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Real-Time Module on NI Linux Real-Time Targets

LabVIEW 2013 Real-Time Module Help

Edition Date: June 2013

Part Number: 370622L-01

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Special Considerations

Keep the following considerations in mind when using an NI Linux Real-Time target:

General

  • The FTP server is disabled by default, and you cannot use it in safe mode. National Instruments recommends using WebDAV as the file transfer mechanism for improved security.
  • Virtual memory is supported, which implies the following:
    • A process crash restarts the process without restarting the target.
    • Monitoring the largest contiguous memory block does not provide useful or necessary information on NI Linux Real-Time targets.
  • System Exec VI is supported.
  • Time zone changes do not require a target restart.

File System and Directory Structure

  • The file system is case-sensitive.
  • Directory paths display in Linux format. For example, paths use forward slashes and do not contain drive letters. If you open a VI created for ETS or VxWorks targets in an NI Linux Real-Time target context, the Windows-style paths automatically convert to Linux-style paths.
  • NI Linux Real-Time targets enforce file and folder access permissions. Refer to the KnowledgeBase for information about these permissions.
  • The RTOS deletes the content in the temporary folder /tmp on target restart. The temporary folder allocates space from RAM up to a maximum size of 64 MB.
  • The c:\ni-rt directory and ni-rt.ini configuration file do not exist on NI Linux Real-Time targets. Refer to the KnowledgeBase for information about the directory mapping on NI Linux Real-Time targets.

Web Services

  • WebDAV is enabled by default.
  • SSL is enabled by default.
  • NI Web-based Configuration & Monitoring is available in safe mode.
  • It is only possible to configure a target reachable via IP address (DHCP, link-local, or static). mDNS is used for target discovery.

Authentication

  • You can log in to a target using NI Web-based Configuration & Monitoring, SSH, or a serial connection. Refer to your hardware documentation to learn about enabling SSH on your RT target.
    Note  National Instruments recommends you set a password to log in using SSH or a serial connection.
  • To reset a forgotten administrator password, you must physically access the target and reset all settings to the factory default. Contact National Instruments for assistance with this process.
  • Your target creates an admin user that is equivalent to the root user in Linux systems.
    Caution  Do not create users in NI Web-based Configuration & Monitoring with the same name as system accounts. For example, do not create a user named root or ssh. Doing so overwrites the system account.
  • SSH supports public keys as an alternate form of authentication.

Unsupported Features

The LabVIEW Real-Time Module does not support certain LabVIEW features for VIs that run on RT targets. For instance, if you attempt to deploy and run a VI that has unsupported functionality on an RT target, the VI might still execute. However, the unsupported functions do not work and return standard LabVIEW error codes. The LabVIEW Real-Time Module does not support the following features on RT targets that run the NI Linux Real-Time RTOS:

  • ActiveX VIs
  • NI TestStand VIs (ActiveX-based)
  • .NET VIs
  • Report Generation Toolkit VIs
  • Windows Registry Access VIs
  • Report Express VI (Uses the unsupported Report Generation Toolkit VIs)
  • Graphics & Sound VIs
  • Database Connectivity Toolkit VIs
  • Menu functions
  • Cursor VIs
  • IrDA functions
  • LabVIEW Digital Filter Design Toolkit VIs
  • File System Web Service LabVIEW API
  • Analysis Workspace to Reduce Jitter in Mathematics and Signal Processing VIs
  • Call Library Function Nodes that access an operating system API other than NI Linux Real-Time
  • Open/Create/Replace File function interactively using a file dialog box
  • Clear indicators when called option of the Execution Properties page
  • Auto Configure option of the Create Histogram Express VI
  • Certain Advanced TDMS functions
  • Certain MathScript functions
    Note   Certain MathScript functions are supported on RT targets only when you assign the output of the function to a MathScript variable.
  • Output Page of the LabVIEW MathScript Probe window—You can use the rt_debugoutput function to send debug strings to the standard output device instead.
  • Largest Available Memory Block Property Node—This property node does not provide useful information for NI Linux Real-Time targets and returns an error if used. Use the Free Physical Memory property node instead.
  • Event structures on RT targets do not support events associated with user interface objects, such as VI front panels or controls. For example, associating the Value Change event with a control does not work. RT targets support only user events.
  • Latch Until Released and Switch Until Released Boolean mechanical actions—Refer to the KnowledgeBase for information about why these Boolean mechanical actions do not work on RT targets.

 

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