I have a StartTech.com 7-port USB 3.0 HUB plugged into a PC. There are seven devices plugged into the hub, and I'm running the 12VDC external power to the HUB as well. The HUB is plugged into a USB 3.0 port on the PC.
If I UNPLUG the power, all devices continue to operate normally. Combined, in full operation, they collectively pull just under 400ma at 4.93VDC. When idle, they draw just under 100ma. Everything is good.
If I return power, that is, I plug-in the 12VDC external power source into the HUB while everything is running, the HUB performs what appears to be a power-on-reset. All devices drop, the current goes to 0.00ma and then the devices come back (via plug-n-play). However comma, SOME devices do not. They don't recover. Windows reports that the hub didn't reset properly.
My question is - is this a normal thing for USB HUBS to do? I've got a number of others and none of them perform a PoR.
I called StarTech.com and got a rather vascillatory response - they aren't sure either.
I'm essentially simulating a power loss scenario. I can't have random pieces of kit not returning to functionality after a PoR from the HUB. The problem really is academic at this point - yes, replace the HUB; simple. However, I'm concerned that we've invested in a number of these if this is normal / to USB-IF spec or flies in the face of convention?