Monday, 23 April 2018

Green Millhouse - Fixing the OpenHAB BroadLink Binding (part 2)

Development of the Broadlink OpenHAB binding has been going very well, but with just one scenario (and arguably the most-common one) not working reliably. With the OpenHAB server up-and-running and the Broadlink binding installed and configured for a particular disconnected device, turn the device on.

The copious logging I've added to the binding told me that this was resulting in an error with code -7 when the device was first detected, and I was a little stumped as to how to proceed. As many before me have done, I started entering random semi-related strings into Google to see what might turn up. And I hit gold. The author of the Python Broadlink library did some great work documenting the Broadlink protocol, and while perusing it a particular sentence jumped out at me:

You must obtain an authorisation key from the device before you can communicate.

Of course! When the binding first boots it calls authenticate for each device it knows about, and it does the same when a device setting is changed. But it does not when, after finding a newly-booted device, tries to get its status!

I added an authenticated boolean in the base Handler class, only setting it when authenticate() succeeds and clearing it whenever we lose contact with the device. Any attempt to communicate with the device first checks the boolean and does the authenticate() dance if necessary. And it works like a charm. We're very nearly there now - I just want to DRY up some of the payload-handling methods which seem to have been copy-pasted, add a 'presence' channel that mirrors the internal state of the binding, and remove the heavy dependence on IP addresses, and I think it's good to go.

4 comments:

  1. I'm very pleased to see you have picked up development of this binding!

    I'm curious how you consider the current state? Is it still alpha, as your github says?

    ReplyDelete
  2. Any update on the status of this???

    ReplyDelete
  3. Hi. I’ve noticed you have posted new blogs but haven’t to replied to any comments here. Can you at least share if you’ve hit a problem or given up?

    ReplyDelete