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From: Roger Hayter <roger@hayter.org>
Newsgroups: sci.electronics.repair
Subject: Re: Re (2): USB functionality.
Date: 12 Mar 2024 19:31:32 GMT
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On 12 Mar 2024 at 19:27:04 GMT, "Dan Purgert" <dan@djph.net> wrote:

> On 2024-03-12, Roger Hayter wrote:
>> On 12 Mar 2024 at 16:29:31 GMT, "peter@easthope.ca" <peter@easthope.ca> wrote:
>> 
>>> In article <2219572717.2fe80b82@uninhabited.net>, Roger Hayter
>>> <roger@hayter.org> wrote:
>>>> But can even USB-C accept a signal input (keyboard and mouse for
>>>> instance) and unrelated signal output (audio for instance) on the
>>>> same physical socket? I ask only out of curiosity.
>>> 
>>> The setup is rarely tried.  Appears that nobody can reply.
>>> 
>>> A keyboard or mouse sends tiny amounts of data; a few bytes per
>>> second. In principle the link should be able to fit that in without
>>> significant drop-outs in audio output.  WIth so many details involved,
>>> a general answer is difficult. When all else fails, we can test and
>>> see what happens.  =8~)
>>> 
>>> Regards,             ... P.
>> 
>> So you could use an overarching protocol which was bilateral (ethernet
>> anyone?) and send and separate messages both ways.  What I was aksing was
>> whether within the USB protocol there was provision for using some pins in for
>> one electrical signal (bi or uni-directional) and other pins for another
>> electrical signal. Because that would be the only way to do it without special
>> software on at least one of the devices.
>> 
> 
> There's only one set of pins (well, two sets if you count USB2 / USB3 --
> but you can only use one set at a time).
> 
> USB2 -> D+/D- (Bi-directional / Half Duplex)
> USB3 -> TX1+/TX1- and RX2+/RX2- (optionally Full Duplex, IIRC)
> 
> As I recall the "Tx" pair is "Host Transmit to Peripheral", and "Rx" is
> "Host Receive from Peripheral", but it's been a while since I read up on
> the USB3 / USB-C implementations.

Usbc seems to have about 20 pins, that's why I asked.

-- 
Roger Hayter