How to connect multiple micro-controllers' USB ports on the same PCB?

Question

I'm designing a PCB with 3 Atmel ATmega16U4-AU micro-controllers on it.

I will be programming them through SPI.

Therefore, I will not be using D+ and D- ports on the USB interface. Then how do I deal with those pins.

Shall I:

Leave them unconnected?
Or Connect them to three different usb ports? (This way looks stupid. I don't want so many usb ports on the PCB)

Why are you using such a sophisticated chip if you're not using one of the largest selling points for it? — Ignacio Vazquez-Abrams, Apr 25 '16 at 21:30
@Ignacio Once, I've selected a PIC with USB because it happened to have the most Flash and RAM in its family. I didn't need the USB. — Nick Alexeev, Apr 26 '16 at 1:11

Houston Fortney · Accepted Answer · 2016-04-25 22:05:18Z

1

You can leave the pins unconnected.

answered Apr 25 '16 at 22:05

Houston Fortney

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Sam · Accepted Answer · 2016-04-26 00:59:22Z

0

With pretty much any modern micro, unless explicitly stated in the manual, unused IO can be left unconnected

answered Apr 26 '16 at 0:59

Sam

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