3 reads the BCR out.
1 also sends out to a THRU box (wired round system)
2 sends out to BCR
So flow is merge (and transform) from master and Miniak.
Modify Miniak signed to unsigned.
Send on to BCR - it sees signed and can update state - the chain is broken (so no midi loops).
Alternatively, BCR knob send signed NRPN.
Arduino reads and changes to signed.
These are then sent to Miniak (via Thru box).
It therefore updates synth to reflect BCR value.
The arduino is also used to zone the master keyboard (up to 8 splits or layers), arpegiator (held or latched) and a 16 step sequencer.
I wrote the midi library myself - since then I see there is a decent lib.
I did have some issues with the buffering (fixed in end - only accept sysex from Miniak - read in the 454 program send bytes, update internal state).
Also I had to use the prog mem to store all the Miniak display settings.
Regards
Steve H