The trouble with tribbles.. I mean USB hubs.

[KA5BBC]

So I discovered that there are several issues with the use of USB hubs with this project, many already documented by other people. I dug significantly deeper than I usually do as this was causing me as much consternation as getting the non-standard audio cards working. It appears that our trouble come down to two main issues:

Backpowering.. This is when a USB hub which is poorly/cheaply constructed feeds voltage back into the Raspberry Pi. This has been a known issue for at least two generations of Raspberry Pi and has been addressed in several wikis and forums. There are two solutions.. The first is to buy one of the many USB hubs which have been confirmed as safe and correctly operational with the Raspberry Pi's. The second is to modify/repair your existing USB hub by fitting a diode on the 5V line to prevent any voltage returning to the Raspberry Pi.

Available current for devices.. Most powered USB hubs come with power supplies somewhere between 500mA and 2A. If you add up the maximum drain for each device that you plug into one of these hubs you will find that, per the spec of the individual ports or the maximum available for all ports, there is woefully insufficient current to run all the devices plugged in - especially SDR transceivers or AV devices. Again there are two solutions.. The first is to upgrade from the supplied power supply to one which can provide the necessary current, this is only applicable where the rating for each port will then support the devices. The second is to obtain one of the working and stable USB hubs which are safe for use with a Raspberry Pi - again ensuring that both overall and individual port current is sufficient for our needs.

Having obtained a couple of different hubs, listed as tested and working correctly, I was able to run the SDR transceivers, AV devices, and audio cards from a hub with no more instabilities.

Here is a link to one list of tested and known working devices as well as those which are problematic and those which do not work at all - It was last edited 2 years ago however provides a good guide as to what we are looking for in newer models (I have actually found several of them available new or used locally just a day).
https://elinux.org/RPi_Powered_USB_Hubs