Integrating my Daikin A/C into HNet and openHAB

Took me some time to find out that RealTime provide devices to interact with Daikin SkyAir indoor units such as mine. This RTD-10 device talks ModBus over RS-485 links, so I also bought a USB to RS-485 adapter that works.

Thankfully, the RTD-10 comes with two cables: one that connects to the indoor unit 16V power supply (X35A undocumented connector), and one to connect the P1P2 network.

Once all was connected, I plugged the USB to my closest Raspberry Pi, [ab]used the unit test client from libmodbus, and quickly got the on/off, setpoint, fan speed and mode information, and could update it too. I can also read the Daikin remote control temperature reading.

HNet was not really ready for ‘system’ integration, but after a few hours I could read and change all settings from my openHAB application (HNet generates the whole configuration for openHAB 1.x). Of course it is now possible to set some integer to text mapping as “mode 1” does not help much, so we have mode heat (or chaud in the French openHAB sitemap).

New versions of my backup software and its companion library

HBackup, my backup software has just seen it version 2.0.0 release. The version bump is due to the enhanced backend which now supports storing file data in chunks. This saves huge amounts on disk space for certain files such as databases and mail files. The former are often modified in some scattered places only, while the latter often get data appended at the end.

The companion library HToolBox has also seen a release that goes with HBackup, at 1.7.0. Nothing really stands out.

I²C bit banging

So I ordered another of those cheapo relay boards from Denkovi. This one has a TCN75 temperature sensor controlled by I²C, thus using two pins of the FTDI FT245R chip.

This is when I realised that I had to implement the I²C bit banging myself, and that the Web was not full of ready-to-work implementations 🙁

This is not a difficult task though and only took me a few hours. The code is in available under the GPL and can be found here.