mioXM / mioXL
These MIDI interfaces will not interface with the MC3/6/8 when the Keyboard interface firmware used. This is not an issue with the MC3/6/8.
This port is not a normal USB port - it is designed solely to enable your interface to act as a stand-alone host for USB-MIDI keyboards and modules. However that means it can only pass MIDI information - you cannot use it as a normal USB port, or pass audio data via it. It is effectively the same as having extra MIDI In and Out ports but in the form of a USB port. This means you cannot use this port to connect a computer, phone, or tablet, or any other type of standard USB device.
As a consequence of this some controllers and synthesizers that have extra functionality which requires a direct connection to a computer may not work fully or work at all via the USB-MIDI Host Port.
We do publish a firmware version without the keyboard interface for users who want to connect to such MIDI interfaces. In this version, the Keystrokes feature is disabled, and your computer will only detect a MIDI controller being plugged in, not a MIDI + Keyboard controller.