Re: Advice on laptop with USB-C port and USB-Type C Multipoint Adapter (and VGA)
On Thu, 3 Dec 2020 at 21:15, <tomas@tuxteam.de> wrote:
> On Thu, Dec 03, 2020 at 08:35:37PM +1100, David wrote:
> > On Thu, 3 Dec 2020 at 02:27, <rhkramer@gmail.com> wrote:
> > > I did find out that a USB-C cable / connector has 24 conductors -- so it is
> > > conceivable (with my lack of knowledge) that some laptop manufacturers
> > > actually put out an (analog) VGA signal on the USB-C cable.
> > Is this just wishful thinking or do you have evidence?
> > Because it's inconceivable, as far as I'm aware. Everything I have read
> > about USB-C indicates that it is purely digital. Even though it seems
> > to be the USB way to have countless variations of every physical and
> > electrical specification, VGA is a standard from 1987, forget finding
> > it on any USB-C connector. Those pins are all used for other things.
> USB-C is a mess. Quoth [1]:
>
> "A device with a Type-C connector does not necessarily
> implement USB, USB Power Delivery, or any Alternate Mode:
> the Type-C connector is common to several technologies while
> mandating only a few of them"
>
> That said, Display Port, Thunderbolt, MHL and HDMI alternate modes seem
> to implement VGA output with an "active" cable, which is an euphemism
> for "there's some chips in there".
>
> So your computer's USB-C socket must fit, your dongle, aka "active
> cable" must fit, and they have to be capable to talk to each other.
Does the active cable have a USB-C connector on the VGA end?
The comment I responded to speaks of analog VGA signals
on a USB-C connector.
I thought "that's weird" so before I wrote I had a quick read of all the main
links under the heading
https://en.wikipedia.org/wiki/USB-C#Alternate_Mode_partner_specifications
and I saw no trace of any such thing.
As always, I'm happy to be corrected if wrong. I take no interest in
"active cables" myself, modern passive cables are unreliable enough,
but if someone wants to provide a link then I will enjoy a chuckle that
someone somewhere thinks this is good engineering.
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