I have an MCU pro and just recently purchased the expander.
 
Running Platinum, naturally.
 
I would LIKE to configure the expander to control the AUX busses(my sub mixes) while the MCU controls tracks.
I have yet to find the config to do this from the platinum menus.Whatever the MCUs control group is set for both units  follow, in fact the expander mirrors the tracks of the MCU

I doubt that mcu functionality in sonar provides a way to control tracks and buses at the same time. At least not the way I managed to set it up with 2 Behringer clones. I could do 16 tracks or 16 buses (I takes one button to jump between both modes) ...

Harrison mixbus did provide access to both at the same time (whatever track or bus is visible is on the mackies)

So in Sonar maybe az control or aux tracks instead of buses may be your friends

I no longer have the whole code in my head... but if I remember correctly, Rob is right, that is not supported (you can set only relative to the main unit position).
 
AZ Controller has no preset for XT. I can create it for your, with advantage it can do what you want, I mean what XT will do can be completely unrelated to what it was supposed to do (f.e. check http://www.azslow.com/index.php/topic,374.msg2172.html#msg2172 , 8 encoders + 18 buttons controlling all aspects of sonar). But I have some "queue" at the moment.
 
I have a mod of original MackieControl which allows to have 2 independent sets of MCU+XT. But since you do not have the second main unit, I doubt it will work for your case.

Here is an old posting that may lead to what your are trying to do.
 
I don't think it was ever accomplished, but this may give some insight.
 
Sonar with MCU and Extenders.

Thanks to ALL here for your time and talents and comments.
 
@ aszlows3 seems to have promise , but I think I will punt on the MCU solution and ask you guys this..
 
what about another SMALL FORM Factor controller ()korg nano studio, or a tiny behringer X touch, although more expensive and larger) I also saw the Novation Launch control with Mackie emulation
I wonder would they be able to be mapped to the aux busses?
 
I tried an old Korg Nano Kontrol here but the edeitor software doesnt see it, nor does Platinum, but it shows up in device manager
 
well drug out my old vs20 got it installed but its just tracks not busses
 
as all have said unless I buy a second mcu per Aszlow3 then I am stuck,
 
its not a show stopper, I just wanted to see if I could emulate a real console

You can use any other units to control buses without AZ Controller, as long as:
a) the controller has native support for Sonar and can control buses (obsolete units like VS700, one strip Faderport)
b) any simple controller with "Cakewalk ACT MIDI" plug-in
but even when that works:
1) any time you start Sonar you will have to switch into Bus mode
2) for (b) no feedback, no motor faders, no LEDs. for (a) the choice is rather limited
 
So I see the only way to do it.  Join corresponding preset development: http://www.azslow.com/index.php/topic,376.0.html
With a bit of luck, you already almost have it (I just had 1 hour free to make that test version), otherwise we will need to fix handshake procedure (most probably XT controls already work, but without handshake the feedback can be broken).

azslow3
You can use any other units to control buses without AZ Controller, as long as:
a) the controller has native support for Sonar and can control buses (obsolete units like VS700, one strip Faderport)
b) any simple controller with "Cakewalk ACT MIDI" plug-in
but even when that works:
1) any time you start Sonar you will have to switch into Bus mode
2) for (b) no feedback, no motor faders, no LEDs. for (a) the choice is rather limited
 
So I see the only way to do it.  Join corresponding preset development: http://www.azslow.com/index.php/topic,376.0.html
With a bit of luck, you already almost have it (I just had 1 hour free to make that test version), otherwise we will need to fix handshake procedure (most probably XT controls already work, but without handshake the feedback can be broken).

 
Thank you sir, I will install your program and test and report back,
 
thank you for ALL you do