STM32H503 USB bootloader

[Neilm]

Hi Guys,

Has anyone every tried to use a STM32H503 processor with the USB bootloader? Specifically - I am trying to use it without a crystal and it does not seem to enumerate when I connect.

The layout of the traces is not wonderful - but the total length is only 18 mm so I doubt it is an imedance issue, although the rising edge looks more like a Mayan pyramid than a smooth rise.

Getting the Nucleo board has been a pain as it has not arrived. I ordered it, designed the schematic, laidout the board, bought the board, built the board, tested the board and it has still not arrived.

If someone can tell me if they have been able to use it like this I can help narrow down this issue.

Thanks

Neil

[aliarifat794]

The STM32H503 does have an internal oscillator calibration feature, but this may not be sufficient for USB operation without an external crystal.

[Neilm]

The STM32H503 does have an internal oscillator calibration feature, but this may not be sufficient for USB operation without an external crystal.

The datasheet seems to suggest the clock will synchronise to the start of frame in the USB packets