[STM32F7,H7] USB MSC+ULPI+HS : handshake in FS instead HS mode

[alexandre23]

Hello,

I have a custom H743 board with Microchip USB3340 external PHY (REFCLK = 24MHz, dedicated external oscillator)
In an code that use ChibiOS, my configuration should achieve HS mode, but ultimately, after handshake, it revert to FS mode (12Mbits/s) : so it works, but it is slow.
In order to understand where I am wrong, I have flashed STM32F7Cube(V1.17.1)/STM32746G-Discovery/Applications/USB_Device/MSC_Standalone/SW4STM32/STM32746G-DISCOVERY_USBD-HS on a discovery F746, but problem is same : when plugged on a computer (tried several : windows and linux, different usb cables) official ST MSC HS demo connect in FS mode, not HS mode with same symptoms : slow transfert rate.

Can some someone can point me a working MSC HS demo, or has clues why ST demo don't do HS, and if there is a way to fix that ?
Thanks

Alexandre

[alexandre23 · Accepted solution]

Problem solved reading this thread on the forum : https://community.st.com/t5/stm32-mcus-embedded-software/stm32f2-f4-problems-with-various-ulpi-usb-phys/m-p/554263#M40349 
this is also documented as an errata section on microchip 334x PHY manuel.

TLDR : setting XCVRDLY bit in the DCFG register solve the problem when using recent ULPI PHY like the microchip 334x.
Alexandre