Here is a quick post about a repair I did for my headphones. I have an older set of Arctis 5 gaming headphones that have begun to show their age. Last year I replaced the earphone cups, but in the past months I've noticed that the insulation on the USB cable had begun degrading; now it's at a point where the insulation is pretty much falling apart.

I decided to replace the cable with a female USB device port, so that I could use any cable I wanted with it in the future. I disassembled the module, and was pleased to see that there were 4 pads where I could easily solder leads for a new USB port. Although, these pads were buried under a gummy layer of epoxy that I needed to use some alcohol and hot air to remove!

I decided to use a USB-C connector, since we had a few breakout boards like this in stock in the maker lab. I soldered wires from the four pads on the module to the appropriate pads on the little dongle, but when I plugged the module into a USB-C port on my PC or my phone, the module never powered up. It would only power up if I used a USB-A to USB-C cable to attach the module to a USB-A port on my PC! My fancy new laptop only has newfangled USB-C ports, so this means that I would need an adapter. A micro-usb breakout board functioned as intended and I was tempted to simply leave the device as such, but a very wise person at the maker lab suggested that the problem might be that I was missing configuration registers.

At this point, it's time for a quick refresher on some USB fundamentals. The USB 2.0 physical layer uses 4 wires: +5V and GND for power, and then a pair of differential data wires called D+ and D-. D- is always the inverse of D+, so it's easy to reconstruct the serial data stream by simply subracting D+ from D-. USB devices place resistors in the D+ and D- that are sampled by the host (e.g. your computer) when the device (e.g. a mouse) is plugged in, and the configuration resistors tell the host whether the device would like to use High-speed communication, or Low-speed communication. I knew about these, and these were the configuration resistors that I initially thought my friend had been talking about.

Well dear reader, it turns out that times had changed since the last time I studied the USB physical specification. USB 3.0 introduced the USB-C connector, which brought with it a raft of new features related to device charging. USB C connectors introduce (amongst a lot more serial data pins for ludicrous transfer speeds) Configuration Channel pins. These pins help two connected USB-C ports decide which one will supply power (called the source), and which port will consume power (the sink). A connected Sink device should connect its CC pins

The USB specification explains how this works in Chapter 3.5. Specifically, section 3.5.7 explains how the USB C receptacle should be wired up:

The breakout board is missing the CC resistors, so from the point of view of my PC (the Source port) there was no device attached (Section 4.5.1.2.1).

I tried to push my fine-pitch soldering skills to the limit by retroactively adding two tiny SMD resistors to the breakout board, but this was far too fragile without appropriate pads. Instead, I purchased some breakout boards from Amazon. A link is in the 'references' section in case you would like to upgrade some of your USB 2.0 devices to USB C ports.

Modeling

Since the breakout board was too large to fit in the equalizer knob enclosure, I designed an extension that could attach to the knob enclosure and 3D printed it. The final result came out pretty nicely! I used a pair of countersunk M3x14mm screws and nuts to keep the extension closed, and support the breakout board. You can download the model for yourself!