CANtrip

An open-source, free alternative to Vector CANalyzer for viewing CAN / CAN-FD bus traffic on Windows, decoding it against DBC files, and graphing signals.

Why CANtrip

A Vector CANalyzer license costs anywhere from a few thousand to tens of thousands of euros, putting it out of reach for students, hobbyists, and small teams. The free/open-source alternatives, meanwhile, tend to be CLI-first tools that expect you to memorize a dozen flags just to open a bus, and reward a typo with a cryptic error three layers removed from what actually went wrong. CANtrip aims to sit in the middle: a GUI tool that's simple to pick up, powerful, free to use, and licensed GPLv3.

How it works

CANtrip does not reimplement CAN capture or low-level frame dissection. Instead it reuses Wireshark's own capture pipeline:

CANtrip (Qt app) --launches--> tshark -T ek --reads from--> extcap: can2pcap
                                                                    |
                                                          AVlabs CAN backend
                                                          /       |        \
                                                   PeakBackend  VectorBackend  Other
                                                       |            |           HW
                                                PCAN-Basic.dll  vxlapi64.dll
                                                       |            |
                                                 PEAK hardware  Vector VN-series hardware

• extcap/can2pcap is a small Wireshark extcap program. It exposes CAN channels from any available backend as capture interfaces to Wireshark/tshark, translating frames into SocketCAN-format pcapng records so Wireshark's built-in SocketCAN dissector decodes ID/DLC/data/FD flags.
• app/ is the Qt desktop application: pick a channel from any installed vendor, configure bus timing (usual presets or expert raw values), import a DBC per channel, and view live traffic in a table that unfolds into per-signal decoded values (via dbcppp).

Graphing, gateway mode, and message transmission are deferred to a later phase.

Multi-vendor hardware support

CANtrip is not tied to one CAN adapter vendor. There's no OS-level CAN abstraction on Windows (unlike Linux's SocketCAN). Every vendor ships its own proprietary DLL and API shape. CANtrip works around this with a vendor-neutral interface, the AVlabs CAN backend (common/AVlabsCanBackend.h); one bus to sniff them all. The extcap and app only ever talk to that interface, never to a vendor SDK directly.

• Each backend dynamically loads its vendor's DLL at runtime (LoadLibrary/GetProcAddress), so CANtrip builds and runs fine with only some (or none) of the vendor SDKs installed.
• common/PeakBackend.h/.cpp wraps PEAK-System's PCANBasic.dll. Supports classic CAN and CAN FD.
• common/VectorBackend.h/.cpp wraps Vector Informatik's vxlapi64.dll (XL Driver Library), verified against a VN1640A and a VN7640. Supports classic CAN and CAN FD, with bit timing computed by common/CanBitTiming.h/.cpp
• common/CanBackendRegistry.cpp is the single place that lists every backend CANtrip knows about.
• Adding support for another vendor (Kvaser's CANlib, ETAS's BOA, etc.) means implementing the AVlabs CAN backend interface once, using that vendor's real SDK header and adding one line to the registry.

Prerequisites (Windows)

• Wireshark installed (provides tshark, dumpcap, and the extcap plugin folder).
• A driver package for whichever CAN hardware you're using - only one is needed, CANtrip just uses whichever it finds:
  • PEAK-System PCAN-Basic (provides PCANBasic.dll), or
  • Vector's XL Driver Library or any Vector driver package that installs vxlapi64.dll (e.g. Vector Driver Setup, CANoe/CANalyzer, Vector Hardware Manager).
• Qt 6 (msvc2019_64 or newer kit) and a matching MSVC toolchain.
• CMake >= 3.21.

Building

cmake -S . -B build -DCMAKE_PREFIX_PATH="G:\Qt\6.7.3\msvc2019_64"
cmake --build build --config Debug

This produces:

• build\extcap\Debug\can2pcap.exe
• build\app\Debug\cantrip.exe

Installing the extcap into Wireshark

After installing Wireshark and downloading CANtrip, copy can2pcap.exe into Wireshark's personal extcap folder so both Wireshark and tshark (and therefore CANtrip) can see it:

copy build\extcap\Debug\can2pcap.exe "$env:APPDATA\Wireshark\extcap\"

Verify it's picked up:

tshark -D

You should see a can2pcap interface listed.

Running CANtrip

Prebuilt binaries are also published under Releases if you'd rather skip building from source. Grab the zip, extract it anywhere, and copy the can2pcap.exein your $env:APPDATA\Wireshark\extcap\ directory.

CANtrip's window is a ribbon, Office-style: each tab across the top shows a different group of controls.

1. Launch build\app\Debug\cantrip.exe (or cantrip.exe from a Release zip).

2. On the Hardware tab, pick a channel from the "Network Hardware" dropdown. No CAN hardware or vendor driver installed yet? Pick "CANtrip synthetic test source (no hardware needed)". It's always listed and fakes traffic so you can try everything below without owning a single wire.

   

3. Still on Hardware, click CAN Controller... to set the bitrate: classic CAN mode by default, or ISO CAN FD/Expert CAN FD for FD (synth source is CAN HS only). ISO mode computes real BRP/TSEG1/TSEG2/SJW register values live from a target bitrate and sample point; Expert mode lets you type those raw values directly.

   

   Don't know the actual settings of your bus? Autodetect scans your selected network hardware for its bus config and applies it:

   

4. On the Home tab, click Start. Frames stream into the table as they arrive; click the arrow next to a row to unfold it into its decoded signals (name, physical value, unit) via dbcppp. Switch between "Waterfall" (newest first) and "Periodic" (one row per ID) display from the same tab, and change the display rate in case of busy buses; click Stop to end the capture.

   

5. On the Analysis & Measurement tab, click Import DBC... and load test/sample.dbc - a small DBC whose four message IDs (0x100, 0x200, 0x300, 0x7E8) deliberately match what the synthetic test source transmits, so you get fully decoded signals with zero hardware.

6. In this same tab, you can switch from the classic CAN trace view to a graphical view. Not much to explain, play around with it to get a hold of how it works:

   

7. Your environment is exactly how you like it and want to save it for later? Under the Home tab, press Save Rune.... Runes are CANtrip's configuration files - save and load them later so CANtrip remembers your bus configuration and graph layout.

   

8. Press Start once your environment is all set up and you'll see your frames, decoded signals, and any bus errors right in the trace view:

   

Contributing

See CONTRIBUTING.md for code conventions and how to verify changes. See RELEASING.md for the version naming scheme and how a release gets cut.

License

GPL-3.0. See LICENSE. CANtrip statically/dynamically links dbcppp (MPL-2.0) and shells out to Wireshark's tshark (GPL-2.0) as a separate process — see individual project licenses for details.

Vector, CANalyzer, and CANoe are trademarks of Vector Informatik GmbH. CANtrip is an independent, unaffiliated open-source project and is not endorsed by or affiliated with Vector Informatik.