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Hobbyist turns $45 USB-C hub into a working Nintendo Switch 2 dock by patching its firmware
The hub now tells the console it’s Nintendo’s own dock.
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A hobbyist going by mkopec turned an approximately $45 Cable Matters USB-C hub into a working Nintendo Switch 2 dock, using only about 540 bytes of code to mod the firmware. That mod lets the hub masquerade as an official dock, as mkopec detailed in a blog post. The edited firmware replies to Nintendo’s vendor messages and returns the same identity as the official dock, and makes TV mode work, which was not the case with the hub’s stock firmware. A separate fix with minor firmware rewriting also corrects washed-out HDR over HDMI, a nice bonus.
The modder, who writes that “Nintendo went in a proprietary direction (as they so often do),” decided to modify the hub’s firmware to make a working travel dock, as Nintendo’s official dock can be bulky. Unlocking the additional functionality did not come with a noticeable cost, as the hub “still works normally with my PC and my phone.” Grabbing an off-the-shelf USB-C hub and turning it into something more is quite the trick.
The stock hub has no problem charging the console, but it shows no picture, even though it negotiates both power and DisplayPort Alt Mode. Capturing the official Switch 2 dock’s traffic with a USB Power Delivery (USB-PD) sniffer, the modder found that it advertises two Standard or Vendor IDs: one for DisplayPort and one for Nintendo’s own mode.
The console enters Nintendo’s mode first, then DisplayPort, and, once DisplayPort is configured, it sends Nintendo’s vendor messages. This is the exchange of proprietary messages for negotiation, although the company told us last year that it “does not have any intention to hinder or invalidate legal third-party dock compatibility.”
The modification only required adding about 540 bytes to a firmware of just 32 KiB. The Cable Matters 7-in-1 triple display hub, like most, is simply an amalgamation of separate, specialized chips, in this case: a VL103 as the USB-PD controller, a VL817 USB hub chip for the USB ports, an RTD2142 DisplayPort Multi-Stream Transport chip for the DisplayPort-to-HDMI function, and XT25F16B flash memory chips. The VL chips are from VIA Labs, the RTD2142 is from Realtek, and the stock hub reports VIA’s vendor ID, which is an identity that needed to be changed for this mod.
The modder first used the WITRN K2 inline USB-PD sniffer on the official dock. Then, it was a matter of dumping the VL103’s firmware with the vli plugin of fwupd, the Linux firmware update tool, before flashing the VL103 with the changes over USB and through the VL817.
Changes were made incrementally, with seven versions in all, starting with answers to Nintendo’s discovery, mode entry, and echo commands, then an update to power delivery to offer 15 V at 2.8 A like the dock, changing the reported vendor ID to Nintendo’s, masquerading entirely as the official dock and getting TV mode working, and finally a full sequence match that removed a pause of about 3 seconds.
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