Re: Re (2): USB functionality.

On 2024-03-13, Dan Purgert <dan@djph.net> wrote:

On 2024-03-12, Roger Hayter wrote:

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

 
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.

USB-C supports SuperSpeed which uses two additional pairs on top
of USB2 and also allows for full-duplex.  That is what the additional
contacts on a USB3 A plug are for.

--
Andrew Smallshaw
andrews@sdf.org