Nut upsuser - Mar 2014 - Generic UPS with serial port

Just a quick query. I had a CPS ups (1200watt) with only a serial port, 
no usb. It worked fine using the genericups driver for some years until 
it committed suicide in a cloud of smoke. No replacement available, was 
forced to try running without the ups but then Ubuntu shutdown 
immediately it was up and ready for logons. Seems the driver was 
mistaking the absence of signals for a problem condition. No big deal - 
just removed the init files and all ok temporarily. Just wondered if 
maybe a small mod might be in order to prevent this. When I got the 
serial port address wrong in the beginning, it just gave off repeated 
messages about the lack of connection, did not shut down.
Have not found anything through Google so far.
Many thanks for all the good work - I really need a ups down here - 
power failures are frighteningly frequent.
Bill

On Mar 11, 2014, at 7:51 AM, William D Turner wrote:
> Seems the driver was mistaking the absence of signals for a problem
condition. No big deal - just removed the init files and all ok temporarily.
Just wondered if maybe a small mod might be in order to prevent this.
I agree that this would be frustrating.

The problem is that for a number of different genericups types (including your
instance, it seems), there is no way to tell for sure whether an UPS is
connected. If the UPS has both sets of relay contacts available (normally open,
and normally closed), you could probably find a configuration that defaults to
"OL" when the cable is unplugged. Remember that the only inputs
available are two binary signals, and there is no "carrier detect" on
a bare serial cable with no data lines connected.

Another thought for those forced to use genericups is to have a loopback DE-9
connector on hand which emulates the "OL" status. I don't see a
CPS model using genericups on our compatibility list, but you could basically
wire the Cable Power (CP) pin to the OL pin.

Come to think of it, we could probably print a warning if the configuration type
is likely to cause a shutdown when the UPS and cable are disconnected.

However, this is specific to the genericups driver: all of the other drivers
(that I am aware of) will do some rudimentary handshaking when they start. Even
the simple USB UPS models which can only report OL/OB/LB will still produce
"Data stale" notifications if the USB cable is pulled.

-- 
Charles Lepple
clepple at gmail