0
\$\begingroup\$

I've been working on this project for a while now and have hit a bit of a wall.

I've been designing a magnetic cable coupler for a automotive device (Comma3X). The device communicates with the car via CAN over a custom-pinned USB-C cable. I assumed this coupler wouldnt be too hard to figure out. After all, it'd just be extending the connection through Pogo pins and traces, right...?

I used KiCad for my design, followed the cable requirements, routed the USB connections to the correct pin/pad, error checked, then ordered.

Here is the pin-out of the connection I'm following:

Comma3X USB-C Pin-out Diagram

Here is my KiCad schematic:

Crop of a KiCad schematic.

Male PCB:

KiCad PCB overview/design

Female PCB:

KiCad PCB overview/design

The male and female pads are flipped/mirrored due to their physical orientation. They mate like so:

3D representation of the connectors assembled.

I have since received the PCB designs and assembled them. I used a USB cable tester to check that there were no shorts, and that all connections had continuity.

However, upon using the coupler I noticed that I wasnt getting a proper connection. Power works fine, but the data lines don't seem to be communicating correctly.

They included a USB-C coupler with the unit, some amazon special: AGVEE USB-C

I've since ordered a pack and disassembled one of them, hoping to spot the difference in my design. Unsurprisingly it was essentially the same thing. The only notable difference was the lack of pins and the much shorter traces.

I know this magnetic pogo pin idea is possible as other users have created such boards and got them to work. I'm quite stumped as to what I'm doing wrong. I sure hope its something obvious that my inexperience has missed! Any help is greatly appreciated!

Edit: Clarify USB wording.

\$\endgroup\$
10
  • \$\begingroup\$ @vir The confusing part of this question is he's not designing a USB coupler, he's designing a (presumably proprietary) OBD over USB-C coupler. \$\endgroup\$
    – user71659
    Commented Mar 19 at 16:58
  • \$\begingroup\$ Your PCB shows no USB connections so it must not be for an USB device? There are CAN buses. Are the CAN buses swapped when you connect your adapters? Did you use standard fully connected Type-C cables that include all the pairs, instead of using only USB2 pairs? \$\endgroup\$
    – Justme
    Commented Mar 19 at 17:10
  • \$\begingroup\$ Also, how did you check for errors? That is called an OBD-C cable. Are they not using even Type-C USB cables? Do they use custom wiring that makes it incompatible with Type-C cable? \$\endgroup\$
    – Justme
    Commented Mar 19 at 17:20
  • \$\begingroup\$ @user71659 Yeah my word choice wasnt the greatest, sorry about that. The only thing that is USB about this coupler is that it uses the USB-C form factor. The specs of the Comma3X (C3X) call for a cable that is at least capable of USB 3.1 Gen. 2 speeds, though I believe thats just to ensure that is a fully populated 24P connector. \$\endgroup\$
    – Gyrohammer
    Commented Mar 19 at 17:53
  • \$\begingroup\$ @Justme Correct, this isnt a USB device, only the connector uses the USB-C form factor. I'll edit the question to clarify. The CAN buses are swapped when the adapter is connected, making the trace connect directly from pin to pin. The OEM cable is a populated 18P cable, confirmed via my tester (The tester I got is some amazon thing, just has little diodes that light up if the wire has continuity). The wiring is custom, as the provided cables dont work with any other USB-C devices that I've tested. \$\endgroup\$
    – Gyrohammer
    Commented Mar 19 at 18:00

0

Reset to default

Browse other questions tagged or ask your own question.