dlms and asn.1

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By HouXiang , 25 November, 2019
Forums
General discussion

Hello,

I'm fairly new to the IEC protocols.
I have a newbi question:

What is the difference between DLMS and ASN.1?

DLMS: Device Language Message Specification which are used by IEC62056
ASN.1:Abstract Syntax Notation One (ASN.1) is a standard interface description language for defining data structures that can be serialized and deserialized in a cross-platform way.

Are they both the same kind of language used in metering protocols?

Thank you for your any help on this.

Best regards,
HouXiang

Kurumi

6 years 6 months ago

Hello HouXiang,

ASN.1 is used in DLMS AARQ/AARE messages when the connection is established.

I don't believe that there are any meters that are using plain ASN.1. ASN.1 is widely used in SNMP.

BR,
Mikko

HouXiang

6 years 6 months ago

Hi, Mikko:

Thank you for your valuable info.
I'm working on a Chinese domestic protocol DL/T698.45 (Data acquisition and management system for electrical energy part4-5： communication protocol - object oriented data exchange protocol), which seems evolved from IEC62056.

In that protocol, it didn't mention DLMS or COSEM at all, but it has Logical Name,Object Identification, Object attribute, Object Method , etc.

I hope I'm able to implement the above mentioned DL/T698.45 protocol. but currently I don't have any
line of code.
would you please suggest How I can start implenment it? which open source protocol stack I can used it as reference implementation?

Thanks,
HouXiang

HouXiang

6 years 6 months ago

and in DL/T698.45, it used ASN.1 to describe the objects, etc, such as SEQUENCE , SEQUENCE OF, CHOICE ,ENUMERATED, etc.

HouXiang

6 years 6 months ago

according to 698.45, the labeling rules uses ASN.1, and encoding rules uses A-XDR

Kurumi

6 years 6 months ago

Hi,

Information that I have at the moment is that DL/T698.45 is a subset from DLMS. If I remember right, the logical name is 3 bytes and not 6. There are also a few other differences.
I don't have DL/T698.45 specification, so I can't verify this.

BR,
Mikko

HouXiang

6 years 6 months ago

Hi,
I only have the Chinese Version of DL/T698.45, if you want it, I can send to you.
From the spec, the Logicial Name is same as OI (Object Identification), it is a 2 bytes value.
Also, there are 26 class ID in the spec.
It uses A-XDR as encoding rule. the interface description language is asn.1.
So where should I start if I want to implement this protocol?
Thanks,
HouXiang

Kurumi

6 years 6 months ago

Hi,

If you can send it to me by email I can check it. We were supporting DL/T 645 and it might be possible that we add also support for DL/T698.45.

BR,
Mikko

HouXiang

6 years 6 months ago

Hi,
I sent the spec to you via email.
Br,
HouXiang

HouXiang

6 years 6 months ago

Hi,Mikko：

One question,according to your descripotion:
"ASN.1 is used in DLMS AARQ/AARE messages when the connection is established."
Then why I can't find any code related to asn.1 in your Gurux.DLMS.c project?
Thanks,
HouXiang

Kurumi

6 years 6 months ago

Hi,

Can you access the Green Book?
Or then check this:
https://www.dlms.com/files/Excerpt_GB8.pdf
You should check 11.2 Encoding of the xDLMS InitiateRequest / InitiateResponse APDU.
I believe it'll help you.

BR,
Mikko