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openHAB: faster loading of rules files

openHAB rules files are lazy loaded. When a rule is used the first time, the entire rule file is loaded and compiled, which apparently is single-threaded and takes a couple seconds. Even on a reasonable powerful Rasperry Pi 4. This happens both after restarting openHAB and after changing the rules file. It also means that whatever the rule in question is supposed to do has to wait a couple seconds when requested for the first time. Imagine you have a light switch, enter a room, press the switch, and it takes 5-10 seconds until the light comes on.

To work around this problem, I add a piece of code in all rules files which triggers an immediate action right after loading the file. This way the rules file is already pre-loaded (which again takes a couple seconds, but likely at a time when the rule is not needed right now).


Remove duplicates from Huginn event stream

One of the things I’m using Huginn for is monitoring for Twitter keywords. Some of them might appear in pairs, as example people like to tag Tweets about PostgreSQL with both #postgresql and #postgres. When I was using IFTTT this always created two emails, one for each hashtag. With Huginn I can deduplicate the events, and only notify about the first occurrence.


Enable Huginn Twitter integration

Huginn comes with a number of Twitter agents, but before they can be used you need to authenticate them. That process requires multiple steps, and they are not well documented.

The basics are described on the “Configuring OAuth applications” Wiki page.

For the Twitter integration one must know that you are using a single Twitter app for all users, but every Huginn user can (and should) have this app authenticated against their own Twitter account. Therefore if you want to use multiple Twitter accounts in Huginn, you need multiple Huginn users.


Monitor software version changes with Huginn

Huginn is a great piece of software, but the documentation is … a bit sparse. Especially when it comes to details of the agents. I’m going to blog about a couple more more examples in the future.

For another project I’m using Leaflet, a JavaScript library for rendering maps in a browser. New versions are released occasionally, and I want to know when it’s time to update the project website. Huginn can do that.


Text-to-Speech in openHAB

In my ongoing endeavor to improve our home, a while ago I added a notification when the washing machine and the dryer are finished. The notification is send to a Telegram channel. Over the summer vacation I added a number new ChromeCast Audio devices (Google no longer offers the Audio CC, if you need one get one now). One is placed in the kitchen. Not only can I listen to music while eating breakfast, I can also output notifications, by using the CC as an audio sink in openHAB.

To make that useful, I decided to use a Text-to-Speech system. openHAB offers a couple different TTS systems, however most of them need a cloud integration, and therefore a working Internet connection. The “Pico TTS” works standalone, and was my favorite choice for this implementation.


openHAB and Tankerkönig gas prices + Telegram integration - Second iteration

In my previous blog post about “Tankerkönig” I explained the details of how to integrate this binding into openHAB and provide a Telegram interface.

Someone on the openHAB community forum pointed out that Telegram bots allow queries, where one can present the user with options, and the user only has to click on one of the options. That makes it easier to use, and less typing is required as well. I went ahead and implemented that.

Most of the implementation does not change, especially all the Things and Items are the same. The Rules change however.


Install openHABian image on Linux

My plan is to reinstall openHABian on a bigger SDcard, and on a Raspberry Pi 4. The latest release (v1.5) supports the new Pi 4, and I decided it’s time to do a fresh install, and see if all my Playbooks are still working.

As always, I’m searching my shell history for the right command how to install the image … but came up empty.


Improve openHAB Rules response time

By default, openHAB only starts 5 threads to deal with execution of Rules. That’s not a lot, and if all threads are busy, rules have to wait until a slot is free. This results in slow Rule response time.

This can be improved.


openHAB: Turn display on and off for a Video ChromeCast

After figuring out if a ChromeCast is currently used, it was time to fix a long-standing problem. At home we don’t have TVs, just “dumb” displays, and stream content using ChromeCasts. However a video ChromeCast never really turns off, but keeps the display running, using a Backdrop app. This app keeps showing pictures on the display when the ChromeCast is not used otherwise, effectively preventing any powersafe mode.

That’s both annoying (who wants to have pictures shown in the living room or working room all night), and consumes energy. It’s also intentional by Google. So far we had to turn the display on and off manually, which is inconvenient.


openHAB: detect if a ChromeCast is currently used or idle

We have a couple of Audio and Video ChromeCasts in use. For an upcoming project I need to figure out if any of them is currently used. That is different for the Audio and the Video devices: the Audio just goes idle=ON, the Video devices however load the Backdrop app and show pictures when idling. Google for whatever reason does not want the attached monitor to go in powersafe mode. So much for saving energy …