I am starting to use the Komodo CAN Duo Interface with the loopback test that was provided with the Komodo Software API. I have tried many times, but I cannot get the test to run, and it’s not consistent: sometimes port A or port B will not enable; sometimes the write command fails.  Am I missing something? What do I need to get this function to work?

Thanks for your question!  We will review getting started with the Komodo CAN Duo Interface, then go into details about running the loopback test.

Initializing the Komodo CAN Duo Interface

For your setup, we recommend following the steps in the document Komodo Installation steps for Windows, which uses the Komodo GUI Software. Here’s a summary of the instructions:

1. Follow the instructions provided in the Komodo CAN Duo Interface Quick Start Guide.
2. To ensure a clean start, uninstall and reinstall the USB drivers and the Komodo GUI Software.
3. Using the Komodo GUI Software, send and verify CAN messages between the Komodo channels.

Running the API Loopback Test

Here are guidelines for running the API loopback test. Note that a termination resistor is part of the setup.

1. Connect the DB-9 CAN A port to the DB-9 CAN B port on the Komodo interface.
2. Connect the USB port on the Komodo interface to the computer USB port.
3. Connect a 1k ohm resistor between CAN+ and CAN- in the Komodo block screw terminal for the CAN A port.
4. Open a terminal on the computer.
5. Enter the command detect.
6. Verify that the two ports A and B are available. Following is an example of the output from the detect

Searching for Komodo Interfaces...
2 ports(s) found:
port=0 (in-use) (1644-328845)
port=1 (in-use) (1644-328845)

7. Enter the command loopback.
8. Verify that the two ports A and B receive the correct data. Following is an example of the output from the loopback command:

Features for CAN A: 0x30, CAN B: 0x1c0
Bitrate for CAN A set to 125 kHz, CAN B set to 125 kHz
Timeout for CAN B set to 1000 ms
Enabled target power for CAN A and disabled for CAN B
Sent data: [ 1 2 3 4 5 6 7 8 ]
Received data: [ 1 2 3 4 5 6 7 8 ]
Verifying data... PASS

Why the Termination Resistor is Needed

From the intermittent failures you experienced, it is likely there is an impedance mismatch. To avoid improper termination, we recommend connecting a resistor between CAN+ and CAN- in the Komodo block screw terminal of the CAN A port.  The value of the resistor can vary per system. Some customers have been successful with 120 ohm resistors, others have been successful with 1k ohm resistors.

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

• Komodo CAN Interface User Manual
• Komodo CAN Duo Interface Quick Start Guide
• Komodo GUI Software User Manual

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

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