CAN1/CAN2 Not Working on Apalis iMX8 with Ixora Carrier Board – Missing Termination Resistors?

Technical Support
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1

I am working with a Apalis iMX8 module on the Ixora Carrier Board and trying to test CAN1 and CAN2 interfaces.

What I’ve done:

  • Connected a Vector CAN transceiver to CAN1.
  • Used candump to listen on CAN1 and cansend to send messages.
  • Internal loopback mode works fine (software tests pass).
  • But in normal mode, I am not able to send or receive any messages with vector CAN transceiver.

Observations:

  • I noticed that termination resistors (120 Ohm) are not populated for both CAN1 and CAN2 on the Ixora board.

Questions:

Is it necessary to populate the 120-ohm termination resistors on the Ixora board for CAN1 and CAN2 to function properly?

2

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Hello! Thank you for your detailed question.

Yes, it is necessary to have proper 120Ω termination resistors at each end of the CAN bus for correct operation, especially when you connect external CAN devices such as your Vector CAN transceiver. The termination ensures reliable communication by matching the impedance of the bus and suppressing reflections.

For the Ixora Carrier Board:

  • The revision history of the board specifically notes that CAN termination resistors are not populated for CAN1 and CAN2 on Ixora V1.1 boards. Therefore, you will need to add external 120Ω termination resistors at the ends of your CAN network wires for reliable operation.(1)
  • Connect your Vector CAN transceiver to the relevant pins:
    • CAN1_L (Pin 1)
    • CAN1_H (Pin 2)
    • CAN1_GND_ISO (Pin 3)
      (2)

Without the termination resistors, the CAN transceivers likely won’t communicate properly, which matches the behavior you’re observing in normal mode. Internal loopback mode doesn’t require the physical CAN bus to be present, which is why your software tests are passing.

Recommendation:

  • Add a 120Ω resistor between CAN_H and CAN_L at each end of your CAN bus segment—one at the Ixora side and one at your external transceiver side.

Once the resistors are in place, you should be able to send and receive CAN frames successfully in normal mode.

Best regards,
Toradex AI Assistant.