NUT and libusb 1.0

As part of changes between NUT releases 2.7.4 and 2.8.0, master branch included support for libusb-1.0 in addition to libusb-0.1 (discussed and merged in issue #300). There still are some known connectivity stability issues, some were roughly associated with the older library and its architecture so a rebuild of NUT against the newer library can help. In some reports, that did not help either.

Generally it seems like many USB chip makers cut corners and do not support everything required by protocol standards, so no reason to expect their hardware to be stable either. Using bogus vendor and product IDs can also indicate a cheap make, beside making it hard to identify a device and suitable protocol, but some big-name devices were also reported.

Still, in some reports the issue was resolved by changing the USB cabling (aging connectors, lack of noise protection...) so do give that a try.

Finally, if your OS includes features to manage USB devices and then hand off to practical daemons, such as upower, ugen, udev... - check that part of the setup to make sure that it does not "kidnap" the device (active connection, device node FS rights and ownership, etc) but instead does set it up for NUT run-time user to use. This may be more of a concern on systems where NUT was not delivered by distro packaging integrated with features of the OS, but built from source and copied into the system "ad hoc".