[knx] Allow sending items with units to KNX bus.

[holgerfriedrich]

Items with dimensions (QuantityType) are now translated and can be sent to the
KNX bus. This requires the correct DPT to be specified in the channel
definition. Fixes #10706.

Signed-off-by: Holger Friedrich mail@holger-friedrich.de

[lolodomo]

What is this unit ?

[holgerfriedrich]

9.023 DPT_KelvinPerPercent, this is a delta and we need to convert to the matching base unit first (automatic conversion °C to K or °F will fail due to the offset/scaling)

[lolodomo]

In fact, my question was: is "°C/%" is a valid unit supported by UoM ?

[holgerfriedrich]

Actually is seem so. DSL rules let you construct this

        var k = 25|K
        var p = 10|%
        var result = k/p
        var dimensionless = p.toUnit("")

Printing to the log gets you

...script.UoM   ] - this is k: 25 K
...script.UoM   ] - this is p: 10 %
...script.UoM   ] - this is k/p: 2.5 K/%
...script.UoM   ] - this is p converted to dimensionless: 0.1

The values are sent to the KNX bus when I use sendCommand, both tested with items defined as Number and Number:Temperature. It leads to same value on KNX side.

[lolodomo]

Ok, strange but if you tested it, I believe you.

[lolodomo]

@SJKA : would you like to review ?

[holgerfriedrich]

@lolodomo thanks for reviewing this

[holgerfriedrich]

@lolodomo I have the feeling that our CODEOWNERS file is outdated.... @SJKA joined github 2021....

@sjsf Did you initially submit the code for the knx binding?

[lolodomo]

@lolodomo I have the feeling that our CODEOWNERS file is outdated.... @SJKA joined github 2021....

@sjsf Did you initially submit the code for the knx binding?

I see "Simon Kaufmann" as author of a lot of classes. Is sjka =Simon Kaufmann ? This is probable...

@kaikreuzer : do you know if there still a maintainer for the KNX maintainer ? If not, I will merge this PR without waiting.

[holgerfriedrich]

@lolodomo but to me it seems that GitHub re-issued this user account to someone else... Just have a look at the two user profiles mentioned above

[kaikreuzer]

@lolodomo Yes, I think Simon is no longer active here - I have thus created #12694 and added me as a code owner as I was the original author of the 1.x binding (the first binding ever written for openHAB ;-)).
If you approve the changes, I can have a short second glance over it, so that we can merge it.

[lolodomo]

If you approve the changes, I can have a short second glance over it, so that we can merge it.

Yes please

[kaikreuzer]

Hm, is it really correct to do an independent "if" here and not check at all the dpt anymore?
I would expect the typeHelper in line 173 to return DecimalType as the expectedTypeClass.
If this is the case, we would probably only need to adapt line 175 to

                    if (expectedTypeClass.isAssignableFrom(command.getClass())) {

so that it also evaluates to true, if command is a QuantityType and not only if it is a DecimalType.

Wdyt? Am I missing something?

[holgerfriedrich]

@kaikreuzer I just did a quick check: expectedTypeClass returns DecimalType, command.getClass()is QuantityType and isAssignableFrom returns false.

I don't think that we nedd to check the dpt - the type conversion will anyway only work if the unit conversion is possible.

[kaikreuzer]

You're right, I forgot that QuantityType does not extend DecimalType. 😞
I would nonetheless prefer to do a proper check of the type in the if clause.
If expectedTypeClass is null, we should never proceed, so the code should imho move into the if statement above.
And then we could simply enhance line 175 to

                    if (expectedTypeClass.isInstance(command) || (expectedTypeClass==DecimalType.class && command instanceof QuantityType<?>)) {

(and slightly change the tracing message).

[holgerfriedrich]

This looks reasonable, updated code as requested.
Thanks Kai!

[kaikreuzer]

Great, thank you!

[butterfly2501]

@holgerfriedrich @kaikreuzer: I debug the component to send items with unit yesterday because my humidity sensor was not working and always got getCommandSpec no Spec found.
It was never working wih the dpt 9.007 with or without unit. So my workaround is now with a seperate field and to change the value from % to °C and use instead dpt 9.001. Can you please check in the code if the unit for humidity % is correct processed.