Reverse engineering the Mastervolt Master Adjust / Mass Combi communication protocol

[jagter]

Dear Lomax,

I am really impressed with your work.

Have you made any further progress on decoding the protocol and building a MassCombi communication module?

[AKA-None]

I wonder if this would be the same as other items in mastervolts catalog

[sailjumanji]

Wow, that's a lot of work. I have a Seawind 1160 Lite that uses Mastervolt equipment. Have a Solar Chargemaster, a Mass Combi, a couple of Mac Plus DC-to-DC chargers, and an MLI Ultra 12-5000 LiFePO4 battery. (Plus a MV AGM start battery.) The equipment is all connected together on a Masterbus system, most of it just daisy-chained with the green connector cables. The MassCombi does require an interface box, and there is a USB interface that allows connection to my computer. (I also have a Mastervolt Easy View display, that allows me to quickly look thru each piece of equipment, monitor, etc. Even turn some equipment on and off. Very convenient to monitor instead of hooking up the laptop.)

Anyway, with everything linked via the Masterbus network, and the USB interface connected to my computer, I can use MasterAdjust software to adjust and program every piece of equipment on the network. It also has the ability to record data for every piece of equipment concurrently, in as little as one second increments - which is invaluable to identify problems. (Although I usually log on 10 second intervals.) You can save the data, import into Excel, and easily plot an of it. The software is free.

The MassCombi is the only piece of equipment that requires the interface to join the network. The other equipment all just plugs together, including the MLI. The USB interface is required to get it to a USB cable. Seems to me that you could just buy the MassCombi interface and the USB interface, and use the MasterAdjust software to program, monitor, etc.

Oh, and some of the new model MassCombi's do not require the interface, and the MasterBus cable just plugs right in. Mine is circa 2018, and did require the interface.

[noelex 77]

Great work on the communication protocol.

One simple option for us mere mortals without the programming skills is to use “Mastervolt easy events” this feature is not often used. It is hidden in the manual and few seem aware of this option, but can be very useful.

It involves “programming” (simple button pushes) one of the Mastervolt displays to control Mastervolt equipment.

For example, I have added three buttons to my display for my alternator regulator. These buttons are labeled bulk, absorption and float. At the push of a button I can force the alternator to bulk, absorption or float charging. Thus if the batteries are already charged via solar, I can force the regulator to skip the normal absorption time and jump to float.

[Lomax]

Originally Posted by jagter

I am really impressed with your work. Have you made any further progress on decoding the protocol and building a MassCombi communication module?

Thank you for the kind comment! I've been away for a long time, so haven't tinkered with the actual code (gotta be careful when remote), but I've gradually realised I've possibly misunderstood the way numerical values are sent; it could be that they use all four bytes for most or even all values, which might explain why I need to divide the (two byte) values by 2048 to get the actual numbers. Perhaps they just need to be shifted to the right? Or something like that.

[Lomax]

Originally Posted by AKA-None

I wonder if this would be the same as other items in mastervolts catalog

So this is one thing I looked into early on, in the hope that while no protocol documentation was available for the "Combi" units it was possible - even likely - that a similar structure would have been used for other products, for which such documentation may exist, and from which some clues could be drawn. The only units I'm fairly sure use a similar protocol are the "Soladin" solar charge controllers - which IIRC were originally made by another company, later bought out by Mastervolt. Perhaps they inherited some tech that was then also used for the "Combi"? In any case, thanks to archive.org (donate today!) there's still some information about reverse engineering the Soladin protocol, which although it differs somewhat from the Combi is similar enough to be useful:



https://web.archive.org/web/20110128...ex.php/Soladin

[Lomax]

Originally Posted by sailjumanji

Wow, that's a lot of work.

More fun than watching the telly

Originally Posted by sailjumanji

I can use MasterAdjust software to adjust and program every piece of equipment on the network. It also has the ability to record data for every piece of equipment concurrently, in as little as one second increments - which is invaluable to identify problems. (Although I usually log on 10 second intervals.) You can save the data, import into Excel, and easily plot an of it. The software is free.

All this is very true, but what if you want to access some or all of that data programmatically, in realtime, on a computer not running Windows? If the official way of doing it works for you, then I'm all for it - it just didn't for me.

[Lomax]

Originally Posted by noelex 77

Great work on the communication protocol.

Many thanks! TBH I'm just happy there's some interest

Originally Posted by noelex 77

One simple option for us mere mortals without the programming skills is to use “Mastervolt easy events” this feature is not often used. It is hidden in the manual and few seem aware of this option, but can be very useful.

Yep, I'm sure the official hardware is quite capable - IIRC there's even an NMEA output that can be used to get some of the data out from some of their control panels? Much easier to work with since it has already been reverse engineered to a high standard, and tried & tested parsers are readily available.

[sailjumanji]

Originally Posted by Lomax

More fun than watching the telly


All this is very true, but what if you want to access some or all of that data programmatically, in realtime, on a computer not running Windows? If the official way of doing it works for you, then I'm all for it - it just didn't for me.

I tap on the Easy View display, and slide thru the various pages to get to the instrument data I want to view. But that said, I am generally just happy with volts, amp-hours and amps going in and out the various pieces of equipment.

Just wanted to make sure you knew there were options available thru MV. But I also noticed a couple of days ago that the interface modules are no longer available.

Enjoy doing what you are doing!

[Lomax]

Originally Posted by Lomax

which might explain why I need to divide the (two byte) values by 2048 to get the actual numbers

I mean 2560, not 2048! A byte is 256, and decimal is base 10, which is why I think I got the value alignment off somehow. Too tired to think, but something's definitely up with that. The data I get feels too coarse, like at least one decimal is missing:

[jagter]

Hi,

If you search on eBay, the MassCombi to MasterBus modules are still available. I actually bought one.

You then need a Masterbus to NMEA2000 Interface and this module is quite expensive

Still thinking about the option

[Lomax]

Originally Posted by jagter

You then need a Masterbus to NMEA2000 Interface and this module is quite expensive

Expensive, and I don't think it will let you do things like modify system settings, or control the inverter & charger. It may not even publish all the data. Not entirely sure, but that's how I've understood it.


Edit: If you look in the manual for the MasterBus <> NMEA2000 interface, sections 6.1 and 6.2, you can see which parameters it allows in each direction.

[shimari]

Old thread - but @Lomax have you seen this project?

https://github.com/pmarches/masterbu...ster/README.md

The Wireshark dissector needs work to handle byte alignment, but it's a really good start.

[pmarches]

Hi Lomax,

In the masterbus protocol, the numbers are encoded as ieee754 floats. I suspect the masteradjust protocol follows the same encoding. Checkout my repository for details.

Can you post the files you have so we can make use of your investigation?

Thanks!