Advanded flows : use KNX sensor values in calculation

Hi. To cope with the fact that KNX power sensor does not work (not showing anything for Dpt14), I would need to read them from an advance flow, compute some formula using them as input (not possible neither) and to store them as tags I can access using a device.
To summarize, I would need:

  1. Logic functions that uses result flow card as inputs to make computation
  2. Create tags easily using result flow card as input
  3. Having a “Tag Device” that can display the value of a tag
  4. And last but not least, a reviewed and improved KNX application to allow display/setup values from/to KNX address group
  5. Homeyscript to easily access value from tags. It’s easy to create them, I cannot guess how to read them

Thanks.

That is quite a wish list😁.

Hi Stéphane and welcome!

Because this is (more or less) a user forum only, please read the Welcome to the forum! topic to find out where you can address your wishes.

Btw, it’s not easy for me to understand your problems. Because in my opinion you don’t provide enough information, from my experience only a few Homey users use KNX and most users will probably have problems understanding the flow, the flow cards because of French language.
Which information should the top KNX flow card give out? What is requested?
Btw, it doesn’t make sense to link action cards (Then…) to an “ALL” card. Only condition cards (And…) can be linked to an “ALL” card.

It looks like feature requests are raised because the avaible functions are not understood.
So my suggestion is to tackle them one by one. Start with reading a KNX parameter, when that is successfull it is easy to see how you can use that parameter in your flow.

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Let me put it this way. When you start a flow (when card) reading a KNX value from the bus, it becomes available as a tag. This is just fine. But if you use the (then card) to read a value from the bus, the value is not returned as a tag and couldn’t be used in the next (then) steps. This is the first issue.
The second issue is the KNX sensor device. This is simply not working. I tried to create one using power sensor (DPT14 data type) and nothing is displayed. I had to use a virtual device to I can set the value from the when card. This is overkill.

As a KNX owner, I would need to be able to display whatever data type in a KNX device.

PS : I succeeded in making my flow working but it took me lots of extra steps to get all my values as tags so I can use them in computation to finally display them in a virtual device. Pfff…

As I don’t own a KNX system, I cannot help you all the way, but just make some suggestion. You can search the forum or ask the de developer of the app.

So your thirst problem is reading from the KNX bus with a THEN card. When you click on the “i” sign of the read card it shows the following information: “Asks the KNX bus to trigger a send. This is useful to get the current value of a group address”.
So it does not read the bus as the card might suggest.
This implies that a corresponding WHEN card shall receive the value of the group address.
Its up to you to verify my assumption :grin:.

If above is true, after making a KNX device, you have to force the device to send a value by forcing a send by using the WHEN read card. As the KNX device is just a listener.

Even if you have already found a solution, I would still like to make a comment.

In addition to the already mentioned mistake that an “ALL” card will never work with action cards, there are also errors in the calculation card of the Custom Logic App:

I think that’s what you’ve explained here, isn’t it?

Even though I don’t use either app, I’m pretty sure you made a mistake. Because such grayed-out tags are displayed when a flow card or device that provides these tags has been deleted.

And now that you have found a solution, it would be kind if you could explain the solution and share a screenshot of the flow so that other users can also benefit from your knowledge.
That’s how a user forum works.

Hi all. I did find a solution for the above issue. Thanks to you all.

Maybe you can share your solutions, so it is available for all users?

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I did revisit all my scenarios. Solution was to use « virtual devices » to publish each KNX change and then to reuse the virtual device value to make the computation. Using “virtual device” application saved my life in many many cases.
The 2 flows below are used to enable my KEBA charging station during the day (when the electricity is expensive). When the solar panels are producing enough, I enable my charging station. I also have a mode to only use what is exported to the electricity network to optimize my auto-consumption. For this, I’m using the HomeWizard application that publishes my electricity input/output in real time and then I force KEBA to only use what’s exported.

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Hi Stephane,

Thanks for sharing the solution.

The bottom flow will never start the KNX Card > The All block should be replaced with an Any block;
Or connect the triggers just in parallels, like you did correctly in the top flow:

Corrected. Thanks. But this was working as the 2 values were changed randomly … Bizarre !