HDMI CEC for HTPC usage

I have been looking into the CEC functionality of my HDMI setup lately. Now it would be nice if I would be able to connect my Kodi HTPC to my TV and receiver that both support CEC. The HTPC does not support CEC, as it is an AMD fusion board with integrated GPU.

My use case would mostly be to the power on the TV and receiver when I turn on the HTPC, and change the TV and receiver to the right channels.

Now I am aware of the Pulse Eight HDMI CEC adapter, but I'm more of a DIY Arduino person. I've found quite a bit of information here and here . There is a library and a project which might offer what I want.

However, I can't seem to figure out how I should use these projects. ???
Are these supposed to be compatible with the Pulse Eight functionality in libCEC? When I connect the arduino (loaded with the mentioned project) to the HTPC via USB, the peripherals menu in Kodi stays disabled, and no CEC functionality is available. How should I control the arduino from Kodi?

Also, in the schematic, only the CEC line is connected in the HDMI connector. But in the topic, another schematic is mentioned where also SDA, SCL and HotPlugDetect lines are connected. What are these used for?

Hopefully someone can help me a bit. The earlier threads are quite old and inactive, so I hope someone is still knowledgeable on this. Thanks!