I would like to use the single USB internal PHY on the STM32H735 to connect to a 2 port hub chip (like the Microchip USB2422) so that I can connect to both a USB stick for firmware upgrades as well as a cellular module. I started connecting everything up and then I came across a multiple sources saying that you can't connect USB Hubs to the internal PHY and you have to use the ULPI interface to connect to an external PHY, but none of the sources really explain why other than saying the internal PHY isn't capable of High Speed operation, and the USB software from ST doesn't allow for hubs. I don't understand what this has to do with interfacing with a hub IC when I'm perfectly fine with operating at Full Speed. So I have a few quesitons:
1) Can I use a USB Hub (like the USB2422) as long as I'm OK with it operating at Full Speed only? Is it technically possible to connect these devices and get them to work?
2) Will the USB Host middleware provided through STM32CubeMX work with USB Hub ICs? Do I have to use a 3rd party USB Host Middleware like Keil MDK's?
3) Assuming I can interface the hub chip how does the VBus pin on the STM32 and Hub's Upstream port work? Do I just connect them together and also to the 5V power supply so that both the STM32 and the Hub see that they are connected and getting 5V?
