This is direct from Boss support. It works !
Set midi channels on pedal -
METHOD
Go into the MIDI menu on the pedal.
***Set and Map #CC 1-18 on the pedal itself **
NOTE
the OPEN MIDI DICTIONARY differs from this list of CC NUMBERS.
IT SHOWS CC MESSAGES 1-17 -
whereas list from Roland Support shows 1-18.
CC#9 appears to be missing from the open dictionary list.
NOTE: for CC messages - set two messages PER MC8 SWITCH ACTION E.G.
#CC 1 - PRESS val =127
#CC1 - RELEASE val = 0
*EXCEPT FOR CC’s that control VOLUME LEVELS
I use CC Value Scroll action with a COUNTER from 0-127 with wrap-around option set.
This applies to CC’s 6-16-17
**CC’s As described here by ROLAND **
When using an MC-8 or any Morningstar Engineering MIDI controller, you’ll need to send the same CC# using two different values.
For example, if CC# 20 is set to control the LOOP STOP function, you’ll need to create a MIDI send from your controller for the same CC# sending on a value of 0 and the other a value of 127.
This mimics the momentary foot switch action that required by BOSS products to turn on and off certain functions.
Make sure to setup your MIDI communication between devices correctly.
In the RC-10R go to the MIDI menu by pressing MENU- use VALUE KNOB to navigate to MIDI and press the VALUE KNOB to enter into the RC-10R MIDI MENU:
Most of these MIDI general setting defaults will get you automatically connected but you’ll still need to program your user CC#s for the functions you want to control from your external MIDI CONTROL devices.
Make sure that the MIDI CONTROL device and RC-10R are set to the SAME MIDI CHANNEL for proper communication.
SET MIDI CHANNELS
RX CONTROL CH: 1 / MIDI CHANNEL 1-16
RX NOTE CH: 1 / MIDI CHANNEL 1-16
TX CONTROL CH: RX (same as RX CHANNEL MIDI CHANNEL 1)
SET PARAMETERS
PC IN/OUT: ON
SYNC CLOCK: AUTO
(will auto sync or slave to external MASTER MIDI devices)
CLOCK OUT: OFF
The following menus will be CONTROL CHANGE CC#s to control the RC-10R looper as long as your external device and RC-10R are set to the same MIDI CHANNEL.
*CC NUMBERS - as MAPPED BY USER ON THE PEDAL
RHY START CC: CC#1 (user choice)
RHY DIVISION CC: CC#2 (user choice)
RHY FILLIN CC: CC#3 (user choice)
RHY STOP CC: CC#4 (user choice)
RHY BREAK CC: CC#5 (user choice)
RHY LEVEL CC: CC#6 (user choice)
LOOP START CC: CC#7 (user choice)
LOOP STOP CC: CC#8 (user choice)
LOOP UNDREDO CC: CC#9 (user choice)
TRK1 START CC: CC#10 (user choice)
TRK1 STOP CC: CC#11 (user choice)
TRK1 UNDOREDO CC: CC#12 (user choice)
TRK2 START CC: CC#13 (user choice)
TRK2 STOP CC: CC#14 (user choice)
TRK2 UNREDO CC: CC#15 (user choice)
LOOP LEVEL CC: CC#16 (user choice)
TOTAL LEVEL CC: CC#17 (user choice)
ALL BREAK CC: CC#18 (user choice)
Hope this helps someone - and save them the HOURS it took me to find this out.