On the ATmega32U4 MCU there are several pins related to USB:
In the datasheet and in almost all reference schematics I find on the Internet, it's explained how to connect those pins when you need the USB.
On my board, instead, I don't need the USB at all. Hence, I want to understand how to connect those pins.
I'm not sure if I can just leave them floating or else.
The datasheet does have that information.
You can make a self-powered USB device as per the datasheet diagrams and imagine the USB cable is unplugged, which gives enough information how the pins should be connected without USB connection.
On my board, instead, I don't need the USB at all. Hence, I want to understand how to connect those pins.
Grab a schematic that uses the USB interface like this: -
And ask yourself what connectivity is important if there isn't anything plugged into the USB connector. You'd end up with this: -
Schematic image taken from here.
So, should VBUS be connected to Vcc - you can always double check that in the data sheet and, is it any great hardship to make that connection anyway? What about UVCC and UGND - well, is it really any problem to connect them to Vcc and GND
