Welcome, I have project with STM32F407IGT6 (it's on XCore407i Development Board) and I cannot set up OTG_FS to work as device. Hardware is OK (I can connect PC with STM32 Bootloader by USB_FS port and it's always working correctly). But in my program - no way. PC says "device not recognized".
In Keil examples for STM324xx there are no for OTG_FS. So I created simple project, set libraries for MSC Device on USB_FS, copy code from example (USB Device Mass Storage - STM32F429-Discovery) and check lines/clocks/settings. Everything seems to be OK (clocks, lines, RTOS settings, stack, heap, etc). Code is the same as in example.
But when I connect cable to PC I see "device not recognized"...
The same project (code, settings), the same board - when I change to OTG_HS and plug cable in second connector everything is working...
What I need to do to use OTG_FS?
KEIL 5.12, the newest libraries.
Just like always - I have found solution just after sending previous post.
USBD_Initialize(0); USB_OTG_FS->GCCFG |= USB_OTG_GCCFG_NOVBUSSENS; <<- disable checking VBus (I don't have it so it wan't working) USBD_Connect(0);