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SBFspot or modbus-tcp

Topics: 1. General
Feb 22 at 7:21 AM

I would like to know the advantages/disadvantages between SBFspot (speedwire ?) and modbus-tcp. I want to read my, soon to be installed SMA inverter, every 60 seconds and store those values in an RRD database.

Which interface provides the best resolution? Can SBFspot access data that is not available over modbus-tcp? Performance considerations? ....

Kind regards,
Feb 23 at 1:54 PM
Don't know the exact differences as I don't have an ethernet connected device.
SBFspot can retrieve almost the same data as Sunny Explorer can. Or even more like internal temperature of the inverter.
Due to the overhead needed for logon/logoff, SBFspot is not designed for a 60sec resolution. Even if it is possible, it should be better to keep the connection open. But I'm afraid this approach will block the access for other devices to the inverter.
Feb 23 at 10:59 PM
One thing that I can not do through modbus (either SMA or Sunspec) is read inverter events.
I'm actually looking into this now, i.e., how to get inverter events...

(modbus is very cheap, there is a perl module too, and you can (I'm doing it) just integrate that into MRTG to have a nice RRD database with, say, power and DC voltage)
Feb 24 at 8:44 AM

Thanks for the reply's. I'll give modbus-tcp a try when my inverter is installed (will take 4 weeks).
I'll write a small C program using libmodbus on linux and will post the results here.

Joris Struyve
Apr 27 at 1:28 PM

Just a follow-up post.
Now that my inverter is installed I've had the chance to test the modbus-tcp interface. I used a small C program I wrote using the latest libmodus.
The mobus interface is not the fastest thing in the world, but theregisters get updated at least every second. All the data I need is available.