datalink

datalink is a Rust aviation datalink workspace with a reusable decode library and a single CLI for demodulating and decoding aviation datalink traffic.

• crates/acars — core library for ACARS, VDL2 AVLC, ADS-C, CPDLC-related payloads, HFDL PDU parsing, and optional demodulators.
• crates/datalink — CLI application for bearer frontends, standalone frame decoding, Airframes.io input, Redis/JSONL output, and merged receiver configurations.

datalink can decode standalone frames, demodulate VDL2 / VHF ACARS / HFDL I/Q sources, consume Airframes.io websocket events, run merged TOML receiver configurations, and emit JSONL or Redis pub/sub output.

CLI overview

datalink [--config datalink.toml] [COMMAND]

Commands:

vdl2          VDL Mode 2 frontend for I/Q and SDR inputs
vhf           Classic VHF ACARS frontend
airframes.io  Airframes.io websocket feed
hfdl          HF Data Link frontend
decode        Decode standalone payloads or frames

When no subcommand is provided, datalink runs merged receiver mode and expects --config <FILE>.

Standalone decode examples

# Decode an ACARS frame from hex
datalink decode acars --direction downlink '<hex>'

# Decode an AVLC frame including FCS bytes
datalink decode avlc '<hex>'

# Decode an ADS-C app payload
datalink decode adsc '/ATSU.ADS....'

VDL2 frontend

datalink vdl2 --format cu8 --sample-rate 1050000 --center-freq 136850000 \
  --channel 136875000 136975000 file://capture.cu8

Useful options:

• --output <file> — write decoded JSONL in addition to stdout.
• --stats — print demod/decode counters.
• --redis-url <url> — publish decoded records to application-specific Redis topics.

Classic VHF ACARS frontend

datalink vhf --format cu8 --sample-rate 1050000 --center-freq 131700000 \
  --channel 131525000 131725000 file://capture.cu8

Useful options:

• --output <file> — write decoded JSONL in addition to stdout.
• --stats — print demod/decode counters.
• --redis-url <url> — publish decoded messages to application-specific Redis topics.

HFDL frontend

datalink hfdl --format cf32 --center-freq 10000000 --sample-rate 8000000 \
  --max-seconds 20 file://capture.cf32

Useful options:

• --stats — print demod/decode counters.
• --redis-url <url> — publish decoded PDUs to application-specific Redis topics.

For SDRUno-style 16-bit stereo WAV I/Q files, .wav input is auto-detected when --format is omitted:

datalink hfdl --max-seconds 60 file://HFDL_10081kHz.wav

Redis publishing uses application-specific topics across all bearers, for example datalink-sq, datalink-acars, datalink-cpdlc, and datalink-other.

Source URLs

VDL2, VHF, and HFDL share the same source direction: WAV I/Q recordings, raw I/Q recordings, and live SDR sources.

VDL2 and VHF currently accept:

• file://... or a bare file path
• - for stdin
• rtlsdr://... when built with rtlsdr
• airspy://... when built with airspy
• hackrf://... when built with hackrf
• soapy://... when built with soapy

Common source query parameters include format, center_freq/freq, sample_rate/rate, channel/channels, gain, bias_tee, and device-specific gain settings. If gain is omitted, datalink applies its per-device default; gain=auto explicitly requests device automatic gain control where supported. HackRF accepts amp_enable/rf_amp for its 14 dB RF amplifier plus lna_gain/if_gain and vga_gain/bb_gain for stage gains.

For file captures, datalink can infer center frequency, sample rate, and cf32 format from Gqrx-style filenames such as gqrx_20260518_114025_136500000_1800000_fc.raw. It can also infer center frequency from SDRUno-style names containing a trailing kHz frequency.

Library notes

The acars crate is the reusable decode library. Its demodulators are behind the optional demod feature so pure parser users do not need to pull in SDR/DSP dependencies.

• Default acars build: decode/parsing only.
• acars with features = ["demod"]: adds VDL2, VHF ACARS, and HFDL demod support.

The datalink CLI enables acars/demod because it includes demodulating frontends. See crates/acars/readme.md for the library API overview until the crate is published on docs.rs.

Cargo features

datalink defaults to SDR and websocket support:

default = ["rtlsdr", "airspy", "hackrf", "websocket"]

Individual SDR features can be disabled or selected with normal Cargo feature flags.

Project direction

The project is Rust-native rather than a direct port of an existing decoder. The goal is a shared Rust library plus a consistent JSON-facing CLI across VDL2, VHF ACARS, HFDL, and external event sources, following the relevant datalink standards and preserving unknown or vendor-specific payloads for later analysis.