LabVIEW for LJM - Windows & macOS

The LJM library is the high level code library for T-Series devices. LabVIEW is one of the most popular programming languages used by our customers. LabVIEW is a graphical programming language, as demonstrated in the code snippet below, but understand that it is still a powerful programming language not a simple software tool.

http://www.ni.com/gettingstarted/labviewbasics/

Note that using a LabJack in LabVIEW is not identical to using NI hardware in LabVIEW. NI hardware communicate using the NI-DAQ driver, while T-series devices communicate using the LabJack LJM library. That means that you will not use measurement & automation explorer, DAQ assistant, or similar NI wizards.

Prerequisites

A T-series LabJack Device
LJM Library - Install the LJM Library (For macOS use April 2021 Beta release or newer)
LabVIEW 7.1 or Newer - LabVIEW is not free, see http://www.ni.com/trylabview
Operating System - Windows, macOS

Latest Windows Downloads

Release Example Package

LabVIEW_LJM_2020_05_13.zip

Compatible with LabVIEW 7.1 or higher.

Beta Example Package

LabVIEW_LJM-beta-2023-03-21.zip

Compatible with LabVIEW 7.1 or higher. Includes examples and wrapper functionality for beta LJM 1.21 and newer. Includes updated examples for T8 support. Added new utility examples such as thermocouple measurement examples, LJM configuration example, I2C troubleshooting utility.

GitHub

Our latest example changes are available in our GitHub repository.

Latest macOS Downloads

macOS Example Package

LabVIEW_LJM_macOS_2021_06_04.zip

Note: requires the LJM April 2021 Beta installer or newer

Getting Started

Experienced LabVIEW programmer? Proceed to next step. If you are new to LabVIEW, you need to know the basics such as loops, case structures, arrays, clusters, data types, indicators and controls. Perhaps most importantly you need to understand the "dataflow" concept, which is one of the biggest differences between LabVIEW and a text language.
Go to your device Quickstart Tutorial and follow the steps to install Windows software and confirm basic operation.
Download the LabVIEW_LJM archive (at the top of this page) and extract the entire archive.
In LabVIEW you will be making calls to our LJM Library to write and read registers on the device. Go to the main LJM Page for an introduction, and proceed to the LJM User's Guide for more details.
For more information about what registers to write and read, see the T-Series Datasheet and the Modbus Map.
Navigate to the folder \LabVIEW_LJM\Examples\Basics and try out "LJM_eReadName Example.vi".
Move on to the very useful example "Write Read Loop with Config.vi".

Control Overview

With the LJM library, pretty much everything you might want to do with a device is accomplished by writing and/or reading some registers. Look at the T-series Datasheet or the Modbus Map to determine what registers you need to write and read, then use eWriteName (or eWriteNames) to write the desired registers and eReadName (or eReadNames) to read the desired registers. The following examples in the Basic folder are a great place to start:

LJM_eWriteName Example
LJM_eWriteNames Example
LJM_eReadName Example
LJM_eReadNames Example
Write Read Loop with Config

Where is an example to do XYZ?

You will find lots of examples in this archive, but there is not an example for everything the LabJack can do. The reason for this stems from the "Overview" section above. Most operations simply involve writing and reading different registers, so you really just need examples that show you how to write and read any register. If we had examples for every operation, they would just be copies of the example "Write Read Loop with Config" with different registers. The typical workflow to do almost anything beside stream is:

Look at the T-series Datasheet or the Modbus Map to determine what registers you need to write and read.
Use the Register Matrix in Kipling to test writing and reading your desired registers and confirm you see what you expect to see. This step is optional and not always applicable.
Use eWriteName (or eWriteNames) to write the desired registers and eReadName (or eReadNames) to read the desired registers. Or just use "Write Read Loop with Config", which provides the basic structure used by many user applications.

LabVIEW_LJM Archive Contents

The downloadable zip file LabVIEW_LJM.zip extracts to a single folder called LabVIEW_LJM which contains a few subfolders. The folder can be stored anywhere, but if you want icons to show up on the LabVIEW function palette (after restarting LabVIEW), place this folder under ...\national instruments\labview #\vi.lib\addons\ (create the addons folder if it does not exist). Be sure the folder containing our LabVIEW functions is named LabVIEW_LJM when added to the LabVIEW addons folder or else the icons may not load properly.

Many people, including us, do not use the palette icons but rather just copy paste from examples and use the "Select a VI..." balloon from the function palette. In that case you can put the LabVIEW_LJM folder wherever you want.

We recommend not having more than one copy of the VIs, and not changing these VIs. If you want to make your own variation of one of the examples, make a copy in a different location and modify that.

If you download new VIs from labjack.com, delete and replace the entire LabVIEW_LJM folder.

The \Functions folder contains simple VIs that do little more than call functions from LJM. Most of these need a valid Handle input so are intended to be sub-VIs not standalone top level VIs.

The \LVUtilities folder contains VIs that encapsulate some useful functions. These are used by other VIs from the \Functions\ and \Examples\ folders to handle things unique to LabVIEW.

The \Examples\Basics folder contains core examples that demonstrate the basics of interfacing LabVIEW with our LJM library. Included here is the very useful "Read Write Loop with Config.vi" example which forms the basis for most customer applications. Use the device datasheet (and/or Modbus Map) to determine what registers you need to write and read and the plug those register names into "Read Write Loop with Config.vi".

The \Examples\More folder has many more examples that demonstrate specific tasks. Some of these demonstrate unique techniques, but many are simply variations of the "Write Read Loop with Config.vi" example with different default register names and values.

The \LJLogM and \LJStreamM folders contain the source code for those sample programs. The executable versions (.exe) are part of the main LabJack software installer for Windows. Advanced LabVIEW programmers might find this source code useful, but most users are better off starting with a more basic example.

Code Snippet

This example uses 5 calls to the LJM library:

LJM_OpenS specifies which device you want to open and returns a handle for that device.
LJM_GetHandleInfo returns information about the device we just opened.
We pass a register name to LJM_eReadName and it reads the value of that register. In this case we are reading the register named "SERIAL_NUMBER" which returns the serial number of the device. For more names refer to the T7 Datasheet or Modbus Map.
LJM_Close closes the connection to the device so it is available to other processes.
LJM_ErrorToString converts the numeric error code to a readable string.

Errorcodes

6000 is added to the LabJack errorcodes to shift them into the LabVIEW user range of 5000-9999. For example, if the open call cannot find the device you requested it will return LabVIEW-LJM errorcode 7227, which is LabJack-LJM errorcode 1227. Many errorcodes are listed in Section 4 of the LJM User's Guide, but no need to look there for the basic string as every LabVIEW program should use LJM_ErrorToString.vi to convert the errorcode to a readable string.

Debugging Sub-VIs

All sub-VIs, which means everything in the Functions and LVUtilities folders, are set to reentrant execution. In older versions of LabVIEW, debugging is not allowed when reentrant is enabled, so debugging is disabled in all sub-VIs.

To allow debugging in sub-VIs in older LabVIEW, you will have to disable reentrent execution. Go to File => VI Properties, set Category = Execution, un-check Reentrant execution, and check Allow debugging. In newer versions of LabVIEW, you can enable debugging with reentrant enabled.

**Note**: 2 substantial changes were made to the LabVIEW_LJM archive with the 2015_01_23 release:

1. In LJM function call VIs that have the NumFrames parameter, that parameter is now optional with a default value of -1 which means "Auto-Detect the Number of Frames". If you do not wire anything to NumFrames, or pass -1, this signals the VI to use the size of aNames or aAddresses to determine the number of frames. This should not break any code using previous versions of these VIs.

2. A few changes were made to the inputs & outputs of LJM_eStreamStart.vi, and these changes will break code using a previous version of this VI. See the front panel of LJM_eStreamStart.vi for more details.

Subsections

Experimental LabVIEW LJM Archives

Version History

For version history, see our Github repository.

All Releases - Windows

Download LabVIEW_LJM-beta-2021-07-09.zip

Includes new examples and wrapper functionality for stream out functions that are currently part of the beta version of LJM(1.21) and our logger source with new config file options.

Download LabVIEW_LJM-beta-2021-03-16.zip