how to parse association view PDU?

By labasvakaras , 19 August, 2024
Forums
Gurux.DLMS

Hello, wanted to ask if there is a tool how to parse association view PDU?

Reading association view gets me this payload:

(example):

[Debug ] TX: 7E A0 13 03 21 BE A5 4A E6 E6 00 C0 02 C1 00 00 00 1E 27 56 7E
[Debug ] RX: 7E A9 09 21 03 1A E0 41 E6 E7 00 C4 02 C1 00 00 00 00 1F 00 82 01 1F 01 16 00 02 04 12 00 04 11 00 09 06 01 00 01 06 04 69 02 02 01 05 02 03 0F 01 16 01 00 02 03 0F 02 16 01 00 02 03 0F 03 16 01 00 02 03 0F 04 16 01 00 02 03 0F 05 16 01 00 01 01 02 02 0F 01 16 00 02 04 12 00 04 11 00 09 06 01 00 01 06 04 6A 02 02 01 05 02 03 0F 01 16 01 00 02 03 0F 02 16 01 00 02 03 0F 03 16 01 00 02 03 0F 04 16 01 00 02 03 0F 05 16 01 00 01 01 02 02 0F 01 16 00 02 04 12 00 04 11 00 09 06 01 00 01 06 04 6B 02 02 01 05 02 03 0F 01 16 01 00 02 03 0F 02 16 01 00 02 03 0F 03 16 01 00 02 03 0F 04 16 01 00 02 03 0F 05 16 01 00 01 01 02 02 0F 01 16 00 02 04 12 00 04 11 00 09 06 01 00 01 06 04 6C 02 02 01 05 02 03 0F 01 16 01 00 02 03 0F 02 16 01 00 02 03 0F 03 16 01 00 02 03 0F 04 16 01 00 02 03 0F 05 16 39 73 7E

using https://www.gurux.fi/GuruxDLMSTranslator only shows nextframe Value, but is there tool to see exactly what this Value mean?

Kurumi

1 year 9 months ago

Hi,

Your data is coming in multiple blocks and you have only one block of data here. You need to read all data blocks from the meter before it's possible to parse the value.

In association view the meter returns the object type, logical name, version and access rights. The association view defines what kind of features the meter can offer.

BR,
Mikko

labasvakaras

1 year 9 months ago

okay, wanted to ask question:

while reading multiple data blocks, i read only 600 data blocks.

But when parsing objects, i get 1900~ cosem objects.

Why is that? Is it possible to know how many objects i read with one request?

Kurumi

1 year 9 months ago

Hi,

The meter splits data into blocks. Each block can contain multiple COSEM objects.

The association view contains a lot of data because all objects are defined there.
You don't usually need to read it, if you know what you want to read from the meter.
You can add COSEM objects manually to the code if you are always reading meters with the same model.

Read more from here from blocks and frames:

https://www.gurux.fi/DLMSInNutshell

BR,
Mikko

labasvakaras

1 year 9 months ago

I understand that i can add objects manually.

My use case is that i am reading whole association view and i want to update status of this. So what i want to do is:

1. Parse objects instantly, as I read the block.
2. Get actual count of objects i just read with one data block.

I asked for a first method in another thread, but this seems to be hard to implement.

Now i am trying to get actual count of objects from one block, but using hlp_getObjectCount2 method does not return real count. Is this even possible? (should be possible i guess, but i don't know what data one data block contains).

Kurumi

1 year 9 months ago

Hi,

1 and 2 are possible if the data is not encrypted. Meters are using more and more encryption, so I suggest that you forget this.

Also meter might return data with General Block mechanism or blocks like in your case. You need to handle both cases.

The count can be found in this, but the index might change if the server address changes.

7E A9 09 21 03 1A E0 41 E6 E7 00 C4 02 C1 00 00 00 00 1F 00 82
01 1F //Count 287 objects.

In short: This is possible but might cause serious problems later.

BR,
Mikko

labasvakaras

1 year 9 months ago

Why encryption has influence on this? Do the key to decrypt object is passed in the end?

Kurumi

1 year 9 months ago

Hi,

The data block is split into frames and you can't decrypt the data block before all the block frames are received. In your hex trace above is only the first HDLC frame.

BR,
Mikko