Serving tech enthusiasts: Plug a Switch 2 into an ordinary USB-C hub and it will charge, but the TV stays dark. That's because the console won't send a picture until the hub answers a proprietary handshake. Nintendo's $125 dock knows the replies, as do third-party docks built to mimic it. Now, a hobbyist has taught a roughly $45 laptop hub the same trick by rewriting a sliver of its firmware.
The hobbyist, who goes by mkopec, explained in a blog post that Nintendo's dock is simply too bulky to travel with. A €40 ($44) Cable Matters 7-in-1 hub looked like a neat replacement, since it already takes video over USB-C. But hooked up to a Switch 2, it only charged the console.
Nintendo's handheld is far stricter about docks than the original Switch, so mkopec put a USB-C sniffer between the console and its official dock. The dock introduced itself as a Nintendo product and offered two modes: regular DisplayPort and Nintendo's own. Oddly, the Switch picks the Nintendo mode first, then fires off a string of vendor-specific messages before any picture appears.
To answer them, mkopec squeezed about 540 bytes of code into empty space on the hub's VIA Labs power-delivery chip. The patch handles Nintendo's messages and passes everything else to the stock firmware. Weirdly, just claiming to be a Nintendo device wasn't enough. TV mode only came to life on the fifth version of the patch, once the hub copied the dock's full identity.
Even so, HDR games looked washed out at first. As mkopec put it, "the pixels were fine all along, only the label was wrong." Specifically, the Realtek chip that converts the hub's video to HDMI was tagging HDR frames with a standard-range color space. So mkopec wrote a 108-byte fix for that chip and flashed it over the same USB-C cable.
Posing as the official dock also unlocked a setting the real one never gets. Nintendo's dock doesn't support variable refresh rate on TVs, yet the Switch now offers VRR through the patched hub. Sadly, the hub's display chip can't keep up with it either. Turning VRR on froze the DisplayPort picture, so mkopec suggests leaving it off.
For anyone brave enough to try it, mkopec has since published a patcher on GitHub. It only supports this one Cable Matters model with untouched stock firmware, and the patcher must be run from a Linux PC. The README also warns that a botched flash can brick the hub.
Of course, even commercial docks haven't had it easy. Nintendo's 21.0.0 update last November cut video output to plenty of them overnight, leaving their makers to rush out firmware fixes. There's nobody pushing updates for a hand-patched hub, so a future system update could just as easily turn it back into a charger.