Hi, @FBL I inserted the __DSB(), but can not solve my issue. But still get the HAL_TIMEOUT return. 

Hi, @FBL I use the USB3340-EZK and checked the clock configuration is correct，and the USB_CoreInit API can return HAL_OK.It's run OK last week, but get the HAL_TIMEOUT in "Flush TX /RX Fifo " this week. I have no change. The local variables below whe...