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

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

Sebastian_Fant — Fri, 05 Nov 2021 07:44:42 GMT

Great thanks,

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

Simonr — Fri, 05 Nov 2021 07:38:13 GMT

Hi Sebastian

Using the D+ and D- pins as vias (stepping stones) will be a no-go. There are parasitic diodes from D+/- to DECUSB. When VBUS is not connected, DECUSB is soft clamped to VSS, and it won't be acceptable to force D+/- high when VBUS is not connected.

Best regards,

Simon

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

Simonr — Thu, 04 Nov 2021 06:32:40 GMT

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

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

Sebastian_Fant — Tue, 02 Nov 2021 22:51:00 GMT

Hello,

So, can they be used as stepping stones?

Best regards,

Sebastian

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

Simonr — Thu, 24 Jun 2021 07:45:52 GMT

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

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

Sebastian_Fant — Wed, 23 Jun 2021 07:48:39 GMT

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.

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

Simonr — Fri, 14 Jun 2019 08:41:32 GMT

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