Formats and their limits

CanViewer reads DBC with its own parser, and every other format through canmatrix, an open-source Python library that runs inside your browser. Both produce the same model, so every view works for every format. What differs is how much of a file comes across: that is measured for each format on real test files, and the numbers are in the format reference.

DBC: complete, instant, with problems per line

DBC files open with CanViewer's own TypeScript parser. It models everything the views show (messages, signals, multiplexing including SG_MUL_VAL_, value tables, comments, attributes, float and double signals), reports every line it cannot read as a problem with its line number, and opens a large file in a few tens of milliseconds. It is tested against 58 real-world databases from carmakers; the DBC reference lists the statements it supports and the corpus it is tested against.

Other formats, through canmatrix

Format	Extension	Notes
ARXML (AUTOSAR)	.arxml	In AUTOSAR 3 files canmatrix finds frames only when the cluster information is ignored, so CanViewer reads such a file a second time that way, and says so in the problems. Some AUTOSAR 4.2 files fail to read
KCD (Kayak)	.kcd	A file can hold several buses; see below
SYM (PEAK PCAN Symbol Editor)	.sym	canmatrix drops multiplexed signals
DBF (Busmaster)	.dbf
Excel	.xlsx	The layout canmatrix itself writes. .xls (the old Excel format) is not supported, see why
JSON, YAML	.json, .yaml, .yml	canmatrix's own schema, not an arbitrary JSON or YAML file. The YAML reader read none of canmatrix's own example files
FIBEX	.xml	The FIBEX reader read none of canmatrix's own example files
ODX	.odx	Untested: no test file is available

canmatrix's readers are less complete than CanViewer's DBC parser, and some of their weaknesses are listed above. Anything canmatrix reports while reading (warnings, errors, and lines it drops) becomes a parse problem, and so does what CanViewer's model cannot show, such as the contained PDUs of an AUTOSAR container frame. CanViewer itself fills in no value the file does not contain: it leaves out the initial value canmatrix makes up.

Some losses happen inside canmatrix without a report, and so stay silent for now (the measured list): in ARXML, a missing byte order becomes big endian, a broken scaling (COMPU-METHOD) gets an assumed one, and an ECU configuration file (.ecuc.arxml) loses its frame IDs and signal types; in every format, a range the file leaves out is filled in from the raw value range, so it looks like one the file gives.

The first import downloads the runtime

canmatrix needs a Python runtime (Pyodide, compiled to WebAssembly). It is part of the app, but the browser fetches it only when the first non-DBC file is opened: about 16 MB for an ARXML file (15,957,759 bytes measured), less where the web host compresses it. Some formats load a small extra package the first time they are used (YAML 113 kB, Excel 269 kB). A session that opens only DBC files downloads none of it.

The first import takes a few seconds while the runtime starts; the stages show at the bottom of the window. The next file opens much faster, and after the first import the runtime is cached, so imports work offline too.

Files with several buses

Some formats can describe several buses (clusters) in one file. CanViewer shows the first cluster that has messages, and the overview lets you pick another. An imported database also shows its source format there, with a note that the conversion may be lossy and a link to the problems canmatrix reported (Importing other formats).

Why no .xls

canmatrix reads the old Excel format with the library xlrd, whose license has a clause that is incompatible with CanViewer's license, the GNU GPL. .xlsx is read with a different library and is supported.

Not supported

• LIN (.ldf): canmatrix's LDF reader needs a library that has no WebAssembly build.
• CANopen (.eds): not part of the formats CanViewer loads.
• Writing other formats: CanViewer writes DBC only (Save as DBC), and exports CSV, JSON and code. It does not write ARXML or the other formats it imports.