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How Do I Interpret and Resolve the Errors I See with CAN Bus Data?
Rena Ayeras

Komodo Duo CAN Interface to analyze CAN data Question from the Customer:

I am trying to use the Komodo CAN Duo Interface, and it looks like I need some help.

In my first setup, I used the Komodo GUI Software to transmit data to the device under test (DUT). The system uses J1939, a standard protocol for communication and diagnostics with vehicle components.  I initiated START CAPTURE to transmit CAN bus data. What I received was a message about data errors:

Many errors have been detected, and capture has been stopped automatically. Please verify your connection and bitrate.

Here are the errors that were displayed, which were repeated many times:

  • CAN Error – Dir. RX Type: Stuff, POS: ID.28 to ID21
  • CAN Error – Dir. RX Type: Other, POS Tolerate Dominant Bits

I then used the Data Center Software – only corrupt data was captured.

My questions - what do the error messages indicate and how can they be resolved?

Response from Technical Support:

Thanks for your questions! We will go over the error messages and recommend a solution for the issues you described.

Komodo CAN Interface Error Messages

Here is a summary of the errors that were displayed:

  • Dir is the direction of the error. If the error is during reception, then it indicates RX, as indicated in the data that you provided. If the error is during transmission, then it indicates TX.
  • Type is the error type.
  • Pos is the field position of the error in the frame.

Resolve Data Errors and Corruption at the Terminal

The Komodo CAN device does not provide termination resistors for the bus. In a typical system, the Komodo is installed on the bus between two endpoints, which provide the proper termination. Based on the data corruption, we suggest connecting a 1 kΩ resistor between the CAN+ and CAN- inputs in the Komodo block screw terminal port. In a general setup, this often resolves improper termination or non-matched impedance that cause corrupt data corruption and error messages.

For more information, we recommend taking a look at Table 14 in Section 5.6.2 General CAN of the Komodo CAN Interface User Manual, as well as Section 6 of the Bosch CAN Specification manual. We also recommend an article we have about debugging CAN bus data communication.

We hope this answers your questions. Additional resources that you may find helpful include the following:

If you want more information, feel free to contact us with your questions, or request a demo that applies to your application.