Monitor Channel Using CAN Database

"""dbmonitor.py -- Read CAN messages using a database

This script will use canlib.canlib and canlib.kvadblib to monitor a CAN
channel, and look up all messages received in a database before printing them.

It requires a CANlib channel with a connected device capable of receiving CAN
messages, some source of CAN messages, and the same database that the source is
using to generate the messages.

In this example the channel is opened with flag canOPEN_ACCEPT_LARGE_DLC (optional).
This enables a DLC larger than 8 bytes (up to 15 for classic CAN). If
canOPEN_ACCEPT_LARGE_DLC is excluded, generated frames with DLC > 8, will attain
a DLC of 8 on the receiving end, which may compromise the DLC equivalence
check.

The source of the messages may be e.g. the pinger.py example script.

"""
import argparse

from canlib import canlib, kvadblib

# Create a dictionary of predefined CAN bitrates, using the name after
# "BITRATE_" as key. E.g. "500K".
bitrates = {x.name.replace("BITRATE_", ""): x for x in canlib.Bitrate}


def printframe(db, frame):
    try:
        bmsg = db.interpret(frame)
    except kvadblib.KvdNoMessage:
        print(f"<<< No message found for frame with id {frame.id} >>>")
        return

    if not bmsg._message.dlc == bmsg._frame.dlc:
        print(
            "<<< Could not interpret message because DLC does not match for"
            f" frame with id {frame.id} >>>"
        )
        print(f"\t- DLC (database): {bmsg._message.dlc}")
        print(f"\t- DLC (received frame): {bmsg._frame.dlc}")
        return

    msg = bmsg._message

    print('┏', msg.name)

    if msg.comment:
        print('┃', f'"{msg.comment}"')

    for bsig in bmsg:
        print('┃', bsig.name + ':', bsig.value, bsig.unit)

    print('┗')


def monitor_channel(ch, db, ticktime):

    timeout = 0.5
    tick_countup = 0
    if ticktime <= 0:
        ticktime = None
    elif ticktime < timeout:
        timeout = ticktime

    print("Listening...")
    while True:
        try:
            frame = ch.read(timeout=int(timeout * 1000))
            printframe(db, frame)
        except canlib.CanNoMsg:
            if ticktime is not None:
                tick_countup += timeout
                while tick_countup > ticktime:
                    print("tick")
                    tick_countup -= ticktime
        except KeyboardInterrupt:
            print("Stop.")
            break


def parse_args(argv):
    parser = argparse.ArgumentParser(
        description="Listen on a CAN channel and print all signals received, as specified by a database."
    )
    parser.add_argument(
        'channel', type=int, default=1, nargs='?', help=("The channel to listen on.")
    )
    parser.add_argument(
        '--db',
        default="engine_example.dbc",
        help=("The database file to look up messages and signals in."),
    )
    parser.add_argument(
        '--bitrate', '-b', default='500k', help=("Bitrate, one of " + ', '.join(bitrates.keys()))
    )
    parser.add_argument(
        '--ticktime',
        '-t',
        type=float,
        default=0,
        help=("If greater than zero, display 'tick' every this many seconds"),
    )
    args = parser.parse_args()
    return args


def main(argv=None):
    args = parse_args(argv)
    db = kvadblib.Dbc(filename=args.db)
    ch = canlib.openChannel(args.channel, canlib.canOPEN_ACCEPT_LARGE_DLC, bitrates[args.bitrate.upper()])
    ch.setBusOutputControl(canlib.canDRIVER_NORMAL)
    ch.busOn()

    monitor_channel(ch, db, args.ticktime)


if __name__ == '__main__':
    raise SystemExit(main())

Description

Any CAN messages received on the specified channel will be looked up in the database using interpret, which allows the script to print the “phys” value of each signal instead of just printing the raw data (as Monitor a Channel does). The script also prints the message’s name and comment (if available), as well as the signals name and unit.

Sample Output

┏ EngineData
┃ PetrolLevel: 0.0 l
┃ EngPower: 12.0 kW
┃ EngForce: 0.0 N
┃ IdleRunning: 0.0
┃ EngTemp: -30.0 °C
┃ EngSpeed: 7735.0 rpm
┗
┏ GearBoxInfo
┃ EcoMode: 0.0
┃ ShiftRequest: 0.0
┃ Gear: 0.0
┗
┏ EngineData
┃ PetrolLevel: 0.0 l
┃ EngPower: 28.0 kW
┃ EngForce: 0.0 N
┃ IdleRunning: 0.0
┃ EngTemp: -30.0 °C
┃ EngSpeed: 3467.0 rpm
┗
┏ GearBoxInfo
┃ EcoMode: 1.0
┃ ShiftRequest: 0.0
┃ Gear: 0.0
┗
┏ EngineData
┃ PetrolLevel: 0.0 l
┃ EngPower: 0.0 kW
┃ EngForce: 0.0 N
┃ IdleRunning: 0.0
┃ EngTemp: -50.0 °C
┃ EngSpeed: 1639.0 rpm
┗
┏ GearBoxInfo
┃ EcoMode: 1.0
┃ ShiftRequest: 0.0
┃ Gear: 1.0
┗
┏ EngineData
┃ PetrolLevel: 60.0 l
┃ EngPower: 0.0 kW
┃ EngForce: 0.0 N
┃ IdleRunning: 0.0
┃ EngTemp: 142.0 °C
┃ EngSpeed: 0.0 rpm
┗
┏ GearBoxInfo
┃ EcoMode: 0.0
┃ ShiftRequest: 0.0
┃ Gear: 0.0
┗
┏ EngineData
┃ PetrolLevel: 172.0 l
┃ EngPower: 51.0 kW
┃ EngForce: 0.0 N
┃ IdleRunning: 0.0
┃ EngTemp: -50.0 °C
┃ EngSpeed: 0.0 rpm
┗
┏ GearBoxInfo
┃ EcoMode: 0.0
┃ ShiftRequest: 0.0
┃ Gear: 0.0
┗

CAN FD version

This example is basically the same as dbmonitor.py above, except we are now using CAN FD.

Note that you also need the dbmonitor.py file, next to dbmonitorfd.py below, since we are reusing the monitor_channel function.

"""dbmonitorfd.py -- Read CAN FD messages using a database

This script will use canlib.canlib and canlib.kvadblib to monitor a CAN FD
channel, and look up all messages received in a database before printing them.

It requires a CANlib channel with a connected device capable of receiving CAN FD
messages, some source of CAN messages, and the same database that the source is
using to generate the messages.

The script also reuses the monitor_channel function defined in dbmonitor.py

The source of the messages may be e.g. the pingerfd.py example script.

"""
import argparse

from canlib import canlib, kvadblib

import dbmonitor

# Create a dictionary of predefined CAN FD bitrates, using the name after
# "BITRATE_" as key. E.g. "500K_80P".
fd_bitrates = {x.name.replace("BITRATE_", ""): x for x in canlib.BitrateFD}


def parse_args(argv):
    parser = argparse.ArgumentParser(
        description="Listen on a CAN channel and print all signals received, as specified by a database."
    )
    parser.add_argument(
        'channel', type=int, default=1, nargs='?', help=("The channel to listen on.")
    )
    parser.add_argument(
        '--db',
        default="engine_example.dbc",
        help=("The database file to look up messages and signals in."),
    )
    parser.add_argument(
        '--fdbitrate', '-f', default=['500k_80p', '1M_80p'], nargs=2,
        help=("CAN FD arbitration and data bitrate pair (e.g. -f 500k_80p 1M_80p), two of " + ', '.join(fd_bitrates.keys()))
    )
    parser.add_argument(
        '--ticktime',
        '-t',
        type=float,
        default=0,
        help=("If greater than zero, display 'tick' every this many seconds"),
    )
    args = parser.parse_args()
    return args


def main(argv=None):
    args = parse_args(argv)
    db = kvadblib.Dbc(filename=args.db)
    ch = canlib.openChannel(
        args.channel,
        flags=canlib.Open.CAN_FD,
        bitrate=fd_bitrates[args.fdbitrate[0].upper()],
        data_bitrate=fd_bitrates[args.fdbitrate[1].upper()],
    )
    ch.setBusOutputControl(canlib.canDRIVER_NORMAL)
    ch.busOn()

    dbmonitor.monitor_channel(ch, db, args.ticktime)


if __name__ == '__main__':
    raise SystemExit(main())