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I need to create a USB-C coupler that connects two USB-C cables, passes the data from one to another while splitting out the USB 2.0 signal from the incoming USB-C plug to an additional receptacle or plug. It is sort of Y-type splitter.

As a first step, I'm trying to recreate a $5 USB-C coupler I'm using successfully to couple a Thunderbolt 3 connection. My current attempt connects all 24 USB-C pins of both connectors, starting with A1 on the first plug to A1 on the second plug and so on. It does not work, in which order do the pins from both plugs need to be connected?

USB-C Receptacle

Coupler Bottom Coupler downside

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What you are trying to do is non-standard and will loose some Type-C features, namely: orientation detection, Power delivery and cable marking.

Look for Table 3-10 in USB Type-C spec. Notice how data pairs are wired, and try to undo this in your receptacle to receptacle fixture in order for a cable+fixture assembly to be looking like a passive extender.

You'll have one problem: cables do not propagate both CC pins. In a plug-to-plug cable, CC is A5 on both ends, B5 is Vconn or tied to ground through Ra and is not wired from one end to the other (see Figures 4-5 and 4-41).

Still, if you dont care about orientation detection and accept to try both possible orientations of your cables on the fixture, you may create such thing.

Note the breakout you have in the picture will most certainly degrade the signal enough for high speed pairs to be unusable, and USB3 be unavailable.

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  • \$\begingroup\$ Thanks a lot, good point about the signal quality. I've tried to replicate the pinning on the coupler but still does not work so it might be the signal quality. Also the break-out has 13 pins while the specification states 12 pin, I think GND is wired twice. \$\endgroup\$
    – petard
    Dec 8 '21 at 11:02
  • \$\begingroup\$ Signal ground are A1, B1, A12, B12. I bet what is labeled GND on the breakout is actually receptacle shield. You should check with a continuity tester \$\endgroup\$
    – Nipo
    Dec 8 '21 at 14:33

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