CANBUS FAQ

Getting started

To get started with the basics of communication with the Karbon units, the Karbon command line utility can be downloaded for Linux and Windows systems. 
This utility will allow you to work the the Karbon Microcontroller which is responsible for the native CAN Bus functionality on the unit. No additional drivers need to be installed to work with the native CAN bus on the system. Although additional python libraries will be needed if you wish to develop python scripts to utilize the native CAN Bus

Connectivity

For this tutorial there will be a K300 running Windows 10 IoT and a K300 running Ubuntu 20.04 with a cable connecting the two units via the CAN Bus port located on the side of the chassis.

The Karbon’s internal CAN device should be attached directly to a CAN Bus, but features no internal termination. Because of this, for proper operation, it may be required to implement an external termination resistor. This resistor should match the nominal impedance of the cable; typically 120Ω, which complies with ISO 11898.

Using Karbon CLI utility to send CAN Messages on Linux

After downloading and extracting the Windows directory from the Karbon Microcontroller Utility, open command prompt and navigate to the directory containing the Karbon.exe CLI utility. From here you can use the command karbon.exe raw devices to query which Virtual COM port in the OS is handling CAN messaging.

We can then use PuTTY to open the CAN interface port and now the PuTTY terminal is listening to the CAN interface of the Microcontroller.

On the Linux system, we can extract the Karbon MCU utility’s Linux directory and navigate to it. Running the Karbon utility with sudo, we can send normal CAN Frames over the systems CAN Bus using the sudo ./karbon op can-message -i 123 -d 11223344 command

The Windows machine’s PuTTY Window will receive and present the sent CAN message

Using Karbon CLI utility to send CAN Messages on Windows

The linux Karbon CLI utility can report which /dev/ address is handling CAN communication with the command sudo ./karbon raw devices

The CAN interface can be opened with an elevated PuTTY command to listen for CAN messages.

On the Windows system using an elevated command prompt, CAN messages can be sent utilizing the karbon op can-message -i 123 -d 11223344 command.

The CAN message will show up on the Linux system’s PuTTY window

$ sudo apt install can-utils

#! /bin/bash

# ASCII Command vs CAN Bitrate
# s0 --- s1 --- s2 --- s3 --- s4 --- s5 --- s6 --- s7 --- s8
# 10     20     50     100    125    250    500    800    1000  Kbits/s
BAUD=8

# Name of slcan device to attach
DEV=can0


# Detect correct port for device interfaces
TERM_PORT=$(ls -l /dev/serial/by-id/ | grep 1fc9_00a3 | sed 's/.*\///g' | awk '{if(NR==2) print $0}')
CANB_PORT=$(ls -l /dev/serial/by-id/ | grep 1fc9_00a3 | sed 's/.*\///g' | awk '{if(NR==1) print $0}')

# Start or stop the service
while getopts ":ks" opt; do
    case $opt in
        k)
            # Stop the SLCAN service and turn off the can device
            echo "Shutting down can interface..."
            sudo ifconfig $DEV down 2> /dev/null
            sudo pkill slcand

            sudo slcand -c /dev/"$CANB_PORT"
            sudo pkill slcand
            ;;
        s)
            # Open the can device, and start the slcan service.
            echo "Terminal interface on: $TERM_PORT"
            echo "CAN Bus  interface on: $CANB_PORT"

            # Set the mode to slcan
            echo -ne "set can-mode slcan" > /dev/$TERM_PORT

            echo "Attaching slcan device..."

            # Attach to the port with slcand
            sudo slcand -s$BAUD -o /dev/"$CANB_PORT" $DEV

            # Give interface time to come up
            sleep .25

            # Enable the inteface
            sudo ifconfig $DEV up
            sudo ifconfig $DEV txqueuelen 1000

            echo "Interface is set up."
            ;;
        \?)
            echo "Invalid option: -$OPTARG" >&2
            exit 1
            ;;
        :)
            echo "Option -$OPTARG requires an argument." >&2
            exit 1
            ;;
    esac
done

$ cansend can0 123#11223344
$ candump can0

$ karbon can -n <COMMAND>

$ karbon can -b 500 <COMMAND>

$ karbon can send [FLAGS] [OPTIONS] <identifier> [data]

$ karbon can send 123 1122334455667788

$ karbon can send -e 999 11223344

$ karbon can send -l 3 123 112233

$ karbon can send -r 123

# ID tests
try:
    n = u32_from_base_16(identifier)
    if not extended and n > 0x7FF:
        return Error  # Invalid ID range
    else if extended and n > 0x1FFFFFFF:
        return Error  # Invalid ID range
    else:
        return Ok
except:
    # Invalid characters, or > 32 bits
    return Error

# Data tests
if length(data) is not even:
    return Error  # Bytes must be complete
else if length(data) > 16:
    return Error  # More than eight bytes

try:
    n = u64_from_base_16(data)
    return Ok
except:
    # Invalid characters, or > 64 bits
    return Error

$ karbon can dump -d

$ karbon can dump -d -c -f 123 7FF -- messages.csv

karbon can dump [FLAGS] [OPTIONS] [--] [output]

$ karbon can dump -c
id,len,data
123,4,11223344

$ karbon can dump -d
      id [l]             data            delta
     123 [4]         11223344         2.907689
     7FF [4]             ABCD         3.386151
     123 [4]         11223344         6.232194
00000999 [8] 1122334455667788         0.000519

$ karbon can dump -f 123 1FFFFFFF 00000999 3AA