J
Jiri Baum
Hello,
Michel A. Levesque, ing., wrote:
> 2. If you want to control machines then keep in mind that almost all plants have invested a great deal of money in I/O hardware. So I/O drivers would be a key issue. So which "open standard" will this project adhere to: DeviceNet ?, Modbus ?, Profibus ?, ControlNet?, Fieldbus ?<
Ideally all of the above, simultaneously on the one computer
In practice, whichever is easiest to implement first ("easiest" includes considerations such as whichever of them happen to be available/useful to the people doing the coding...), then the others as possible.
> 4. Some manufacturers are coming out with Ethernet I/O. The communication card is inexpensive, but I would NOT put my control system on Ethernet.<
Well, that's a bit out of the scope of the project. Put a warning in the docs is about all we can do about it. Maybe watch /proc/net/dev and warn if collisions become frequent (shocking as that sounds).
> 5. As far as the GUI of the programming language...since we are starting fresh here, let's drop the ladder language.<
Why? It can just be one of the options... if the base API is in C (it really has to be, anyway), then we can have any number of languages. If
(when) the project supports more than one kind of bus, we can even have a "grab these from bus A and show them to bus B like this" language...
Anyway, ladder language is very simple if you stick with the text version (LD X001 / AND X002 / ...). A couple of days back I wrote a simple
interpreter in an afternoon, just to see if it really was that easy... (I'll upload it if there's an exp(erimental) directory in the CVS.)
> 6. In the beginning of this diatribe I mentionned that the HMI should be seperate. I would think that everyone would want to keep the
HMI on a seperate machine altogether.
Yes, though that'd really be the implementer's decision, if it's done properly. The module should be designed to work either way.
(One of the usage modes should be as an HMI box, anyway, in which case you want the HMI module and the industrial bus interface on the same machine.)
Jiri
--
Jiri Baum <[email protected]>
Michel A. Levesque, ing., wrote:
> 2. If you want to control machines then keep in mind that almost all plants have invested a great deal of money in I/O hardware. So I/O drivers would be a key issue. So which "open standard" will this project adhere to: DeviceNet ?, Modbus ?, Profibus ?, ControlNet?, Fieldbus ?<
Ideally all of the above, simultaneously on the one computer
In practice, whichever is easiest to implement first ("easiest" includes considerations such as whichever of them happen to be available/useful to the people doing the coding...), then the others as possible.
> 4. Some manufacturers are coming out with Ethernet I/O. The communication card is inexpensive, but I would NOT put my control system on Ethernet.<
Well, that's a bit out of the scope of the project. Put a warning in the docs is about all we can do about it. Maybe watch /proc/net/dev and warn if collisions become frequent (shocking as that sounds).
> 5. As far as the GUI of the programming language...since we are starting fresh here, let's drop the ladder language.<
Why? It can just be one of the options... if the base API is in C (it really has to be, anyway), then we can have any number of languages. If
(when) the project supports more than one kind of bus, we can even have a "grab these from bus A and show them to bus B like this" language...
Anyway, ladder language is very simple if you stick with the text version (LD X001 / AND X002 / ...). A couple of days back I wrote a simple
interpreter in an afternoon, just to see if it really was that easy... (I'll upload it if there's an exp(erimental) directory in the CVS.)
> 6. In the beginning of this diatribe I mentionned that the HMI should be seperate. I would think that everyone would want to keep the
HMI on a seperate machine altogether.
Yes, though that'd really be the implementer's decision, if it's done properly. The module should be designed to work either way.
(One of the usage modes should be as an HMI box, anyway, in which case you want the HMI module and the industrial bus interface on the same machine.)
Jiri
--
Jiri Baum <[email protected]>