Regarding USB C you are right that there are four differential pairs on the connector. However, for communication only two pairs are used because the USB 3.1 protocol only uses two. On the device that has a USB C connector you need a dedicated controller that manages the orientation of the plug. Then the two data lines are connected to the right pins on the connector through a multiplexer. The other two pairs on the connector are for no use in USB mode but if you want to use USB C in alternate mode (e.g. DisplayPort), signals can be rerouted.

You can find all the information on usb.org (zip archive with full specification).

This basically means that the EOMA68 standard has two differential pairs that are not used for USB but if your intention was to make it available for USB C, an internal multiplexer would be needed.

Kind regards

Julius Lehmann

On Feb 5, 2017, at 14:20, Luke Kenneth Casson Leighton < lkcl@lkcl.net> wrote:

---
crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68


On Sun, Feb 5, 2017 at 11:44 AM, Internet <internet@devpi.de> wrote:

   

     Hey there!
    

    
 I was wondering about the USB3.1 pinout in the EOMA68 standard. In my
    
 research on the USB Type C connector I found out that USB3.1
    
 (Superspeed+) has only two differential signal pairs (one for receiving,
    
 one for transmitting)
    

   

http://pinoutguide.com/Slots/usb-type-c_pinout.shtml

two for receiving, two for transmitting, each 5gbit/s for a total of
10gb/sec.  the connector and thus the pinouts are rotatable by 180
degrees so the pinouts on the first 12 pins (top row) are *identical*
layout to the second 12 pins (bottom row) except in the reverse order.
D+ and D- (the USB2 pins) are *missing* on one row of the receptacle
so that you don't connect them up twice (which would be bad).

you *may* be thinking of USB 3.0 which is connector-compatible with
USB 2.0 and is what you find on most laptops and desktop computers
these days:

http://pinoutguide.com/Slots/usb_3_0_connector_pinout.shtml

that is *only* one set of (5gbit/sec) tx-rx differential pairs.

scared me for a minute that i'd messed it up... :)

l.


   

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