I used an ESP8266 as processor which determines the energy used in my house and sends that data via ModBus protocol over my WiFi network.
For the ModBus I mimicked the registers of the EM24, as this is standard recognised by the Victron.
The register you can find in the datasheet of the EM24, for example see: https://www.gavazziautomation.com/fileadmin/images/PIM/OTHERSTUFF/COMPRO/EM24_E1_CP.pdf
The registers I used includs the model (EM24DINAV23XE1PFB), as well a HW + a FW version = 1E, and a dummy serial number.
And for the rest just the registers of a 3 phase system (voltages, currents, power, and Energy of each phase).