Making a DIY usb hub with per-port-power-switching using an existing hub.
So you want to use uhubctl to do power control for USB devices but like everyone else you found that hubs with PPPS wired up are rare.
If you can find a USB hub with buttons like the RSH-516-4 then the chances are that the buttons drive transistors/mosfets to control VBUS. If the hub chip inside exposes all of the PPPS control signals like the RTS5411 in the RSH-516-4 does then you can remove the buttons and wire the PPPS control signals to the VBUS transistor/mosfets instead and have a PPPS capable USB hub.
For the RSH-516-4 this wasn't so easy. There are pads in the footprint for the signals but the PCB is apparently made of toilet paper. One hub died during this experiment because all of the pads including the usb signal pads came off the board when trying to attach wires to the PPPS signals.
It is much easier to grind off the corner of the chip where the PPPS signals are and solder directly to the lead frame instead. See the photos to see what I did but the basic idea is to slowly use a file on the corner of the RTS5411 to expose the 4 PPPS signals. Go slow to avoid going right through the lead frame. Once some metal is exposed you can tin the metal and have some pads to solder on to. The soldering process is difficult but not impossible. Once you have good connections use some 5 minute epoxy to make everything solid and then you can attach your PPPS signals to the pads from the buttons.
Maybe a small flex pcb could make this process easier.
- RSH-516-4 - Realtek RTS5411 - can be done, need good soldering skills
- "Atolla USB 3.0 HUB " - Renesas UPD720210 - Much easier, PPPS pins are brought out onto resistors so you can very easily tack wires on. PPPS signals are 3.3v and push-pull and can't directly drive the p-channel mosfets used to control the VBUS lines. You need a 3.3V -> 5v logic doodad or make some transistors to drive the mosfet gates. See here.
- Sabrent 4 port (HB-UM43): GL3510 hub doesn't have per port port control pins switches directly connect and disconnect VBUS from the ports.