I basically started with this thread: http://www.domoticz.com/forum/viewtopic.php?f=42&t=7648 - you should read at least the information written by gizmocus to get an idea how it works... pretty neat!
Building the Arduino node with IR receiver/transmitter and connect it to domoticz was the simple part. The tricky part was reading the IR code and especially storing the IR code within the Arduino sketch.
For reading the code, I used one of the IRlib example sketches which I modify to give me IR signal timings. Obviously there are some other programs doing the same, but measuring them in frequency ticks instead of ms (pre 1.3) and I wasted a lot of time wondering why remote control does not work and finally realizing that. Now the modified version of that program gives me the Copy&Paste ready array lines for the commands via serial monitor.
A big problem was storage. I had to store 6 code arrays, but storing more than one was too much for the variable memory of the Arduino Nano and it stopped working properly due to a lack of RAM. The solution was to store the command arrays not in the variable memory but in the program memory/flash. How data can be stored and retrieved can be read here: http://playground.arduino.cc/Main/PROGMEM
The advantage is, that this gives the possibility to store quite a lot of command arrays, if memory get's low one can strip down the program code to save some memory. This should even be enough to store some longer HVAC command sequences
Below you can find the 2 Arduino sketches I used for reading the code and programming the mysensors IR transceiver controller for the ceiling fan. It's mostly already existing code with some modifications done by me - there's for sure room for optimisation. But... it works
Read IR Data (can also be used to check receiving and transmitting codes):
https://github.com/blitzkneisser/MySens ... record.ino
MySensors modified Sketch to store IR commands in program memories:
https://github.com/blitzkneisser/MySens ... ler_DV.ino