I tried to replicate the usb part of NUCLEO-F439ZI dev board to a project, without success. I'm using vbus to power supply the MCU, through a voltage regulator. For the MCU I'm using the stm32f427, not the 39, as in the development board, but they seemed compatible with my project features.When I connect the board to my laptop via USB, the overcurrent led turns on, and my operating system (ubuntu) does not detect any new USB device.If I connect boot0 to VCC, the command lsusb in ubuntu takes some seconds to respond.Can you please give me some suggestions?Thank you in advance