108 lines
4.4 KiB
Text
108 lines
4.4 KiB
Text
Desc: Contact closure hardware
|
|
File: contact-closure.txt
|
|
Date: 14 March 2004
|
|
Auth: Russell Kroll <rkroll@exploits.org>
|
|
|
|
This is a collection of notes that apply to contact closure UPS
|
|
hardware, specifically those monitored by the genericups driver.
|
|
|
|
Definitions
|
|
-----------
|
|
|
|
"Contact closure" refers to a situation where one line is connected to
|
|
another inside UPS hardware to indicate some sort of situation. These
|
|
can be relays, or some other form of switching electronics. The generic
|
|
idea is that you either have a signal on a line, or you don't. Think
|
|
binary.
|
|
|
|
Usually, the source for a signal is the host PC. It provides a high
|
|
(logic level 1) from one of its outgoing lines, and the UPS returns it
|
|
on one or more lines to communicate. The rest of the time, the UPS
|
|
either lets it float or connects it to the ground to indicate a 0.
|
|
|
|
Other equipment generates the high and low signals internally, and does
|
|
not require cable power. These signals just appear on the right lines
|
|
without any special configuration on the PC side.
|
|
|
|
Bad levels
|
|
----------
|
|
|
|
Some evil cabling and UPS equipment uses the transmit or receive lines
|
|
as their reference points for these signals. This is not sufficient to
|
|
register as a high signal on many serial ports. If you have problems
|
|
reading certain signals on your system, make sure your UPS isn't trying
|
|
to do this.
|
|
|
|
Signals
|
|
-------
|
|
|
|
Unlike their smarter cousins, this kind of UPS can only give you very
|
|
simple yes/no answers. Due to the limited number of serial port lines
|
|
that can be used for this purpose, you typically get two pieces of data:
|
|
|
|
1. "On line" or "on battery"
|
|
2. "Battery OK" or "Low battery"
|
|
|
|
That's it. Some equipment actually swaps the second one for a
|
|
notification about whether the battery needs to be replaced, which makes
|
|
life interesting for those users.
|
|
|
|
Most hardware also supports an outgoing signal from the PC which means
|
|
"shut down the load immediately". This is generally implemented in such
|
|
a way that it only works when running on battery. Most hardware or
|
|
cabling will ignore the shutdown signal when running on line power.
|
|
|
|
New genericups types
|
|
--------------------
|
|
|
|
If none of the existing types in the genericups driver work completely,
|
|
make a note of which ones (if any) manage to work partially. This can
|
|
save you some work when creating support for your hardware.
|
|
|
|
Use that information to create a list of where the signals from your UPS
|
|
appear on the serial port at the PC end, and whether they are active
|
|
high or active low. You also need to know what outgoing lines, if any,
|
|
need to be raised in order to supply power to the contacts. This is
|
|
known as cable power. Finally, if your UPS can shut down the load, that
|
|
line must also be identified.
|
|
|
|
There are only 4 incoming and 2 outgoing lines, so not many combinations
|
|
are left. The other lines on a typical 9 pin port are transmit,
|
|
receive, and the ground. Anything trying to do a high/low signal on
|
|
those three is beyond the scope of the genericups driver. The only
|
|
exception is an outgoing BREAK, which we already support.
|
|
|
|
When editing the genericups.h, the values have the following meanings:
|
|
|
|
Outgoing lines:
|
|
|
|
line_norm = what to set to make the line "normal" - i.e. cable power
|
|
line_sd = what to set to make the UPS shut down the load
|
|
|
|
Incoming lines:
|
|
|
|
line_ol = flag that appears for on line / on battery
|
|
val_ol = value of that flag when the UPS is on battery
|
|
line_bl = flag that appears for low battery / battery OK
|
|
val_bl = value of that flag when the battery is low
|
|
|
|
This may seem a bit confusing to have two variables per value that
|
|
we want to read, but here's how it works. If you set line_ol to
|
|
TIOCM_RNG, then the value of TIOCM_RNG (0x080 on my box) will be anded
|
|
with the value of the serial port whenever a poll occurs. If that flag
|
|
exists, then the result of the and will be 0x80. If it does not exist,
|
|
the result will be 0.
|
|
|
|
So, if line_ol = foo, then val_ol can only be foo or 0.
|
|
|
|
As a general case, if line_ol == val_ol, then the value you're reading
|
|
is active high. Otherwise, it's active low. Check out the guts of
|
|
upsdrv_updateinfo() to see how it really works.
|
|
|
|
Custom definitions
|
|
------------------
|
|
|
|
Late in the 1.3 cycle, a feature was merged which allows you to create
|
|
custom monitoring settings without editing the model table. Just set
|
|
upstype to something close, then use settings in ups.conf to adjust the
|
|
rest. See the genericups man page for more details.
|