Add support for new APC Modbus protocol

[aquette]

From APCUPSD (http://apcupsd.cvs.sourceforge.net/viewvc/apcupsd/apcupsd/ReleaseNotes?pathrev=Release-3_14_11):
"APC publicly released documentation[1] on a new UPS control and monitoring protocol, loosely referred to as MODBUS (after the historic industrial control protocol it is based on). The new protocol operates over RS232 serial lines as well as USB connections and is intended to supplement APC's proprietary Microlink protocol. Microlink is not going away, but APC has realized that third parties require access to UPS status and control information. Rather than publicly open Microlink, they have created another protocol to operate along side it.

Many existing Microlink UPSes can be upgraded to support MODBUS via a firmware update. See [2]. Certain older models are not upgradeable. APC support will be your best contact for determining if your UPS supports a MODBUS upgrade the information linked below does not make it clear."

[1] http://www.apc.com/whitepaper/?an=176
[2] http://www.schneider-electric.us/support/index?page=content&country=ITB&lang=EN&id=FA164737
[3] http://www.apcupsd.com/manual/manual.html

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Add support for MODBUS over RS232 and USB in NUT.
This effort must be synchronized with the general Modbus support in NUT ( #50 )

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Implementation notes:

• serial version: use the serial RTU support from libnutdrv_modbus (WIP)
• USB version: 2 possibilities
  • create a HID subdriver, that marshals Modbus => better integration, easier for users
  • create a new driver, which uses interrupt support in NUT libusb, but not libhid (for the 2 usages ModbusRTURx and ModbusRTUTx) => smaller driver footprint

[ggershwf]

I'm not having much success with this, unfortunately. I'm sure I'm doing something wrong, but I'm not sure what. I've got an APC Smart UPS 1500 (made in 2013). It appears that I've defined it correctly, since the drivers starts, but I get a continuous stream of "Data Stale" from upsmon. I am using Network UPS Tools upsc 2.6.5, if that makes any difference.

[clepple]

@ggershwf if you are referring to the nutdrv-modbus branch, then as of commit eddcd7e, the driver does not actually retrieve anything yet. It just links against the modbus library, and attempts to open the serial device.

It does not matter if you use an earlier version of upsc - as seen in the README file, any 2.0+ client (e.g. upsc) can talk to a 2.0+ server. The interface that is not guaranteed to be stable between versions is the driver-upsd socket interface.

[clepple]

@aquette link 1 is broken; searching for the filename turned up this:

http://www.apcmedia.com/salestools/MPAO-98KJ7F/MPAO-98KJ7F_R0_EN.pdf

The paragraph at the bottom of the second page looks troubling.

[ggershwf]

@clepple Thanks. I guess it's working up to that point, then.

[aquette]

Yep guys, sorry.
I was in the middle of this when I got caught by family vacations.
Resuming ops...

(sent from my eeePad... please excuse my brevity)

[jeffsf]

I'd definitely like to see this as well, especially as SUA-series APC units that aren't trashed are getting pretty scarce and the SMT-series units are coming down to a reasonable point (finally).

I have two SMT1500 units that I can work with here to help support the effort.

[anthonysomerset]

throwing my hat into the ring with an offer to support with testing

i have an SMT2200

ups.firmware: UPS 09.3 / ID=18 ups.mfr: American Power Conversion
ups.mfr.date: 2016/11/26 ups.model: Smart-UPS 2200
ups.productid: 0003

[edalquist]

Is there any progress here? I have a SMC1500 and two SMT1500s. They both have basic functionality in NUT but don't report input/output voltage or load.

"All Data" dumps of the two units: https://gist.github.com/edalquist/3fb91870830242fe8016710449ce0a14

[clepple]

Question for those who have offered to test: does your APC UPS have a serial port, and if so, do you know if it supports MODBUS?

I ask because the effort mentioned in issue #50 seems to be focused on using libmodbus - but that library currently supports only serial and TCP. APC's method of tunneling MODBUS over USB HID reports is probably similar to the serial stream, but it sounds like it will involve rewriting a lot of code.