Thanks for joining the NUC community.
I understand you are connecting this NUC for robot project
I would like to know what exactly you call USB busses. Are you referring to Host controllers? Or how many devices can you hook to this unit through USB port?
See product specifications here on page 24:
Intel NUC Board D33217CK Technical Product Specification
The board supports seven USB 2.0 ports. The port arrangement is as follows:
• Three front panel ports (via one dual-port internal header and one front panel
• Two ports are implemented with vertical back panel connectors
• One port is reserved for the PCI Express Half-Mini Card
• One port is reserved for the PCI Express Full-Mini Card
All seven USB 2.0 ports are high-speed, full-speed, and low-speed capable