Testing the waters.


Thread Starter

David Nichols

Hi All -

My name is David and I found a link to this project in July's Linux Journal.

For various reasons, I'm very interested in an open source PLC. I'll admit that I'm a Linux newbie, first looking at Linux to make my life easier than it presently is with NT Server, so what I'm about to say may seem very "babe in the woods".

What you seem to be pursuing is software for a Linux PC that, when running, results in a "soft PLC" that is programmable in a structured language of your design and communicates with I/O over some type of distributed network. Is this an accurate assessment? If it is, then what I've envisioned is different from what you are pursuing and probably much more difficult to obtain.

What I've envisioned is a traditional PLC system that is entirely open source and designed around open standards such as the VMEbus. A board would control the open PLC standard once it is developed. Everything from the programming software to processors to I/O modules would be open source with the possibility of closed modules if the companies that design them take full responsibility for keeping them in-sync with the open source standard. I envision that the processor would end up looking like an internet appliance, running Real Time services for the I/O scans, ftp for file transfers, web services for monitoring, and e-mail for emergency notifications.

So here are my two newbie questions. 1) Is my vision reasonable? 2) If reasonable, what's involved in obtaining it?

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Curt Wuollet

Hi Dave

I'm with you all the way! In fact that is the ultimate goal, that we be able to run both on desktop or rackmount hardware and on embedded platforms. The Open Hardware is possible, although certification requires resources.
We can do an Open Protocol or two of our own, but that is arguably making the problem worse as there are too many incompatible programs out there. In my opinion, VME is expensive to implement and the PC commodity busses are not unreasonably legally encumbered. I am working right now on a dedicated small din rail mount machine to host the lplc with full internet
capability. If this happens I'm not sure if I can open source it or not. The hardware and chip vendors want licenses for some things. I wouldn't want to discourage anyone. If you can write VMEbus
support I'm sure we can include it, although that's more a Linux issue. With the real possibility of low latency scheduling points getting into the 2.4 kernel series, realtime becomes more optional, but we will support it as long as I have anything to say about it.

As for what's involved in getting there, code!. All we need is people to write it.

Come on in, it's just getting interesting!


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