Dustin Holden, the brains behind the Project Stellar Xbox mod, has just revealed how he uncovered a "hidden" USB port on the original Xbox after five years of research.
In a lengthy thread on Twitter, Holden explains that the venture began in 2018, when fellow modder @Ryzee119 released the 'OGX360' mod, which allows four Xbox 360 wireless controllers to connect to the original Xbox.
The release of this mod caused many people to ask if an internal solution was possible. It was then discovered that the Nvidia chipset used in the Xbox family “supports” six USB ports. The next step was to reverse-engineer the PC motherboard and cross-reference it with the Xbox motherboard – at which point, a "secret" USB port was found, separate from the four controller ports.
"So that’s it, everything works now?" says Holden. "Not quite. This is where this part of the project went dormant for years. Unused Xbox USB ports have overcurrent tied high, so OHCI detects a device but won’t enumerate it. The signal isn’t exposed outside the BGA footprint, so there’s no hardware fix."
On the software side, Holden had to submit a Pull Request to the open-source Xbox toolchain "to fix the overcurrent issue and add support for the internal USB port." This led to even more work. "XDK titles (retail + older homebrew) are tougher," he explains. "The USB stack is baked into each game and wasn’t designed for this. Over 6 months, we uncovered numerous bugs in Microsoft’s stack - requiring 250,000+ patches."
However, the groundwork laid here makes the new Project Stellar Plus mod possible. Stellar Plus is described by Holden as "the world's most powerful add-on for the Original Xbox" and has been "built on years of research and a commitment to pushing the limits. It opens the door to what’s next."
Stellar Plus features new hardware, faster components, built-in Wi-Fi, Bluetooth Classic, and Bluetooth Low Energy, the latter two features being powered by BlueRetro. This means you can connect wireless controllers, power on your console remotely and apply firmware updates over Wi-Fi.
The new version of the mod also enjoys "deeper integration" with StellarOS, the first legal re-implementation of the Xbox BIOS.