108 lines
4.3 KiB
Plaintext
108 lines
4.3 KiB
Plaintext
Contact closure hardware information
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This is a collection of notes that apply to contact closure UPS
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hardware, specifically those monitored by the genericups driver.
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Definitions
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~~~~~~~~~~~
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"Contact closure" refers to a situation where one line is connected to
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another inside UPS hardware to indicate some sort of situation. These
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can be relays, or some other form of switching electronics. The generic
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idea is that you either have a signal on a line, or you don't. Think
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binary.
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Usually, the source for a signal is the host PC. It provides a high
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(logic level 1) from one of its outgoing lines, and the UPS returns it
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on one or more lines to communicate. The rest of the time, the UPS
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either lets it float or connects it to the ground to indicate a 0.
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Other equipment generates the high and low signals internally, and does
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not require cable power. These signals just appear on the right lines
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without any special configuration on the PC side.
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Bad levels
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~~~~~~~~~~
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Some evil cabling and UPS equipment uses the transmit or receive lines
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as their reference points for these signals. This is not sufficient to
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register as a high signal on many serial ports. If you have problems
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reading certain signals on your system, make sure your UPS isn't trying
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to do this.
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Signals
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~~~~~~~
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Unlike their smarter cousins, this kind of UPS can only give you very
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simple yes/no answers. Due to the limited number of serial port lines
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that can be used for this purpose, you typically get two pieces of data:
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1. "On line" or "on battery"
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2. "Battery OK" or "Low battery"
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That's it. Some equipment actually swaps the second one for a
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notification about whether the battery needs to be replaced, which makes
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life interesting for those users.
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Most hardware also supports an outgoing signal from the PC which means
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"shut down the load immediately". This is generally implemented in such
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a way that it only works when running on battery. Most hardware or
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cabling will ignore the shutdown signal when running on line power.
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New genericups types
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~~~~~~~~~~~~~~~~~~~~
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If none of the existing types in the genericups driver work completely,
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make a note of which ones (if any) manage to work partially. This can
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save you some work when creating support for your hardware.
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Use that information to create a list of where the signals from your UPS
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appear on the serial port at the PC end, and whether they are active
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high or active low. You also need to know what outgoing lines, if any,
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need to be raised in order to supply power to the contacts. This is
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known as cable power. Finally, if your UPS can shut down the load, that
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line must also be identified.
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There are only 4 incoming and 2 outgoing lines, so not many combinations
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are left. The other lines on a typical 9 pin port are transmit,
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receive, and the ground. Anything trying to do a high/low signal on
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those three is beyond the scope of the genericups driver. The only
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exception is an outgoing BREAK, which we already support.
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When editing the genericups.h, the values have the following meanings:
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Outgoing lines:
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- line_norm = what to set to make the line "normal" - i.e. cable power
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- line_sd = what to set to make the UPS shut down the load
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Incoming lines:
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- line_ol = flag that appears for on line / on battery
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- val_ol = value of that flag when the UPS is on battery
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- line_bl = flag that appears for low battery / battery OK
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- val_bl = value of that flag when the battery is low
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This may seem a bit confusing to have two variables per value that
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we want to read, but here's how it works. If you set line_ol to
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TIOCM_RNG, then the value of TIOCM_RNG (0x080 on my box) will be anded
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with the value of the serial port whenever a poll occurs. If that flag
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exists, then the result of the and will be 0x80. If it does not exist,
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the result will be 0.
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So, if line_ol = foo, then val_ol can only be foo or 0.
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As a general case, if 'line_ol == val_ol', then the value you're reading
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is active high. Otherwise, it's active low. Check out the guts of
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upsdrv_updateinfo() to see how it really works.
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Custom definitions
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~~~~~~~~~~~~~~~~~~
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Late in the 1.3 cycle, a feature was merged which allows you to create
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custom monitoring settings without editing the model table. Just set
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upstype to something close, then use settings in ups.conf to adjust the
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rest. See the linkman:genericups[8] man page for more
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details.
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