VBus triggered by Data pins STM32H743?

[CBUnmanned]

I have a board that uses the H743 and have been having major problems with the USB side of things. I've only just realised that I left VBus floating all this time, so I'm assuming that's a major cause of my issues..

 

The board I have is designed as a solder on stamp, and has a fixed 5v input that powers multiple LDOs etc. The problem lies in that I don't really want to sacrifice one of my castellated edge pins for vbus sensing, but the stamp isn't always connected to USB so I cant simply connect VBUS to 3.3v, can I? 

 

The board is always "Self Powered", ie the 5v from USB is not directly connected to the main power in. Is there any way to trigger the VBUS pin only using the data lines? 

[Muhammed Güler]

https://www.st.com/resource/en/application_note/an4879-introduction-to-usb-hardware-and-pcb-guidelines-using-stm32-mcus-stmicroelectronics.pdf

You can review this document.
By the way you can disable the VBUS pin.
For example, you cannot define VBUS and SOF pins on STM32F373.
If you have a connection problem, you should first check the signal integrity.

 

[FBL]

Hi @CBUnmanned 

Any 5V tolerant pin with external interrupt functionality can be used with an external resistor divider, to fulfill AMR conditions. See Management of VBUS sensing for USB device design - STMicroelectronics Community

[CBUnmanned]

I should have been more clear. 

I have a "Module" (Yellow) which contains some supporting circuitry and some sensors. 

It is normally soldered onto a "Carrier" (Green) which has a USB plug to act as a slave to a host PC.

The problem is that the Module is small and has limited space for edge connections, so I am trying to avoid dedicating one to VBUS sensing. Is there anything I can do using just the Data signals to trigger VBUS (Blue) rather than dedicate an edge pin (Red)?

 

My Module is powered through a 5v power input, which might or might not be self powered/bus powered so cant be directly tied to VBUS (through a resistor divider). What happens if VBUS is always tied high but there's no USB attached?

 

[FBL]

I guess it would not be possible to get a direct solution for triggering the VBUS pin using only the data lines. The standard approach for VBUS sensing involves detecting the presence of the VBUS voltage itself, not through the data lines.

[CBUnmanned]

I have since got another board revision made that has the VBUS broken out separately but still have the same device descriptor request failed error.

 

Vbus is triggered through a Voltage divider as pictured below which is only active when the USB is plugged in. 

I am using ChibiOS and have the VBUS sense pin set to an opendrain input.