Re: Ada for Automation

["Björn Lundin" <b.f.lundin@gmail.com>]

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