2017 / January 2018; 2 months ago ( 2018-01):, analysis and, design Website Laboratory Virtual Instrument Engineering Workbench ( LabVIEW): 3 is a system-design platform and development environment for a from. The graphical language is named 'G'; not to be confused with. Originally released for the Apple in 1986, LabVIEW is commonly used for, and industrial on a variety of (OSs), including, various versions of, and. The latest versions of LabVIEW are LabVIEW 2017 SP1 and LabVIEW NXG 2.0, released in January 2018. Contents. Dataflow programming The programming paradigm used in LabVIEW, sometimes called G, is based on data availability. If there is enough data available to a subVI or function that subVI or function will execute.
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Execution flow is determined by the structure of a graphical block diagram (the LabVIEW-source code) on which the programmer connects different function-nodes by drawing wires. These wires propagate variables and any node can execute as soon as all its input data become available. Since this might be the case for multiple nodes simultaneously, LabVIEW can execute inherently in parallel.: 1–2 and hardware is exploited automatically by the built-in scheduler, which multiple OS threads over the nodes ready for execution. Graphical programming LabVIEW integrates the creation of user interfaces (termed front panels) into the development cycle. LabVIEW programs-subroutines are termed virtual instruments (VIs). Each VI has three components: a block diagram, a front panel, and a connector panel.
The last is used to represent the VI in the block diagrams of other, calling VIs. The front panel is built using controls and indicators. Controls are inputs: they allow a user to supply information to the VI. Indicators are outputs: they indicate, or display, the results based on the inputs given to the VI. The back panel, which is a block diagram, contains the graphical source code. All of the objects placed on the front panel will appear on the back panel as terminals.
The back panel also contains structures and functions which perform operations on controls and supply data to indicators. The structures and functions are found on the Functions palette and can be placed on the back panel. Collectively controls, indicators, structures, and functions are referred to as nodes. Nodes are connected to one another using wires, e.g., two controls and an indicator can be wired to the addition function so that the indicator displays the sum of the two controls. Thus a virtual instrument can be run as either a program, with the front panel serving as a user interface, or, when dropped as a node onto the block diagram, the front panel defines the inputs and outputs for the node through the connector pane.
This implies each VI can be easily tested before being embedded as a subroutine into a larger program. The graphical approach also allows nonprogrammers to build programs by dragging and dropping virtual representations of lab equipment with which they are already familiar. The LabVIEW programming environment, with the included examples and documentation, makes it simple to create small applications. This is a benefit on one side, but there is also a certain danger of underestimating the expertise needed for high-quality G programming. For complex algorithms or large-scale code, it is important that a programmer possess an extensive knowledge of the special LabVIEW syntax and the topology of its memory management. The most advanced LabVIEW development systems offer the ability to build stand-alone applications.
Furthermore, it is possible to create distributed applications, which communicate by a, and are thus easier to implement due to the inherently parallel nature of G. Widely-accepted design patterns Applications in LabVIEW are usually designed using well-known architectures, known as. The most common design patterns for graphical LabVIEW applications are listed in the table below. Jeffrey., Travis, (2006).
Upper Saddle River, NJ: Prentice Hall. Rowe, Martin. Retrieved 16 September 2017. Bress, Thomas J. Effective LabVIEW Programming.
S.l.: NTS Press. National Instruments whitepapers. 8 September 2011. Retrieved 21 September 2017. National Instruments whitepapers. 7 October 2015. Retrieved 21 September 2017.
National Instruments whitepapers. 24 August 2016. Retrieved 21 September 2017.
Retrieved February 1, 2016. Retrieved 2016-03-31.
Further reading. Bress, Thomas J. Effective LabVIEW Programming. S.l.: NTS Press. Blume, Peter A.
The LabVIEW Style Book. Upper Saddle River, NJ: Prentice Hall. Travis, Jeffrey; Kring, Jim (2006). LabVIEW for Everyone: Graphical Programming Made Easy and Fun (3rd ed.). Upper Saddle River, NJ: Prentice Hall. Conway, Jon; Watts, Steve (2003).
A Software Engineering Approach to LabVIEW. Upper Saddle River, NJ: Prentice Hall PTR. Olansen, Jon B.; Rosow, Eric (2002). Virtual Bio-Instrumentation: Biomedical, Clinical, and Healthcare Applications in LabVIEW.
Upper Saddle River, NJ: Prentice Hall PTR. Beyon, Jeffrey Y. LabVIEW Programming, Data Acquisition and Analysis. Upper Saddle River, NJ: Prentice Hall PTR. Travis, Jeffrey (2000).
Internet Applications In LabVIEW. Upper Saddle River, NJ: Prentice Hall PTR. Essick, John (1999). Advanced LabVIEW Labs. Upper Saddle River, NJ: Prentice Hall. Articles on specific uses. Desnica V, Schreiner M, Vladan; Schreiner, Manfred (October 2006).
X-Ray Spectrometry. 35 (5): 280–286. Keleshis C, Ionita C, Rudin S, C.; Ionita, C.; Rudin, S. (June 2006). Medical Physics. 33 (6): 2007. CS1 maint: Multiple names: authors list.
Buku psikologi kepribadian pdf editor. Biasanya buku-buku text tentang teori kepribadian bahasanya terjemahan jadi terasa kurang nyaman di baca.
Fedak W., Bord D., Smith C., Gawrych D., Lindeman K., W.; Bord, D.; Smith, C.; Gawrych, D.; Lindeman, K. American Journal of Physics. 71 (5): 501–506. CS1 maint: Multiple names: authors list Articles on education uses. Belletti A., Borromei R., Ingletto G., A.; Borromei, R.; Ingletto, G.
(September 2006). Journal of Chemical Education. 83 (9): 1353–1355. CS1 maint: Multiple names: authors list. Moriarty P.J., Gallagher B.L., Mellor C.J., Baines R.R., P. J.; Gallagher, B. L.; Mellor, C.
J.; Baines, R. (October 2003). American Journal of Physics. 71 (10): 1062–1074. CS1 maint: Multiple names: authors list. Lauterburg, Urs (June 2001).
A white paper about using LabVIEW in physics demonstration and laboratory experiments and simulations. Drew SM, Steven M. (December 1996). Journal of Chemical Education. 73 (12): 1107–1111.
Muyskens MA, Glass SV, Wietsma TW, Gray TM, Mark A.; Glass, Samuel V.; Wietsma, Thomas W.; Gray, Terry M. (December 1996). Journal of Chemical Education. 73 (12): 1112–1114. CS1 maint: Multiple names: authors list. Ogren PJ, Jones TP, Paul J.; Jones, Thomas P. (December 1996).
Journal of Chemical Education. 73 (12): 1115–1116. Trevelyan, J.P. International Conference on Engineering Education Research. External links., National Instruments.
Ecosystem of LabVIEW Add-on products, contributed by NI and the community. NI's entire set of online help documentation for LabVIEW 2012. NI's entire set of online help documentation for LabVIEW 2010.
NI's entire set of online help documentation for LabVIEW 2009. NI's entire set of online help documentation for LabVIEW 8.5. NI's entire set of online help documentation for LabVIEW 8.20. NI's 'LabVIEW Zone' web site. Independent community, with discussion forums and a code repository.
A LabVIEW. LabVIEW utilities. A user editable LabVIEW knowledge base powered. This course was authored by NI, and is hosted. Turkish. Italian.
Labview source codes for labview programmers, Visit. Basics of LabVIEW including tutorial.
Included in the Section. LabVIEW Users can save time when developing instrument control applications by using the LabVIEW Instrument Driver Finder (IDFinder) to automatically identify the instruments connected to their systems, install the appropriate instrument driver libraries for programming, and launch an application example to verify communication. The installed instrument driver generates the application example; therefore, as a LabVIEW user, you also already have a template from which to begin your own customized test applications. Accessing IDFinder From Measurement & Automation Explorer (MAX) You can launch the IDFinder and immediately download the compatible instrument driver for your connected instrument from directly within MAX.
Start by clicking on the instrument within the configuration tree located on the left side of the window. If you don't see your instrument,. Once you select the instrument, you see the Find and Download Instrument Drivers section in the lower area of the center portion of the window. Accessing IDFinder from MAX Select the version of LabVIEW that you intend to use to develop your instrument control application. You can select only from the LabVIEW versions currently installed on your machine. Once you have selected the applicable version, click Go to launch IDFinder.
When the IDFinder window opens, click Login and log in to your NI user profile. If you do not have an account yet, follow the given steps to create one. User profile accounts are free, and they grant you access to thousands of free instrument drivers from NI as well as valuable development content located throughout ni.com. Log In to Your User Profile Account Scanning, Identifying, and Installing Next, click on the Scan for Instruments button. This scans for all instruments connected to any ports on your machine.
The identified instruments are displayed in the tree on the left side of the IDFinder window. Double-click on the instrument for which want to find an instrument driver to have the instrument's information automatically populate the search fields.
Labview Programming Examples
Scan for Instruments Click Search to locate your instrument driver. You should see a list of the instrument drivers available for your instrument. The right side of the window displays information about the instrument driver including which ADEs, models, buses, and OSs are supported, as well as the user ratings of the driver and the minimum required support software needed to use the driver. Click on the driver you want to download and then click Install.
Installing the Instrument Driver Using the Instrument Driver The fastest and easiest way to get to your measurement is by using one of the examples located within the instrument driver. Double-click on an example to open it within the LabVIEW environment. For this tutorial, the Acquire Waveform.vi example was selected. Using Examples Select the VISA Alias from the drop-down menu that you applied to your instrument within MAX (see ), adjust the control facets as necessary, and click on the Run arrow at the top of the Front Panel to run the VI. Select VISA Resource Name (Alias) in the Acquire Waveform.vi Exploring the Instrument Driver Palette Navigate to File » New VI to open a blank VI.
You can see all of the functions provided by an instrument driver from the palette. To access the palette, switch to your LabVIEW block diagram (the development window with the white background), right-click to open your Functions palette, and navigate to Instrument I/O » Instrument Drivers to see the drivers you have installed. Navigate to the Instrument Driver Palettes Many instrument drivers contain the VI Tree. When accessed, the VI Tree displays a categorized chart of all VIs contained within the instrument driver. To open the VI Tree, click and drag the VI Tree icon onto the block diagram and then double-click the icon.
You now see the front panel of the VI; however, you need to access the block diagram of the VI to see the contents. Use to open the block diagram of the VI Tree.vi. Tektronix TDS 200 1000 2000 VI Tree Use to open the Context Help window and then hover over a VI with your mouse to get more information. By using the VI Tree, you become more familiar with the categorization of VIs within the LabVIEW development environment. This assists you in becoming a more efficient LabVIEW developer and gets you to measurements and analysis much faster.
Summary Instrument drivers are powerful pieces of software that combine the granular, low-level command strings needed for configuration and measurement into higher-level functions such as initialize, reset, and read waveform. Instrument libraries make instrument control easier and help you focus on taking measurements, developing complete tests, and making decisions versus learning the nuts and bolts of how to make your instrument take a measurement. NI provides a complete selection of the most popular instrument drivers requested by users today. To obtain more information or request additional instrument drivers, visit the.
As part of the National Instruments, this set of tutorials helps you learn about a specific common instrument control topic through theory explanations and practical examples. What You Learn An instrument driver is a set of high-level functions that control and communicate with instrument hardware in a system. Each of these high level functions provides some functionality on your instrument ranging from initialization and configuration to triggering and acquisition. This set of documents and tutorials will assist you in using Instrument Drivers in your setup.
To view the complete list of in-depth instrument control tutorials, please return to the Main Page. The NI Instrument Driver Network is a source for instrument drivers for over 8,000 instruments. This site also helps in the creation and submission of instrument drivers, as well as providing the option to request drivers for instruments that don't have drivers currently available.
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This site gives a short explanation of what instrument drivers are and the different types of drivers available. Plug and Play and Interchangeable Virtual Instrument (IVI) are two technologies used by National Instruments LabVIEW and LabWindows/CVI instrument drivers. Each driver type offers advantages for different use cases and application needs. This document describes how to create Plug and Play Drivers in NI LabVIEW.
This white paper explains the benefits of adopting IVI and the differences to be aware of when choosing between the IVI-C and IVI-COM standards This tutorial gives a walkthrough of how to use Instrument Drivers in LabVIEW. This tutorial gives a walkthrough of how to use Instrument Drivers in LabWindows/CVI. This tutorial shows how to create an instrument driver in LabWindows/CVI using the Instrument I/O assistant.
This tutorial walks through the process fo using an IVI-COM driver in LabVIEW (Multimedia Content) This 45 minute Webcast on Demand is another tutorial for using Instrument Drivers in LabVIEW. (Multimedia Content) This Breeze Tutorial shows some new tools in LabVIEW 8 for creating Instrument Drivers. This KnowledgeBase article goes through several common steps for troubleshooting instrument drivers. Related Links.
This document, which describes the standards and practices for LabVIEW Plug and Play drivers, is intended for driver developers and describes the standards for structuring VIs, instrument I/O, style, and error reporting. It also describes instrument driver components and how to integrate these components.
In addition, this document describes a process for developing useful instrument drivers. Other resources for instrument driver developers include the instrument driver templates and the Instrument Driver Guidelines, both of which are available from the National Instruments Instrument Driver Network. To use this document, you should have a basic understanding of instrument control and be familiar with the operation of LabVIEW. You also should be familiar with the with Virtual Instrument Software Architecture (VISA) application programming interface (API).
Table of Contents. What Is a LabVIEW Plug and Play Instrument Driver? A LabVIEW Plug and Play instrument driver is a set of VIs that control a programmable instrument.
Each VI corresponds to an instrument operation, such as configuring, triggering, and reading measurements from the instrument. Instrument drivers help users get started using their instrument from their computer and saves them development time and cost because users do not need to learn the programming protocol for each instrument. With open-source, well documented instrument drivers, end users can customize their operation for better performance. A modular design makes the driver easier to customize. Using a standard architecture for all LabVIEW instrument drivers has the following benefits:. Improves the consistency of instrument drivers for the benefit of end users. Improves the quality of the drivers.
Minimizes duplicated effort. Improves ease of use for end users by providing a consistent methodology for using instrument drivers from a variety of sources. Streamline the instrument driver development process for the benefit of instrument driver developers. The contains instrument drivers for a variety of programmable instruments, including GPIB, USB, TCP/IP, VXI, RS-232, and PXI instruments. Instrument drivers contain high level VIs with intuitive front panels, so end users can quickly test and verify the remote capabilities of their instrument. They do not need to know low-level instrument control and instrument-specific commands and syntax. Users create instrument control applications by building VIs using instrument driver VIs as subVIs on their block diagrams.
LabVIEW Plug and Play Instrument Driver Model Many programmable instruments have a large number of functions and modes. With this complexity, it is necessary to provide a consistent design model that aids both instrument driver developers as well as end users who develop instrument control applications. The LabVIEW Plug and Play instrument driver model contains both external structure and internal structure guidelines. The external structure shows how the instrument driver interfaces with the user and to other software components in the system. The internal structure shows the internal organization of the instrument driver software module. Instrument Driver External Structure An instrument driver consists of the API VIs the user calls from a higher level application. The figure below illustrates how the instrument driver interacts with the rest of the system.
LabVIEW Instrument Driver External Structure The external structure illustrates how the instrument driver presents both an interactive interface and a programming interface. The application programming interface (API) is the set of user-callable instrument driver VIs used in end-user systems. For example, a manufacturer test system might make instrument driver calls to communicate with a multimeter or an oscilloscope.
The end user learns about the API through the instrument driver front panels. By interactively running the front panels of the instrument driver VIs, end users understand how each control affects the instrument. After they understand the settings, end users can incorporate the instrument driver VIs in their application.
The Virtual Instrument Software Architecture (VISA) I/O interface is the set of LabVIEW functions the driver uses to communicate with the instrument hardware. VISA is an established standard instrumentation interface that controls GPIB, USB, serial and other instrument buses. Refer to the LabVIEW Help for descriptions of VISA functions and controls. Support VIs are VIs that you do not intend the end user to access directly.
Therefore, support VIs are not part of the instrument driver API. For example, instrument drivers often call the Default Setup VI during initialization to set the instrument in a state that allows for robust instrument control by the rest of the instrument driver VIs. Only the Initialize and the Reset VIs use the Default Setup VI as a subVI, so it is considered a support VI. Instrument Driver Internal Design Model The internal structure of the instrument driver defines the organization of the instrument driver VIs. All user-accessible API VIs are organized into a modular hierarchy based on instrument functionality. The figure below shows the internal structure of LabVIEW instrument drivers. End users have the necessary granularity for controlling instruments properly in applications.
For example, end users can initialize all instruments once at the start, configure multiple instruments, and then trigger several instruments simultaneously. Also, they can initialize and configure an instrument once, and then trigger and read from the instrument several times. For end users, the model provides a consistent instrument driver model. After users understand one instrument driver, they can apply that knowledge to other LabVIEW instrument drivers. LabVIEW Instrument Driver Internal Structure Instrument Driver API VIs Instrument driver API VIs are organized into the following six categories: Initialize - All LabVIEW instrument drivers should include an initialize VI. This VI establishes communication with the instrument, so it is the first instrument driver VI called. Optionally, the VI performs an instrument identification query and reset operations.
It also can place the instrument in its default power on state or in some other state. Configuration - Configuration VIs are a collection of software routines that configure the instrument to perform specific operations. Usually instrument driver APIs include several configuration VIs, The number of configuration VIs for an instrument driver depends on the unique capabilities of the instrument. After you call these VIs, the instrument is ready to take measurements or stimulate a system. Action/Status - There are two types of action/status VIs.
Action VIs cause the instrument to initiate or terminate test and measurement operations. These operations include arming a trigger or generating a stimulus. These VIs differ from the configuration VIs because they do not change the instrument settings.
Instead, they command the instrument to carry out an action based on its current configuration. Status VIs obtain the current status of the instrument or the status of pending operations. Status VIs are usually created when required by other functions. Data - The data VIs transfer data to or from the instrument.
Examples include VIs for reading a measured value or waveform, and VIs for downloading waveforms or digital patterns to a source instrument. The specific routines in this category depend on the instrument. Utility - Utility VIs perform a variety of auxiliary operations, such as reset and self-test, and can include other custom routines, such as calibration or storing and recalling instrument configurations.
Close - The close VI terminates the software connection to the instrument. All LabVIEW instrument drivers should include a close VI. Each category of VIs, with the exception of initialize and close, contains several modular VIs. Much of the important work in developing an instrument driver lies in the initial design and organization of the instrument driver API VIs. You can download template VIs from National Instruments, and customize them to perform operations common to almost all instruments, such as initialize, close, reset, self-test, and revision query. The template VIs contain modification instructions for their use in a specific instrument driver for a particular instrument.
Refer to the LabVIEW Instrument Driver Templates section for more information about customizing template VIs. In addition to these common functions, you add additional VIs to perform instrument-specific operations. The specific VIs you develop depend on the unique capabilities of your instrument. However, whenever possible, adhere to the six instrument driver VI categories.
Using the internal design structure as shown in Figure 2, an end user can combine instrument driver VIs to create applications. The block diagram in the figure below shows how instrument drivers API VIs programmatically control the HP34970A acquisition system.
HP34970A Current Measurement Example VI Block Diagram Figure 4 shows the block diagram of one of the instrument driver API VIs, which use built-in LabVIEW functions and VISA functions to build command strings and send them to the instrument. The VISA functions perform device management, standardized instrument I/O, and error handling.
The specific VI in Figure 4 below creates a command string by combining string formatting operations, then wiring the resulting string into the VISA Write function. The VISA Write function sends the command string to the instrument. The VISA Read function returns the response string from the instrument.
The response string then gets formatted into a numeric array for use in the end user's application. The reformatting of the response string is beneficial to the user by allowing them to view the response data in a format that they prefer. The Error Query VI checks for errors and updates error cluster. Creating a Command String Additional VIs Distributed with the Instrument Driver In addition to the API VIs described by the internal structure, an instrument driver also includes example VIs and a VI Tree VI. Instrument Driver Example VIs All instrument drivers include example VIs. These examples show users how to combine the instrument driver VIs for basic test and measurement operations with the instrument.
They demonstrate test and measurement functionality by configuring the instrument for a common mode of operation, triggering, and taking measurements. Example VIs also verify communication with the instrument. These examples should be added to the NI Example Finder through the. The figure below shows the front panel of the HP34970A Current Measurement Example VI. LabVIEW Instrument Driver Development This section describes the procedure for developing a LabVIEW Plug and Play instrument driver. The ideal LabVIEW instrument driver allows an end user to control all functionality of the instrument. Because it is not possible to specify required functionality of all different instrument types, such as multimeters, counter/timers, this section focuses on the architectural guidelines for all drivers.
Use this information to help organize and package your drivers in a consistent way while still implementing functionality unique to your instrument. Complete a three-step process to develop a LabVIEW instrument driver. In Step 1, you design the instrument driver structure.
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In Step 2, you use the Instrument Driver Project Wizard to create new instrument driver VIs. In Step 3, you add developer-defined VIs and create example VIs.
Design the Instrument Driver Structure The ideal instrument driver does what the user needs - no more and no less. No particular type of driver design is perfect for everyone but by carefully studying the instrument and grouping controls into modular VIs, you can satisfy most of your users. When the number of programmable controls in an instrument increases, so does the need for modular instrument driver design. Do not try to implement all of the functionality of an instrument with a single VI. However, do not design an instrument driver where each VI controls a single feature. This approach could result in an API with hundreds of VIs.
Also, this could force the end user into understanding instrument-specific rules for command order and interaction. Modular design simplifies the programming needed to control the instrument. Devise the overall structure of your instrument driver before you build the individual VIs. Design an instrument driver with the application and end user in mind. Understanding the instrument is critical to the design process The following steps outline one approach to developing the structure for a LabVIEW instrument driver. Familiarize yourself with the instrument operation. Read the operating manual thoroughly.
Learn how to use the instrument interactively before you attempt any VI development. Use the instrument in an actual test configuration to get practical experience. The operating manual might explain how to set up a simple test. Study the programming section of the manual. Read the instruction set to learn about the controls and functions available and their organization.
Decide upon the best features for programmatic use. Examine existing instrument drivers to see if you can find any that control similar instruments. Often instruments from the same family have similar programming command sets that you can modify for your instrument. Look for controls that are used together to perform a single task or function to aid in developing the structure of the driver. Often, the sections of the manual correspond to the functional groupings of an instrument driver.
Develop the driver structure by organizing instrument commands The organization of an instrument driver defines the hierarchy and overall relationship of the instrument driver component VIs. There are two types of API VIs in an instrument driver: those that are common to all instruments and those that expose the unique capabilities of the instrument. Template instrument driver VIs (initialize, close, reset, self-test, revision query, and error query) perform these common operations.
You, as the instrument driver developer, define the VIs that expose the unique capabilities of the instrument. Some instrument drivers might define additional categories, such as “route” or “scan” for switch instruments. Group common and developer-defined VIs into categories. A category is a group of VIs that perform similar operations. The most common categories of VIs are configuration, action/status, data, and utility.
The following table shows an example instrument driver organization for a simple oscilloscope. At the highest level of the hierarchy, you see the template VIs (initialize and close) and the typical VI categories. Example Subpalette for the FL45 Front Panel Style In addition to the controls required to operate the instrument, the front panel should include the VISA resource name control, VISA resource name out indicator, error in control, and error out indicator.
Refer to the Drivers Support Libraries section for more information about the VISA session handles. In LabVIEW 7.1 or earlier, refer to Chapter 6 of the LabVIEW User Manual (linked below) for more information about the error in and error out parameters. In LabVIEW 8.0 or later, refer to the Handling Errors topic in the LabVIEW Help (linked below).
Use the following style guidelines to ensure uniformity with other LabVIEW front panels as you design front panels. Refer to the Control/Indicators: Naming and Data Representation and Front Panels section of the Instrument Driver Guidelines for the complete requirements and recommendations for creating instrument driver front panels. Use the default (Application) font for all labels. LabVIEW includes this font, so it is available to all other users. Format control and indicator names as bold.
Capitalize the first letter of each word in the control labels, such as Configure Trigger Source. VISA resource name, error in, error out, and well-known acronyms such as AC or FM are exceptions. Enclose default information in plain text in parentheses in the control label so the defaults appear in the Context Help window. This aids in wiring to the VI on the block diagram. For example, label a function selector ring control with a default of DC volts at item zero as Function (0:DCV), and label a Boolean switch that defaults to TRUE indicating automatic enabled as Auto Trigger Delay (T:On). Place the VISA resource name control in the upper left, the VISA resource name indicator in the upper right, the error in control in the lower left and the error out control in the lower right. Edit all control and indicator descriptions.
Refer to the LabVIEW Help for more information about creating control descriptions. Icon and Connector Pane Reserve the upper left terminal of the connector pane for the VISA resource name control and the upper right terminal for the VISA resource name out indicator. Reserve the lower left terminal for the error in control and the lower right terminal for the error out indicator to simplify wiring to subsequent error terminals.
Select a connector pane pattern that has more terminals than the number of controls and indicators because you might add controls or indicators to the connector pane at a later time. This precaution prevents you from changing the pattern and replacing all instances of calls to a modified subVI.
Place inputs on the left and outputs on the right to promote a left-to-right data flow on the block diagram. Use meaningful icons for every VI. Use the icons found in the Icon Art Glossary whenever possible. Also, you can borrow icons from similar VIs in other instrument drivers or use the icon library Icon256.vi located in the labview examples instr insticon.llb directory. Include the instrument driver prefix at the top of the icon so users can identify VIs from the driver API.
Create an icon using glyphs and images that represent the VI functionality. The figure below shows sample configuration icons from the Icon256.vi. Sample Icons Refer to the Icon & Connector Pane section of the Instrument Driver Guidelines for specific requirements and recommendations for creating meaning icons and designing connector panes. Block Diagram After you design the front panel, create the block diagram.
Use the Format into String function to create instrument command strings. This expandable function formats multiple values and multiple data types into a string. Double-click the function to enter format commands using the Format Strings dialog box. Also, use the Append True/False String and Pick Line functions to manipulate strings.
For example, use the Append True/False String function to convert the value from a front panel Boolean to a string. This function selects the proper string and concatenates it to the command string in one step. Use the Pick Line function to convert a text ring value to a string. This function selects the proper string based on the label value and concatenates it with the command string. Refer to the LabVIEW Help (linked below) for descriptions of these functions.
The block diagram in the figure below demonstrates the preferred methods for building command strings. Techniques for Building Strings Many instruments comply with the Standard Commands for Programmable Instruments (SCPI) programming command set and syntax. These SCPI-based instruments let you join multiple commands together to send in one I/O write operation. The String functions described above let you build strings that include multiple commands.
Wire the combined string to the VISA Write function. The block diagram is the primary way end users learn how the VI works, so it is important to make the block diagrams as easy to read as possible. Most of the recommendations for instrument driver block diagrams are similar to best practices for all LabVIEW applications, which include following a left-to-right layout of the diagram, minimizing bends in the wires, and using efficient and consistent coding techniques. Refer to the Block Diagram section of the Instrument Driver Guidelines for specific requirements and recommendations for creating an instrument driver block diagram.
The block diagram in the figure below adheres to the requirements and recommendations detailed in the Instrument Driver Guidelines. Simple Block Diagram that Follows Style Guidelines See Also: 4. Driver Support Libraries LabVIEW tools for instrument driver development include a library of template VIs that serve as a starting point for creating your own drivers, the Instrument Driver Project Wizard that customizes those templates, VISA functions to perform the instrument I/O, icon libraries to aid in creating meaningful icons, and support files and functions. This section describes the VISA functions and the Instrument Driver Template VIs. VISA The VISA functions contain the I/O interface used by instrument drivers to communicate with programmable instruments.
VISA is a single interface library for controlling VXI, GPIB, serial, TCP/IP, and other types of instruments. Refer to the VISA VIs and Functions topic of the LabVIEW Help (linked below) for descriptions of VISA functions and controls. The front panel of most instrument driver VIs include a VISA resource name control and a VISA resource name out indicator. These controls and indicators pass session information between instrument driver subVIs.
The VISA resource name identifies the resource on which the VI operates. It also differentiates between different sessions of the instrument driver. VISA resource name is a unique identifier reference to a device I/O session (except for the Initialize VI). It identifies the device with which the VI communicates and passes all necessary configuration information required to perform the I/O. VISA resource name out contains the same identifier information as VISA resource name. It passes the reference out of the VI and into other subsequent VIs that access the same instrument.
Wiring VISA resource names together establishes data dependencies. You also pass the VISA resource name into and out of VISA functions on the block diagram.
Instrument Driver Template VIs The LabVIEW instrument driver templates, located in the instr.lib folder, contain a set of VIs common to most instruments. NI updates these templates periodically, and includes them in the latest version of LabVIEW. Use these VIs as a starting point for your instrument driver development. The templates have a simple, flexible structure, and they establish a standard format for all LabVIEW drivers.
The template VIs contain instructions for modifying the VIs for a particular instrument. Use the template VIs with both message-based instruments (GPIB, VXI, and serial) and VXI register-based instruments. Because the templates were designed for IEEE 488.2 compatible instruments, minimal modifications are needed for IEEE 488.2 compliant instruments. For other instruments, use the template VIs as a shell or pattern for your VIs by substituting your instrument-specific commands where applicable. Important Considerations Documenting VIs Document the VIs you create so information appears in the LabVIEW Context Help window for each instrument driver. Refer to the Documenting VIs topic of the LabVIEW Help (linked below) for more information about documenting VIs. Select Help»Show Context Help to access the Context Help window.
When you move the cursor over front panel or block diagram objects, or over the icon in the upper right corner of the front panel or block diagram, a description for that object appears in the Context Help window that includes documentation. Also, use free labels on the front panel and the block diagram to aid the user.
On the block diagram, show all terminal labels (plain text) and color the borders transparent. Use bold text in free labels in that appear in Case and Sequence structures to make the comment stand out and the VI easier to understand and modify. Error Reporting Error reporting in instrument drivers is similar to error reporting in most other LabVIEW applications. The VISA functions check the Boolean state of the error in cluster to determine if a previously executed VI or function generated an error. If the VI or function detects an error, the VISA function does not perform its usual operation.
Instead, it passes the error information to the error out cluster without modification. If the VI or function does not detect an error, the VISA function executes normally and determines whether it generated an error. If so, the function returns new error information in the error out cluster. Otherwise, the function returns the error in information in the error out cluster. The first error triggers subsequent VIs not to execute (or some other action defined by the user) and the error code and the source of the error propagate to the top-level front panel. Additionally, warnings (error codes and source messages with the error Boolean set to FALSE) pass through without triggering error actions. In addition to VISA error codes, the error and warning codes listed in the table below are reserved for instrument drivers.
The instrument driver VIs should return these codes when the appropriate conditions occur. You might see error codes like -1300 for instrument specific errors in older instrument drivers and older instrument driver templates. However, use the codes in the following table to ensure compliance with instrument driver standards.
Instrument Driver Error Codes Decimal Code Decimal Code Hex Code Meaning 0 0 No error: the call was successful to 3FFC0800 to 3FFC0FFF WARNING: Developer defined warnings - BFFC0011 ERROR: Identification query failed - BFFC0F80 ERROR: Instrument Defined Error - to - BFFC0801 to BFFC0FFF ERROR: Developer defined errors The Initialize VI uses the “Identification query failed” error. The Error Query VI uses the “Instrument Defined Error code.'
Query Instrument Status Almost all instruments have some mechanism to report instrument defined errors. Instrument defined errors include command errors, execution errors and query errors. Many recently manufactured instruments include a query command to determine if an instrument error occurred.
For SCPI instruments, the standard command to retrieve instrument errors is “SYST:ERR?”. The response to this command includes an error code and an error message. If no error occurred, the response is “0, “No error”. If the instrument does not support the “SYST:ERR?” command, but does support the IEEE 488.2 status registers, you can query the Standard Event Status Register to determine if an error occurred. Use the Error Query VI in your instrument driver VIs to implement the instrument error reporting mechanism to report instrument errors to the user. Instrument drivers do not re-define instrument errors in the instrument driver. Instead, the Error Query VI reports the error code and associated message the instrument reports.
If you do not use the Error Query VI to query the instrument for errors, you might leave end users unaware that an instrument error occurred, even if they use the Simple Error Handler. It is possible to send and receive data from the instrument without causing an I/O error, but this does not necessary report an instrument error.
To better assist users in getting timely instrument error information, most API VIs call the Error Query VI after all I/O operations. When an instrument error occurs, the standard LabVIEW error handling techniques, such as calling the Simple Error Handler VI, automatically notifies users of the error. The Error Query VI updates the error cluster with error code code - (Hex: BFFC0F80) if an error is detected and places the error information returned from the instrument into the source message.
The LabVIEW error handler VIs identify error code code - as an instrument-specific error and generate an appropriate error message. The figure below shows the front panel of the Error Query VI.
Front Panel of the Error Query VI Low level API VIs do not call the Error Query VI. Many low-level API VIs are designed primarily to improve performance or to provide more control over instrument operations.
For example, an oscilloscope instrument driver might implement a Read Waveform VI to return channel-based waveform data. To give advanced users more control, you should implement Initiate and Fetch VIs. The low-level Initiate and Fetch VIs give users more control over when the operations occur, so these low-level VIs do not call the Error Query VI. Some instruments have an error queue, which stores errors and events as they are detected. This queue is first in, first out (FIFO), with a minimum length of two messages. In the event of overflows, the instrument retains the most recent errors/events, and replaces the least recent error/event with a queue overflow message. In your instrument driver, use this queue to detect and report instrument errors by querying the instrument after commands are sent.
By issuing the:SYST:ERR? Command, SCPI instruments return one entry from the queue, which can be an error, an overflow warning, or the message 0, 'No error'. Some end users want to retrieve the entire error queue, so many instrument drivers also include an Error Query (Multiple) VI. This VI queries the instrument with the:SYST:ERR?
Command until the error queue is empty. The code generated by the Instrument Driver Project Wizard includes the Error Query VI. Instrument driver VIs typically do not perform range checking on input parameters. If a user passes an invalid value, the instrument should report an instrument-specific error. The Error Query VI detects this instrument error and reports the out-of-range condition to the user. Document range information in the VI and control help so the user does not encounter out-of-range errors.
Additional Style Guidelines Users appreciate consistency among instrument drivers. Developing simple front panels and block diagrams with an easy-to-understand layout makes end users less intimidated about modifying the code. Some users might need to modify the code to optimize it for their special needs. Refer to the Instrument Driver Guidelines for more information about style guidelines. Testing the Operation Test your instrument driver as you develop it. Although most users will use the Context Help window to determine the inputs to the VIs, some end users might not use the Context Help window to determine the inputs to the VIs and might pass invalid data to the VIs. Therefore, test your VIs with invalid data, boundary conditions and ranges, and unusual combinations of inputs.
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If a subVI requires string or array information, wire an empty array or empty string to the VI input. Conclusion Defining the structure of the VIs is the most important step in the development of an instrument driver. Group related instrument controls into modular VIs, each of which performs a task the way you actually would use the instrument from its front panel. With this type of structure, each VI gives users exactly what they need to perform a particular instrument operation. Determining which controls belong on each VI is the greatest challenge in developing instrument drivers. For the end user, the logical structure, documentation, and error reporting are the most important features of the instrument driver.
Include appropriate comments in all description boxes and document your code with comments in the block diagrams. Build useful error reporting into your VIs using the techniques described in this document. Thoroughly test all your VIs to ensure that they work properly. Instrument driver development is more than building and sending strings to instruments. Use the Instrument Driver Project Wizard and the thousands of instrument drivers available on National Instruments Instrument Driver Network. Templates contain VIs common to most instruments and demonstrate the desired style and structure of instrument driver VIs.
Use existing instrument drivers to help guide you through creating your own instrument driver. Follow the internal design structure and keep in mind the categories of API VIs as you build your VIs. Use the Instrument Driver Guidelines throughout your driver development process to ensure you create high quality instrument drivers. These tools help you design instrument drivers that are acceptable to a wide range of users. Related Links.
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