{canscope}

CAN bus sniffer and SAE J1939 protocol analyzer. Reads CAN frames in candump format, decodes them using a J1939 Digital Annex (xlsx), and presents results in an interactive terminal UI or as JSON output.

Features

• TUI mode - full-screen interactive terminal interface (FTXUI). Multiple display modes per CAN ID: deployed, brief, verbose, manual, little-endian
• Headless mode - JSON output to stdout or file, for scripting and automation
• Recording - decoded J1939 SPN values saved to SQLite database with gzip compression and batch flushing
• J1939 decoding - PGN/SPN lookup, bit-level value extraction from payload
• CAN playback - replay recorded CAN frames
• Custom SPN configuration - per-parameter settings, parameter export
• Real-time - 30 fps UI refresh

Build

Requirements:

• clang++ with C++23 support
• CMake >= 3.13
• System libraries: boost (signals2, spirit, phoenix), sqlite3, systemd, zlib

The rest of the dependencies are fetched automatically via CMake FetchContent:

• FTXUI - terminal UI framework
• tiny-process-library - subprocess management
• sqlite_modern_cpp - modern C++ SQLite wrapper
• xlnt - xlsx reading
• fmt - text formatting
• nlohmann/json - JSON library
• spdlog - logging
• clipp - CLI argument parsing

cmake -B build -S . && cmake --build build -j$(nproc)

Binary: build/canscope

Docker

docker build -t canscope .

# TUI mode -- requires terminal and CAN interface access
docker run -it --network=host canscope -e "candump can0" -j1939 /app/thirdparty/j1939da_2018.xlsx

# Headless mode
docker run --network=host canscope -hl -e "candump can0" -j1939 /app/thirdparty/j1939da_2018.xlsx

# Read from stdin
candump can0 | docker run -i canscope -j1939 /app/thirdparty/j1939da_2018.xlsx -hl

Usage

# TUI mode (default)
./build/canscope -e "candump can0" -j1939 thirdparty/j1939da_2018.xlsx

# Headless -- JSON to stdout
./build/canscope -hl -e "candump can0" -j1939 thirdparty/j1939da_2018.xlsx

# Headless -- JSON to file
./build/canscope -hl -e "candump can0" -j1939 thirdparty/j1939da_2018.xlsx -of output.json

# Read from stdin (pipe)
candump can0 | ./build/canscope -j1939 thirdparty/j1939da_2018.xlsx

# Headless with stdin
candump can0 | ./build/canscope -hl -j1939 thirdparty/j1939da_2018.xlsx

# Docker -- TUI with CAN interface access
docker run -it --network=host canscope -e "candump can0" -j1939 /app/thirdparty/j1939da_2018.xlsx

# Docker -- headless
docker run --network=host canscope -hl -e "candump can0" -j1939 /app/thirdparty/j1939da_2018.xlsx

# Docker -- read from stdin
candump can0 | docker run -i canscope -hl -j1939 /app/thirdparty/j1939da_2018.xlsx

# Record to SQLite database
./build/canscope -rec -db recording.db -e "candump can0" -j1939 thirdparty/j1939da_2018.xlsx

# Record + TUI
./build/canscope -rec -db recording.db -tui -e "candump can0" -j1939 thirdparty/j1939da_2018.xlsx

Note: J1939 decoding has only been tested with the Digital Annex 2018 edition. Other editions may work but are not guaranteed.

CLI flags

Flag	Long form	Description
-j1939	--j1939-document	(required) J1939 Digital Annex xlsx file
-e	--execute-command	Command to read CAN frames from (e.g. "candump can0")
-hl	--headless	Headless mode (no TUI)
-of	--output-file	Output file path (headless mode)
-rec	--record	Record decoded values to SQLite
-db	--database	SQLite database path (required with -rec)
-tui		Show TUI alongside recording
-h	--help	Show help

Roadmap

• Cross-platform support - Windows and macOS in addition to Linux
• Docker deployment - pre-built image for quick setup without manual compilation
• CANopen protocol support - CANopen decoding alongside J1939
• Other small features and enhancements - UI improvements, performance optimizations, additional export formats