Got it!

Yes, yes, YES! I love it 🙂

The rethinking of the OpenTherm bit capturing strategy I did a few days ago really did improve things quite a lot, as can be seen on a screendump of my OT Decoder:

"My" OpenTherm decoder

Below is what the Opentherm Monitor, a tool that belongs to the OpenTherm Gateway (yep, I’ve got one of those too, since a week or so 😉 ) is showing in the log:

Gateway Opentherm Monitor

This is great, wonderful result! And the time it took to come this far was well spent, cause I’ve learned a lot in the past days. I’m starting to know the Opentherm Data ID’s by heart, I know some more about the ATMega timers and Manchester decoding has no secrets for me anymore.

You may notice that in my case only the Master (lines with a ‘T’ in them, in both screendumps) frames are decoded and not the Slave response frames (Slave=Boiler, starting with a ‘B’ in the lower screendump), but that’s because I added a delay that causes the sketch to skip the Slave responses.

So the sketch is going to be the next thing I’m going to work on in the next couple of days. But for today, I’m going to relax and and stop thinking about microseconds, timers, prescalers and ISRs;  it’s time for something completely different: a Somfy RS-485 RTS Transmitter for our rolling shutters which will (hopefully) arrive in  a few weeks! That’s why I like Domotica so much – the diversity of things to do and learn.


Tagged , , . Bookmark the permalink.

4 Responses to Got it!

  1. Freddy Martens says:

    Hello Robert,

    This is good news. You deserve a Chouffe 🙂

    This triggers me to update (better pads to make soldering easier) the schema file and compare the Elektor schema with the one provided at palebluedot. But before I can do that, I need to finalize my other projects first 🙁


  2. Hi Freddy,
    Thanks. My work isn’t completely finished yet, but I’m sure the hardest part has been done. The final sketch will only have the 4 Opentherm bytes as output, which sounds like a good basis for further use – either connecting it to a Serial port or maybe add a RF transmitter to get those OT frames (only 8 bytes per second) there where you want them. And from there, all you need is the Opentherm documentation to process the data. 🙂

  3. Freddy Martens says:


    I had to laugh reading your blog, you look like Tigger, Pooh bear’s mate bouncing from one project to another. It’s hard to keep up 🙂 I hope to have some time available comparing the palebluedot schematic with the one from Elektor. If they match, then your sketch would be really helpfull.


  4. Pingback: Opentherm Monitor finished

Leave a Reply

Your email address will not be published. Required fields are marked *