The Linux PLC Project

It also prevents you from referencing things such as member functions, which are not accessible without name mangling. Of course, they wouldn't mean much to C anyway.

One of the strengths of COM is that it does provide a C level binary interface to a very useful subset of C++ class/member functionality. Of course the C interface is a pain and the Microsoft COM definition requires that it be based on their compiler's vtable layout, but much of that is hard to avoid. (See the first chapter of Essential COM for more insight on this view of the technology, which is rather different from the Microsoft party line.)

Please folks, this last paragraph is just a technical observation, it is neither a proposal that we use COM nor an invitation to yet another
COM/CORBA flame fest.
 
Can you not call the member functions from within the exported C function?

I.e. the C++ member functions are 'private' within the program module, while the exported C methods are public.
 
R

Ralph G. McDonald

> > 5. A discussion is under way with our Intellectual Property counsel about licensing approaches. There are some real issues here, that require real legal advice. For instance, the standard GPL might (*might*) be interpreted as requiring user programs (i.e., the program for running your machinery) to be given away. Obviously, this is not the intent, and would inhibit the use of the system. We'll need a license which insures free distribution of the controller code, but provides the user community with the necessary assurances to support its use.<

> Why wouldn't this be the intent? Why is it important for the system software to be "free" (as defined by the Free Software Foundation)

> but user programs need proprietary protections? What's the difference between someone developing a driver or other utility/enhancement to the Linux PLC (which would supposedly by implication be required to be licensed under GPL) and someone developing a control program to run a process? They both will supposedly make use of LinuxPLC APIs.

> Regards,
> Ralph Mackiewicz
> SISCO, Inc.


I have been programming PLCs for many years, going back to the old 5TI with 256 words of menory. Many of my clients in industry would not allow a control program to be released because of concerns about security. I have to sign non-disclosure agreements in order to work on thier systems for process control. If they had to release the actual control programs they would not use the system. However they would probally authorize me to release a driver that I had to write for a specific divice such as a MicroMotion mass flowmeter. In order to be usefull in an industrial setting we must be careful to allow the seperation of common and propritery software.

I would also like to help with this project, however my programming experience has been Ladder Logic, Intellution Fix HMI, Forth, AB Basic, and 6502 & 6809 assembler. No C, C++ yet. I may be of more help in testing then writing code.

Keep up the good work.

Ralph McDonald

Spicer Group
 
T
I'm kinda interested, having about 20 years programming experience, including C and C++ and more recently being very much into python (if there's any need for that). I'm an OO designer of some capability. But I'm fairly new to control systems, so I'd need a lot of help. Got a lot going on in my life (a control system, a youth ministry, songwriting, etc) but it sounds like a good gig. It could be fun in my evenings off ;-)

A lot of my experience is in the Uni (unixen?), though I'm a little linux-challenged.
 
Hi Ashok,
I gave you a call but I couldnt reach you. I work for a company called Aerotech and we are
trying to implement softplc logic interpreter in
a potion of the c code, which is interrupted
every millisec. This interrupt will send commands to a digital controller. The interpreter code should use shared memory which will be accessible both by the softlogic interepreter engine and the controller code. We are thinking of using linux on a single board computer. I would like to share your idea with this. Please reply if you can.

Thanks,

Ratin
Aerotech INC
412-519-0180
[email protected]
 
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