Datentypen

[S. De Bruyne]

Diskussion des Wiki-Artikesl Datentypen. Wenn Du eine Anmerkung machen willst, klicke bitte den Antworten-Button.

[S. De Bruyne]

Datatypes is mostly what software programmers know.
It mainly defines the kind of data that is encoded (string, signed or unsigned number, ...) and its format (ASCII, unicode, 16 bit, float, ...). It however gives no indication about the meaning of the data.
A C-program would without further problem accept a directive as:
FainCoilSpeed = BlindsPosition

In KNX, to ensure Interworking, you have agree on more than only the format. We also have to agree on units, ranges and on how to go from a physical reality to a value or vice versa.
Is Window Open = 0 or is Window Open = 1?
Software programmers can live with any encoding. Interworking between products requires this to be fixed.

That is why we intentionally do not talk about datatypes but about Datapoint Types.
(Though other systems and even European Standardisation have come up with other explanations of that word.)
The KNX Datapoint Types can be found at:
http://www.knx.org/fileadmin/downloa...20v13%20AS.zip

[Uwe!]

for me "Window open" means 1=open, 0=close

if I need it vice versa, I name the Groupaddress "Window close"!

[MarkusS]

Please consult the specs: The DPT is DPT_OpenClose (1.009) where open == 0 and close == 1

Regards
Markus

[S. De Bruyne]

To both answers.
- All is of course a matter of consensus between the manufacturers, so, none of the choices is correct or incorrect. Yet, there are a few rules that we follow!

Rule: a device has Group Object values in RAM; mostly after reset, RAM has value 0. After reset, the default state is mostly taken. This makes that it is more easy that 0 encodes the default state. Therefore the rule: 0 is the coding for the default state.
What is the default state of windows and doors?
Right. Closed. ==> DPT_DoorWindow.
But what is it for a valve? Mostly open. ==> DPT_OpenClose.
This contradicts, but as indicated, there is no choice that is always correct. We try to use as much as possible DPT_WindowDoor, and control through the Interworking specifications that Interworking is guaranteed where expected.
This is not such a fine example; but the 1 bit may be the more difficult one.