[sdiy] Does usb c alternative mode allow analog signals on the multi-purpose pins?

[cheater cheater]

Yep, there are ones with codecs in them. You probably want /an even
cheaper one/. Which exact one did you get? How much was it?

The cheapest ones might be the passive ones - but who knows. You can
find a schematic in appendix A of the doc that Chromatest posted. It's
on page 312. The next page has a schematic of that + a charger input
port.

The page 312 schematic only has the usb c plug / port, the 1/8" jack
with a plug-present switch, and wires. That's it. You can build it
yourself quite easily either by cutting off a usb c cable, or by
getting a usb c breakout pcb.


On Thu, Nov 17, 2022 at 11:23 PM Eric Brombaugh via Synth-diy
<synth-diy at synth-diy.org> wrote:
>
> I bought one of those cheap USB C headset adapters as an experiment to
> see how well they work.
>
> https://www.amazon.com/gp/product/B07XYQ2ZKH
>
> Physically it's tiny - barely larger than the USB and 3.5mm connectors
> (plus short cable between them). Tried it out and it worked well, but
> then as I dug deeper it turns out that it's *not* passive - it actually
> has a full codec + amps inside. Plugging it in enumerates a device on
> the bus that's unrelated to my laptop's built-in audio:
>
> ID 0572:1b09 Conexant Systems (Rockwell), Inc. Hi-Res Audio
>
> Amazing.
>
> On 11/17/22 02:31, cheater cheater via Synth-diy wrote:
> > If you go to amazon, you'll find nearly infinite USB C to headset
> > adapters following this standard, and they're as cheap as 4 euro.
> > They'll probably work well, too - even the worst C plugs I've
> > encountered on cheap cables are still very resilient. The mini jack on
> > the other hand, I mean who knows, but it'll probably take a bunch of
> > cycles. The more expensive ones are up to 10 euro, but not more.
> >
> > On Thu, Nov 17, 2022 at 10:25 AM cheater cheater
> > <cheater00social at gmail.com> wrote:
> >>
> >> Thanks for the pointer to the spec. Appendix A talks about passive
> >> audio adapters from USB C to headset TRRS. That includes both input
> >> and output analog signals on the pins of a USB C port.
> >>
> >> Glad that you linked me to the pdf, the last time I tried searching
> >> for USB specs I found something completely different and it didn't
> >> answer my question.
> >>
> >> On Tue, Nov 15, 2022 at 9:23 PM Chromatest J. Pantsmaker
> >> <chromatest at azburners.org> wrote:
> >>>
> >>> "NOTE: Adopters may only use the USB Type-C® cable and connector to implement USB or third party functionality as expressly described in this Specification; all other uses are prohibited."
> >>> From:
> >>> https://www.usb.org/sites/default/files/USB%20Type-C%20Spec%20R2.0%20-%20August%202019.pdf
> >>>
> >>>
> >>> On Tue, Nov 15, 2022 at 11:08 AM cheater cheater via Synth-diy <synth-diy at synth-diy.org> wrote:
> >>>>
> >>>> As in subject. Is there anything in the spec that speaks against this?
> >>>> Where would one go in order to get a definitive answer to this?
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