Back UPS Pro 900GR - unable to connect to Nut using a serial connection

[Anonymous user]

Hi all,
I'm trying to configure Nut (http://www.networkupstools.org/) to connect to a newly
bought APC BackUPS Pro 900VA. Therefore I've connected it to a serial port using the
original APC 940-0128D cable. Unfortunately I've not yet managed to read any data
from the ups.
If I try to load the apcsmart driver it tells me that it cannot communicate with the ups.
In the meantime I learned that the UPS should only understand an APC specific *simple*
serial protocol which is not compatible with a standard serial protocol 😞
I fear that I've spend money for that UPS without realising this important difference.

Could anyone tell me if it will be possible at all to communicate to the UPS using Nut?

Thanks

J.ED

[Anonymous user]

You won't be able to use smart signaling (or the APC Smart protocol) over serial with nut and your Back-UPS Pro 900. Only simple signaling capability is provided when you use a serial port (if that much -- I'm not certain that anything newer than the white tower XS/RS models actually support simple serial signaling any longer).

The simple signaling protocol will provide "on battery" and "low battery" notifications, as well as a way for the computer to request the UPS to turn off when everything has been safely shut down. So it's not very fancy but it is better than nothing. I believe nut can support this, and if using different UPS management software is an option, apcupsd  definitely will. (I have personally done the latter.)

If a USB connection is an option, nut will certainly support it (using the generic HID UPS driver) and you will get a lot more information from the UPS. apcupsd  also supports communication over the USB  cable.

If you require smart signaling over a conventional serial port, the Smart-UPS is probably your best bet. Be aware that the newer (around 2010-2011 to the present day) Smart-UPS models no longer use the old APC  smart (UPSlink) protocol. They use a closed protocol known as Microlink  that apcupsd  and nut do not support. Current production models can optionally communicate over modbus, and some older Microlink  models can have their firmware updated to add such capability. apcupsd  does support Modbus, I don't know about nut. There's also a legacy communications card available for Microlink  UPSes  that provides UPSlink  support.

[BillP · Accepted solution]

Hi William,

One correction to your post, APCUPSD will communicate with MicroLink UPS via USB. The difference is between MicroLink and UPSLink with APCUPSD is you will see - receive more data from a UPSLink than a MicroLink.See screen shots below.

MicroLink

 

The above screen shot is from a SMX1500 connected to Windows 7 OS running APCUPSD version 3.14.13 USB Comm

UPSLink

The above screen shot is from the same SMX1500 but with the AP9620 card installed USB Comm.

APCUPSD also offers communications via Modbus (serial and USB). Some but not all MicroLink UPS support comm via Modbus. We have Application Note 176 that discusses Smart-UPS and Modbus.