Sunday, 25 February 2018

Green Millhouse - Temp Monitoring 2 - Return of the BroadLink A1 Sensor!

So after giving up on the BroadLink A1 Air Quality Sensor a year ago, I'm delighted to report that is back in my good books after some extraordinary work from some OpenHAB contributors. Using some pretty amazing techniques they have been able to reverse-engineer the all-important crypto keys used by the Broadlink devices, thus "opening up" the protocol to API usage.

Here's the relevant OpenHAB forum post - it includes a link to a Beta-quality OpenHAB binding, which I duly installed to my Synology's OpenHAB 2 setup, and it showed itself to be pretty darn good. Both my A1 and my new BroadLink RM3 Mini (wifi-controlled remote blaster) were discovered immediately and worked great "out of the box".

However, I discovered that after an OpenHAB reboot (my Synology turns itself off each night and restarts each morning to save power) the BroadLink devices didn't come back online properly; it was also unreliable at polling multiple devices, and there were other niggly little issues identified by other forum members in the above thread. Worst of all, the original developer of the binding (one Cato Sognen) has since gone missing from the discussion, with no source code published anywhere!

Long story short, I've decided to take over the development of this binding - 90% of the work has been done, and thanks to the amazing JAD Decompiler, I was able to recover the vast majority of the source as if I'd written it myself. At the time of writing I am able to compile the binding and believe I have fixed the multiple-device problems (the code was using one shared static Socket instance and a shared mutable Boolean to try and control access to it...) and am looking at the bootup problems. And best of all, I'm doing the whole thing "in the open" over on Github - everyone is welcome to scrutinise and hopefully improve this binding, with a view to getting it included in the next official OpenHAB release.

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