STM32F730 USB High Speed Device fail to be recognized after jumping from application to bootloader

[JYeh.9]

Hi,

I am now using STM32F730 and its embedded High Speed USB to do my project.

The following sequences are made:

1. In the bootloader, a USB HID device is created and connected to PC. I use this bootloader to download the application code into flash.
2. After successful downloading, it would jump from bootloader code to application code.
3. In the application code, if a specific button is pressed, it would jump from the application code to bootloader again to upgrade firmware.
4. Back to step 1.

However, the USB HID device could not be recognized in step 4., i.e. after jumping from the application code to bootloader.

I've check the return values of the USBD_Init and USBD_Start API and there's no any error.

The USB HID device just would not appear.