[Nut-upsdev] Best UPS protocol for home-made firmware?

[Chris Boot]

Hi all,

I'm writing the firmware for a home-made 12V UPS, which will be used to 
power low-voltage equipment in my home like my ADSL modem, router, 
switches and a Soekris net4801. The home-made UPS can run those devices 
on the same batteries as my 230V UPS, but last for several hours rather 
than a few minutes due to increased efficiency. The microcontroller I'm 
using has a serial interface that's presented using a USB to serial 
converter.

I'd really like this UPS to interface with NUT so that I can use a 
variety of tools to monitor it, such as Nagios and cacti, etc... I 
really don't want to have to write my own driver for NUT if I can avoid 
doing so, so the main question is which serial interface is the most 
sane for me to implement in my controller. The megatec driver seems to 
be one of the most popular but I can't find much documentation about the 
protocol.

In addition I'm wondering how much NUT looks at various parameters like 
input / battery / line voltage, since in my case it would be 12-18V and 
not the more common 110/230V. :-)

Once finished I plan to open-source my firmware (written in a mix of 
C/C++ for the Arduino IDE for AVR microcontrollers) and document my 
build for all to see.

Thanks,
Chris