ar-drone

An implementation of the networking protocols used by the Parrot AR Drone 2.0.

Install via npm:

npm install ar-drone

Introduction

The AR Drone is an affordable, yet surprisingly capable quadcopter. The drone itself runs a proprietary firmware that can be controlled via WiFi using the official FreeFlight mobile app (available for iOS and Android).

Unlike the firmware, the client protocol is open, and Parrot publishes an SDK (signup required to download) including a good amount of documentation and C code. Their target audience seems to be mobile developers who can use this SDK to create games and other apps for people to have more fun with their drones.

However, the protocol can also be used to receive video and sensor data, enabling developers to write autonomous programs for the upcoming robot revolution.

Control

The drone is controlled by sending UDP packets on port 5556. Because UDP does not guarantee message ordering or delivery, clients must repeatedly send their instructions and include an incrementing sequence number with each command.

For example, the command used for takeoff/landing (REF), with a sequence number of 1, and a parameter of 512 (takeoff) looks like this:

AT*REF=1,512\r

To ease the creation and sending of these packets, this module exposes an UdpControl class handling this task. For example, the following program will cause your drone to takeoff and hover in place.

var arDrone = require('ar-drone');
var control = arDrone.createUdpControl();

setInterval(function() {
  // The emergency: true option recovers your drone from emergency mode that can
  // be caused by flipping it upside down or the drone crashing into something.
  // In a real program you probably only want to send emergency: true for one
  // second in the beginning, otherwise your drone may attempt to takeoff again
  // after a crash.
  control.ref({fly: true, emergency: true});
  // This command makes sure your drone hovers in place and does not drift.
  control.pcmd();
  // This causes the actual udp message to be send (multiple commands are
  // combined into one message)
  control.flush();
}, 30);

Now that you are airborne, you can fly around by passing an argument to the pcmd() method:

control.pcmd({
  front: 0.5, // fly forward with 50% speed
  up: 0.3, // and also fly up with 30% speed
});

That's it! A full list of all pcmd() options can be found in the API docs below.

With what you have learned so far, you could create a simple program like this:

var arDrone = require('ar-drone');
var control = arDrone.createUdpControl();
var start   = Date.now();

var ref  = {};
var pcmd = {};

console.log('Recovering from emergency mode if there was one ...');
ref.emergency = true;
setTimeout(function() {
  console.log('Takeoff ...');

  ref.emergency = false;
  ref.fly       = true;

}, 1000);

setTimeout(function() {
  console.log('Turning clockwise ...');

  pcmd.clockwise = 0.5;
}, 6000);

setTimeout(function() {
  console.log('Landing ...');

  ref.fly = false;
  pcmd = {};
}, 8000);


setInterval(function() {
  control.ref(ref);
  control.pcmd(pcmd);
  control.flush();
}, 30);

UdpControl API

arDrone.createUdpControl([options]) / new arDrone.UdpControl([options])

Creates a new UdpControl instance where options can include:

• ip: The drone IP address, defaults to '192.168.1.1'.
• port: The port to use, defaults to 5556.

udpControl.raw(command, [arg1, arg2, ...])

Enqueues a raw AT* command. This is useful if you want full control.

For example, a takeoff instructions be send like this:

udpControl.raw('REF', (1 << 9));

udpControl.ref([options])

Enqueues a AT*REF command, options are:

• fly: Set this to true for takeoff / staying in air, or false to initiate landing / stay on the ground. Defaults to false.
• emergency: Set this to true to set the emergency bit, or false to not set it. Details on this can be found in the official SDK Guide. Defaults to false.

udpControl.pcmd([options])

Enqueues a AT*PCMD (progressive) command, options are:

• front or back: Fly towards or away from front camera direction.
• left or/ right: Fly towards the left or right of the front camera.
• up or down: Gain or reduce altitude.
• clockwise or counterClockwise: Rotate around the center axis.

The values for each option are the speed to use for the operation and can range from 0 to 1. You can also use negative values like {front: -0.5}, which is the same as {back: 0.5}.

udpControl.flush()

Sends all enqueued commands as an UDP packet to the drone.

Video

Documentation to be written ...

Navdata

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