Re: USB output in ucom

On Sun, 13 Jul 2025, Emmanuel Dreyfus wrote:

> Using ktrace on screen, on the receiving end:
> " "
> "EL"
> "L"
> "O"
> " "
> "W"
> "O"
> "RL"
> "D"
> "!\r\n"
> "X"
> "x"
>
> On first insight, I thought the first output was just discarded
> and the trailing x was just there because the same buffer was used.
>
> But on first output I give usbd_setup_xfer() a 16 characters length,
> on second output, 15 characters. I cannot make up an explanation why
> the trailing x is there. Perhaps the receiving kernel does some
> processing?
>
>> If that's real hardware, I'd guess that the symptoms come from
>> a hardware problem like a missing ground.
>
> The link works find with other usages.
>

Does the link have working HW flow control (RTS/CTS)? If only 3 wires are
active (Rx/Tx/GND), then you'll have to set very low speeds.

-RVP