Getting data from OpenHab to an Arduino

I’d need an idea or some working solution to get a value from OpenHab (Raspberry) to my Arduino Pro Mini via a wireless connection. My first idea was to use an ESP8266 Module (ESP-01) as I2C slave on the Arduino, but I found out that they don’t really like I2C slave mode.
Is there any known simple and working solution without lots of other hardware that might solve my problem?

The value I want to transfer is a power value from my Fronius inverter.

You are probably going to be better off asking on an Arduino forum. Once you do get your Arduino on the network using whatever hardware you end up using, MQTT is the most common approach I’ve seen to get the two communicating.

I second that. Using MQTT on wired Arduinos.

Ok, thanks.
I’m allready sitting here trying to get it running with an Arduino Uno and a WS5100 ethernet shield.
I’ve found the following example:
I modified the IP adresses of the Arduino and the Server => Openhab and installed the MQTT binding and the embedded MQTT broker. After that I found a new item at my inbox, that I added as “mybroker”, so I got a new thing.
But how to continue now? When I run the script, I only get a message, that the server connection doesn’t work.
I think some things have to be configurated on OpenHab but what is it, I allready tried to add a gerneric MQQT thing but that didn’t help, maybe there is still something wrong with the MQTT server configuration on OpenHab? But I didn’t really find anything to configure there (on the PaperUI).

You need to verify you broker is running. There are mqtt debug tools. I use mqttfx. This tool will allow you to send test messages to and from openhab and Arduino. It will also just show all traffic on a topic.

In my “Things” list, the broker is online.

But at the moment I’m working on another solution: I used the Arduino with the Ethernet Shield to extract data directly from the API of the Fronius Inverter, that is allready working fine now. The only thing that I still have some troubles now is sending that data to the main Arduino via I2C.

I have a house full of pro-mini’s. here is a nice framework.