CAN Setup

1. Connect CAN Hardware

1. Using Onboard CAN (if available):

   • For JetCore boards with onboard CAN, you just need to connect the CAN_H and CAN_L lines to your CAN network.

2. Using an External CAN Transceiver (e.g., MCP2515):

   • Connect the CAN_H and CAN_L lines from the external transceiver to your CAN network.
   • Connect the SPI pins on JetCore to the MCP2515, typically as follows:
     • SCK to SCK on the transceiver.
     • MOSI to MOSI on the transceiver.
     • MISO to MISO on the transceiver.
     • CS (Chip Select) to a free GPIO pin (e.g., GPIO 8).

3. Termination:

   • Use a 120-ohm termination resistor at each end of the CAN bus to ensure signal integrity, especially for longer runs.

2. Enable CAN Interface

1. Check if CAN is already enabled:

   Check if the CAN interface is already present on your system by running:

   ifconfig -a
   • You should see a can0, can1, or similar interface if the device is recognized.

2. Enable the CAN interface (if using SPI transceiver):

   • Enable the SPI interface by modifying the Jetson's device tree settings or loading the kernel modules.

   For MCP2515, load the appropriate modules:

   sudo modprobe can
   sudo modprobe can_raw
   sudo modprobe mcp251x
   sudo modprobe spi_bcm2835

3. Create the CAN interface:

   After loading the necessary modules, bring up the CAN interface with:

   sudo ip link set can0 up type can bitrate 500000
   • Replace can0 with the appropriate interface name and set the bitrate to your desired CAN bus speed (e.g., 500 Kbps).

4. Verify CAN interface:

   Verify the CAN interface is up and running:

   ifconfig can0
   • You should see the CAN interface listed with the status "UP".

3. Test the CAN Interface

1. Send CAN messages:

   You can use cansend (part of the can-utils package) to send test CAN messages:

   cansend can0 123#deadbeef
   • This sends a CAN message with ID 123 and data deadbeef.

2. Listen for CAN messages:

   Use candump to listen for messages on the CAN bus:

   candump can0
   • This will show all incoming CAN messages on the can0 interface.

3. Use other can-utils tools for advanced CAN operations, such as:

   • canplayer: To replay CAN traffic from a log file.
   • cansend: To send specific CAN frames.

4. Use CAN in Your Application

Python: You can use the python-can library to interact with CAN from Python:

pip install python-can

Example Python code to send a CAN message:

import can
bus = can.interface.Bus(channel='can0', bustype='socketcan')
message = can.Message(arbitration_id=0x123, data=[0xDE, 0xAD, 0xBE, 0xEF], is_extended_id=False)
bus.send(message)

• C++: Use the socketcan interface in C++ to communicate with the CAN bus.

5. Troubleshooting

   • CAN interface not detected:

     • Check if the mcp251x module is loaded properly by running lsmod | grep mcp251x.
     • Verify wiring and connections for SPI or onboard CAN.

   • No messages are being sent/received:

     • Check the CAN network for proper termination resistors.
     • Use candump to ensure that the messages are being received.
     • Make sure the CAN bus speed (bitrate) is correctly configured.