From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-0.9 required=5.0 tests=BAYES_00,FORGED_GMAIL_RCVD,
	FREEMAIL_FROM autolearn=no autolearn_force=no version=3.4.4
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!mx02.eternal-september.org!.POSTED!not-for-mail
From: =?UTF-8?B?QmrDtnJuIEx1bmRpbg==?= <b.f.lundin@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Ada for Automation
Date: Tue, 18 Nov 2014 11:43:12 +0100
Organization: A noiseless patient Spider
Message-ID: <m4f7p3$7lt$1@dont-email.me>
References: <3e877e3f-c9ad-48a5-941d-08a7f5c3f317@googlegroups.com>
 <m4f190$hhq$1@dont-email.me> <18cxzhton11yu.1s3cu5zea772b.dlg@40tude.net>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
Injection-Date: Tue, 18 Nov 2014 10:41:39 +0000 (UTC)
Injection-Info: mx02.eternal-september.org;
 posting-host="23e59b4906029a0ce22afc4c4b1f25ee";
	logging-data="7869"; mail-complaints-to="abuse@eternal-september.org";
	posting-account="U2FsdGVkX18JfGV8FtnjO/HXOJOir+7f"
User-Agent: Mozilla/5.0 (X11; Linux x86_64;
 rv:31.0) Gecko/20100101 Icedove/31.1.2
In-Reply-To: <18cxzhton11yu.1s3cu5zea772b.dlg@40tude.net>
Cancel-Lock: sha1:NZRcOY7lbJqD6H+AMEYgLLyOWFA=
Xref: news.eternal-september.org comp.lang.ada:23516
Date: 2014-11-18T11:43:12+01:00
List-Id: <comp.lang.ada>

On 2014-11-18 10:28, Dmitry A. Kazakov wrote:
> On Tue, 18 Nov 2014 09:52:13 +0100, Björn Lundin wrote:
> 
>> Very few sites use OPC, which was believed to be THE way of
>> communicating in the early 2000s
> 
> Huh.

Sorry. I'm talking about communication between a host system (WCS) and
a PLC with the purpose of moving pallets on a conveyor.
OPC was something most vendor talked about, but
not to many implemented it. As a transportation layer.
The actual data being passed is different between most if not all vnedors.

>  
>> Talking modbus directly would be nice, but in my field, I don't see
>> any of the vendors preferring that to TCP/IP.
> 
> ModBus TCP is actually far more wide spread than ModBus RTU.
> 
> The design of middleware should support easy developing on new interfaces.
> That is the idea of middleware, to decouple the application from the
> hardware.

Yes, that is why I think Ada for Automation is interesting.
But in practice, i still see the dominating way of this kind of
communication to be TCP/IP with vendor-specific data content.

The standard question, with each new vendor we meet, is
'Can you do this'? and then they hand over a protocol specification -
TCP/IP and a propriatary data content, with a small variation of
* who is server?
* one or two sockets?
* protocol level acks
* re-transmissions (if no nak, timeout and re-send)
*
*
*





--
Björn