[Nut-upsdev] APC Back-UPS 500

Rob Crittenden rcrit at greyoak.com
Fri Dec 30 01:11:05 UTC 2005

I'm using nut 2.0.2 from Fedora Core 4 and had some trouble getting my 
APC Back-UPS 500 working. I ended up having to rebuild the RPM myself 
after making some code changes.

I had to increase the upsd synchronization timeout from 5 to 15 seconds. 
It seems like 10 is the sweet spot but allowing a few extra seconds 
doesn't seem to hurt anything. At 5 the UPS would timeout 5 out of 6 times.

The second problem is that my UPS, a USB model using the newhidups 
driver, doesn't send PresentStatus (840002) in its updates. This means 
that ups.status is always empty and upsmon has a fit over it.

My fix was to simply remove "PresentStatus." from the ups.status entries 
in apc-hid.h. I haven't been able to come up with any sort of 
semi-elegant solution for this. My fix could break any UPS that relies 
on PresentStatus for its updates.

This is a pretty old UPS. I worked with Russell back in 2001 (nut-0.45 
era) to get it working once before with the first USB driver (nutusb.c). 
So it may be that it simply isn't complaint to the spec and should be 
ignored. I looked at the spec and it is a tad unclear to me whether it 
is required or not.

I'm open to suggestions.


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