current status???

J

Thread Starter

Johan Bengtsson

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Phil Covington

As time permits, I have been testing normal Linux 2.2, RTAI enhanced Linux, and Windows 2000. I have been using a combination of Optilogic Ethernet I/O and Automation Direct 205 I/O with the Host Engineering Ethernet Base Controller module. Both companies have a free SDKs so I have been able to use both systems on Windows and Linux.

The new RTAI Linux with the LXRT user space real time looks promising but it is still somewhat unstable. Many of my concerns about normal Linux and Windows 2000's suitability for real time control use have disappeared when running on new modern hardware (PIII 500, 128 MB RAM, UDMA, 8 MB video, PCI Ethernet card, etc...) and this will only improve as hardware becomes faster.

I was also concerned about using ethernet I/O, but on a dedicated network I am seeing update times around 2-3 ms with the Automation direct I/O and HEI EBC modules when running under Windows 2000.

I have been using Windows 2000 since beta 2, but have only recently started investigating its suitability for control with its final release in Feb. I must say that I very much like what I am seeing and have been able to keep scan times down in the 10-15ms range even under heavy system load. I find W2K to be extremely stable (very uncharacteristic of Microsoft's other OSes,
both NT4 and 9x). I think competition from other OSes (Linux especially) has prompted Microsoft to finally give stability first consideration. The
new ability to tune quantums (amount of time that a thread gets the CPU) under Windows 2000 is helpful also. I have never just taken people's word about any particular OSes advantages or liabilities, so I tend to do a lot of testing for myself. Too many people have very strong opinions about Windows and Linux without having extensive experience using or programming
in both OSes - I want to see proof though testing and experimentation myself.

Since my interest in this project has been primarily in a open source soft PLC with primarily ethernet based I/O, I am leaning heavily towards W2K. I know that this statement might distress some of the more rabid Microsoft
haters here, but I am more concerned with using whatever tools that will get me to my goal with the least pain possible. I have been keeping an eye on the GCOM effort in Linux, but I am not willing to give up the power that COM+ and DCOM gives me, so if GCOM becomes more mature on Linux I might rethink my direction. There are plenty of examples of open source projects for Windows and I don't see any problems with this for what I am interested in. I am also moving away from the idea that a open source PLC project must support Ladder Logic (visual assembly language <g>) and towards a object oriented approach in programming the soft PLC.

If anyone here is interested in joining me in developing a open source soft PLC to run under W2K, let me know. And if my goals are not compatible with being here on the LinuxPLC list please say so and I'll move along to another
place :)

Regards,

Phil Covington

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Curt Wuollet

Hi Phil,

You have a place on the list as far as I'm concerned and you won't find a more committed Linux bigot:^) There is no reason we can't share ideas even if we can't share code. I cannot get behind an NT implimentation for moral, legal,
ethical, financial and technical reasons, but, Open means open to everyone. At the point where we exclude anyone, I'll be moving along. To answer JB's original question, I am pretty much back to the original plan. As I have time,
I will be coding to fill a map from the Modbus/TCP driver, such as it is, and writing an experimental framework to perform logical operations against it. I was simply waiting, but, with each passing day the interest and drive for a
Open Source Linux PLC is waning and I intend to proceed until I have something to post. That's what I can do to make it happen. A working toy
is better than elegant vaporware, and I need a basic engine for testing. I have been pretty much swamped with my day job, but, if I want it bad enough, the nights just get a little longer. Opto22 has not responded, I must have pissed
them off somehow, perhaps dismissing their other proto for the ENET stuff because they are the only ones using it. The recent rumblings have unsettled me somewhat also. So, to keep from getting discouraged, I'm going to code. Wago has introduced a Modbus/TCP coupler for their modular I/O. I have used the system in it's Beckhoff incarnation with DeviceNet and I like it. If I can
get a coupler, it's well worth checking out.


Regards.

Curt Wuollet,
Wide Open Technologies.


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Phil Covington

Hi Sheldon,

Yes, there are a lot of interesting projects going on right now in Linux and I am going to keep an eye on them...

I have the opportunity to do some development of a soft PLC on W2K in relation to my day job, so that is what I will be concentrating on for a
while. I am confident that many of the ideas (and some of the code) will be useful for the LinuxPLC here though...

Regards,

Phil Covington

----- Original Message -----
From: "Sheldon Gill" <[email protected]>

> GCOM isn't your only option here. There has been a fair bit of COM
compatibility work done elsewhere, especially in the KDE camp. Corel has
recently added a lot more.
>
> I believe that there is a branch of GNOME looking into COM/CORBA
compatibility as well.
>
>
> Regards,
> Sheldon



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Phil Covington

Rob,

Yes I am able to communicate to the 205 EBC from Linux. I emailed Host Engineering and requested the source code to their SDK and was able to
compile it for Linux... Works good!

Phil Covington
 
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