Questions about CAN (can0–can3) usage on Jetson Thor

Robotics & Edge Computing Jetson Systems Jetson Thor
1

Hello,

I am trying to use CAN communication on Jetson Thor.
Using the commands ip link show and lsmod | grep can, I confirmed that Jetson Thor has built-in CAN interfaces
(can0, can1, can2, can3, mttcan).

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I have the following three questions:

  1. Through the docs page and Jetson_Thor_Module_Carrier_Board_Spec_SP-12533-001_v1.2.pdf, I was able to find guidance for can0 and can1.
    According to the documents, the pin assignments are:

    • can0: J47 pins 3 and 5

    • can1: J47 pins 7 and 9

    However, in the documentation I also see:

    • pin 4 – FSI_CAN0_TERM

    • pin 8 – FSI_CAN1_TERM

    What are these pins used for? There is no related explanation in the Carrier Board Spec.

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  2. Is a 120-ohm termination resistor built in on the carrier board, or does it need to be added externally?

  3. I would also like to use can2 and can3, but I am having difficulty finding any related guides or documentation.
    How can can2 and can3 be used on Jetson Thor?

Thank you in advance for your help.

3

Hi wono,

Please refer to the following part in developer guide for their connection.

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No, you don’t need external 120-Ohm and CAN transceiver for Thor.

Please configure them as following in pinmux spreadsheet.

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4

Thank you for the quick response. @KevinFFF

I will try the approach you suggested.

After checking the schematics PDF, I was able to find the pinout for J47 (2x13 pin header).

  • Pins 11, 12, 13: AURIX_CAN1_H, AURIX_CAN1_TERM, AURIX_CAN1_L

  • Pins 15, 16, 17: AURIX_CAN2_H, AURIX_CAN2_TERM, AURIX_CAN2_L

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I have the following questions:

  1. Is it correct that these signals are mapped as follows?
pin 11 AURIX_CAN1_H  -> pin D59 CAN2_DOUT
pin 13 AURIX_CAN1_L  -> pin F58 CAN2_DIN
pin 15 AURIX_CAN2_H  -> pin H61 CAN3_DOUT
pin 17 AURIX_CAN2_L  -> pin B61 CAN3_DIN

  1. In the schematics, it is stated that there is a 120-ohm resistor across FSI_CAN0_L and FSI_CAN0_TERM.

    In that case, is the correct wiring to connect:

    • short pin 3 and pin 4 together and connect them to CAN_H

    • connect pin 5 to CAN_L?

shorted(pin 3, pin 4) -> CAN_H
        pin 5         -> CAN_L

(I have confirmed that all CANx_L and CANx_TERM pairs have a 120-ohm resistor. If the above method is correct, I plan to apply the same wiring approach to the other CAN interfaces as well.)

5

Yes, it is the expected connection to work with CAN0.
Please connect CAN-H/CAN-L to your CAN device to verify.

6

Thank you for checking. @KevinFFF
I’ll try it out.

To use CAN2 and CAN3, is it correct to connect the following pins on J47 (2×13 pin header)?

  • pin 11 → CAN2_H

  • pin 13 → CAN2_L

  • pin 15 → CAN3_H

  • pin 17 → CAN3_L

Please let me know if my understanding is correct.

7

You may also need to short PIN11/PIN12 before connecting to CAN2_H, and PIN15/PIN16 before connecting to CAN3_H.