From: andrews@sdf.org   
      
   On 2024-03-13, Dan Purgert  wrote:   
   > On 2024-03-12, Roger Hayter wrote:   
   >> On 12 Mar 2024 at 19:27:04 GMT, "Dan Purgert"  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   
      
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