USB D+- as simple GPO how do this?

RE: USB D+- as simple GPO how do this?

hmolesworth — Mon, 11 Jan 2021 18:38:52 GMT

Oh, just re-read the post - I see you are short of pins so this won't help. Try SWO; you can treat it as a Tx-only uart and PWM the LED (maybe)

RE: USB D+- as simple GPO how do this?

ovrebekk — Mon, 11 Jan 2021 15:41:22 GMT

I discussed this with the developer, and he agreed that it should be possible to override the data lines by using the DPDMVALUE registers, but please keep in mind that you can't control the two pins separately.

USB is a differential bus with the D+ and D- lines having the opposite state in normal operation, so at most you would get a single extra output signal.

Best regards
Torbjørn

RE: USB D+- as simple GPO how do this?

Turnaev — Fri, 08 Jan 2021 18:55:41 GMT

Hello!

Yes, I use nRF52820.

Best regards,

Sergey Turnaev

RE: USB D+- as simple GPO how do this?

ovrebekk — Wed, 06 Jan 2021 09:28:53 GMT

I assume you are using the nRF52820?

I don't think there is any way to manually override the state of the USB pins. These pins are handled by the USB IP, which takes care of the physical layer signalling, and only provides a higher level USB API to the rest of the system.

I will verify this with the USB developers to be sure.

Whether or not this is possible this would be using the chip outside it's specification, since we don't test these pins for any other use than as USB data pins. This is very risky as it means there might be negative side effects of using these pins, and you might end up with malfunctioning devices in the field.

I will strongly recommend that you look for alternative ways to handle the lack of IO, such as upgrading to a larger part (the nRF52833 for instance), attaching a GPIO extender, or revising your existing IO assignments to see if there is some other pins that can be optimized out.

If you want to share hardware schematics of your design I can make the case private.

Best regards
Torbjørn

RE: USB D+- as simple GPO how do this?

Stian Røed Hafskjold — Mon, 28 Dec 2020 13:23:11 GMT

Hi,

I have not tried this before so not sure if it will work. But because of Christmas holidays I will have to come back to you in the first week of January. Sorry for the inconvenience.