Help with troubleshooting inline USB C connector

Hey there!

Live chat suggested someone here might be able to help me troubleshoot…

I’ve been working on some custom USB C to USB A cables recently (4 pin USB 2.0 only). Finished my first cable, plugged it in with the excitement of biting into a new flavour of ice cream for the first time and… nothing. I can’t figure out where I’ve gone wrong. Perhaps someone here might be able to point me in the right direction.

  • Here’s the datasheet for the USB C connector I’m using. I’ve added some color coordinated lines to help with the confusing presentation of the pin mapping. 954.pdf (277.2 KB)

  • Here’s my novice soldering work (2 sets of USB C to A cables) :
    I’ve checked for shorts using my multimeter and everything checks out.
    I’ve also checked continuity from one end to the other end of the wire, as well as from the soldering pads on the USB C PCB to the pins connecting to the plug (so from C4 to A6, C5 to A7, D5 to B4/B9 etc.)

I’m at a complete loss here as to why the cable won’t work! Have I wired something wrong or is there something else I’m missing?

Update: When attempting to plug in a keyboard I get “Port Reset Failed” under the Device Manager.

The only thing I can think of is a host/device setting issue (USB C needs to be told to operate as a host or as a device end). But there are no resistors on the USB C board to switch the setting and no documentation for the part as two what it’s factory setting is.

Appreciate any guidance whatsoever!


Hi @Sxander, double check your wiring against USB’s documents:

“USB Type-C® Cable and Connector Specification Revision 2.0” Page 78


Pretty sure I have looking at the datasheet. If I’ve got something wrong would you be able to point it out?

Your Shield isn’t connected to the Type-C, double check that all the GND’s and Vcc’s are correctly connected together. Also verify A5 is connected as mentioned in Note 1:


Thanks Robert,

Forgive my ignorance, I presumed all the GND and VBUS pins in the PCB were traced together within the PCB. Is that not the case? Can’t understand why they wouldn’t be. Am I meant to wire together A1, B1, A12 and B12, as well as A4, B4, A9 and B9?

I only have some 10k and 330 ohm resistors. I can wire them in series but this thing is gonna look like Frankenstein!

When looking at the connectors on the USB-A do you have the Blue wire to pin 1 or Pin 4. From the angle of the picture it appear it is Pin 1 which is then connected to D1 which connects to B1.

Per this diagram Left being USB-A and Right Being USB-C Pin 1 would go to A4, B4, A9, B9. A simple continuity check should be able to verify the correct wiring.



1 Like

You’re my hero! I’d been using this diagram without realising that the plug pins were facing away from me as opposed to my USB-A which has the both plug and cable side pins facing towards me. I had the USB A wired in reverse!!!

Desoldered, flipped it, resoldered, and it’s now functional!

Wish I could buy you guys a pint!