Note: Work in progress, feel free to contribute.

# gdl90

[![GDL90 Parser on crates.io][cratesio-image]][cratesio]
[![GDL90 Parser on docs.rs][docsrs-image]][docsrs]
[![GitHub last commit][ghcommit-image]][ghcommit]

[cratesio-image]: https://img.shields.io/crates/v/gdl90.svg
[cratesio]: https://crates.io/crates/gdl90
[docsrs-image]: https://docs.rs/gdl90/badge.svg
[docsrs]: https://docs.rs/gdl90
[ghcommit-image]: https://img.shields.io/github/last-commit/roby2014/gdl90
[ghcommit]: https://github.com/roby2014/gdl90/

This crate provides types and structures for handling [GDL90 messages](https://www.faa.gov/sites/faa.gov/files/air_traffic/technology/adsb/archival/GDL90_Public_ICD_RevA.PDF).

It uses Rust crates such as [binrw](https://github.com/jam1garner/binrw) and [modular-bitfield](https://github.com/Robbepop/modular-bitfield) to efficiently
represent and manipulate these message types.

## What is GDL90?

> GDL 90 is designed to transmit, receive and decode Automatic Dependent Surveillance-Broadcast (ADS-B)
messages via onboard datalink. It broadcasts your aircraft's position, velocity, projected track, altitude
and flight identification to other equipped aircraft in your vicinity, as well as to ground-based transceivers maintained by the FAA.

Many ADS-B transponders (such as [uAvionix ping20Si](https://uavionix.com/products/ping20si/)) use this protocol for their I/O interfaces. With this crate, you can easily integrate one of those in your *rusty* system.

You can find the full specification [here](https://www.faa.gov/sites/faa.gov/files/air_traffic/technology/adsb/archival/GDL90_Public_ICD_RevA.PDF).

## Usage

```toml
[dependencies]
gdl90 = "0.1.0"
```

```rs
use std::io::Cursor;
use gdl90::datalink::Gdl90DatalinkMessage;
use gdl90::Gdl90Message;

// hardcoded, but you should read this from transponder
let parsed = gdl90::read_raw(&[0x7E, 0x00, 0x81, 0x41, 0xDB, 0xD0, 0x08, 0x02, 0xB3, 0x8B, 0x7E]).unwrap();
dbg!(&parsed);

match parsed.message_data {
    Gdl90DatalinkMessage::Heartbeat { status_byte_1, status_byte_2, uat_timestamp, message_counts } => { } ,
    Gdl90DatalinkMessage::Initialization { configuration_byte_1, configuration_byte_2 } => { },
    Gdl90DatalinkMessage::UplinkData { time_of_reception, payload } => { },
    Gdl90DatalinkMessage::HeightAboveTerrain { hat } => { },
    Gdl90DatalinkMessage::OwnshipReport { report } => { },
    Gdl90DatalinkMessage::TrafficReport { report } => { },
    Gdl90DatalinkMessage::OwnshipGeoometricAltitude { ownship_geo_altitude, vertical_metrics } => { },
    Gdl90DatalinkMessage::BasicReport() => { },
    Gdl90DatalinkMessage::LongReport() => { },
    Gdl90DatalinkMessage::Unknown => { },
}
```

Result:
```
&parsed = Gdl90Message {
    message_data: Heartbeat {
        status_byte_1: HeartbeatStatusByte1 {
            uat_initialized: true,
            ratcs: false,
            gps_batt_low: false,
            addr_type: false,
            ident: false,
            maint_reqd: false,
            gps_pos_valid: true,
        },
        status_byte_2: HeartbeatStatusByte2 {
            utc_ok: true,
            csa_not_available: false,
            csa_requested: true,
            timestamp_msb: false,
        },
        uat_timestamp: 53467,
        message_counts: 520,
    },
    frame_check_seq: 35763,
}
```

## TODO:

- Add more strong typying structures, no raw bits like `B4`, ...
- Add and test remaining messages.
- Try removing `bitfield`s as maximum as possible, replacing it with custom types, using `binrw` directives and magic macros.

## References

- [binrw](https://binrw.rs/)
- [modular-bitfield](https://github.com/Robbepop/modular-bitfield)
- [GDL90 spec](https://www.faa.gov/sites/faa.gov/files/air_traffic/technology/adsb/archival/GDL90_Public_ICD_RevA.PDF).