I have an STM32 board I am currently designing which is going to use the USB bus for communication and programming. The ground connector on the USB will be tied to the board ground, and the D+ and D- lines will go to the STM32's USB_DP and USB_DM with a pull up on the D+ line to signal full speed.
What I want to know is what to do with the USB VBUS line. I have no need for the board to be running off of the 5v USB power, it will always be connected to an external power supply. However I have read that the VBUS line may be important for communications, so I do not want to leave it floating, as that may make the communications inoperable.
What is the best thing to do with the VBUS line in a situation like this?