Re: Re (2): USB functionality.

On 2024-03-12, Roger Hayter wrote:

On 12 Mar 2024 at 19:27:04 GMT, "Dan Purgert" <dan@djph.net> wrote:

On 2024-03-12, Roger Hayter wrote:

[...]
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.

Yeah, that's just to allow the connector to be flipped over, and still
connect to the host / peripheral.  The host/peripheral ports themselves
only have one orientation.


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