I’ve put together a brief summary about CME WIDI devices that can be used with Zynthian:
DIN MIDI:
WIDI Master – This device connects to a standard MIDI DIN interface. I haven’t tested it personally. I must admit that I don’t own an official Zynthian kit, and none of my three Zynthians have a standard DIN MIDI interface. They do have MIDI on their soundcards, but that’s a different story.
WIDI Jack + 25DIN5 cables - I assume the same behavior as WIDI Master.
WIDI Thru6 BT + DIN/DIN cables - I assume the same behavior as WIDI Master.
USB MIDI:
WIDI Uhost – This device connects to Zynthian via a USB-C to USB-A cable (USB-A on the Zynthian side).
WIDI Bud Pro – direct connection to a USB port.
As @riban wrote, the BLE connection built into the raspberry pi is not used in connection with Zynthian and WIDI devices. I personally have it turned off, as you can see in the picture. BLE connections are handled by chips in WIDI devices. You can build your own widi device, just buy a WIDI Core and connect it via RX/TR to a microcontroller.
From the CME WIDI group, I own WIDI Master, WIDI Thru6 BT, WIDI Uhost and WIDI Bud Pro devices. I can connect the ARTinoise RE.CORDER and Genki Wave Ring to them. The connection is made using the CME app on my mobile phone, which sometimes frustrates me. But once you get it set up, the connection is made without any problems.
EDIT: Should I make a note of this in the wiki?
EDIT2: Maybe the next official kit will have holes for soldering WIDI Core? 