Reverse Engineering Elgato Eve Energy HomeKit Characteristics

I got myself an Elgato Eve Energy power sensor and switch to get a feeling for HomeKit in general and how I can make use of it.

The hardware itself looks clean and stylish and the installation is a breeze: You simply plug it in, fire up the Eve app and pair it. After about a minute of setting things up I was able to switch the outlet on and off and get statistics about the current power consumption in W and total power consumption in kWh.

After another minute of playing around I was also able to talk to the outlet using Siri, how cool is that? Asking Siri "Is the living room outlet turned on?" resulted in her answer "Your outlet is turned on", telling her “Turn off the oulet in the laundry room” switched the outlet off. Awesome.

Talking to my outlets and getting statistics is nice and all but what I really want is setting up triggers and do stuff depending on each other like sending notifications once the washing machine is done. I knew that the whole HomeKit framework is not yet where I want it to be (e.g. apps working with your accessories need to be running in the foreground) and the Eve accessories aren’t there es well (e.g. no triggers) but as already said, first of all I want to get a feeling for it.

To dive in deeper I fired up Xcode and played around with the HomeKit API, looking at what the outlet exposes to see where it takes me… Oh my, what a letdown! HomeKit has the concept of characteristics that tell you about the different aspects of an accessory. This is supposed to be standardized so all HomeKit apps can communicate with all kind of HomeKit hardware but Elgato does not seem to be interested in playing along: Yes, the characteristics are available but there is not the slightest bit of information about what the individual characteristics are representing and neither about their format.

Asking the Elgato support about a documentation of characteristics resulted in a short "Nope, documentation is not available". Thank you!

After being annoyed for a couple of hours I decided doing some reverse engineering to see what characteristics Eve Energy exposes and to make some sense of it. To do that I tried several test scenarios and dumped the value of all characteristics as well as the output of the Eve app in these.

Now it was simply a task of comparing characteristics, guessing formats and some calculations. To cut a long story short I summarized what I learned about Eve Energy in a Gist on GitHub. I haven’t made sense of everything up to now but it should be a good start. I try updating the Gist as I learn more and am open for comments and additions.