Largely related to https://www.reddit.com/r/hardwarehacking/comments/99eh5u/hacking_the_logitech_z906_speaker_system/ but that thread took an approach of taking apart the console, sensing some of the local state and emitting IR to behave like the physical remote control does.

The comments in that thread talked a little about the wiring between the subwoofer and the user interface board and inserting a device in between those to have full control without having to disassemble. I am trying to achieve this a year later.

The system I want to develop would either complement the physical user interface if I am able to update its state through the external wiring otherwise it'll replace it, offering control as an IoT device.

I have mapped the DB15 wiring onto the internal colour codes and am working through finding the usages of each pins:

Pin mappings

It looks like the digital communication between the two devices happens over a pair of pins seemingly transmitting MIDI-looking things, one for each direction.

Sample data payload

I am fairly new to the hardware hacking scene, have a CS background which has gotten me this far. I have tried to figure out the protocol structure by trial and error changing one variable and seeing what the transmission looks like.

Any tips on what this Data might be, tips on how to best figure out unknown protocol structures etc are all appreciated. Alternately would it be worth trying to pull the code off the flash and reverse engineering that instead?

Thanks!