Hey Chris,
this definition seems valid to me but is lacking one thing which is the "killer
feature" for me, the "symbolic addressing".
I spent some time the last week to "disassemble" parts of the TIA file format
(zap14).
The aim is to take the zap14 file and to extract all symbolic names and the
respective offsets (in not optimized blocks, of course).
I plan then to be able to init something (Connection, EntitiyManager) with
these information and use the symbolic names for the rest of the "session".
And my feeling is that this would fit better in an layer on top of the current
Connection than directly in the Connection.
What do you think?
Or is this something you would not incorporate in our JPA at all?
Julian
Am 24.08.18, 10:25 schrieb "Christofer Dutz" <christofer.d...@c-ware.de>:
Hi Julian,
well I think I would define that "JPA" (Java PLC API ;-) ) layer the
following way (Joking, but lacking a name, I'll just call it JPA):
- Each driver can provide the types he likes
- Each request item can address exactly one of these types
- As soon as someone wants to reference more items with one query and
eventually re-use that --> This is where JPA comes in
Would that be a valid definition?
We already thought about something like that and there was a thread to this
[1] so maybe it's worth following up on that thread ... Have to admit that I
also have to re-read it first ;-)
Chris
[1]
https://lists.apache.org/thread.html/dfca30f6c3319e592c4a6412924edc9a31f2e18844204dc373eebc5d@%3Cdev.plc4x.apache.org%3E
Am 24.08.18, 10:18 schrieb "Julian Feinauer" <j.feina...@pragmaticminds.de>:
Hi all,
I decided to start a new thread to answer to Sebastians mail below
regarding the Plc4X JPA Like layer.
First, I think, we should get a feeling of what we all think this layer
could or should do and what kind of features we want to incorporate there.
From my perspective this layer should allow the following:
1. Provide access to fields via “symbolic names” or aliases. They
could be provided by the system (S7CommPlus) or they could be registered with
the “EntityManager”
2. Annotations for POJOs “PlcEntities”
I Imagine something like
@PlcEntity
class Pojo {
@PlcTimestamp
private long timestamp;
@PlcField(“%DB8:DBL4:INT”)
private int value;
}
Of course this is a very first sketch but I suggest to collect our
ideas on a Confluence to develop the idea “over time”.
Best
Julian
Am 24.08.18, 09:03 schrieb "Sebastian Rühl"
<sebastian.ruehl...@googlemail.com.INVALID>:
Hi Julian,
Depending on the type of change this might something I could
implement to ADS locally if its just a change of the Address format.
Chatting with Chris we stumbled over the size attribute in a
ReadRequestItem. This might become obsolete too as in its form right now it
isn’t that helpful.
FYI: I was about to read something like this from the plc
https://infosys.beckhoff.com/index.php?content=../content/1031/tcplclibutilities/html/tcplclibutilities_timestruct.htm&id=
<https://infosys.beckhoff.com/index.php?content=../content/1031/tcplclibutilities/html/tcplclibutilities_timestruct.htm&id=>
What we can see here that we need read 8 words from the plc. We can
do that by suppling the IndexGroup/IndexOffset and a Length(ADS) of 16 Bytes.
Then I would need to chunk the response into 2 bytes. Im still not sure if this
is something I would integrate into the plc4x directly or into a layer above
aka JPA/Plc4xJPA (Java Persistence Layer alike) [maybe for the basic structs of
ADS it might be worth it]. Then there are complex types which are mixed
https://infosys.beckhoff.com/index.php?content=../content/1031/tcplclibutilities/html/tcplclibutilities_timestruct.htm&id=
<https://infosys.beckhoff.com/index.php?content=../content/1031/tcplclibutilities/html/tcplclibutilities_timestruct.htm&id=>.
Here a chunking into 8 would not work as you would need to read fixed
different chunks (aligned to it type) from a byte stream. For this I would then
use a „RAW“ read and slice it in the application level (or PLC4XJPA).
Maybe working on the Plc4xJPA (working title you name it ;) would
be a good idea to get some impression of requirements from that side too (I’ll
will scope that on my next TODOs).
What is still missing in your PR suggestion „3) Define 2 types of
ItemRequest/-Responses:“. But that might be ok as these changes are an addition
to that and as I wrote in the first sentence this might be local to the S7
address format in the first step anyway so in my opinion you are good to go
(Maybe leave out the renaming of the query for now to keep the PR footprint a
bit lower).
Regarding API design: Its hard. It should be simple yet powerful.
So if the first iteration doesn’t fit well we just refactor it :)
Sebastian
