possible to control all the features I need over Bluetooth. There is only one issue: the only thing I've ever reversed is a USB msi keyboard to implement support on Linux. I don't know much about how Bluetooth works, nor about Android and from what I could gather, I can't live capture the Bluetooth traffic (on my device) like I did for USB.

It is nothing that can't be fixed by a bit of reading and some work, so let's do this.

It's amazing to me that a lot of more obscure and less popular hardware has Linux support only because some random person in Nowhere, Nebraska, had a need for it.