Newbie to Simucube Question to X3 X4

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.

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.

thanks! :slightly_smiling_face: