SHALL-LabVIEW: Package for programming SEC nodes in LabVIEW

The package allows the creation of SEC nodes in LabVIEW. It's interface is designed to be easily integrated into existing projects. The package uses the [SHALL] (https://github.com/SampleEnvironment/SHALL) libraries at its core to handle all SECoP communication and message handling. If you are interested in learing more about the SECoP Protocol please refer to the project website.

Note: The VIs in this project have been built using LabVIEW 2023. The Releases are also available for LabVIEW2019 in the Release Assets.

A. Installation

1. Getting the Source

You can either clone the project directly, which will give you the latest version of the project, or select a Release, where you can also download a version that has been exported for LabVIEW 2019.

Clone the Repository: git clone https://github.com/SampleEnvironment/SHALL-LabVIEW.git

Depending on your LabVIEW version you will able to use the Project as is, or export it for the specific version of LabVIEW you have installed.

2. Setting Up the Platforms Folder

In order for the Qt libraries to work properly, a softlink must be created to the platforms folder (PLATFORMS_PATH = ./shall-labview/[32bit|64bit]/platforms) inside your LabVIEW installation directory.

• First, determine if you have the 32-bit or 64-bit version of LabVIEW installed. And where the installation directory is. From here on I will refer to the installation directory as LABVIEW_PATH:

  • 32bit is usually located under LABVIEW_PATH = C:\Program Files (x86)\National Instruments\LabVIEW 20XX
  • 64bit is usually located under LABVIEW_PATH = C:\Program Files\National Instruments\LabVIEW 20XX

• Next you also need the path PLATFORMS_PATH to the correct platforms folder :

  • LabVIEW 32bit --> PLATFORMS_PATH = ...\shall-labview\32bit\platforms
  • LabVIEW 64bit --> PLATFORMS_PATH = ...\shall-labview\64bit\platforms

• Finally, create the symbolic link inside the LabVIEW installation directory

mklink /d LABVIEW_PATH\platforms PLATFORMS_PATH

3. Check your installation

To check if your installation was successful, you can open the SECoP.lvproj project file and open random-demo/dcy03.vi before running the VI, the correct DLL path must be entered.

It is the same as PLATFORMS_PATH minus the /platforms postfix. It should look something like this:

D:\shall-repos\shall-labview\64bit

or

D:\shall-repos\shall-labview\32bit

If you entered the DLL path correctly and run the Vi, a small SECoP Status window should open.

B. General Overview

A Vi that uses SHALL-LabVIEW to construct a SEC Node, can conceptually be divided into three distinct Sections.

1. Initialisation: In this Section the SHALL Librarys are initialised and the Structure of the SEC Node is specified. After you have specified all SEC Nodes, the Node Complete Vi has to be called to finish initialisation.
2. Main Loop: The main loop can be subdivided further into two sections. First the Get Command loop, that calls GET CMD or GET CMD2 in an infinite loop. It´s purpose is to handle all requests coming from clients, to read fresh data from the hardware, set values, or execute SECoP commands. Furethermore if a pollinterval is set for certain Parameters, the library generates read requestes acording to the time set in the pollinterval. The second section is somewhat optional and would represent your existing project. Here you can just add UPDATE PARAM or UPDATE PARAM2 Vis everytime you read from the Hardware. This ensures that clients connected to the SEC node receive fresh data, when it is available.
3. Exit: The Exit Vi ensures that all nodes that were started inside a given Vi are stopped and removed from the environment. A special eventhandler that is triggered on Panel Close ensures that the nodes are removed even if the panel window is closed without pressing the stop button. Otherwise the node would remain runnign in the background as long as the LabVIEW process is running.

Main Sections marked for random-demo/dcy03.vi:

C. Writing your First SEC Node

Please refer to the Wiki Pages for the tutorial:

1. Initialisation
2. Main Loop
3. Exit

Additional info

Pollinterval

The pollinterval can be set either as a module property or on a per parameter basis as a parameter property. It is the time in seconds that should elapse between each read. Internally, every time a pollinterval is reached for a given parameter, a read request is added to the queue, which is eventually handled by the `Get Command' loop.

Setting a very small pollinterval can severely reduce the responsiveness of a SEC node, especially on nodes with many parameters, and if the acquisition of a new value from the hardware is slow. This would cause the job queue to fill up with read requests generated by polling, resulting in delayed processing of SECoP messages from clients.

Note:

• A parameter property pollinterval overrides the pollinterval set in a module property.
• A pollinterval set to 0 means no polling.

Context ID

The Context_ID enables the independent creation and deletion of SEC nodes in seperate Vis.

Since the SHALL library is architected in a way, where new elements are always added to the last added element of a SEC node, concurrent instantiation will lead to concurrrency problems. These problems are avoided by seperating instantiation contexts by their Context_ID. This means that within a single context, nodes need to be constructed serially, but entire contexts can be started in parallel without issues. In case of the SHALL-LabVIEW integration we have a Context_ID for each Vi.

When the Exit sub Vi is called, only the nodes that were instaniated within the context are stopped and deleted.

Note:

• Context_ID must be globally unique
• If there is only a single node whinin a context you can set: Context_ID == node_id