{canscope}

CAN bus sniffer and SAE J1939 protocol analyzer. Reads CAN frames in candump format, decodes them using a J1939 Digital Annex (xlsx or csv), 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. Supports xlsx and csv input formats
• 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
• Ninja
• System libraries: boost (signals2, spirit, phoenix, regex), sqlite3, zlib, icu

Dependencies fetched automatically via CMake FetchContent:

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

Available targets

make list              # Show all targets

make build             # Native build (dynamic linking)
make build_static      # Native build (static linking)
make install           # Install to PREFIX (default /usr/local), requires patchelf
make install_static    # Install static binary to PREFIX

make docker-run ARGS='...'       # Build and run in Docker (cross-platform)
make build_arm64                 # Cross-compile for arm64 (dynamic)
make build_arm64_static          # Cross-compile for arm64 (static)

make clean             # Remove all build artifacts

Native build

make build
./build/native/canscope -e "candump can0" -j1939-xlsx thirdparty/j1939da_2018.xlsx
# or with CSV (faster parsing)
./build/native/canscope -e "candump can0" -j1939-csv thirdparty/j1939da_2018.csv

Docker (cross-platform)

Works on Linux, macOS (?), and Windows (?). Requires only Docker and Make.

# TUI mode - local CAN interface
make docker-run ARGS='-e "candump can0" -j1939-xlsx thirdparty/j1939da_2018.xlsx'

# TUI mode - remote CAN interface via SSH (no data if will ask password - use public key access or sshpass utility)
make docker-run ARGS='-e "ssh user@remote candump can0" -j1939-xlsx thirdparty/j1939da_2018.xlsx'

# Discover mode - find out what PGNs/SPNs are on the bus
make docker-run ARGS='-discover -e "candump can0" -j1939-xlsx thirdparty/j1939da_2018.xlsx'

# Headless mode - stream decoded values
make docker-run ARGS='-hl -e "candump can0" -j1939-xlsx thirdparty/j1939da_2018.xlsx'

Cross-compile for arm64

make build_arm64           # dynamic linking
make build_arm64_static    # static linking

Requires Docker. SSH keys from ~/.ssh and /etc/hosts are forwarded into the build container for fetching private git dependencies.

Usage

All operating modes are mutually exclusive. If none is specified, TUI mode is used.

# TUI mode (default) — interactive terminal interface
canscope -e "candump can0" -j1939-xlsx thirdparty/j1939da_2018.xlsx

# Discover mode — output PGN/SPN structure (no values) to stdout or file
canscope -discover -e "candump can0" -j1939-xlsx thirdparty/j1939da_2018.xlsx
canscope -discover -of discovered.json -e "candump can0" -j1939-csv thirdparty/j1939da_2018.csv

# Headless mode — stream all decoded values (NDJSON) to stdout
canscope -hl -e "candump can0" -j1939-xlsx thirdparty/j1939da_2018.xlsx

# Record mode — write all decoded values + timestamps to SQLite
canscope -rec -db recording.db -e "candump can0" -j1939-xlsx thirdparty/j1939da_2018.xlsx

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

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

Modes

Mode	Flag	Description
TUI	(default)	Interactive full-screen terminal UI
Discover	-discover	Output PGN/SPN structure (no values) to stdout or file (-of)
Headless	-hl	Stream all decoded PGN/SPN values as NDJSON to stdout
Record	-rec	Write all decoded PGN/SPN values + timestamps to SQLite (-db)

CLI flags

Flag	Long form	Description
-j1939-xlsx		J1939 Digital Annex xlsx file
-j1939-csv		J1939 Digital Annex csv file (faster parsing)
-e	--execute-command	Command to read CAN frames from (e.g. "candump can0")
-discover		Discover mode
-hl	--headless	Headless mode
-rec	--record	Record mode
-of	--output-file	Output file path (used with -discover)
-db	--database	SQLite database path (required with -rec)
-h	--help	Show help

Roadmap

• NMEA 2000 protocol support - NMEA 2000 decoding using canboat PGN database (JSON). Same 29-bit CAN ID as J1939, requires Fast Packet protocol implementation
• CANopen protocol support - CANopen decoding alongside J1939 (11-bit CAN ID, SDO/PDO/NMT)
• Other small features and enhancements - UI improvements, performance optimizations, additional export formats