USB hardware requirements

Posted on May 17, 2011 at 13:46

I am also doing USB on a custom board.

Strictly speaking, is VBUS required if the STM32 is not powered through USB and the STM32 is in device mode?

Posted on May 17, 2011 at 13:46

Still trying to get it to work.

It looks like for a OTG device, you have to connect DM, DP, ID and VBUS directly.

My concern is that I use VBUS to power the board. So, VBUS is connected to a 3.3V regulator used to power the STM32.

Is it OK to connect VBUS to the regulator AND to the VBUS pin of the STM32?

If not, how could it be set up? Since I plan to use self-regulated devices with the board (this design is not for production), I dont feel like I need current regulation, but I dont understand how VBUS works while using it as the whole board power supply.

Posted on May 17, 2011 at 13:46

Thanks all for your replies;

Currently the board connects D- and D+ directly, VBUS is used to power the whole board (also connected on VBUS pin on the STM32).

What do you mean by using a resistor?

Isnt the device/host pullup mechanism implemented in the STM32, since it is an OTG device?