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STM32F407 USB device without VBUS monitoring

Question asked by diez.r on Feb 4, 2016
Latest reply on Feb 5, 2016 by wolff.roger
Hi all:

I am developing a device with an STM32F407. The device will always be powered by its own power supply. It will have a USB socket so that it can act as a "USB device" (a USB slave) that shows up as a serial port on the host PC.

I am using Ethernet, CAN2 and almost all UARTs and I cannot spare pin PA9 for the VBUS sensing option. The other USB interface has similar pin conflicts.

I found this thread about VBUS sensing on another STM32 family:

"STM32F207 USB device with no VBUS monitoring"

https://my.st.com/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Flat.aspx?RootFolder=https%3a%2f%2fmy.st.com%2fpublic%2fSTe2ecommunities%2fmcu%2fLists%2fcortex_mx_stm32%2fSTM32F207%20USB%20device%20with%20no%20VBUS%20monitoring&FolderCTID=0x01200200770978C69A1141439FE559EB459D7580009C4E14902C3CDE46A77F0FFD06506F5B&currentviews=1844

However, the answers are not conclusive. I also looked at the reference manual etc., and I couldn't find a final statement on the subject. Therefore I am asking these questions again:

1) Is it possible to design a USB device without VBUS sensing?

2) If I do VBUS sensing manually on another pin, will that work with the USB driver?

Many thanks,
  R. Diez

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