ok, I've now sampled both the mixer and the controller together and am seeing zero frame errors.
Looks like it's a baud of 8752... :\
Strange, but ok.
And with that I get the following data:
I'm certain the left is the mixer and the right is the controller.
The mixer sends 7 00's until the controller is connected at which point the controller sends a single 02 in response.
00 00 00 00 00 00 00 00 00 00 00 00 02 00
The following 6 packets are then exchanged:
00 00 00 00 00 00 21 13 72 02 16 07 02 00
00 00 00 00 00 00 53 13 72 02 16 07 02 00
00 00 00 00 00 00 21 13 72 02 16 07 02 00
00 00 00 00 00 00 53 13 72 02 16 07 02 00
00 00 00 00 00 00 21 13 72 02 16 07 02 00
00 00 00 00 00 00 53 13 72 02 16 07 02 00
There are then a whole load of the following packet pairs are exchanged until the mixer has finished its start up (making whirring noises - to reset the proportioning valve I would guess):
00 00 00 00 00 00 16 13 72 02 16 07 02 00
00 00 00 00 00 00 53 13 72 02 16 07 02 00
After the mixer's start up completes, the following pairs are exchanged ad infinitum:
00 00 00 00 00 00 16 13 72 02 16 07 02 00
00 00 00 00 00 00 51 13 72 02 16 07 02 00
so now to try to replicate the mixer pattern with arduino...