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LabVIEW for LJM - Windows

LJM LabVIEW Examples (Software Platform)

LabVIEW example VIs for the LJM library.


LJM LabView Examples (Referencable)

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.


Note that using a LabJack in LabVIEW is not identical to using NI hardware in LabVIEW.  The NI hardware is talked to through the NI-DAQ driver, while the T7 or T4 is talked to through the LabJack LJM library.  That means that you will not use measurement & automation explorer, DAQ assistant, or similar NI wizards.


Getting Started

  1. Go to the T4 or T7 Quickstart Tutorial and follow the steps to install Windows software and confirm basic operation.
  2. Download the LabVIEW_LJM archive (at the top of this page) and extract the entire archive.
  3. 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.
  4. For more information about what registers to write and read, see the T4 or T7 Datasheet and the Modbus Map.
  5. Navigate to the folder \LabVIEW_LJM\Examples\Basics and try out "LJM_eReadName Example.vi".
  6. Move on to the very useful example "Read Write Loop with Config.vi".


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 device's datasheet (T7 or T4) 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 are a great place to start:

  • LJM_eWriteName Example.vi
  • LJM_eWriteNames Example.vi
  • LJM_eReadName Example.vi
  • LJM_eReadNames Example.vi
  • Write Read Loop with Config.vi

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\.

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.


      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.

      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 Write Read Loop with Config.vi with different registers. The typical workflow to do almost anything beside stream is:

      1. Look at the T-series Datasheet or the Modbus Map to determine what registers you need to write and read.
      2. 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.vi, which provides the basic structure used by many user applications.

      An optional step in between those 2 is to use the Register Matrix in Kipling to test writing and reading your desired registers.

      Stream mode and other operations that don't fit in Write Read Loop with Config.vi will usually have specific examples, and if something seems to be missing let us know.


      **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.


      File list

      LabVIEW_LJM_2018_06_28.zip contains:

      Examples\Basics\eNames Loop.vi
      Examples\Basics\eReadName Multiple Call Loop.vi
      Examples\Basics\eReadNames Loop.vi
      Examples\Basics\LJM_eAddresses Example.vi
      Examples\Basics\LJM_eNames Example.vi
      Examples\Basics\LJM_eReadAddress Example.vi
      Examples\Basics\LJM_eReadAddresses Example.vi
      Examples\Basics\LJM_eReadName Example.vi
      Examples\Basics\LJM_eReadNames Example.vi
      Examples\Basics\LJM_eWriteAddress Example.vi
      Examples\Basics\LJM_eWriteAddresses Example.vi
      Examples\Basics\LJM_eWriteName Example.vi
      Examples\Basics\LJM_eWriteNames Example.vi
      Examples\Basics\Write Read Loop with Config with Constants.vi
      Examples\Basics\Write Read Loop with Config.vi
      Examples\More\AIN\Dual AIN Loop.vi
      Examples\More\AIN\Read Multiple AIN.vi
      Examples\More\AIN\Single AIN with config.vi
      Examples\More\AIN\Single AIN.vi
      Examples\More\AIN EF\AIN EF Config Tool for build.vi
      Examples\More\AIN EF\AIN EF Config.vi
      Examples\More\AIN EF\AIN EF Read Values.vi
      Examples\More\AIN EF\AINEFConfigTool.bld
      Examples\More\Config\Cal Constants Array to Cluster.vi
      Examples\More\Config\Cal Constants Cluster to Array.vi
      Examples\More\Config\Read Cal Constants.vi
      Examples\More\Config\Read Config.vi
      Examples\More\Config\Read DeviceName String.vi
      Examples\More\Config\T7 Cal Constants Tool.vi
      Examples\More\Config\Write DeviceName String.vi
      Examples\More\Config\Write Power Config.vi
      Examples\More\DIO\Single DIO Read.vi
      Examples\More\DIO\Single DIO Write.vi
      Examples\More\DIO EF\DIO EF Config & Read 10 Counters Loop.vi
      Examples\More\DIO EF\DIO EF Config 1 Pulse Out.vi
      Examples\More\DIO EF\DIO EF Config 1 PWM and 1 Counter.vi
      Examples\More\DIO EF\DIO EF Config 1 PWM Output.vi
      Examples\More\DIO EF\DIO EF Config 2 Frequency Inputs.vi
      Examples\More\DIO EF\DIO EF Config FIO0-3.vi
      Examples\More\DIO EF\DIO EF Frequency Output.vi
      Examples\More\DIO EF\DIO EF Line-to-Line with Constants.vi
      Examples\More\DIO EF\DIO EF Read FIO0-3.vi
      Examples\More\DIO EF\DIO0 EF Config & Read.vi
      Examples\More\Ethernet\Read Ethernet Config.vi
      Examples\More\Ethernet\Read Ethernet MAC.vi
      Examples\More\Ethernet\Write Ethernet Config.vi
      Examples\More\Ethernet\UD Calls\LJUD_Close.vi
      Examples\More\Ethernet\UD Calls\LJUD_ErrorToString.vi
      Examples\More\Ethernet\UD Calls\LJUD_OpenLabJackS.vi
      Examples\More\I2C\I2C EEPROM Read.vi
      Examples\More\I2C\I2C EEPROM Write-and-Read.vi
      Examples\More\I2C\I2C EEPROM Write.vi
      Examples\More\I2C\I2C LJTick-DAC DACA.vi
      Examples\More\I2C\I2C Utility\I2C Utility Example EEPROM Read.vi
      Examples\More\I2C\I2C Utility\I2C Utility Example EEPROM Repeat.vi
      Examples\More\I2C\I2C Utility\I2C Utility Example EEPROM Write-and-Read.vi
      Examples\More\I2C\I2C Utility\I2C Utility Example EEPROM Write.vi
      Examples\More\I2C\I2C Utility\I2C Utility.vi
      Examples\More\Misc\Buffer read loop.vi
      Examples\More\Misc\Lots of Software Counters - T7.vi
      Examples\More\Misc\Multiple T7 Loop.vi
      Examples\More\Misc\Pulse Generation Using WAIT.vi
      Examples\More\Misc\Read Write Loop with Connection Healing.vi
      Examples\More\Misc\Parallel Execution\Parallel Execution A.vi
      Examples\More\Misc\Parallel Execution\Parallel Execution B.vi
      Examples\More\Misc\Parallel Execution\Parallel Execution.vi
      Examples\More\Stream\Stream Basic with autorestart.vi
      Examples\More\Stream\Stream Basic with Config.vi
      Examples\More\Stream\Stream Basic with Stream-Out.vi
      Examples\More\Stream\Stream Basic with Waveform Data Type.vi
      Examples\More\Stream\Stream Basic.vi
      Examples\More\Stream\Stream Low Latency.vi
      Examples\More\Stream\Stream No Loop.vi
      Examples\More\Stream\Stream Sequential AIN.vi
      Examples\More\Stream\Stream with External Scan Clock - T7.vi
      Examples\More\Stream\Stream with FFT.vi
      Examples\More\Testing\AIN Noise Test.bld
      Examples\More\Testing\AIN Noise Test.vi
      Examples\More\Testing\AIN-EF Speed Test.vi
      Examples\More\Testing\C-R Speed Test AIN eAddresses.vi
      Examples\More\Testing\C-R Speed Test AIN eNames LJMIntervals.vi
      Examples\More\Testing\C-R Speed Test AIN eNames LVTiming.vi
      Examples\More\Testing\C-R Speed Test AIN eNames.vi
      Examples\More\Testing\C-R Speed Test eWriteAddresses.vi
      Examples\More\Testing\Write Read Loop with Config Speed Test eNames.vi
      Examples\More\Watchdog\Read Watchdog Config.vi
      Examples\More\Watchdog\Write Watchdog Config.vi
      Examples\More\WiFi\Read WiFi Config.vi
      Examples\More\WiFi\Read WiFi MAC.vi
      Examples\More\WiFi\Read WiFi RSSI.vi
      Examples\More\WiFi\Write WiFi Config.vi
      Functions\Type Converters\LJM_ByteArrayToFLOAT32.vi
      Functions\Type Converters\LJM_ByteArrayToINT32.vi
      Functions\Type Converters\LJM_ByteArrayToUINT16.vi
      Functions\Type Converters\LJM_ByteArrayToUINT32.vi
      Functions\Type Converters\LJM_FLOAT32ToByteArray.vi
      Functions\Type Converters\LJM_INT32ToByteArray.vi
      Functions\Type Converters\LJM_UINT16ToByteArray.vi
      Functions\Type Converters\LJM_UINT32ToByteArray.vi
      LJLogM\sub\change working directory.vi
      LJLogM\sub\get app name.vi
      LJLogM\sub\get user directory.vi
      LJLogM\sub\get working directory - no dialog.vi
      LJLogM\sub\get working directory.vi
      LJLogM\sub\LJM read open config.vi
      LJLogM\sub\Quit LabVIEW if Executable.vi
      LJStreamM\sub\Internet Version Check.vi
      LJStreamM\sub\LJstreamM apply formula to array.vi
      LJStreamM\sub\LJstreamM process data.vi
      LJStreamM\sub\LJstreamM tc formula handler.vi
      LJStreamM\sub\LJstreamUD add data to file.vi
      LJStreamM\sub\LJstreamUD apply formula in tc.vi
      LJStreamM\sub\LJstreamUD build header string.vi
      LJStreamM\sub\LJstreamUD data file write.vi
      LJStreamM\sub\LJstreamUD exec SignedMSWLSW.vi
      LJStreamM\sub\LJstreamUD get file name.vi
      LJStreamM\sub\LJstreamUD globals.vi
      LJStreamM\sub\LJstreamUD graph processing.vi
      LJStreamM\sub\LJstreamUD parse formula.vi
      LJStreamM\sub\LJstreamUD prepare custom formula.vi
      LJStreamM\sub\LJstreamUD read config.vi
      LJStreamM\sub\LJstreamUD write config.vi
      LJStreamM\sub\Quit LabVIEW if Executable.vi
      LJStreamM\sub\Write To File Util.vi
      LVUtilities\8-Byte Array To MAC.vi
      LVUtilities\Cal Constants Array to Cluster.vi
      LVUtilities\Cal Constants Cluster to Array.vi
      LVUtilities\eWriteName and eReadName.vi
      LVUtilities\eWriteNames and eReadNames with Open.vi
      LVUtilities\eWriteNames and eReadNames.vi
      LVUtilities\Expand Array To Size.vi
      LVUtilities\Force Array To Size.vi
      LVUtilities\Keep Last n Rows 2D.vi
      LVUtilities\Noise & Accuracy Processing.vi
      LVUtilities\Noise Processing.vi
      LVUtilities\raw checksum.vi
      LVUtilities\Read String.vi
      LVUtilities\Write String.vi
      Old\Flatten Array Of Strings.vi


      when I run "DIO EF Config 1 PWM and 1 Counter.vi" I have an error message: "LabJack Error #2508:  HW_CNTR0_NOT_AVAILABLE occured at LJM_eWriteAddresses.vi"

      The problem is that that example enables Clock0 for the PWM output.  Clock0 uses CounterA & CounterB so they are not available:


      We will change the example to use CounterC on CIO2.

      In the config list use:


      ... and then read:


      Forgot to click the "List" box.  Now it is showing.

      "LabJack Error #1298:  LJME_ATTR_LOAD_COMM_FAILURE occured at LJM_OpenS.vi"

      LV2014, 64bit machine.  The LJControlPanel and LJStreamUD work just fine.

      The .dll is installed in the systems32 folder.

      What LabJack are you using? The LJM driver and examples only support the LabJack T7 and Digit. For UD devices (U3/U6/UE9) use the UD driver and examples: