generate C# classes from JSON data

It’s a common use case: you’ve got some JSON formatted data and you want to interface with it using your favourite programming language C#. You can write the appropriate classes yourself, or you could use the fabulous json2csharp helper page.

Source 1: http://json2csharp.com/
Source 2: http://jsonclassgenerator.codeplex.com/
Source 3: http://json.codeplex.com/

openHAB – home automation bus

It certainly is just me thinking: this home automation / smart home thing gains more momentum every week. Now there’s a java based home automation bus initative taking care of the software standardization side. Quite interesting. And beside all that they had some fantastic ideas how a user interface for those things should look like. Like for example how you would interact with your house while planning when things power on and off. Use Google Calendar! This is just plain genius!

“The open Home Automation Bus (openHAB) project aims at providing a universal integration platform for all things around home automation. It is a pure Java solution, fully based on OSGi. The Equinox OSGi runtime and Jetty as a web server build the core foundation of the runtime.

It is designed to be absolutely vendor-neutral as well as hardware/protocol-agnostic. openHAB brings together different bus systems, hardware devices and interface protocols by dedicated bindings. These bindings send and receive commands and status updates on the openHAB event bus. This concept allows designing user interfaces with a unique look&feel, but with the possibility to operate devices based on a big number of different technologies. Besides the user interfaces, it also brings the power of automation logics across different system boundaries.”

I especially like the idea of that calendar integration – sending scripts through an appointment is a great idea – having some sort of scripting language is another one. A little bit on the marketing side is the option to chat with your house through XMPP / Jabber… that might take the idea a little bit too far out – but who would want to blame them? Fantastic stuff!

Source 1: http://www.openhab.org/
Source 2: http://kaikreuzer.blogspot.de/2012/08/openhab-1.html

home automation example: domotica

For several years now I am interested in this home automation thing – I even got a little bit of my own home automation going. But with websites like domotica you can get an idea of what is achieveable and how it might look for the people actually using it every day.

Source 1: http://www.hekkers.net/domotica/Default.aspx

reverse-engineering the ELV MAX! Cube protocol

I had a couple of hours to tinker with my ELV MAX! Cube and there is some progress with the protocol reverse engineering.

Of course there is the domotica forum helping out with some information the guys over there have found but in addition to their very helpful findings I want it to be integrated into h.a.c.s. – and along with it I maybe want to have a way to find eventual protocol changes quick and easy in the future.

So yesterday I partied on the ‘first contact’ – today I am a bit deeper into the protocol itself:

Here are some explanations to the picture:

When a tcp connection to the cube is opened you can immediately read from it – the cube is throwing information at you. There’s always a character at the beginning of each line which marks the type and beginning of the message.

There seem to be these types of messages in the first package of information:

  • H – Header maybe?
    •  it contains the serial number of your cube, the RF address, the firmware version and several other things like time information
  • M – Metadata?
    • this seems to be some kind of global metadata list, containing the rooms with their IDs (it’s the %) in the screenshot). Furthermore it contains the serial numbers and names of the devices in that room – at the moment there’s just a window-state-sensor in that first room called “Fensterkontakt 1”
  • C – Configuration?
    • since there are multiple C messages these seem to contain detailed configuration data specific to a device in the MAX! network. Each device seems to be addressed by a RF Address and it’s serial number.
    • the first C message in the screenshot is associated to the cube itself
    • the second C message is associated to the window-state-sensor – you can clearly see in there the room id “%)” and the serial of the window-state-sensor.
  • L – live status?
    • this message seems to contain room status information. In our case there is only the room with id “%)”. When the window-state-sensor changes state the last byte changes value – interesting, eh?

On the coding side I’ve got several things set-up in my little debug tool. I’ve wrapped those message types into various classes to handle them more easily later on in h.a.c.s.. Furthermore I used a little decompiler-wisdom to extract some more information from the included ELV MAX! cube software.

Thanks to german UrhG paragraph § 69e (german copyright law) I am allowed to decompile the included software in order to achieve interoperability (and only that). That’s exactly what I would like to achieve: Interoperability. And for the record: besides that I also filed a support request to ELV in which I ask them if I could get access to a presumably existing documentation of that protocol.

While waiting on that documentation I am using JD-GUI as a decompiler user interface for java – since the software of the cube is written in java.

There are many interesting things in there but it’s a slow process to get ahold of all the things necessary. There are already some very nice things showing up. Like when you want to know if there’s a cube (or more) in the network you just need to send a multicast ip packet containing a characteristic signature and all the cubes in your network will try to connect back to you with some basic information – nice, isn’t it? Or what about that AES Encryption/Decryption that seems to be built into the cube? Yes that’s right! It seems to be possible to send commands to either encrypt or decrypt according to the AES. Thoughtfully these commands are marked with ‘e’ and ‘d’. Or that if you send “l:” as a command with CR+LF at the end you get a device listing with all stats… and so on.

Some open question to EQ-3/ELV for the end of this article:

  • Why this strange protocol? Why all the work on both sides? Just because an HTTP server implementation with a RESTful service would have been that more difficult?
  • Base64 encoded data? The 90s called, they want their 8th bit back.
  • why that complex local webserver approach when you could have done everything in a java app anyways?

That’s it for today, I just pushed a feature to the Git repository which allows you to run whatever command you like on your cube with the debugging tool:

Enjoy! :-)

Source 1: http://www.domoticaforum.eu/viewtopic.php?f=66&t=6654&sid=f8f912914163cb44d447cfa3de44d63d
Source 2: http://en.wikipedia.org/wiki/Decompiler
Source 3: http://www.gesetze-im-internet.de/urhg/__69e.html
Source 4: http://java.decompiler.free.fr/?q=jdgui
Source 5: http://en.wikipedia.org/wiki/Advanced_Encryption_Standard

ELV Max! Cube – home automation for the heating

For several years now I am building my own home automation tools by putting together existing hardware and self-written software. As the central software core of my home automation system I use h.a.c.s. – “home automation control server” which I put up as open source software on GitHub.

Throughout the years I was able to embedd a lot of daily tasks and measurements in one place which can be accessed by a simple web page. It currently looks like this:

You can find some articles on this blog about h.a.c.s. if you want to know more about it.

As of today I can control and measure the states of switches, windows, doors, temperature and humidity and power consumption. Scenarios like “when this door opens, switch on that light” are easy things to do with h.a.c.s.

Now “Winter’s coming!”. And therefore I want to take control of the heating of each and every room in the house. I want to set a goal for a temperature and I want the heating to fire up or cool down with that goal. And of course I want to monitor manual changes of each and every radiator in the house.

Last week then I stumbled upon a piece of kit called “ELV MAX! Cube”. It’s a white cube (as the name implies) which offers a USB port from which it is powered and an RJ-45 ethernet port which connects the cube to the home network.

The cube itself does not draw much power and it can be powered by the routers USB port easily. It allows you to connect some peripherals using 868 mhz rf. Those peripherals can be: window state sensors (closed/open) and thermostats to control the radiators (and a switch but, well… hopefully not necessary).

It comes with it’s own user interface – a java application that connects to the device and allows you to configure it. Quite nice – it runs on Windows and Mac. You can use a cloud service to control the device over the internet, but I have no intention in trying that out right now.

My plan is to extend h.a.c.s. to get information from the cube and handle them and in the end even control the cube by setting temperatures and controlling the outcome of those changes.

As of now there are some efforts to decode the quite interesting protocol the cube is talking. You communicate with the cube over TCP (my cube listens on port 62910).

Currently I am building a small debug application which allows me to experiment with the output of the cube faster than plain telnet would. And within this I had the first contact tonight:

As always all my efforts can be seen in the hacs repository.

Source 1: https://github.com/bietiekay/hacs
Source 2: http://www.schrankmonster.de/?s=hacs
Source 3: http://www.elv.de/max-cube-lan-gateway.html
Source 4: http://www.domoticaforum.eu/viewtopic.php?f=66&t=6654