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I need to come up with a CM process for PLC code.

Currently, the system is developed using RSLogix 5000. The build product is a monolithic file that can be loaded onto a PLC for execution and edited directly in the development environment. With multiple developers, this has become a problem. They're stepping on each others changes.

As an analogy, it's as if, when doing Java development, the only wway to edit and save the source would be to load up a *.jar file into your IDE, make the change, and then save it back to the jar file. This is less than ideal.

How can I coordinate changes between multiple developers working with PLC's?

Dave
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9 Answers9

7

You need specialized versioning system for PLCs like VersionDog.

From the manufacturer:

"Special support with Smart Compares for SIMATIC S5, SIMATIC S7, SIMATIC PCS 7, WinCC, WinCC flexible, InTouch, CoDeSys, TwinCAT, Phoenix PC WORX, RSLogix, Schneider Modsoft, Schneider Concept, Schneider Unity, SINUMERIK 840D, Bosch IndraWorks and more. Also robot programs from ABB and Kuka and office related data formats like Microsoft Word, Microsoft Excel and Adobe PDF are perfectly supported by versiondog.

Update: Here is a screenshot showing ladder version compare. I guess that's what most PLC folks are interested in. We also use it to schedule e-mail report if PLC offline and online application versions are a match, as an alarm that something has been changed in PLC but not put into version control server.

avra
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  • There are also some videos on YouTube showing versiondog in action: https://www.youtube.com/watch?v=bfaBcd6y2vQ&list=PLf5juRU8pcLKZgGhl0T-S1Im-OurpZ-A-&index=4 – mihca Aug 26 '21 at 09:43
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If we are talking about one big binary files, then a VCS (centralized or decentralized) is not the best tool for the job.
An external referencial (a shared disk for instance) where a batch will copy and label the current PCL state is better.
See "Tracking Software History"

To avert discontinuities in the historical record of revisions, old versions of programs must be stored.
“We take it a step further, though. Using our MDT AutoSave, we actually go out and interrogate the equipment. Overnight or at whatever frequency is specified, the software reads the programs in the PLCs and then compares that information to the last known program. The version-control software will copy the new program and store it and [then] compare it to the last one.

Launching version control is fairly simple. Required is software installation and then hardware configuration. “You would need a server and a couple of weeks of engineering and you’re good to go,” Perysyn says. However, his company uses a “shrink-wrap approach” that involves installing the software and then customization by users filling in the blanks.

That being said, when you have multiple changes from multiple developers, you need an integration environment where a first delivery can be done and validated, before pushing it to the actual server.

See also this post.

Fabian
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VonC
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7

I use Unity Pro, so this may not apply for other brands.

Unity can export an "archive" file which is XML which describes the PLC program and IO setup in its entirety. After commissioning changes, I create an export and check it in to my local Git repo. This gets me an annotated history of changes, but no visual comparison. I can always use UnityDiff for comparison.

Check out http://www.mdtsoft.com/ also

v0n_hydro
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5

RSLogix5000 has always prohibited multiple users from opening and editing on the same .ACD simultaneously. However, if multiple users have identical .ACD files, open them, and all make connections to the same target controller, they each can edit on the controller simultaneously, but only if they are working on different routines. Other's edits appear automatically, if they were to look at another programmers routine.

Note that working online like this is usually done with the PLC running, even sometimes with the target system (some kind of machine) operating. This kind of arrangement for the purpose of completing work faster, or in some cases because the system is huge. No one develops like this, as it is really a debug tool and impractical for significant changes.

If one programmer finishes, and another is not done, the unfinished work of the other will be saved to the first programmer's .ACD when they save. Whoever saves last will have everyone's work.

Like others have mentioned in this thread, using file date is fairly reasonable. Some companies use a version control variable that is usually displayed on a connected HMI. Other companies use a separate document that documents who and what changes. Sometimes version notes are placed in a lengthy rung comment in the main routine.

My company uses a separate change log, and dated archive copies are maintained. Multiple programmers are only used in the most extreme cases. Someone is always designated to maintain the offline file integrity, usually the person who will be working the longest, or the project manager.

It is important to note that rung comments are not carried from one user to another before RSLogix5000 v21 because previous versions didn't store comments on the controller.

All this said, you might be trying to manage offline development. I haven't seen any sophisticated methods for this. Usually programmers write the needed routines separately, and a project manager will assemble them into a single project. The cleanest approach I've seen is where a project manager will create an architecture with global functionality, and assign routine work to others, giving them a copy of the .ACD to work with. They return the .ACD with changes, and the project manager copies and pastes their routines into the "master" project.

Dennis
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  • Your last paragraph is what we were doing. Coming from a conventional software background, I was hoping for more, but as shown here (and confirmed by the PLC dev's on that program), that's about as good as it can get. Also, welcome to StackOverflow. – Dave Mar 24 '15 at 11:52
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About RSLogix5000 specifically, I have seen developers use an emulated PLC and make their changes online. The final product once developed is then put together with all the comments (as they are not contained in the PLC) and then commissioned. There are issues with changes that cannot be done online, such as AOIs. There are tools in place to stop two people editing the same logic online at once and to take ownership of sections. Backups can be done in the form of uploads, but there isn't any way to track changes.

It is a messy problem, messier still for when you are maintaining a system as you want an .ACD that you can go online with, as unless you are somehow doing a diff with the RSLogix compare tool you just see unreadable machine code like "+|Éû³´¬ÙÆW×晵‚>Ù,"

The most common revision control I have seen (sadly) is just saving the the latest file, then taking a copy and adding the current date to the file name, like the recommended control.com post described.

Montag451
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daniel
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  • Thanks for the response. This is no longer my problem, but I'm still definitely interested in possible solutions. I've had this problem before with PowerBuilder, and it was just as ugly. – Dave Jun 10 '11 at 13:54
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This is a very good question and it really depends on what you want it to do. If you are only using Rockwell equipment it might be helpfull to look at their solution, I think it's called FactoryTalk AssetCentre. Currently I am looking into using Bazaar from Canonical. One thing that VonC pointed out is that a piece of software that can interogate the PLC is a deffinate plus, not a must in my oppinion but it sure as hell helps.

Am I reading your question properly and you have multiple developers working on the same PLC code at the same time? It's a scary thought but I know it sometimes needs to happen, Siemens PLC's are a bit easier to program with multiple developers but I would assign one person to consolidate and test all the changes before committing to the PLC. Any CVS system will let you create branches for every developer but how you would get them to consolidate their changes is the million dolar question.

Bart.

Bart
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  • I'm not a PLC coder, so I can't say definitively that they're working on the *same* code, i.e. both working in Foo.java at the same time, but thay are definitely trying to independantly extract Foo.java and Bar.java from Baz.jar, make their respective changes, and then independatnly check in Baz.jar. Does that analogy make sense? – Dave Dec 01 '10 at 12:57
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    It's the exact same problem you see with PowerBuilder and the *.pbl files. – Dave Dec 01 '10 at 13:01
  • Sorry I should have clarified that I meant working in the same file but different sections of the code. If you are programming a PLC using RSLogix it has one file (.ACD) but this file holds the PLC configuration, code for different routines etc. If one programmer changes routine #1 and another changes routine #2 they will both return file.ACD and someone then needs to merge these. – Bart Dec 01 '10 at 14:18
  • Right. This is typical software development: if two people change the same file, somebody gets to do a merge. The only thing special about the problem being discussed is that merges happen often. OK, get a good merge tool. Is there another issue? – Ira Baxter Feb 06 '11 at 00:54
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    Ira, I totally agree with you here but the tools available to PLC/SCADA programmers are not up to the same level as what I have seen for other development systems. As far as I know the only merge tool that you have is yourself, Rockwell do have a descent compare tool. – Bart Feb 06 '11 at 16:54
  • There are decent merge tools that will work with arbitary text, including ACD files. See http://stackoverflow.com/questions/572237/whats-the-best-three-way-merge-tool. I'll agree they aren't integrated into the IDEs very well, and yeah that's a PITA. But that's just a procedural pain. The tools exist. FWIW, my company builds Smart Differncing tools, and has handle Rockwell files in the past. See http://www.semanticdesigns.com/Products/SmartDifferencer – Ira Baxter Feb 10 '11 at 23:47
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A simple thing to do would be to do a text diff on the .l5k files so you can easily see whether a developer has been messing with part of the file that is outside of their scope.

  • Yeah, that's pretty much what we're stuck with. – Dave Feb 01 '11 at 20:03
  • @Dave: How is this different than general software development? You may have a number of modifications going on by different developers; what you need is typical configuration management tool merge process in which the latest guy to check has to merge his changes carefully. ... you might want to look at advanced "diff" tools, such as our http://www.semanticdesigns.com/Products/SmartDifferencer tools, which is layout insensitive. We have L5K front ends that could be used with such a tool. – Ira Baxter Feb 02 '11 at 20:16
  • @Ira: in general development, the source code is split up into many small files instead of one monolitic file. – Dave Feb 03 '11 at 13:31
  • @Dave: ... and why do you do that? If it is split up the same way each time, then treat each fragment as a development file. Our SmartDiff tool won't be able to help you because you only have code fragments, so you'll be stuck with regular diff. – Ira Baxter Feb 03 '11 at 15:04
  • @Dave: Sorry, I didn't initially understand what you meant: "in normal development, there are typically a lot of files (small? maybe) and coders tend to work in separate files." True, but sometimes they work in the same file, and then you have merge problem; this is NORMAL. And it isn't different than your situation. You need a merge tool, you'll just use it more often than the typical development process. – Ira Baxter Feb 06 '11 at 01:02
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I saw this question just now from a link at stack exchange: Are There Realistic/Useful Solutions for Source Control for Ladder Logic Programs. Rather than have a link only answer, I'll dupe my answer here:

There is actually a canned solution - from GE-IP of all places. Check out Proficy Change Management. This product does version control from a PLC control systems point of view, rather than a pure version control of files point of view - it works as a layer sitting on top of a VCS (the scary part is that originally this VCS was Visual SourceSafe) and handles rights management, reporting and checkout/checkin.

While the product is from GE-IP, it is designed to support a variety of PLC and HMI systems out of the box.

Full disclosure, I used for work for a company selling and installing PCM (but that was 7 years ago). So if you ask me what it was like back then I'm likely to tell you where it all went wrong!

Community
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Peter M
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In my company we just started a trial with Copia.io Check it out. Our first tests look very promising! It brings, branching, merging, ladder diff etc... for multiple PLC platforms (Rockwell, Siemens, Codesys)..

PS. I work for a company that builds machines, we were looking for version-dog alike solutions with a bit more power in collaboration and diffing capabilities. I used tools like Mercurial, Git, Tortoise in past companies (not for PLC though).

AintLifeGrand
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