Monitor a Channel Using a 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.

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

"""
import argparse

from canlib import canlib, kvadblib


bitrates = {
    '1M': canlib.canBITRATE_1M,
    '500K': canlib.canBITRATE_500K,
    '250K': canlib.canBITRATE_250K,
    '125K': canlib.canBITRATE_125K,
    '100K': canlib.canBITRATE_100K,
    '62K': canlib.canBITRATE_62K,
    '50K': canlib.canBITRATE_50K,
    '83K': canlib.canBITRATE_83K,
    '10K': canlib.canBITRATE_10K,
}


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

    msg = bmsg._message

    # form = '═^' + str(width)
    # print(format(" %s " % msg.name, form))

    print('┏', msg.name)

    if msg.comment:
        print('┃', '"%s"' % msg.comment)

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

    print('┗')


def monitor_channel(channel_number, db_name, bitrate, ticktime):
    db = kvadblib.Dbc(filename=db_name)

    ch = canlib.openChannel(channel_number, canlib.canOPEN_ACCEPT_VIRTUAL)
    ch.setBusOutputControl(canlib.canDRIVER_NORMAL)
    ch.setBusParams(bitrate)
    ch.busOn()

    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


if __name__ == '__main__':
    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()

    monitor_channel(args.channel, args.db, bitrates[args.bitrate.upper()], args.ticktime)

Description

Any CAN messages received on the specified channel will be looked up in the database using canlib.kvadblib.Dbc.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
┗