Driver Integration

If you have ever integrated any kind of device into a LabVIEW application, chances are you looked for a LabVIEW driver, perhaps through the NI Tools Network. Many instrument vendors provide a LabVIEW driver for their device, but some do not. In these cases, drivers may instead be provided for Python or C#. 

If the device doesn’t have a provided LabVIEW driver, you aren’t out of luck! Whether it’s Python or C#, you can still use that driver to integrate the device with your LabVIEW software (though this blog will focus only on C#). 

Reuse Code 

If your company has multiple projects and uses multiple programming languages, it can be helpful to reuse code between projects. Reuse code improves efficiency and consistency, reduces the amount of time you spend making updates to systems, and makes it easier to train up and onboard new engineers onto your team. Developing core functionality in C# allows both .NET developers and LabVIEW developers to take advantage of it. 

Library Compatibility 

LabVIEW has a lot of functionality, but there’s always that functionality that pops up that you know is available in another package, but you just can’t find a LabVIEW version. For example: 

• JSON serialization 
• Database interaction 
• Calls to web services 
• Interaction with Windows features (e.g., Active Directory) 
• Cryptographic utilities  

Best Practices for Using C# DLLs in LabVIEW

Storing Source Code and DLLs 

DMC always recommends keeping your source code in source control such as GitLab. Source control enables you to track changes that have been made over time and improve overall project quality. You can also configure GitLab or GitHub to build your library automatically when changes are made and to store the output. This way, you don’t need to worry about different developers’ build environments, and you have a common storage location for the output. This practice is called Continuous Integration/Continuous Deployment, or CI/CD. 

If you’re using CI/CD, the best practice for storing built code is to store it as an artifact from your CI/CD pipeline in the source control system rather than committed to the repository. If the artifact is ever deleted, you can manually trigger a rebuild in most systems to rebuild. For more information on CI/CD pipelines, check out this DMC article by Gabby: Intro to CI/CD Pipelines. 

If you are using a library written in C#, C, or C++ and you are not building using CI/CD, I recommend keeping the DLL file somewhere in your class hierarchy near the VIs using it. For example, if you have a set of VIs for reading from a device that will use this DLL, place the DLL in the same folder as the VIs. Alternatively, place all of the DLLs together at the root of your project. This ensures that anyone copying or backing up the code will have the libraries in the correct location. 

For more information on the benefits of CI/CD, check out this article on quality from Chris: ADG Mission Critical Applications: Quality Matters.

Versioning and Metadata

If, in the process of troubleshooting or upgrading a system, you need to edit your custom DLL, you should use C#’s version control features to help you and LabVIEW keep track of what version is being used in the code. You can set the version and the metadata for the DLL using the Assembly Information menu in Visual Studio. 

When you replace the DLL in your code by deleting the old DLL and copying the new one in, you will get a warning pop-up notifying you that the LabVIEW code is pointed at a new DLL version. If you intended this change, this is a helpful reassurance that your change was found. This is also good to know if you’re opening a LabVIEW project and you aren’t sure that the version of the DLL your code is using matches the version last used in the LabVIEW project. If the DLL versions are unexpectedly different, that can indicate that you need to verify the DLL’s usage for any changes. 

Use LabVIEW-Friendly Types 

Not all C# types are easily usable in LabVIEW. Many are accessed in LabVIEW as .NET references, rather than native types that you’re used to in LabVIEW. One example that comes up frequently is Lists vs Arrays. In C# development, Lists are used frequently to store multiple items. However, if you try to use a List as an input or output from a C# method in LabVIEW, you’ll need to put in a lot of property nodes to get the data you actually want.  

In the following example, I have a simple class that returns either an Array or a List of strings. 

When I use that class in LabVIEW, the Array comes through as a LabVIEW Array of strings, which will be easy to handle natively! The List, however, comes in as a .NET object reference. It is possible to use but it will be more difficult and messier. 

If you are integrating a C# DLL that uses LabVIEW-unfriendly .NET types like List, you can create a wrapper DLL that translates the difficult-to-use elements into natively supported LabVIEW types. Continuing the List and Array example, if my Device Driver provides its readings as a List. 

I can create a wrapper class for the driver that will convert the readings from a List to an Array. Now I can more easily call my wrapper in LabVIEW instead of the original driver. 

Troubleshooting

If the C# DLL doesn’t work immediately, you’ll need to do some troubleshooting. The following tips can be helpful for troubleshooting the interaction between the DLL and LabVIEW.

Debugging DLL Calls Made in LabVIEW

The best way to troubleshoot is to see how your DLL behaves when it receives data from LabVIEW. To do this, it can be helpful to configure the Visual Studio debugger so that you can hit breakpoints in your C# code when the library is called from LabVIEW. Note: for this process, you will need to be using a DLL built in the debug configuration. 

In Visual Studio, select Debug > Attach Process. 

In the Attach to Process pop-up, select LabVIEW from the list. Click Attach. 

Place breakpoints in your C# code as needed. When you’re ready to debug, open LabVIEW first, then run the Visual Studio debugger (after the first configuration described above, you can run the debugger again by selecting Debug > Reattach to LabVIEW.exe). Run the LabVIEW VI that calls the library, and when your VI calls the DLL you will see the breakpoint hit in Visual Studio. 

Creating a Console Application

Alternatively, you can quickly create a Console Application to test your library. In the same Visual Studio Solution, create a new project of type Console Application, use it to access the methods in your library, attempt to run it, and print troubleshooting information to the console. In this way, you can isolate your testing to just the C# library, without involving the LabVIEW code. 

Review the Errors on the Property and Method Nodes

The errors that come out of the C# nodes can give you a clue as to what’s happening under the hood. When an exception occurs in the DLL, you’ll get a pop-up like this in LabVIEW. 

I have annotated the parts of the pop-up that include information that is helpful for troubleshooting. When searching for information on these errors, make sure you don’t include the LabVIEW-specific sections and use only the actual C# exception. All errors from a .NET node have LabVIEW error code 1172 (shown at the top). The actual exception from .NET, which will be useful in your search, is shown at the bottom. 

Do you have a complicated driver or library that you need help with? DMC loves a challenge! Submit an inquiry today, and we will be happy to help. 

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DMC values the close connections our employees have with each other, both in and out of work. One of the reasons why we are so close is our activity fund, which is a monthly budget set aside for DMCers to connect with each other through fun events and has been a DMC staple for many years. For this month’s activity fund event, we decided to have a virtual pizza party!

Pizza Preparation

Each participating DMC employee was given $25 to spend on whatever pizza ingredients they wanted. In addition, a few people decided to use this as an opportunity to clean out their fridges and finally use their near-expiration veggies, languishing bottles of olives, and in one case, some leftover fettuccine. Why not kill two birds with one stone? We are engineers after all—we know a thing or two about efficiency.

Around twenty DMCers participated in the pizza party, and as you can imagine, there was a wide variety of pizza interpretations. We believe that every pizza is beautiful and delicious in its own right, so pizzas weren’t ranked from best to worst, no matter how “interesting” they were. Right off the bat with the crust, many chose to go with an untraditional route. There were bagels, whole-grain flatbreads, and many rectangular pizzas. Come on, circles are hard!

Toppings?

As you can probably imagine, toppings were a hot debate topic, and we’re not just talking about pineapple. To the shock and dismay of our fungi- and veggie-loving coworkers, some DMCers absolutely detest mushrooms and olives on their pizza. Lauren decided to avoid these savory pizza toppings politics altogether and made an apple pie dessert pizza. And of course, as mentioned earlier, Ramone’s topping of choice was leftover fettuccine, which he alleges was actually quite delicious. Say what you will, but you can’t say DMCers aren’t creative!

The night was not without incident, however. Elizabeth managed to set off the smoke detector five times, which I assume must be a record. But the pizza fortunately survived, and the virtual pizza party was a smashing success for everyone involved. We can’t wait for the next activity fund event!

Check out some pictures of the other pizzas below and read more about other fun DMC activities!

David’s pizza with artichoke hearts and peppers

Lauren’s apple pie pizza

Lillian’s homemade pizza

Nick’s pizza with mushrooms, spinach, and peppers 

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DMC had our second virtual trivia night on January 27, hosted by The Castle, a favorite board game cafe of our Boston office. In total, there were eight teams of five to eight people, including both DMC employees and some lucky plus-ones. Since most of us are engineers, the question categories were largely science and technology-oriented. That is, except for one category: DMC Youtube.

Our Youtube Channel

For the past eleven years, DMC has published almost 300 videos to our YouTube channel. From peeks into some of DMC's exciting projects to detailed technical guides, we post a lot of useful content for engineers. However, as stated earlier, DMCers like to have fun— and we like to show that off on our Youtube channel. 

We wanted to test our fellow DMCers' knowledge on some of our most iconic videos, like DMC Boston's "Nobody But Me" officewide lipsync or DMC Houston's "Gotta Solve 'Em All." We went through our videos and compiled a list of challenging trivia questions. For example, what food does the St. Louis office review in "DMC Public Radio? Sandwiches, of course (the actual title is "All Sandwiches Considered"). In "Room Pronunciation Guide," who introduces the new Boston office room names? Duh, Muppets!

Try to answer this question: "In a DMC Texas music video, what parody did the office perform?" Do you think it was SCADA Boi/Skater Boi or "She thinks my code is sexy"? Spoiler alert: It was both. 

Trivia Night Results

In the end, only one team came out on top. Congratulations to DMC's Lillian Walker, Jacob Bruce, Chris Cilino, Abby Greentree, and Nick Leisle, whose team narrowly beat out the others to win top prize! We look forward to hosting more DMC trivia nights and we would love to hear how you're staying connected.

Read more about other fun DMC activities!

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BLUG meets regularly to discuss various LabVIEW programming techniques, technologies, application design pattens, and much more. 

Come collaborate with LabVIEW software and NI hardware users in the Greater Boston area to improve on your current projects and get fresh ideas. 

Discussion Topic:

• Presentation by Paul Ross from Composed Systems on designing an even logging framework that complies with SOLID Software Design Principals
• User Group 2020 Planning
• There is an opening for an additional presentation. Please email Lillian.Walker@localhost to volunteer to present

Event information:

Where:
DMC, Inc. 
20 Holland Street,
Suite 408
Somerville, MA 02144

When:
February 27th, 2020 from 5:30-7 P.M.

Arrival by Train:
DMC is located a few feet from the David Square Red Line T Stop.

Arrival by Car:
Parking is available on top of the Buena Vista Lot for $1/hr. for up to 3 hours. Alternative parking can be found at Alewife Station for $7/day or $8/overnight. Take the train one stop to the Davis station.

Dinner will be provided by NI.

For more information about BLUG visit the NI forum and register here.

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Come collaborate with LabVIEW software and NI hardware users in the Greater Boston, MA area to improve on your current projects and to get fresh ideas.

Discussion Topics

• NI Measurement Studio: LabVIEW DAQmx in Visual Studio .NET
• Little LabVIEW Lectures: Community Supplied Tips & Tricks. Demos are welcome!

Location, Registration, & Additional Information

DMC, Inc.
20 Holland Street
Suite 408
Somerville, MA 02144

By Train
DMC is located a few feet from the Davis Square Red Line T Stop.

By Car
Park on top of the Buena Vista Lot, and it is $1/hr for up to 3 hours. It's a $30 fine if you go over, and they will always get you. Alternatively, park at Alewife Station for $7/day or $8/overnight. Take the train one stop to Davis Station.

Learn more about DMC Boston.

Find out more details about this great event and register to join in.

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This isn’t an out of the box feature for a WinCC Professional trend control, but with some simple scripting, it was ready to go! Check out this quick guide to get started.

Step 1: Create the Required Tags

On the HMI, we will need to have access to three tags:

Cycle Start Time – A DateTime tag of the start time of the trend

Cycle End Time – A DateTime tag of the end of the trend

Cycle Start – A boolean tag that is changed after the cycle start and end times are set

Step 2: Create the Trend Control

1. Add an online trend control to your screen.
2. From the properties list, select Trends.
3. Edit the Data Source for the default trend to point at the tag you want to trend.

Step 3: Create the UpdateTimeAxis Script

1. In the project tree, expand your IPC project and drill down to Scripts > VB scripts > Add new VB function.
2. Name the new function. I named mine UpdateTimeAxis.
3. Fill in the script with the following:

Function UpdateTimeAxis()
'Declare variables
Dim objTrendControl

'Get the trend view
Set objTrendControl = HMIRuntime.Screens("Home Screen").ScreenItems("f(t) trend view_1")

'Set the Online option to False
objTrendControl.Online = False

'Set the start and end time parameters for the trend view
objTrendControl.TimeAxisBeginTime = CDate(SmartTags("StartDateTime_Trend"))
objTrendControl.TimeAxisEndTime = CDate(SmartTags("EndDateTime_Trend"))

'Release the objects
Set objTrendControl = Nothing

End Function

Function UpdateTimeAxis()
'Declare variables
Dim objTrendControl

'Get the trend view
Set objTrendControl = HMIRuntime.Screens("Home Screen").ScreenItems("f(t) trend view_1")

'Set the Online option to False
objTrendControl.Online = False

'Set the start and end time parameters for the trend view
objTrendControl.TimeAxisBeginTime = CDate(SmartTags("StartDateTime_Trend"))
objTrendControl.TimeAxisEndTime = CDate(SmartTags("EndDateTime_Trend"))

'Release the objects
Set objTrendControl = Nothing

End Function

In essence, this script finds the trend control on the page, configures the start and end time of the axis, and then cleans up after itself.

Step 4: Configure a Trigger for the Script

1. In the Project Tree, select Scheduled Tasks.
2. Add a new scheduled task.
3. Under Properties > General > Starting Time, set the Trigger as a Tag Trigger and select the Cycle Start tag you configured in Step 1.

Conclusion

Now when you run your application, when that Cycle Start tag is changed, the Time Axis of the trend should update to show the time frame from the Cycle Start Time to Cycle End Time tags.

Learn more about DMC’s experience in SCADA systems or contact us to get started on a project today.

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We were setting the IP Address on a new Allen Bradley CompactLogix PLC using Rockwell's BootP utility. When we tried to submit our changes, we go the following error:

Credit: Rockwell Automation

Error message text: "Communication Error. Failed to complete the requested operation. See status bar for further information then press OK when ready to continue."

What's The Quick Solution?

Like us, your first instinct might be to close the error message, but what you need to do is leave the popup open for about a minute. Then click OK and try again. And miracle of miracles, the second time it worked!

So the next time you're setting the IP Address for a PLC and get this error message, just slow down and take a minute before closing that pop-up!

Learn more about DMC's Allen Bradley PLC Programming and Rockwell FactoryTalk expertise. 

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Not too long ago, Friday mornings were consistently celebrated with waffles for breakfast as a way to ring in the weekend. Realizing that none of the newer engineers even knew we had a waffle maker, Adam and I decided to bring back Waffles for Business!

Bright and early, we started whipping up some waffle batter, including gluten-free batter for our gluten-intolerant friends.

For waffle toppings, we had a variety of berries, whipped cream, and maple syrup. Alexander brought in a Lebanese topping that he described as "marshmallow with rose water." This sparked a long discussion of the magic of rose water, prompting everyone to commit to heading to their local Middle Eastern market to pick up a bottle.

Waffles For Business was a great way to kick off the weekend and I hope that we can continue to make our delicious breakfast from time to time.

Learn more about DMC's company culture.

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