So I’m working on a custom Framework 13 based device and I desperately need more USB ports. It has already been demonstrated that this is possible with the input cover interface. If you look at the PCB file in KiCad, it is very straightforward. It’s essentially just a breakout board that routes all GND pins to a single through hole and provides three additional through holes for D+, D-, and either 5VS or 5ALW (user’s choice).
I am wondering if a similar setup could be implemented using the webcam interface, and possibly even the display interface.
Looking at the pinouts, the webcam is already wired as a USB 2.0 device, but unfortunately it runs on 3.3V instead of the 5V needed for a standard USB port. Assuming all 5V sources on the board share a common rail, it seems theoretically possible to tap into another source, but which one? Obvious candidates include the fan header or the unused 5V on the input cover. However, it is unclear to me how to determine whether any of these can reliably supply an additional 500 mA. The same uncertainty applies to the GND line. Would the existing webcam GND be sufficient, or would GND also need to be sourced from elsewhere? Without a reliable way to verify this, it feels like a bit of a dice roll.
As for the display connector, D+ and D- do show up in the pinout, but it is unclear if they are actually implemented. I imagine it would be fine to tap into them and test, but the +5V and GND sourcing questions remain. In this case, it is further complicated by the fact that the display side pinout splits GND into multiple categories: Signal GND, Digital GND, and Backlight GND. Presumably these cannot be bridged without breaking the display functionality or worse.
I would really like to make this work, but I am not entirely sure how to proceed. If anyone has tried something similar, or spots anything I have overlooked, I would greatly appreciate your input. If I can’t reach a definitive answer, then I’ll probably just have to pick up a secondhand mainboard and send it, but I would prefer not to burn money on this if it can be avoided.