I could use some help. I have to implement a USB Mass Storage device on a STM32L476. The final hardware is not ready jet, so I started by using a stm32476RG Nucleo board. I’ve started with the MSC_Standalone example, that is shipped with the STM32 Cube library version 1.4. I’ve replaced all storage callbacks with empty stubs (that currently just asserts(false)). The software builds fine under GCC and runs after initializing into the main loop without any faults or asserts. I wired an USB cable to the Nucleo (D+ to PA12, D- to PA11 and 5V to PA9; PA10, the configured ID Pin is open), no external pullup resistors are used.
The 8MHz from the stlink part of the board is connected to the HSI input (OSC_IN).
When I connect the USB cable to a PC, nothing happens. I can measure 5V at PA9, but on both D+ and D-, 0V and no signals. No I’ve checked the content of all OTG (device) registers, but found no obvious error.
Have you any suggestions for me, how to debug / trouble shoot this? Any tests that I can make to get more insight in my issue?
Thank you very much in advance and kind regards,