How use usb data line without usb core

[Vlad Mokhnachov]

Hi, Nordic! We have connected gpio pins to usb data line pins for using usb or i2c in different times. But even if USB core disconnected, usb lines hinder for i2c lines. Is it possible connect usb d+ and d- to GPIO?

[Jakub Oller]

Hi,

I have the same exact question and I can see that it has not been fully answered yet. 

I want to have a single connector for either USB or GPIO depending on VBUS voltage (we will use USB if VBUS is present, GPIOs if VBUS is at 0V or floating). The question is: what happens (electically) to D+ and D- pins when VBUS is at 0V or floating? Are they high impedance?

[Turbo J]

The D+/D- pins will not be powered - which is not the same as high impedance. According to PS description, the PHY with the data pins is powered from VBUS via USB LDO.

Which means you cannot share these pins in a connector - the unpowered USB pins would act as (sort of) pull downs and might reverse-power the USB PHY because there are probably diodes from the pins to he voltage rail at DECUSB.

[Jakub Oller]

Thanks!