Computing stuff tied to the physical world


(Not so) Home Easy

In Software on Apr 23, 2010 at 00:01

Here’s the Elro / Home Easy AB440R remote control:

Dsc 1351

On the surface, it looks like a very clean 433 MHz protocol:

Screen Shot 2010 04 17 at 12.16.22

Here are some bit patterns, as I see them coming in:

Screen Shot 2010 04 17 at 12.15.26

All the pulse widths are in the expected range (first two are timestamp and pulse count):

Screen Shot 2010 04 17 at 12.38.38

This is completely in line with the protocol description I found. Given that it uses a special 0-0 pattern for extended group codes, I decided to pass all the transitions back, leaving the interpretation to higher-level code:

Screen Shot 2010 04 17 at 12.31.28

Here’s what comes out:

Screen Shot 2010 04 17 at 12.30.50

Several very odd problems with this:

  • the incoming bit patterns are less than 50 bits
  • the KAKU decoder also matches these patterns
  • I’m getting spurious empty lines reported

The KAKU decoder match is very surprising, since it only fires when receiving exactly 12 bits! As it turns out, the other way leads to false positives as well: the KAKU transmitter currently triggers the HEZ decoder – but that’s more logical, since the HEZ decoder isn’t checking exact packet sizes yet.

Something very fishy is going on, but I can’t see where :( – despite this, I’ve updated the code.

Oh well, can’t win ’em all…

  1. Don’t have the advanced protocol devices myself. Did you look at http://code.google.com/p/homeeasyhacking/source/browse/trunk/Arduino/HomeEasy.cpp

    Rinie Kervel 25 April 2010 at 11am

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