About

CAN BUS tools in Python 3.

• DBC, KCD, SYM, ARXML 4 and CDD file parsing.
• CAN message encoding and decoding.
• Simple and extended signal multiplexing.
• Diagnostic DID encoding and decoding.
• candump output decoder.
• Node tester.
• C source code generator.
• CAN bus monitor.

Project homepage: https://github.com/eerimoq/cantools

Documentation: https://cantools.readthedocs.io

Installation

pip install cantools

Example usage

Scripting

The example starts by parsing a small DBC-file and printing its messages and signals.

>>> import cantools
>>> from pprint import pprint
>>> db = cantools.database.load_file('tests/files/dbc/motohawk.dbc')
>>> db.messages
[message('ExampleMessage', 0x1f0, False, 8, 'Example message used as template in MotoHawk models.')]
>>> example_message = db.get_message_by_name('ExampleMessage')
>>> pprint(example_message.signals)
[signal('Enable', 7, 1, 'big_endian', False, 1.0, 0, 0.0, 0.0, '-', False, None, {0: 'Disabled', 1: 'Enabled'}, None),
 signal('AverageRadius', 6, 6, 'big_endian', False, 0.1, 0, 0.0, 5.0, 'm', False, None, None, ''),
 signal('Temperature', 0, 12, 'big_endian', True, 0.01, 250, 229.53, 270.47, 'degK', False, None, None, None)]

The example continues encoding a message and sending it on a CAN bus using the python-can package.

>>> import can
>>> can_bus = can.interface.Bus('vcan0', bustype='socketcan')
>>> data = example_message.encode({'Temperature': 250.1, 'AverageRadius': 3.2, 'Enable': 1})
>>> message = can.Message(arbitration_id=example_message.frame_id, data=data)
>>> can_bus.send(message)

Alternatively, a message can be encoded using the encode_message() method on the database object.

The last part of the example receives and decodes a CAN message.

>>> message = can_bus.recv()
>>> db.decode_message(message.arbitration_id, message.data)
{'AverageRadius': 3.2, 'Enable': 'Enabled', 'Temperature': 250.09}

See examples for additional examples.

Command line tool

The decode subcommand

Decode CAN frames captured with the Linux program candump.

$ candump vcan0 | cantools decode tests/files/dbc/motohawk.dbc
  vcan0  1F0   [8]  80 4A 0F 00 00 00 00 00 ::
ExampleMessage(
    Enable: 'Enabled' -,
    AverageRadius: 0.0 m,
    Temperature: 255.92 degK
)
  vcan0  1F0   [8]  80 4A 0F 00 00 00 00 00 ::
ExampleMessage(
    Enable: 'Enabled' -,
    AverageRadius: 0.0 m,
    Temperature: 255.92 degK
)
  vcan0  1F0   [8]  80 4A 0F 00 00 00 00 00 ::
ExampleMessage(
    Enable: 'Enabled' -,
    AverageRadius: 0.0 m,
    Temperature: 255.92 degK
)

Alternatively, the decoded message can be printed on a single line:

$ candump vcan0 | cantools decode --single-line tests/files/dbc/motohawk.dbc
  vcan0  1F0   [8]  80 4A 0F 00 00 00 00 00 :: ExampleMessage(Enable: 'Enabled' -, AverageRadius: 0.0 m, Temperature: 255.92 degK)
  vcan0  1F0   [8]  80 4A 0F 00 00 00 00 00 :: ExampleMessage(Enable: 'Enabled' -, AverageRadius: 0.0 m, Temperature: 255.92 degK)
  vcan0  1F0   [8]  80 4A 0F 00 00 00 00 00 :: ExampleMessage(Enable: 'Enabled' -, AverageRadius: 0.0 m, Temperature: 255.92 degK)

The dump subcommand

Dump given database in a human readable format:

$ cantools dump tests/files/dbc/motohawk.dbc
================================= Messages =================================

  ------------------------------------------------------------------------

  Name:       ExampleMessage
  Id:         0x1f0
  Length:     8 bytes
  Cycle time: - ms
  Senders:    PCM1
  Layout:

                          Bit

             7   6   5   4   3   2   1   0
           +---+---+---+---+---+---+---+---+
         0 |<-x|<---------------------x|<--|
           +---+---+---+---+---+---+---+---+
             |                       +-- AverageRadius
             +-- Enable
           +---+---+---+---+---+---+---+---+
         1 |-------------------------------|
           +---+---+---+---+---+---+---+---+
         2 |----------x|   |   |   |   |   |
     B     +---+---+---+---+---+---+---+---+
     y               +-- Temperature
     t     +---+---+---+---+---+---+---+---+
     e   3 |   |   |   |   |   |   |   |   |
           +---+---+---+---+---+---+---+---+
         4 |   |   |   |   |   |   |   |   |
           +---+---+---+---+---+---+---+---+
         5 |   |   |   |   |   |   |   |   |
           +---+---+---+---+---+---+---+---+
         6 |   |   |   |   |   |   |   |   |
           +---+---+---+---+---+---+---+---+
         7 |   |   |   |   |   |   |   |   |
           +---+---+---+---+---+---+---+---+

  Signal tree:

    -- {root}
       +-- Enable
       +-- AverageRadius
       +-- Temperature

  Signal choices:

    Enable
        0 Disabled
        1 Enabled

  ------------------------------------------------------------------------

The generate C source subcommand

Generate C source code from given database.

The generated code contains:

• Message structs.
• Message pack and unpack functions.
• Signal encode and decode functions.
• Frame id, length, type, cycle time and signal choices defines.

Known limitations:

• The maximum signal size is 64 bits, which in practice is never exceeded.

Below is an example of how to generate C source code from a database. The database is tests/files/dbc/motohawk.dbc.

$ cantools generate_c_source tests/files/dbc/motohawk.dbc
Successfully generated motohawk.h and motohawk.c.

See motohawk.h and motohawk.c for the contents of the generated files.

In the next example we use --database-name to set a custom namespace for all generated types, defines and functions. The output file names are also changed by this option.

$ cantools generate_c_source --database-name my_database_name tests/files/dbc/motohawk.dbc
Successfully generated my_database_name.h and my_database_name.c.

See my_database_name.h and my_database_name.c for the contents of the generated files.

In the last example we use --no-floating-point-numbers to generate code without floating point types, i.e. float and double.

$ cantools generate_c_source --no-floating-point-numbers tests/files/dbc/motohawk.dbc
Successfully generated motohawk.h and motohawk.c.

See motohawk_no_floating_point_numbers.h and motohawk_no_floating_point_numbers.c for the contents of the generated files.

Other C code generators:

• http://www.coderdbc.com
• https://github.com/howerj/dbcc
• https://github.com/lonkamikaze/hsk-libs/blob/master/scripts/dbc2c.awk
• https://sourceforge.net/projects/comframe/

The monitor subcommand

Monitor CAN bus traffic in a text based user interface.

$ cantools monitor tests/files/dbc/motohawk.dbc

The menu at the bottom of the monitor shows the available commands.

• Quit: Quit the monitor. Ctrl-C can be used as well.
• Filter: Only display messages matching given regular expression. Press <Enter> to return to the menu from the filter input line.
• Play/Pause: Toggle between playing and paused (or running and freezed).
• Reset: Reset the monitor to its initial state.

Contributing

1. Fork the repository.

2. Install prerequisites.

   pip install -r requirements.txt
   

3. Implement the new feature or bug fix.

4. Implement test case(s) to ensure that future changes do not break legacy.

5. Run the tests.

   make test
   

6. Create a pull request.