USB Type C, beginner question on extending from male to female

[Jackster]

Hi all

I have a small project that I am working on.

Got this USB Type C drive that I need to plug into a circuit board using a male Type C SMT connector.
Then there is a Type C female SMT socket for the regular cable to connect into.

Example



What I am trying to get my head around is how to wire this up on the PCB.
Am I right to presume that one can just do A1 to A1 and B12 to B12 as the devices on either end don't care and will sort out what they are using?

Thank you
Jack

[bson]

The short answer is you can't properly extend USB 3.1 cables because they have all kinds of info in an ID chip.

The second matter is that USB C cables cross TX/RX (TX on one end goes to RX on the other and vice versa).  So if you want to pretend two cables are one the signals will need to be crossed an odd number of times, and with two standard cables this means your little adapter gadget has to cross them as well.  And they cross A/B (top/bottom), so for example A2 goes to B2 and vice versa.  Your adapter will need to do the same.

The best is probably to make it look like USB 2 for both upstream and downstream.

Receptacle (end-on view):


Plug (end-on view):


Some brief info and the full spec:
https://www.reclaimerlabs.com/blog/2017/1/12/usb-c-for-engineers-part-2
http://www.usb.org/developers/docs/

Edit: actually, they also seem able to cross left-right, or both, with the plug CC pins on the device end used to determine how to mux them in the device transceiver.

[Ziya]

The short answer is you cannot. The long answer is in the wiring diagram in the technical specs. You end up putting a resistor on one set of the VBus pins to tell the USB C end to switch over to USB 2.0 and operate in that mode.

There's quite a few videos about bad USB C to A connectors floating around that don't have the resistors correctly bridging the right connections.

Better Explanation
https://electronics.stackexchange.com/questions/323128/wiring-diagram-for-usb-c-to-usb-a-cable

YouTube Guy's Rant
https://www.theregister.co.uk/2016/08/30/anker_usbc_cables_recalled/

[amyk]

If you just make a straight passthrough extension, then that would work; but as mentioned by others, things get messy with separate cables because they have their own "intelligence".

Given the choice I would stay very very far away from USB3.

[Jackster]

Thanks for the info guys.

I sort of need USB 3 for the transfer speeds. This project is dead without it.

[bson]

Then you need a hub on it and forget about cables and passthroughs - that simply won't work with USB 3, much less SS or proper power negotiation.  The easiest would be to use an existing, small hub.

[Sceadwian]

I'm curious why you decided to take a DIY approach on something that you can just buy online already, especially with USB 3.0 where you're talking about very high speed signals.

[rs20]

Wait wait wait. I'm missing something. The OP seems to be clearly indicating that his/her board has one female and one male connector on it, and both ends can speak USB-C. I.e., the USB drive could, electrically, be plugged directly into the host board, but for some reason (physical conflict?), that can't happen. So this is a little standoff board that basically just moves the host's plug out a little bit. OP, please let me know if that's not what you're going for.

Meanwhile, all the responses are talking about USB-C to USB-A conversion and ID-chip in cables and all this stuff that doesn't seem necessary to what would be a simple standoff. Is the signal integrity of USB 3.0 really so delicate that a couple of centimeters extra length will completely ruin everything?

I'm reminded of the recent thread where a dodgy SATA cable turned out to be simple 0.1" ribbon cable instead of the dual twinax magic that it's supposed to be. Thing is, it actually almost kinda worked: over 300mm of ribbon cable. I'd be surprised if USB-C was so much more sensitive that it couldn't survive 20mm of decently designed PCB and an extra connector pair.