File formats

Log files

Read and written through python-can; the format follows the extension.

Extension	Format	Notes
.asc	Vector ASCII log	Text; widely supported by analysis tools
.blf	Vector binary logging format	Compact binary; channel names are stored as numbers (CANExplorer drops channel names that do not fit)
.csv	Comma separated values	One frame per line
.log	can-utils candump -l	Text; readable by canplayer
.trc	PEAK trace	Text
.db	SQLite	One table of frames
.mf4	ASAM MDF 4	Binary measurement data format of ASAM, read by tools such as asammdf and CANape; needs the optional mf4 extra (see below)
.asc.gz, .csv.gz, .log.gz, .trc.gz	The text formats, gzip compressed	Typically 5–10 times smaller; other tools may need the file decompressed first (gunzip)

Every format can be recorded, exported, replayed and replayed on a bus. Timestamps are kept, so replays reproduce the original timing.

MF4 support uses the asammdf package, which brings numpy and pandas along and is therefore optional:

uv sync --extra mf4

Without it, MF4 is not offered in the file dialogs and opening an .mf4 file explains what to install.

Signal databases

Extension	Format	Read	Write	Library
.dbc	Vector CANdb++	✓	✓	cantools
.dbf	BUSMASTER database 1.3	✓	✓	CANExplorer
.arxml	AUTOSAR system description 3.x and 4.x	✓		cantools
.kcd	Kayak network definition	✓	✓	cantools
.sym	PEAK PCAN Symbol 6.0	✓	✓	cantools
.ldf	LIN description file 1.3–2.2A	✓		ldfparser
.cdd	Vector CANdelaStudio diagnostic description	✓		CANExplorer

BUSMASTER DBF

BUSMASTER databases are text files, written in the Windows ANSI code page with CRLF line endings:

[START_MSG] <name>,<id>,<length>,<signal count>,<byte order>,<S|X>,<sender>
[START_SIGNALS] <name>,<length>,<byte>,<bit>,<type>,<max>,<min>,<byte order>,<offset>,<factor>,<unit>,<multiplex>,<receivers>
[VALUE_DESCRIPTION] "<text>",<raw value>
[END_MSG]

• <byte> counts from 1 and <bit> from 0. They address the least significant bit of the signal, also for Motorola (big endian) signals, whose DBC start bit is the most significant bit; CANExplorer converts between both conventions like BUSMASTER.
• <byte order>: 1 Intel (little endian), 0 Motorola (big endian).
• <type>: U unsigned, I signed, B boolean, F 32-bit and D 64-bit float.
• <max> and <min> are raw values: physical = raw × factor + offset.
• <multiplex>: M for the multiplexer, m<n> for signals present when it is n.
• For [PROTOCOL] J1939 the identifier is the PGN; reading assigns priority 6 and source address 0xFE.

Comments of nodes, messages and signals are kept. Value tables, attributes (e.g. cycle times) and network comments are not converted.

CANdelaStudio CDD

CANExplorer reads the data identifiers (DIAGINST with STATICVALUE) of the ECU and the layout of their data:

• Data types with a coded value (IDENT, LINCOMP, TEXTTBL and others with CVALUETYPE): unsigned, signed, IEEE float and text (asc, utf) encodings, big (bo="21") and little (bo="12") endian, linear scaling (COMP), units and text tables (TEXTMAP, including value ranges).
• Structures, unions (all alternatives over the same bits) and shared DID structures (DIDDATAREF).
• Field offsets count bits from the least significant bit of each byte, like CANdelaStudio; big endian fields are located by their most significant bit.

Services, diagnostic trouble code descriptions and structured data types without a coded value are not read.

LIN frames on SocketCAN

LIN drivers following the sllin convention carry LIN as CAN frames with the LIN identifier (0x00–0x3F) as standard identifier, headers as remote frames and responses as data frames. Recordings of LIN connections therefore use the ordinary log formats.