canviz 0.1.2

Open-source browser-based CAN bus analyzer

CANviz

Open-source, browser-based CAN bus analyzer.
Works with cheap (~$10) USB-C CAN modules. No GUI install. Just pip install and open a browser.

pip install canviz
canviz --interface gs_usb
# → browser opens at http://localhost:8080

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What it does

CANviz is a web-based CAN bus analyzer that runs entirely in your browser. You plug in a USB CAN module, run one command, and get a live view of your CAN bus, no desktop app to install, no compiling from source.

v1 features:

• Live message table: ID, DLC, data bytes, frame count, rate (fps), last seen
• DBC file support: upload a .dbc file and see decoded signal values inline
• Filter by message ID or signal name
• Send CAN frames manually from the UI
• Record sessions to .asc and .csv
• Replay recorded log files with speed control
• REST API + WebSocket - scriptable and automation-friendly

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Hardware

Primary (plug and play on Windows):
Any CAN module running Candlelight firmware - including the FYSETC UCAN (STM32F072, ~$8).
These show up in Windows Device Manager as gs_usb / WinUSB - no COM port, no reflash needed.

Also supported:

• slcan devices (COM port) - CANable and others running slcan firmware
• SocketCAN - Linux, Raspberry Pi, WSL2
• PEAK PCAN-USB, Kvaser, Vector - via python-can config
• Virtual bus - for development and CI (no hardware needed)

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Quick Start

Windows (Candlelight / gs_usb device)

pip install canviz
canviz

Auto-detects the connected gs_usb device. Browser opens at http://localhost:8080.

Windows (slcan / COM port device)

pip install canviz
canviz --interface slcan --channel COM3 --bitrate 500000

Raspberry Pi / Linux (SocketCAN)

# One-time setup
sudo ip link set can0 up type can bitrate 500000

pip install canviz
canviz --interface socketcan --channel can0

No hardware (virtual bus)

pip install canviz
canviz --interface virtual

Frames loop back on themselves. Useful for testing and development.

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Interface Notes

Interface	When to use	Windows	Linux
gs_usb	Candlelight firmware devices (default)	✓	✓
slcan	Devices that enumerate as a COM port	✓	✓
socketcan	Native SocketCAN	-	✓
virtual	No hardware, development/CI	✓	✓

Candlelight vs slcan: If your device shows up as a COM port in Device Manager, use --interface slcan --channel COMx. If it shows as gs_usb / WinUSB with no COM port, use --interface gs_usb (the default).

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CLI Reference

canviz [OPTIONS]

Options:
  --interface   gs_usb | slcan | socketcan | virtual  (default: gs_usb)
  --channel     COM port or SocketCAN channel (e.g. COM3, can0)
  --bitrate     CAN bitrate in bps (default: 500000)
  --host        Host to bind to (default: 127.0.0.1)
  --port        Port to bind to (default: 8080)

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API

The backend exposes a REST API and WebSocket. Useful for scripting and automation.

Method	Path	Description
POST	/connect	Open CAN interface
POST	/disconnect	Close interface
GET	/status	Connection state
POST	/send	Transmit a frame
WS	/ws/frames	Live frame stream (JSON)
POST	/dbc/load	Upload DBC file
GET	/dbc/messages	List decoded messages
DELETE	/dbc	Unload DBC
POST	/log/start	Start recording
POST	/log/stop	Stop recording
GET	/log/download/{file}	Download log file
POST	/replay/start	Start log replay
POST	/replay/stop	Stop replay

Full interactive API docs available at http://localhost:8080/docs when running.

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Known Limitations

• USB timestamp jitter ~1ms - not suitable for sub-millisecond timing analysis
• High bus loads (>5000 fps) may require server-side throttling (planned for a future release)
• Tested on Chrome; Firefox and Edge are best-effort
• CAN FD (>8 byte payloads) display support is planned for a future release
• Replay timing accuracy depends on the asyncio scheduler - not wall-clock perfect at high bus loads

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Stack

Backend: Python 3.10+ · FastAPI · python-can · cantools · aiofiles
Frontend: React 18 · TanStack Table · Zustand · Vite
Supported OS: Windows 10/11 · Linux · Raspberry Pi OS · macOS (best-effort)

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License

MIT