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One-way vBus to json over IP using an Arduino Ethernet


Because I wanted to see what my solar collector is doing when I'm away, or am simply too lazy to walk up to where the controller is mounted.

I did it in json in order to make it easy to put it together with some bootstrap or something and make a nice status page.


I am using Arduino Ethernet with PoE. It has more than enough power for the meager needs of the vBus to TTL level converter; that is the reason I left a 3-pin header in the circuit design. Pin 2 goes to the rx of the serial port of the Arduino, and the other 2 to +5V and GND.

Note that the rx of the serial port is pin 0 on the Arduino Ethernet. This means that you need to disconnect the vBus2TTL pin from pin 0 when uploading the sketch; otherwise you won't be able to do it. If you use a Mega, it has more serial ports and you can use a different one, for example Serial1.


This sketch, vBusIP.ino.

I have tested it with a Roth BW/H Komfort, which is a rebranded Resol Deltasol M.

This is based off which provided the basis for this sketch, as well as a great deal of hints.

Also take a look at the library version at


I got all the information I needed from the document RESOL VBus Protocol Specification dated 11.10.2007, which I found somewhere (can't recall exactly where). The document came in a PDF file titled VBus_Protokol_en_20071218.pdf.

Many a source and the circuit schematic came from Piamble blog

Other sources are hinted at in the sketch.

That is all the info I have for now. Feel free to ping me if you believe I could clarify matters here and there.


Not very exciting, to be honest. curl is your friend:


Replace with the IP address you have given to your Arduino, and if everything is connected you're good to go.


Contributors are welcome. The code needs some cleanup and perhaps it could be expanded to understand other vBus speaking controllers.


One-way vBus to json over IP using an Arduino Ethernet







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