Uno2 + Boss Katana Head Mk2 #UnO2


Hi all - just installed Uno2 chip and am fumbling my way through learning MIDI as is applicable to the Katana. Have a few questions/comments and would like some input from the group. I'll break this up into subsequent responses within this message thread as discussion builds. Will start off with basic logic and setup as per published documentation before adding in more complex configuration variables.

NOTE - I have lurked here for a few weeks, reading through a fair amount of past messages to get a head start on things prior to yesterday's Uno2 chip delivery/installation.

Per the published Katana documentation, it looks like device control is limited to:
  • Changing of Katana "channels" via program change (9 total)
  • Toggle on/off of Katana effects via control change (6 total)
  • Sweep of pedal effects via control change (3 total)
  • Toggle on/off of foot switchs via control change (2 total)
NOTE - I am purposely emphasizing "published" documentation as I am not sure if/how subsequent releases have expanded Katana MIDI capabilities. Boss has not, to my knowledge, updated the documentation accordingly.

It seems that a reasonable use case for myself would see the FCB layout support switching of 4-5 Katana channels plus stompbox on/off of 4-5 effects across 2-3 FCB banks, all while probably configuring the two FCB pedals for volume and wah. With this in mind, I plagiarized the Katana setup file posted by mathesonewan in the Files section with some minor edits as a baseline configuration setup. Things pretty much work successfully (leave the FCB pedals out of conversation for now) but I need some more understanding for potential tweaks:

  • ProgChange offset - more of a FYI than a question, had to decrease the ProgChange value by -1 for each Preset. Note how value is a "0" in below screenshot while comparison to Katana documentation says it should be a "1". Same dynamic does not seem applicable to the CtrlChange values, they map with Katana documentation and function properly.

  • Initial startup after power cycle - I would like the Katana to be on Bank A/Channel 1, reflected on the FCB with the corresponding Footswitch1 LED being lit. I defined all variable definitions correctly and both devices work successfully with the exception of the footswitch LED. Below are applicable setup code excerpts. What is the missing command(s) syntax?



That's it for now, more to follow in a few days. Thanks in advance!


Just installed the Uno2 chip and compiled a basic setup. Would like some input on a few questions, which I'll add to this master topic thread as the discussion builds.

First off, screenshot below shows the published MIDI documentation from Boss. Seems that a realistic use-case for my scenario is to switch amongst Katana channels along with stomp box toggle of assigned pedals across 2-3 banks of the FCB. Also planning on using the foot pedals for volume and wah. Save comments on pedals for a bit as I need to do some more prep work on their configuration and utilization.


QUESTION 1 (two parts)
  1. Can a footswitch LED be toggled ON as part of default initialization after FCB power cycle? If so what is the command syntax? Use case result is to have the Katana on Bank A/Channel 1 while the FCB is on Bank 1 but with the LED for Footswitch 1 also being ON. Current result is Katana on Bank A/Channel 1 while FCB is on Bank 1 but the Footswitch 1 LED remains OFF. Also see applicable screenshots from Question 2.
  2. Can a Preset be sent instead of spelling out the ProgChange in my example? I.e -- SendMidi [PRESET NAME] or something similar?

Why did the Program Change values need to be decreased -1 in comparison the Boss documentation for Katana channel switching? Meaning sending a "1" for preset KatanaA1 actually resulted in a switch to Bank A/Channel 2 instead of Bank A/Channel 1. This was not the case for Control Change values as they seem to map properly to the Boss documentation. Applicable code snippets follow below, including the resulting KatanaA1 preset updated to function properly.

     PRESET CODE (with -1 offset applied)

     PRESET DEFINITIONS (Note - I remapped the MIDI assignments in Boss Tone Studio to follow the channel order as seen in the screenshot)


That's it for now, more to follow in the upcoming days. Thanks in advance.


a) UnO2 doesn't have a command to activate a preset 
b) the SendMIDI commands always show actual MIDI values, which are in the range 0-127. Many manufacturers use the range 1-128 to specify preset numbers because people like to start counting from 1, but this results in ProgChange values which are 1 lower than the corresponding preset numbers.


Follow up questions...

Using a setup as I presented in my original post (each Bank with Katana channel switching on footswitches 1-5 and Katana effects on 6-10, essentially in a stompbox mode), can the corresponding effects LEDs be configured to reflect actual status upon initial selection of the relative Preset?

Use-case example, my goal is to eliminate the need to go through the last bullet point. 

  • Preset = KatanaA1
  • Applicable Katana channel is configured (in Boss Tone Studio) with Boost/Mod/FX all ON but Delay/Reverb OFF
  • Press FCB Footswitch01 lights its LED and switches Katana to Bank A/Channel 1
  • Footswitches 6-10 remain unlit despite actual effects status within the Katana
    • This should be expected as there is no two-way comms between the FCB and the Katana, correct?
  • Presses of Footswitches 6-8 light LEDs, bringing their status in sync with that of the Katana but making no changes as those effects were already ON

Can this preemptively be done through code? Granted, one would need to plan this out relative to each Katana channel tone value. And that gets even more complicated if one makes changes to any of those channels.


Check out the "SwitchOn" / "SwitchOff" commands (chapter 4.2 of the manual)


Thank you for your replies ossandust.

I have looked at SwitchOn/SwitchOff as an option. I am not seeing the intended behavior where LEDs of the selected preset footswitch and its corresponding activated effects all toggle ON. The MIDI commands all get sent but the effects LEDs remain OFF. Code snippet:

   Preset Test =
      SendMidi Katana ProgChange 2
      SwitchOn Mod  
      SwitchOn FX  

When the UP or DOWN footswitches are subsequently pressed (queue change to "new" FCB bank), those two effects LEDs do toggle ON. They continue to remain on if switching between preset footswitches of the "new" FCB banks. When returning to the original FCB bank via the UP and DOWN switches, those two LEDs toggle OFF.

When pressing UP and then DOWN (no preset switching in between) or vice versa, the effects LEDs toggle ON upon the first press and then OFF upon return to the original bank. No MIDI commands are sent after initial selection of the preset footswitch.

What am I overlooking??


if the preset Test is in bank 3 of your setup snippet above, it's expected behavior, since that bank doesn't contain the Mod and FX effects. These are in bank 1 and 2 only.