D
Curt,
Definitely, you're right about the costs inherent with installing a fieldbus type system. They always require a formal controller board at
the top (DeviceNet, Profibus, InterBus, LonWORKS, etc.) which introduces considerable cost to the project. However, it is my experience that having that controller board takes the burden from the programmer. Using a controller card means they won't have to worry about what's
going on down at the lower four layers of the ISO/OSI network model. The programmer can then free up to write code for the upper three, including the wonderful Application layer.
(The code necessary to support below the fourth layer can get horrendous.)
With DeviceNet, Profibus and InterBus (not sure about LonWORKS), there is no licensing fee beyond purchasing a controller board for the
computer. Otherwise, that would really suck. Their controller boards handle pretty much everything, save setting up the IRQ, I/O port address and MPM addresses.
The audience we're catering to, especially via this organization, may eventually be the paying audience that wants the Puffin PLC to run
their dairy farm, manage their material handling system, build their automobiles (hey, we can dream, can't we?), or refine their oils. In this market, the company is not going to be enamored with the idea of it being totally free, but will definitely want it to be robust.
Regarding the IEC-61131 side, I can offer some information, as I use this in my job.
-Dan
***********************************************************************************
Curt wrote:
"On the fieldbus thing, It's not that we're enamored with Modbus. It's that
Modbus is pretty close to Open by our definition. That means we don't have
to license anything, buy anything, join anything, or even sign anything to use
it. Most other offerings may be open by _their _ definition, but what that
typically means is that if we throw a lot of money their way and watch the
licensing or join the association or sign NDA's then we're free to use it.
Or that their licensed product will work with any licensed product, with
licenses requiring $25,000.00 worth of conformance testing. As you can see
this type of extortion is not compatible with the nature of our project.
Especially since the budget for buying proprietary products is up to $0.27.
If you can find a way that we can impliment those protocols without massive
cash outlay and compromising legal agreements, I'm all ears.
The only route that seems open for supporting these is to write for cards
that have the protocols embedded. That way all the proprieties belong to
the company that makes the card. This has the disadvantage of being
rather expensive. It does however have advantages in that these rather
busy protocols run on their own processor.
On the IEC-61131 side, we can definately use some detailed knowledge as
eventually we will want to support these."
_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
Definitely, you're right about the costs inherent with installing a fieldbus type system. They always require a formal controller board at
the top (DeviceNet, Profibus, InterBus, LonWORKS, etc.) which introduces considerable cost to the project. However, it is my experience that having that controller board takes the burden from the programmer. Using a controller card means they won't have to worry about what's
going on down at the lower four layers of the ISO/OSI network model. The programmer can then free up to write code for the upper three, including the wonderful Application layer.
(The code necessary to support below the fourth layer can get horrendous.)
With DeviceNet, Profibus and InterBus (not sure about LonWORKS), there is no licensing fee beyond purchasing a controller board for the
computer. Otherwise, that would really suck. Their controller boards handle pretty much everything, save setting up the IRQ, I/O port address and MPM addresses.
The audience we're catering to, especially via this organization, may eventually be the paying audience that wants the Puffin PLC to run
their dairy farm, manage their material handling system, build their automobiles (hey, we can dream, can't we?), or refine their oils. In this market, the company is not going to be enamored with the idea of it being totally free, but will definitely want it to be robust.
Regarding the IEC-61131 side, I can offer some information, as I use this in my job.
-Dan
***********************************************************************************
Curt wrote:
"On the fieldbus thing, It's not that we're enamored with Modbus. It's that
Modbus is pretty close to Open by our definition. That means we don't have
to license anything, buy anything, join anything, or even sign anything to use
it. Most other offerings may be open by _their _ definition, but what that
typically means is that if we throw a lot of money their way and watch the
licensing or join the association or sign NDA's then we're free to use it.
Or that their licensed product will work with any licensed product, with
licenses requiring $25,000.00 worth of conformance testing. As you can see
this type of extortion is not compatible with the nature of our project.
Especially since the budget for buying proprietary products is up to $0.27.
If you can find a way that we can impliment those protocols without massive
cash outlay and compromising legal agreements, I'm all ears.
The only route that seems open for supporting these is to write for cards
that have the protocols embedded. That way all the proprieties belong to
the company that makes the card. This has the disadvantage of being
rather expensive. It does however have advantages in that these rather
busy protocols run on their own processor.
On the IEC-61131 side, we can definately use some detailed knowledge as
eventually we will want to support these."
_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc