STM32H743 USB device transmits zeros to the Host

lw23 · ‎2025-05-19

Everything else is working fine.

Setup packet with SET_ADDRESS received and processed.

Next GET_DESCRIPTOR for DEVICE which is sent back ok

I've verified the data written to the Tx FIFO is correct.

Correct number of bytes it transmitted but the bytes are not correct.

I'm using a STM32H743-EVAL board, hardware is working fine

Any suggestions?

p.s. the Device Descriptor received displayed by USB View

FBL · ‎2025-05-19

Hi @lw23

Would you double-check the device descriptor data you are writing to the Tx FIFO. Ensure that all fields are correctly populated according to the USB specification. The bLength field should be 18 for a standard device descriptor.

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TDK · ‎2025-05-19

Is data cache enabled? Disable it during the debugging stage. If that fixes it, you'll need to instrument your code with appropriate cache handling.

> I've verified the data written to the Tx FIFO is correct.

How, exactly?

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