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.
- C source code generator.
- CAN bus monitor.
- Graphical plots of signals.
Project homepage: https://github.com/eerimoq/cantools
Documentation: https://cantools.readthedocs.io
Installation
python3 -m pip install cantoolsExample 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 | 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:
$ 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.
$ 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
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.
$ cat candump-2021-01-04_180521.log | python3 -m cantools plot tests/files/dbc/abs.dbc '*33.*fl:-<' '*33.*fr:->' - '*33.*rl:-<' '*33.*rr:->'
Signals with a different range of values can be displayed in the same subplot on different vertical axes by separating them with a comma.
$ 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'
Matplotlib comes with different preinstalled styles that you can use:
$ cat candump-2021-01-04_180521.log | cantools plot tests/files/dbc/abs.dbc --style seaborn
You can try all available styles with
$ 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'"
doneFor more information see
$ python3 -m cantools plot --helpNote that by default matplotlib is not installed with cantools. But it can be by specifying an extra at installation:
$ python3 -m pip install cantools[plot]The dump subcommand
Dump given database in a human readable format:
$ 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:
$ 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: DisabledThe 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.
$ 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).
$ 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.
$ 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.
$ 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.
$ cantools generate_c_source tests/files/dbc/motohawk.dbc --node PCM1
Successfully generated motohawk.h and motohawk.c.
See `motohawk_sender.h`_ and `motohawk_sender.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.
$ python3 -m 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
Fork the repository.
Install prerequisites.
python3 -m pip install -r requirements.txt
Implement the new feature or bug fix.
Implement test case(s) to ensure that future changes do not break legacy.
Run the tests.
make test
Create a pull request.