Collaboration

[erwindouna]

Opening this as an introduction as much as a proposal. I'm one of the code owners of the SMA integration in Home Assistant Core, and a member of the Home Assistant Core team; so pysma sits directly downstream of work I'm responsible for. :)

@kellerza and I have been exchanging emails about this, and he suggested getting introduced to @rklomp as the current maintainer. Rather than turning up with unsolicited code, I'd rather start with the direction and see whether it fits how you want the library to grow.

While experimenting with my own inverter I got it working over Modbus TCP, including write access. But after testing both paths side by side, Webconnect is clearly the better data source: sensor coverage is more complete and the values are more reliable. Several things I expected to work over Modbus either returned nothing usable or didn't map cleanly to what the integration already exposes.

So I'd like to correct the direction I originally floated with @kellerza over email: this shouldn't be "replace Webconnect with Modbus". At first webconnect stays the primary transport, and Modbus is added narrowly for the one thing Webconnect can't do.

My main idea:

1. Webconnect first. The definitions were already moved to their own file, I understood of Johann. Anything Modbus does better on the read side is a later, evidence-driven decision, I suppose.
2. Modbus as an optional control layer. A separate, opt-in SMAmodbus client used specifically for writes.

Looking forward to your responses and I hope we can started extending pysma! :)

[kellerza]

I have no objections to add modbus support. Since modbus might need additional HW, it should be optional and additive to WebConnect.

Modbus should allow you to write to the control registers, which will be very useful. There has been issues asking for this in the past.

Since this is integrated into Home Assistant, I suggest modbus-connection as the underlying library. I've recently switched to it in my Sunsynk app as well. It has a useful way of defining sensors, their registers and way of decoding as Components

[erwindouna]

Sounds good. Personally I'd like to start with the WebConnect. That brings in more features and has less impact on the current HA integration. After that, I think it's a nice project to work on modbus support and indeed for the modbus-connection library from OHF. :)

[burmistrzak]

I've been cooking up a Modbus-only integration consuming my sma-modbus library. It's based on modbus-connection and follows the latest guidelines for such integrations.

Development is highly automated, using an agentic workflow to transform the official SMA Modbus parameter lists into testable device definitions. This would allow us to add support for new devices as soon as official documentation is published. ☺️
The Modbus interface has been incredibly stable in my experience and should work with every SMA device.