LabWindows™/CVI: Driving Efficient and Productive Test Development for More than 20 Years

NI LabWindows/CVI is a proven ANSI C development environment for test and measurement that greatly increases the productivity of engineers and scientists. They use LabWindows/CVI to develop high-performance, stable applications in the manufacturing test, military and aerospace, telecommunications, design validation, and automotive industries. LabWindows/CVI streamlines development in these areas with hardware configuration assistants, comprehensive debugging tools, and interactive execution capabilities that developers can use to run functions at design time. Using built-in measurement libraries, you can rapidly develop complex applications, such as multithreaded programs and ActiveX server/client programs. With the flexibility of LabWindows/CVI, you can protect your code investment by reusing legacy code in a familiar environment and seamlessly integrate distributed test systems running on Windows, Linux®, or real-time platforms.

20 Years of Reliability and Innovation

LabWindows/CVI 8.5 software introduces new technologies for enhanced developer flexibility including:

• Collapsible source code regions for improved code readability and outlining
• Streamlined tabbed workspace for immediate access to function panels and source files with tabbed browsing
• Support for editing code while debugging, thus tightening the loop between finding a bug and implementing a fix
• Advanced multicore technology in LabWindows/CVI 8.5 Real-Time, with the ability to fully control thread execution on different cores

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What's New with LabWindows/CVI

Integrated Environment

LabWindows/CVI 8.5 enhances the fully integrated workspace provided by LabWindows/CVI 7.0, which replaced the Project window with a Workspace window that you can use to manage multiple projects and windows from one environment. LabWindows/CVI 8.5 now integrates function panels and debugging windows, such as the Variables, Watch, and Memory Display windows, into the Workspace window.

The Workspace window is divided into five main areas – the Project Tree, the Library Tree, the Window Confinement Region, the Output Region, and the Debugging Region.

Figure 1. LabWindows/CVI features a streamlined tabbed workspace in which you can quickly develop, debug, and manage large applications.

• The Project Tree contains the files for each project in your workspace. You can right-click on the items in the Project Tree to access various options, such as the open file, compile file, and remove file from the project options. The right-click menu options vary depending on the file that you select in the Project Tree. You also can view information about each file, customize projects and workspaces, add or remove projects, and specify the order in which projects appear from the Project Tree. You can use the Edit Project dialog box to add, remove, and replace files in a project. You also can specify include paths and source code control options in this dialog box.

• The Library Tree contains a tree view of all LabWindows/CVI library functions, loaded instruments, and instrument drivers. The tree view provides an intuitive interface for finding and instantiating functions. You also can use the Library Tree to access known functions. To find a function quickly, simply right-click on the Library Tree and select Find.

• The Window Confinement Region contains open Source, User Interface Editor, Function Panel Editor, and Function Tree Editor windows and function panels. When you open any of these windows, the menu and toolbar change to reflect specific options for that window. If you prefer the traditional LabWindows/CVI workspace style, you can easily release the windows from the Window Confinement Region.

• The Output Region contains tabbed error, debug output, and search results windows. When LabWindows/CVI finds build errors, run-time errors, and source code control errors in your project, it displays those errors in the Output Region. Double-click an error in the Output Region to highlight the incorrect line in your code. You also can double-click a search result in the Output Region to highlight the found item in your code.
• The Debugging Region contains tabbed Variables, Watch, and Memory Display windows. The Variables window contains a list of all variables, both local and global, and their corresponding values in the current scope. The Variables window also includes the option to jump between locations on the stack. The Watch window displays only user-selected variables and their corresponding values. The Memory Display window displays memory address and value information. You can drag variables from the Source, Interactive Execution, Variables, or Watch windows and drop them into the Memory Display window.

State-of-the-Art Hardware Functionality

Often the most critical process in a measurement application is connecting to an instrument and taking measurements. LabWindows/CVI provides two measurement assistants, which streamline the acquisition process, and a new data acquisition interface, which increases performance up to 20 times for multithreaded measurements and 10 to 20 times for single-point I/O.

New Data Acquisition Architecture

LabWindows/CVI works with the NI-DAQmx Library, which contains functions for communicating with and controlling data acquisition devices. NI-DAQmx next-generation driver software achieves loop rates up to 40 times faster than traditional NI-DAQ when implementing concurrent I/O. Additionally, NI-DAQmx provides 10 to 20 times performance improvements for single-point I/O. These performance gains are realized because NI-DAQmx is a multithreaded driver optimized for NI data acquisition (DAQ) devices.

DAQ Assistant

In addition to the integrated NI-DAQmx Library, LabWindows/CVI features the DAQ Assistant, an interactive interface to the new driver framework. The DAQ Assistant, pictured in Figure 3, interactively defines a measurement task, determines the measurement capabilities of the data acquisition device you specify, and generates code modules that contain the acquisition functionality. When you create a new data acquisition task, you specify the measurement type for the task and the channels to add to the task. For new tasks, you also can select whether to store the task in the project or in NI Measurement & Automation Explorer. If you store the task in the project, the DAQ Assistant generates source code to create the specified task programmatically. The generated source and header files define an entry point function that configures the task and returns a task handle. The DAQ Assistant also generates a .mxb file, which contains a binary description of the task. When you edit tasks in the DAQ Assistant, it uses this file to automatically add all three files to the project when you create a project-based task. The DAQ Assistant also features context-sensitive help topics that describe how you can use it based on your task. The tight integration of the DAQ Assistant and NI-DAQmx with LabWindows/CVI offers engineers who perform data acquisition the most efficient, productive way to take measurements in an ANSI C environment.

M Series

LabWindows/CVI introduces full compatibility with M Series devices, the next generation of multifunction data acquisition devices. These revolutionary DAQ devices offer sampling rates as high as 1.25 MHz, resolution up to 18 bits, timing at 80 MHz, and patented polynomial curve-fit calibration, all at a lower cost per I/O channel. M Series delivers up to 48 digital I/O channels, 32 analog inputs, four analog outputs, and two counters in a single device. For more information about M Series, visit the M Series home page.

Instrument I/O Assistant

Engineers and scientists in the test industry recognize that easy connectivity to various instruments from different vendors is crucial when selecting a software package. LabWindows/CVI, along with NI LabVIEW software, is an industry leader in instrument control and connectivity through an Instrument Driver Network of more than 5,000 instrument drivers from more than 200 vendors. You can use these drivers to easily program instrument control applications. LabWindows/CVI takes instrument control to the next level of productivity with the Instrument I/O Assistant, with which you can generate code to communicate with devices such as serial, Ethernet, and GPIB instruments without using an instrument driver.

Figure 3. The LabWindows/CVI Instrument I/O Assistant automatically parses instrument data, generates reusable code, and interactively defines basic communication.

The Instrument I/O Assistant offers a simple interface you can use to quickly prototype applications and autoparse instrument data, without any programming. You can easily import the generated code into any existing application, which removes the tedium of writing instrument connectivity, basic communication, and string parsing code. By writing two lines of code, you can invoke more than 300 lines of code created by the Instrument I/O Assistant and quickly focus on taking measurements.

See Also:
DAQ Software
M Series Multifunction DAQ Devices

Deterministic Performance with the LabWindows/CVI Real-Time Module

It is difficult to implement highly reliable and deterministic applications using general-purpose OSs such as Microsoft Windows. Reliable, deterministic applications require more control over all operations running on the system – a level of control that general-purpose OSs typically do not provide. Therefore, test and control engineers often turn to real-time OSs to implement applications that require deterministic performance or high reliability.

LabWindows/CVI works with the LabWindows/CVI Real-Time Module so you can create reliable, deterministic applications that target dedicated real-time hardware. This feature reduces development time for real-time applications by helping you:

• Reuse existing ANSI C code and the familar LabWindows/CVI development environment
• Target commercial off-the-shelf (COTS) hardware targets, specifically PXI and PC targets, as well as I/O
• Use a single toolchain for real-time and Windows development

After you deploy your DLL to a real-time target, you can debug your DLL remotely using the full functionality of the LabWindows/CVI debugger.

Figure 4. With the LabWindows/CVI Real-Time Module, you can create reliable, deterministic applications that you can run and remotely debug on dedicated real-time hardware.

See Also:
LabWindows/CVI Real-Time Module

Multicore Execution Tracing and Debugging

Executing tasks in parallel often uncovers design flaws that go unnoticed in single-threaded applications – especially when correct application behavior depends on the precise timing of execution, memory access, and communication between multiple tasks. LabWindows/CVI not only provides simplified ANSI C thread synchronization functions and optimized threading constructs to address these challenges but also contains several advanced features that simplify troubleshooting and design optimization on multicore systems.

In particular, you can use the LabWindows/CVI Threads window to view detailed debugging information on a per-thread basis. The Threads window lists all threads in the program that are being debugged.

Figure 5. With the LabWindows/CVI Threads window, you can easily switch between threads currently being debugged in the environment.

You can use this dialog box to select the threads whose local variables and call stack you want to view. When you select a thread from this dialog box and click View, LabWindows/CVI displays the local variables for the selected thread in the Variables window and displays the current source position of the thread in the Source window. The Up Call Stack, Down Call Stack, and Call Trace commands in the Run menu display information about the currently selected thread.

In addition, the Real-Time Execution Trace Toolkit includes a Highlight CPU Mode option that you can use to highlight all thread activity that executed on a particular CPU. By highlighting all the thread activity on a particular CPU, you can trace the execution path of each CPU in the system to determine whether the threads executed as you intended. Also, by seeing processor use in the Real-Time Execution Trace Toolkit, you can prototype the performance potential of different designs based on your assignment of various portions of your code to particular processors.

Figure 6. Select a particular CPU from the Highlight CPU Mode option to highlight all thread activity that executed on that CPU.

See Also:
Debugging Multicore ANSI C Applications with LabWindows/CVI

Simplified Cross-Platform Communication

As businesses continue their drive toward enterprise connectivity, applications requiring distributed solutions continue to grow. This trend raises significant challenges for the programmer implementing these solutions. There are numerous types of hardware, software, and protocols used across applications. This complexity forces a programmer to negotiate between the different protocols to transfer data, which requires a great deal of development time and resources. LabWindows/CVI takes a major step forward in simplifying the programming necessary for such applications. The new Network Variable Library, which is based on the NI Publish-Subscribe Protocol (NI-PSP), provides a simplified API for you to use if you need to share live measurement data between two applications on the same system or across the network. You can also use this API to pass data between real-time systems without impacting performance. The API is designed in a way to abstract the low-level communication protocol, such as TCP/IP or DDE, while being flexible enough to be compatible with a wide variety of measurement data types, such as scalars, multidimensional arrays, and structs.

The LabWindows/CVI Network Variable Library provides the following functionality:

• Subscriber – receive new data that is published to a network variable
• Buffered Subscriber – receive buffered data and get events when buffer is empty, overwritten, or stale
• Writer – update network variable with new data
• Buffered Writer – asynchronously update published data
• Reader – read new data stored in a network variable
• Asynchronous Reader – read new network variable data in an independent thread
• Data Functions – manipulate network variable data
• Network Variable Browser Popup – automatically browse for available network variables
• Browser Functions – create a custom interface to browse network variables

Figure 7. Network variables describe software items that exist on a network and can communicate between programs, applications, remote computers, and hardware.

The network variables send data to a server called the shared variable engine, which then publishes the data to all clients on the network reading the network variable. Because a publish-subscribe architecture is used to transfer data, many clients can read and write to the same variable without writing additional code. Furthermore, the shared variable engine can be hosted on Windows PCs and real-time targets.

The LabWindows/CVI Real-Time Module expands the functionality of network variables. With LabWindows/CVI Real-Time, you can configure a network variable in conjunction with a thread-safe queue when handling data. Using thread-safe queues ensures that passing data between tasks or over the network does not add jitter to an application.

See Also:
Network Variable Resource Page

Advanced Data Management and High-Speed File I/O

LabWindows/CVI introduces a new data storage format called technical data management streaming (.tdms), which contains both binary data to efficiently store more than 100 billion data points and metadata with information describing the data and channels. This format is optimized for high-speed data streaming, and, by combining binary data and metadata, offers the benefits of both efficient file storage and self-describing files. The descriptive information located in the TDMS file, a key benefit of this format, provides an easy way to document the data without having to design your own header structure. As your documentation requirements increase, you do not have to redesign your application; you simply extend the TDMS data model to meet your specific needs. You can use the TDMS file format in both LabWindows/CVI and NI DIAdem, a powerful data management tool capable of handling more than 100 billion data points in a single file. After you have acquired large amounts of data, you can use DIAdem to interactively manage, inspect, analyze, report, and automate your data.

See Also:
Introduction to the LabWindows/CVI TDM Streaming Library

Scientific Advanced Analysis

LabWindows/CVI provides powerful algorithms and functions designed specifically for measurement analysis and signal processing. The LabWindows/CVI functions for analysis include signal processing tools you can use to condition and transform your signal using smoothing windows, digital filters, and frequency-domain transforms. With the mathematics functions, you can easily manipulate 1D and 2D arrays as well as perform complex numeric arithmetic. You can also use these functions to apply various user-defined formulas to your data for vector and matrix algebra. With these functions, you do not have to write your own algorithms to turn raw data into critical information. To make sense out of raw data, you need to manipulate, process, and analyze acquired data and extract information. With the LabWindows/CVI Advanced Analysis Library, available in the LabWindows/CVI Full Development System, you can:

• Extract information from acquired data and unique measurements
• Generate, modify, process, and analyze signals
• Add intelligence and decision-making capabilities to your applications
• Perform inline and offline analysis
• Use common-purpose as well as specialized tools and add-ons
• Take advantage of academic analysis examples

Figure 9. LabWindows/CVI includes a powerful, comprehensive set of functions for analyzing data.

See Also:
Complete List of LabWindows/CVI Analysis Functions

Open Technologies – .NET, Internet, and XML Libraries

Because industry standards are pushing more open technology, such as .NET and XML Web services and Internet-enabled applications, LabWindows/CVI incorporates these technologies.

.NET Library

With LabWindows/CVI, you can take advantage of the latest Microsoft .NET technologies to invoke methods and set and get properties from .NET assemblies. The .NET assemblies are the building blocks of all .NET applications; thus, LabWindows/CVI programmers can use this functionality to call Web services such as those for sending automated e-mails, accessing rich database functionality, and interacting directly with Microsoft Windows API methods including those for viewing CPU use and logging errors.

Internet Library

LabWindows/CVI includes the Internet Library, which you can use to instantly connect your applications to the Web through e-mail, FTP, Telnet, and ping. The LabWindows/CVI Internet Library provides the following functionality:

• FTP – Connect to an FTP server with a username and password and upload and download files.
• Telnet – Read from and write to a Telnet server on a remote machine.
• POP3 – Connect to your e-mail server to download and send e-mail.
• SendMail – Quickly send e-mail by specifying the address, server, subject, body, and attachments.
• LaunchDefaultWebBrowser – Launch your default Web browser with a specified URL.
• Ping – Quickly locate other computers on your network with ping functionality.

With this added functionality, you now can send e-mail or text messages to notify operators of specific events, such as a machine overheating. You also can log acquired data to an FTP server. The existing TCP Support Library also features a comprehensive offering of communication functions, including RegisterTCPServer and ClientTCPRead.

XML API

LabWindows/CVI also contains an XML function library. The cvixml.fp instrument driver includes functions you can use to create and modify XML documents. An XML document is a hierarchical representation of data, similar to a tree with parent/child relationships. The data appears as elements, which consist of a tag name and a value. Elements also can contain attributes. The cvixml.fp instrument driver includes the following classes:

• Document Functions – Open XML documents for modification, create new XML documents, and save and format modified XML documents.
• Element Functions – Create new elements, modify existing elements, copy elements, search for elements by their tags, and delete elements.
• Child Element Functions – Get the number of children of an element, the children of an element, and the parent of an element.
• Attribute Functions - Get the number of attributes of an element, get the attributes of an element, create new attributes, modify existing attributes, and delete attributes.
• Error-Processing Functions – Process errors.
• Low-Level Functions – Get the ActiveX handle of a document, the ActiveX handle of an element, and the ActiveX handle of an attribute.

Saving Function Panels in XML Format
In addition to the XML API, LabWindows/CVI also provides the option to save function panel files in the XML format and load function panel files from the XML format. Select Options >> Save in XML Format in the Function Panel Editor to convert function panels to XML documents. You can open the resulting .fpx file in any XML editor or text editor, or in Microsoft Internet Explorer.

Visualize Test and Measurement Data

Each version of LabWindows/CVI continues to offer additional user interface controls and capabilities that you can use to create professional front ends for your test and measurement applications.

Native Windows-Style Controls

In LabWindows/CVI, you can visualize test and measurement data on instrumentation-specific controls and now you can make use of the updated user interface appearance of Windows-style controls. You can display controls such as tabs, switches, rings, and buttons based on your local Windows system theme.

Figure 10. You can create modern user interfaces with updated theme-based controls.

Interactive Graph Axes

To help you visually inspect acquired measurement data more effectively, LabWindows/CVI graphs offer rich interaction at run time, including changing the appearance of plots through the interactive legend. In addition, you can interactively edit the range of an axis and invert the axis at run time by clicking on the axis end labels for graph controls.

Extended User Interface Events

You now have the ability to capture more user interaction with your applications. Without using low-level programming, you can easily capture additional mouse interactions such as sensing whether a user scrolls on a tab or list control and detecting panel movements and resizing actions. For instance, if you want to control your users’ experiences if they resize or move the user interface, you can detect these actions, programmatically handle the associated events, and call appropriate functions.

Productive Development Tools

LabWindows/CVI also includes key productivity features with which you can efficiently create end-to-end solutions. Some additional productivity tools include new project and file templates for easily implementing consistent programming style while reducing the amount of redundant tasks performed between multiple applications.

New Project Wizard

It is common for developers on a team to use a consistent code or user interface template when starting new projects. Common settings such as source code control or build options typically have to be reset from project to project if development is performed on different machines. With the new Project Wizard, you can create new project or source files based on existing templates. If you would like all user interfaces to have a company logo at the bottom left corner and all source files to have copyright information, in LabWindows/CVI, you can either use the built-in templates or create custom templates to enforce this consistency. The templates can apply to file-naming conventions, code documentation, build and target options, and user interface design.

Function Panel HTML Documentation

In addition to new tools to quickly begin new projects, LabWindows/CVI now helps you quickly distribute documentation at project completion. LabWindows/CVI is commonly used to develop instrument drivers, which are stored as function panels. With the new function panel HTML generation capabilities, you can take the documentation already included in your instrument drivers or in the open source instrument drivers available in LabWindows/CVI and generate Web-ready documentation that can be easily distributed and searched. After generating HTML documentation, you have a top-level HTML page that displays the high-level documentation for the instrument driver, including separate pages documenting each function featured. You also have quick navigation links in the HTML-generated source so you can navigate alphabetically or through the function hierarchy for specific function documentation and example code.

Set Next Statement

LabWindows/CVI provides the Set Next Statement command, which you can use to skip over code you know is going to fail or investigate code that failed when you executed it. This command changes the next statement to execute while you are debugging. Simply move the cursor to the statement you want to execute and select Run >> Set Next Statement.

Source Code Name Completion

To help you quickly develop your application, LabWindows/CVI offers the name completion option in Source windows. Press <Ctrl-Space> to view a list of potential matches for the function, variable, or macro name you are typing.

Collapsible Source Code Regions/Code Folding

Delimiter Matching

Source Code Variable Declaration

Function Prototype Help

[+] Enlarge Image

Editable Data Tooltips

Additional Enhanced Functionality

Additional NI Software Capabilities for LabWindows/CVI

NI TestStand Integration

NI TestStand introduces the latest test management software technology for developing automated test systems more quickly and effectively. NI TestStand has features specially designed to develop LabWindows/CVI test systems quickly, including a LabWindows/CVI flexible module adapter and NI TestStand user interface (UI) controls for LabWindows/CVI.

The LabWindows/CVI flexible module adapter ensures maximum return on your software development investment by increasing code reusability. You now can call functions within any LabWindows/CVI .c, .obj, .lib, or .dll file regardless of the function prototype. The LabWindows/CVI flexible module adapter has also been updated to improve parameter visualization when you configure a module in NI TestStand. These improvements substantially reduce development times and eliminate unnecessary programming.

Figure 14. With the new flexible LabWindows/CVI adapter, you can call functions within any LabWindows/CVI file from NI TestStand, regardless of the function prototype.

NI TestStand User Interface Controls for LabWindows/CVI

The NI TestStand UI controls eliminate more than 90 percent of the complexity associated with developing an NI TestStand operator interface. These new controls encapsulate all of the required communication between NI TestStand and your operator interface. In addition, the new controls are automatically installed with the latest version of NI TestStand. With the LabWindows/CVI operator interface provided with NI TestStand 3.0, you can reduce the amount of code you must write by more than 11,000 lines.

Figure 15. With the NI TestStand UI controls, you now can communicate seamlessly between LabWindows/CVI and NI TestStand, reducing your code by 90 percent.

See Also:
NI TestStand Home Page

Conclusion

The proven LabWindows/CVI development environment can make your ANSI C application development more productive with integrated workspace and development tool enhancements, more robust hardware functionality, real-time connectivity capabilities, advanced data management tools, and tight test management integration.

• See the LabWindows/CVI User Interface Gallery
• Evaluate LabWindows/CVI
• See the Latest LabWindows/CVI Pricing Information
• LabWindows/CVI Home Page

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