This page last changed on Jun 06, 2011 by mkozlina.


I am developing .NET driver for KNXnet/IP, based on EN 13321-2.
Main goal is to create library that will simplify KNX integration.
Thing that made me start this is Falcon driver. Is one of the worst organized libraries I have ever seen,
not to mention that there is no any valuable documentation or tutorial.
Everything is working perfectly on IP level, but I would be very grateful if someone could clarify lower levels.
Since I can't afford to buy KNX Specification book (cca 1000 Eur), 'cEMI' is a riddle to me.

Here are my questions:
1. Searching the Internet I have found out that cEMI is not the same for every communication type and layer.
90% of all software has L_Data cEMI implemented and I have done the same, but this cEMI type cannot be used
for L_Busmon type and any message type constants starting with 'M_' !?
Everybody are talking about layers and how cEMI structure depends on them.
Can anyone explain this layering and how many there are?
What are all cEMI formats for specific layer?
L_Data cEMI is 'Data Link Layer' message, but it has APDU (Application Protocol Data Unit) which is application layer payload!?

2. Can APDU in L_Data cEMI hold more than one Data Point Type?
Can it hold more than one DPT in any format?

3. If DPT is less or equal to 6 bits, it can be encoded in the last 6 bits of APDU.
I have found a way how to check if DPT is encoded in APDU, but I am not sure that this is the right way.
Is there a way to know for sure if there is data in APDU?

4. How do I know what type of data is being sent in cEMI?

5. CRI structure in CONNECT_REQUEST frame for tunnel connection requires two additional bytes at the end.
For now I know that I have to put 0x02 and 0x00 to be able to establish (Link layer|Data link layer|Application layer) messages.
What are the other values I can use?

6. CRD in CONNECT_RESPONSE contains some additional values at the end.
Can someone explain what are these for?

I think that is all for now

Thank you!


Lol you said "simplify KNX integration". Boy that's funny.

Posted by marcf at Jun 06, 2011 21:28
Document generated by Confluence on Jun 05, 2016 09:31