What do you do with the USB pins if you are not using USB?

[Keith Brafford]

I am using the nRF52840 but am not using its USB peripheral.  Is it safe just to ground all the pins (D-, D+, VBus)?

[Simonr]

Hi Keith

You have to ground VBUS. D- and D+ can be left floating, or you can ground them. This is how the reference schematics deals with these pins when not using the USB.

NOTE: You can not use these pins as GPIOs, as they are USB only. 

Best regards,

Simon

[Sebastian_Fant]

Hi Simon, I wonder if I can use the AD4 and AD6 as stepping stones to fan out other GPIO, lets say AC9 and AC11. It is the same idea as for reset on the dongle. Both AD2 and AC5 will be grounded.

[Simonr]

Hi

This is not as straight-forward of a question as I anticipated, and I am currently awaiting a reply internally, as I need to make sure that D+ and D- will behave as expected if used for "stepping stones" like this when the USB peripheral isn't used, seeing as these pins aren't like the other GPIOs in terms of drive current etc.

Best regards,

Simon

[Sebastian_Fant]

Hello,

So, can they be used as stepping stones?

Best regards,

Sebastian

[Simonr]

I'm sorry, but I never got any feedback on that particular question Sebastian. I have pinged the internal case again. I don't think they can be used as stepping stones as I think D+ and D- will be "grounded" and not floating when the USB peripheral is disabled.

Best regards,

Simon