Newbie to Simucube Question to X3 X4

[astonmartin]

Got my new Simucube programmed now, with the SimuCube Configurator tool, now the Firmware update wizard starts.
The USB cable is on X3.

Just for my General understanding, when do I use USB X3, and when X4.

There are 2 µP on the board, the main STM32F407, and a smaller STM32F103.
I guess X3 connects to STMF407?
When updating, do I always use X3?, the bootloader was on X4.
thanks,
Johannes

[Mika]

The X3 USB port is for the SImucube processor. You install bootloader and the Simucube firmware by that, and that port will then show up as a game controller.

The X4 USB port is for configuring the IONI servo drive via the Granity software.

[astonmartin]

thanks!