[Nut-upsuser] Tripp-Lite USB constantlly disconnecting.

Charles Lepple clepple at gmail.com
Wed Nov 19 01:40:57 UTC 2014

On Nov 18, 2014, at 6:28 PM, Shade Alabsa <shade34321 at gmail.com> wrote:

> I then noticed that in ups.conf I did not set the pollinterval, we normally set it to 15, so I set it to test on a RHEL 6.6 machine which caused this issue to happen again. On our own custom system we took the poll interval out and prelim testing doesn't showing the repeated disconnects/reconnects. I started playing more with this pollinterval and noticed that up to 14, exclusive, it seems to be fine.

pollinterval defaults to 2, so maybe the UPS is disconnecting due to inactivity on the bus? (It shouldn't, but it might be a workaround for other systems.)

The usbhid-ups driver splits the polling into two categories: "quick updates", to catch OL/OB/LB transitions, and "full updates" to catch everything else. It is possible that the higher pollinterval values are colliding with the pollfreq interval of 30 seconds.

The UPS is requesting that the OS (or in the case of Linux, a program like NUT which uses libusb) poll the interrupt endpoint at least every 40 ms, which is fairly often, and would cause higher CPU load. The defaults in NUT strike a compromise.

Note that the man page for the MGE SHUT driver does recommend a higher value of pollinterval, but that is a special case (it is essentially USB over a serial cable, and the baud rate is not high enough for the defaults) and wouldn't apply to your UPS.

Charles Lepple
clepple at gmail

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