# mode-s-demodulator

> A JavaScript module for demodulating and decoding Mode S / ADS-B messages from aviation aircrafts

Latest version **1.0.1** (published 2017-12-11) · MIT license · 0 weekly downloads

## Install

```sh
npm install mode-s-demodulator
pnpm add mode-s-demodulator
yarn add mode-s-demodulator
bun add mode-s-demodulator
```

## Health

**Score 15/100 (F)** — status: abandoned.

Positive: no vulnerabilities.

Warnings: low downloads; no types; no esm support.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 1.0.1 |
| Published | 2017-12-11 |
| First published | 2017-12-10 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | none |
| Module format | CommonJS |
| Dependencies | 2 |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 35 |
| Author | Thomas Watson |
| Maintainers | watson |
| Keywords | decode, decoder, demodulate, demodulator, modes, mode-s, adsb, ads-b, sdr, rtlsdr, rtl-sdr, librtlsdr, radio, aircraft, airplane, airplanes, plane, 1090, 1090mhz |

## Links

- npm: https://www.npmjs.com/package/mode-s-demodulator
- Repository: https://github.com/watson/mode-s-demodulator
- Homepage: https://github.com/watson/mode-s-demodulator#readme
- Issues: https://github.com/watson/mode-s-demodulator/issues
- npm.io page: https://npm.io/package/mode-s-demodulator

## Dependencies (2)

- [mode-s-msglen](https://npm.io/package/mode-s-msglen.md) ^1.0.2
- [mode-s-decoder](https://npm.io/package/mode-s-decoder.md) ^1.0.0

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## Recent versions

- 1.0.1 (latest) — 2017-12-11
- 1.0.0 — 2017-12-10

## README

# mode-s-demodulator

A JavaScript module for demodulating and decoding Mode S / ADS-B
messages from aviation aircrafts.

Mode S is an aviation transponder interrogation mode used by Secondary
Surveillance Radar (SSR) and Automatic Dependent Surveillance-Broadcast
(ADS-B) systems.

For an example of this module in use, see
[AirplaneJS](https://github.com/watson/airplanejs).

[![Build status](https://travis-ci.org/watson/mode-s-demodulator.svg?branch=master)](https://travis-ci.org/watson/mode-s-demodulator)
[![js-standard-style](https://img.shields.io/badge/code%20style-standard-brightgreen.svg?style=flat)](https://github.com/feross/standard)

## Installation

```
npm install mode-s-demodulator --save
```

## Usage

```js
const Demodulator = require('mode-s-demodulator')

const demodulator = new Demodulator()

// data contains raw IQ samples from an RTL-SDR device
demodulator.process(data, data.length, function (message) {
  // got new Mode S message from an airplane
  console.log(message)
})
```

Tip: Use together with the [rtl-sdr](https://github.com/watson/rtl-sdr)
module to get raw IQ samples that can be processed by this module.

## API

### `Demodulator.UNIT_FEET`

A constant indicating that the unit used to encode `message.altitude` is
feet. Check against `message.unit`.

`message` is an object given as the first argument to the
`demodulator.process` or `demodulator.detectMessage` callback.

### `Demodulator.UNIT_METERS`

A constant indicating that the unit used to encode `message.altitude` is
meters. Check against `message.unit`.

`message` is an object given as the first argument to the
`demodulator.process` or `demodulator.detectMessage` callback.

### `demodulator = new Demodulator([options])`

Initialize a new demodulator object.

Arguments:

- `options` - An optional options object

The available options are:

- `fixErrors` - Set to `false` to disable automatic error correction
  (default: `true`)
- `aggressive` - Set to `true` to use an aggressive error correction
  algorithm (default: `false`)
- `checkCrc` - Set to `false` to disable checksum validation (default:
  `true`)
- `crcOnly` - Set to `true` to only validate the checksum of the Mode S
  messages without trying to decode them any further than necessary in
  order to validate the checksum (default: `false`)
- `mag` - An optional pre-initialized magnitude Uint16Array used by the
  `process` function. If not provided it's expected that `process` will
  always be called with the same amount of data

### `demodulator.process(data, size, onMsg)`

A convenience function that takes care of everything related to
processing the provided `data`.

It handles initializing a magnitute array (if not provided to the
`Demodulator` constructor) and calling `computeMagnitudeVector` and
`detectMessage` respectively.

Arguments:

- `data` - A buffer object containing raw IQ samples
- `size` - The size of the `data` buffer
- `onMsg` - Called for each new message detected in `data`. Will be called
  with the message as the only argument.

### `demodulator.computeMagnitudeVector(data, mag, size[, signedInt])`

Calculate the magnitude of each sample in the signal.

Arguments:

- `data` - A buffer object containing raw IQ samples
- `mag` - An `Uint16Array` to which the magnitude of each sample will be
  written. Since each IQ sample in `data` consists of two bytes, the
  array should be at least half the size of the `data` buffer
- `size` - The size of the `data` buffer
- `signedInt` - Optional boolean indicating if the IQ samples are
  encoded as signed integers (default: `false`)

### `demodulator.detectMessage(mag, size, onMsg)`

Detect Mode S messages in the magnitute array.

Arguments:

- `mag` - The `mag` array computed using `computeMagnitudeVector()`
- `size` - The size of the `mag` array
- `onMsg` - Called for each new message detected in `mag`. Will be
  called with the message as the only argument.

## Acknowledgement

This project is a JavaScript port of the popular
[dump1090](https://github.com/antirez/dump1090) project by Salvatore
Sanfilippo. It modularizes the code into separate functions and removes
all non-essentials, so that only the demodulation and decoding logic is
left.

## License

MIT

---
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