This is an answer to a question calberts asked in a thread on FS2 controllers . I Thought it better to open a new thread to answer.

Hi Chris,

USB hubs (or rather USB as such) are a major and most annoying topic. You will find an number of concerning topics in this forum

Only recently we tested 7 different powered USB hubs (USB2 as well as USB3) connected to the controlling PC of our public observatory and than connected to two different Fujitsu laptops, all running KStars/EKOS/INDI
.
The hubs were connected to the PC/laptops by high qualitiy "active" 3m USB2 and USB3 cables which had been tested successfully separately with every single device. The hubs then were step-wise "loaded" with a Canon 750D, a QHY5LII mono, a MGen autoguider, and a SonyA7II - no mount controller was attached since that worked over a RS232 serial connection. But I found mount controllers are a minor issue on hubs.

Result of our tests: only 3 out of 7 hubs worked at all with all devices attached (one USB3 hub, the two others were USB2) - but only one of the USB2 hubs worked satisfying when connected to the laptops as well!
Connected to the laptops one or another hub would work with more or less devices attached. Some hubs worked part-time with only some of the devices connected, some combinations of hub and devices failed completely. Different USB cables between hub and devices were tested and these obviously come in different qualities as well. Starting streaming from the QHY also seemed to degrade the stability of the connections. And to some extent bugs or some kind of sensitivity on the side of the INDI drivers might as well interfere and stop devices from working at all.

Our results which, i am afraid, will differ from those of others with different setups, are as follows:
USB2 tends to be more stable/reliable with most devices; hub power should be at least 3,5A at 5V. Use high quality cables as well. The male connectors should fit firmly and not shaky. And make sure not to use a mere charging USB cable! (Happened to us while testing) Streaming devices should connect directly to an USB port at the PC. We believe one has to try out combining material until it works reliable - and that may change with an additional device.

I still wonder how people get these USB devices to work, especially cameras, connected to a RasPi?!

PS: At our observatory we changed to a compact € 300 PC with 10 USB ports that are connected to two internal hubs (USB2 and USB3) and use long (>= 2m) USB cables to connect to the devices. (OK, one USB hub is used to power some cross-hair LEDs).

CS
Michael

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