I am working on an Arcade Stick/Fight Stick enclosure. Internally, the PCB (Brook UFB) runs USB over a standard Ethernet cable, to a Neutrik RJ45 passthrough. I typically then create an RJ45 to USB A cable to use the Arcade Stick on my PC, and I have never had any issues with this in previous builds.

I decided I wanted the convenience of the symmetrical USB C connector. I purchased a USB A to USB C cable, cutoff the USB A end, and wired it to the RJ45. This particular cable has only Red (VCC), Black (GND), Green and White (D-/D+) conductors. After plugging the cable in to my PC's USB C port, the PCB does not power up. When I plug the cable into a USB A port using a USB C to USB A adapter, everything works just fine. What might be going on here? Thanks for any insight you can provide.

For reference, the Brook PCB RJ45 USB pinout is below.


3 D-

4 D+



closed as off-topic by Matt Young, Jasen, Finbarr, RoyC, Lior Bilia Dec 2 '18 at 14:28

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  • 1
    \$\begingroup\$ questions about the use of computer peripherals belong on superuser.com \$\endgroup\$ – Jasen Nov 28 '18 at 5:22
  • \$\begingroup\$ @Jasen, this is not about the "use", it is about a device rework for a different connector type. \$\endgroup\$ – Ale..chenski Nov 28 '18 at 6:28
  • \$\begingroup\$ it's just a matter of using the correct cables \$\endgroup\$ – Jasen Nov 28 '18 at 17:59
  • \$\begingroup\$ @Jasen It's not just a matter of using the correct cables, as the correct cables do not exist - unless you are aware of a 15ft RJ45 to USB-C cable pre-made, this requires a custom made cable. I was most interested in the technical reasoning the cable worked via A to C adapter, but not directly plugged into a C port. Ale..chenski's answer address the issue. \$\endgroup\$ – roadrunner343 Nov 28 '18 at 18:03
  • \$\begingroup\$ type C OTG adaptor + regular USB cable gets you there. \$\endgroup\$ – Jasen Nov 28 '18 at 19:10

Your rework doesn't work because you used wrong Type-C cable.

The Type-A to Type-C cable is designed to plug its A-end into the standard Type-A USB host PC port. To make it look like a host in Type-C standard the Type-C end is wired as "host". This means that one of CC pin is pulled up to VBUS with 56k resistor, and this signifies that this Type-C end is "host side". This resistor is embedded into Type-C overmold, and you can't access or change it without destroying the connector housing. So when you plug this end into your Type-C PC port, you are connecting USB host to USB host, and your PC port doesn't engage.

You are however making a USB device. Type-C port on USB device must have 5.1k pull-down. If you manage to have your Type-C end with 5.1k pull-down on CC pin, this pull-down will connect with CC pull-up inside your Type-C port, and the PC port will recognize it as a device, and will turn the VBUS on, and everything will be fine.

To manage the correct CC pull-down you either need to find a Type-C plug fixture like this one,

enter image description here

Or use so-called Type-C OTG Adapter, and cut the A-receptacle side:

enter image description here

This Type-C end has correct pull-downs, but might be a bit short for your purpose.

  • \$\begingroup\$ Thanks for the clear explanation. I suspected something like this may be going on. I have used USB-C female ports in projects in the past, so I was familiar with the 56k pull-up resistor, but did not know about the 5.1k pull down. Luckily, I have some of those connectors on hand. My concern is, how do I go about making a very sturdy connection? Simply soldering and heat shrink wrapping will not be strong enough, but I've not seen any DIY mold/strain relief connectors for USB C ports. \$\endgroup\$ – roadrunner343 Nov 28 '18 at 12:42

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