Cantools Save
CAN bus tools.
|github-actions| |coverage| |nala|
About
CAN BUS tools in Python 3.
-
DBC,KCD, SYM, ARXML 3&4 and CDD file parsing. -
CAN message encoding and decoding.
-
Simple and extended signal multiplexing.
-
Diagnostic DID encoding and decoding.
-
candumpoutput decoder. -
Node
tester_. -
Csource code generator. -
CAN bus monitor.
-
Graphical plots of signals.
Project homepage: https://github.com/cantools/cantools
Documentation: https://cantools.readthedocs.io
Installation
.. code-block:: bash
python3 -m pip install cantools
Example usage
Scripting
The example starts by parsing a small DBC-file_ and printing its
messages and signals.
.. code-block:: python
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.
.. code-block:: python
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.
.. code-block:: python
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.
.. code-block:: text
$ candump vcan0 | python3 -m 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:
.. code-block:: text
$ candump vcan0 | python3 -m 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 plot subcommand ^^^^^^^^^^^^^^^^^^^
The plot subcommand is similar to the decode subcommand but messages are visualized using matplotlib_ instead of being printed to stdout.
.. code-block:: bash
$ candump -l vcan0
$ cat candump-2021-01-04_180521.log
(1609779922.655421) vcan0 00000343#B204B9049C049C04
(1609779922.655735) vcan0 0000024A#120527052E051905
(1609779923.657524) vcan0 00000343#C404C404CB04C404
(1609779923.658086) vcan0 0000024A#8B058B058B059205
(1609779924.659912) vcan0 00000343#5C04790479045504
(1609779924.660471) vcan0 0000024A#44064B0659064406
(1609779925.662277) vcan0 00000343#15040704F203F203
(1609779925.662837) vcan0 0000024A#8B069906A706A706
(1609779926.664191) vcan0 00000343#BC03B503A703BC03
(1609779926.664751) vcan0 0000024A#A006A706C406C406
$ cat candump-2021-01-04_180521.log | python3 -m cantools plot tests/files/dbc/abs.dbc
.. image:: https://github.com/cantools/cantools/raw/master/docs/plot-1.png
If you don't want to show all signals you can select the desired signals with command line arguments.
A * can stand for any number of any character, a ? for exactly one arbitrary character.
Signals separated by a - are displayed in separate subplots.
Optionally a format can be specified after a signal, separated by a colon.
.. code-block:: bash
$ cat candump-2021-01-04_180521.log | python3 -m cantools plot tests/files/dbc/abs.dbc '*33.*fl:-<' '*33.*fr:->' - '*33.*rl:-<' '*33.*rr:->'
.. image:: https://github.com/cantools/cantools/raw/master/docs/plot-2-subplots.png
Signals with a different range of values can be displayed in the same subplot on different vertical axes by separating them with a comma.
.. code-block:: bash
$ cat candump-2021-01-04_180521.log | cantools plot --auto-color tests/files/dbc/abs.dbc --
--ylabel 'Bremse 33' '_33.fl:-<' '_33.fr:>' '_33.rl:3' '_33.rr:4' ,
--ylabel 'Bremse 2' '_2.fl:-<' '_2.fr:>' '_2.rl:3' '_2.rr:4'
.. image:: https://github.com/cantools/cantools/raw/master/docs/plot-2-axes.png
Matplotlib comes with different preinstalled styles that you can use:
.. code-block:: bash
$ cat candump-2021-01-04_180521.log | cantools plot tests/files/dbc/abs.dbc --style seaborn
.. image:: https://github.com/cantools/cantools/raw/master/docs/plot-seaborn.png
You can try all available styles with
.. code-block:: bash
$ cantools plot --list-styles . | sed -n '/^- /s/^- //p' | while IFS= read -r style; do cat candump-2021-01-04_180521.log | cantools plot tests/files/dbc/abs.dbc --style "$style" --title "--style '$style'" done
For more information see
.. code-block:: bash
$ python3 -m cantools plot --help
Note that by default matplotlib is not installed with cantools. But it can be by specifying an extra at installation:
.. code-block:: bash
$ python3 -m pip install cantools[plot]
The dump subcommand ^^^^^^^^^^^^^^^^^^^
Dump given database in a human readable format:
.. code-block:: text
$ python3 -m 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 list subcommand ^^^^^^^^^^^^^^^^^^^
Print all information of a given database in a human readable format. This is very similar to the "dump" subcommand, but the output is less pretty, slightly more comprehensive and easier to parse by shell scripts:
.. code-block:: bash
$ python3 -m cantools list -a tests/files/dbc/motohawk.dbc
ExampleMessage:
Comment[None]: Example message used as template in MotoHawk models.
Frame ID: 0x1f0 (496)
Size: 8 bytes
Is extended frame: False
Signals:
Enable:
Type: Integer
Start bit: 7
Length: 1 bits
Unit: -
Is signed: False
Named values:
0: Disabled
The generate C source subcommand ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Generate C source code from given database.
The generated code contains:
-
Message
structs_. -
Message
pack_ andunpack_ functions. -
Signal
encode_ anddecode_ 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.
.. code-block:: text
$ python3 -m 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 this example we use --use-float so floating point numbers in the generated
code are single precision (float) instead of double precision (double).
.. code-block:: text
$ python3 -m cantools generate_c_source --use-float tests/files/dbc/motohawk.dbc Successfully generated motohawk.h and motohawk.c.
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.
.. code-block:: text
$ python3 -m 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 next example we use --no-floating-point-numbers to generate
code without floating point types, i.e. float and double.
.. code-block:: text
$ python3 -m 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.
In the last example --node is used to generate
message pack functions only for messages sent by the specified node and unpack
functions only for messages with its signal receivers belonging to that node.
.. code-block:: text
$ cantools generate_c_source tests/files/dbc/motohawk.dbc --node PCM1 Successfully generated motohawk.h and motohawk.c.
See motohawk_sender_node.h_ and
motohawk_sender_node.c_ for the contents of the
generated files.
Other C code generators:
The monitor subcommand ^^^^^^^^^^^^^^^^^^^^^^
Monitor CAN bus traffic in a text based user interface.
.. code-block:: text
$ python3 -m cantools monitor tests/files/dbc/motohawk.dbc
.. image:: https://github.com/cantools/cantools/raw/master/docs/monitor.png
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
#. Fork the repository.
#. Install prerequisites.
.. code-block:: text
python3 -m pip install -e .[dev]
#. Implement the new feature or bug fix.
#. Implement test case(s) to ensure that future changes do not break legacy.
#. Run the linters
.. code-block:: text
ruff check src
mypy src
#. Run the tests.
.. code-block:: text
tox -e py
#. Create a pull request.
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.. _small DBC-file: https://github.com/cantools/cantools/blob/master/tests/files/dbc/motohawk.dbc
.. _motohawk.dbc: https://github.com/cantools/cantools/blob/master/tests/files/dbc/motohawk.dbc
.. _python-can: https://python-can.readthedocs.io/en/master/
.. _DBC: http://www.socialledge.com/sjsu/index.php?title=DBC_Format
.. _KCD: https://github.com/julietkilo/kcd
.. _tester: http://cantools.readthedocs.io/en/latest/#cantools.tester.Tester
.. _encoding: http://cantools.readthedocs.io/en/latest/#cantools.database.can.Message.encode
.. _encode_message(): http://cantools.readthedocs.io/en/latest/#cantools.database.can.Database.encode_message
.. _decodes: http://cantools.readthedocs.io/en/latest/#cantools.database.can.Database.decode_message
.. _examples: https://github.com/cantools/cantools/blob/master/examples
.. _structs: https://github.com/cantools/cantools/blob/master/tests/files/c_source/motohawk.h#L58
.. _pack: https://github.com/cantools/cantools/blob/master/tests/files/c_source/motohawk.h#L88
.. _unpack: https://github.com/cantools/cantools/blob/master/tests/files/c_source/motohawk.h#L102
.. _encode: https://github.com/cantools/cantools/blob/master/tests/files/c_source/motohawk.h#L116
.. _decode: https://github.com/cantools/cantools/blob/master/tests/files/c_source/motohawk.h#L125
.. _defines: https://github.com/cantools/cantools/blob/master/tests/files/c_source/motohawk.h#L42
.. _motohawk.h: https://github.com/cantools/cantools/blob/master/tests/files/c_source/motohawk.h
.. _motohawk.c: https://github.com/cantools/cantools/blob/master/tests/files/c_source/motohawk.c
.. _my_database_name.h: https://github.com/cantools/cantools/blob/master/tests/files/c_source/my_database_name.h
.. _my_database_name.c: https://github.com/cantools/cantools/blob/master/tests/files/c_source/my_database_name.c
.. _motohawk_no_floating_point_numbers.h: https://github.com/cantools/cantools/blob/master/tests/files/c_source/motohawk_no_floating_point_numbers.h
.. _motohawk_no_floating_point_numbers.c: https://github.com/cantools/cantools/blob/master/tests/files/c_source/motohawk_no_floating_point_numbers.c
.. _motohawk_sender_node.h: https://github.com/cantools/cantools/blob/master/tests/files/c_source/motohawk_sender_node.h
.. _motohawk_sender_node.c: https://github.com/cantools/cantools/blob/master/tests/files/c_source/motohawk_sender_node.c
.. _matplotlib: https://matplotlib.org/
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