CAN Cyclic Message Transmitting at an Unexpected Rate in Vehicle Communication Toolkit

Updated Feb 27, 2026

Reported In

Hardware

  • cRIO-9034

Software

  • Vehicle Communication Toolkit
  • VeriStand
  • PROVEtech:RBS for VeriStand

Issue Details

One of my CAN cyclic messages on a cRIO transmits at a different rate than expected when using the Vehicle Communication Toolkit (VCOM) with VeriStand PROVETECH RBS custom device.
I see that my CAN frame is transmitting at an unexpected or incorrect cyclic rate compared to the rate defined in the database or expected from the VeriStand configuration.

Solution

The cyclic rate of a transmitted CAN frame depends on multiple configuration layers:

  • The default cycle time defined in the database file (DBC or RBS descriptor).
  • The TX_CycleTime signal exposed in VeriStand, which can override the database value.
  • Any System Definition mappings or custom VeriStand channels that may overwrite the TX_CycleTime at runtime.
  • External factors such as connected ECUs/DUTs causing bus interactions.
If any layer provides an unexpected cycle period, the resulting CAN transmission timing may differ from the expected value.
 
 
Steps to troubleshoot similar issues:
 
  1. Remove ECUs and test in a clean loopback setup
    1. To eliminate external influences, disconnect all real ECUs/DUTs and create a loopback configuration on the  to test network file and settings used
  2. Verify the default cycle time in the database using the WebUI
    1. Check the default value set in your database (DBC or RBS descriptor) through the Web UI.
    2. Confirm that:
      • The message has the correct intended cycle time.
      • There is no conflicting repetition or transmission property defining another rate.
  3. If using a PROVETECH RBS descriptor, open and review the RBS-generated file.
    1. Verify:
      • The cycle time value matches your expectation.
      • No overridden timing values are embedded in the RBS export.
  4. Validate the TX_CycleTime channel in VeriStand
    1. Place the TX_CycleTime channel on the VeriStand Workspace.
    2. Check:
      • Does the displayed value match the expected message cycle time?
      • If you manually change the value, does the CAN message rate change accordingly?
      • If modifying TX_CycleTime changes the transmission rate, then something in the system is overriding the value.
  5. Check System Definition mappings
    1. If the TX_CycleTime keeps reverting to a non‑default value:
      • Review the SDF channel mappings.
      • Ensure that no model variables, calculated channels, alarms, or custom devices are writing to the TX_CycleTime channel.
      • Remove or adjust mappings as needed so that TX_CycleTime is not unintentionally overwritten.
Unexpected CAN cyclic message rates typically originate from conflicting configuration layers, most often the TX_CycleTime override in VeriStand. By validating the database definition, reviewing TX_CycleTime behavior, and inspecting the SDF mappings, you can identify and correct the cause quickly.

Related Links

Other Support Options

Ask the NI Community

Collaborate with other users in our discussion forums



Request Support from an Engineer

A valid service agreement or active software subscription may be required, and support options vary by country.