Android Brain Computer Interface devices gadgets iOS Mobile

Connecting to the Parrot AR.Drone 2.0 from Delphi XE5

My first thought when I see cool technology is to figure out how to connect to it with Delphi. So the day I got the Parrot AR.Drone 2.0 quadricopter I started working on Delphi interface. By the time evening rolled around the batteries were dead (after a couple recharges), but I had a basic interface working. The official developer guide seemed to be a little out of date, or I was reading it wrong, but once I got my facts staight, connecting was really easy. The Parrot AR.Drone has it’s own access point. Once you’ve connected to it, then it is simply a matter of sending UDP packets for the basic controls. To accomplish that I simply used the Indy UDP Client: TIdUDPClient. Each command is sent with an increasing sequence number, so I initialize my interface as follows:

  udp := TIdUDPClient.Create(nil);
  udp.Host := '';
  udp.Port := 5556;
  seq := 1;

The AR.Drone is always at since it is the access point, and the port for communication is 5556 (one of a few ports, but the one we need for now.) It is worth pointing out that if you’ve previously flown your AR.Drone with the FreeFlight mobile app then you may need to reset your drone to unpair it. Otherwise it is paired to only that device. The commands are formatted with an AT* prefix, and a series of arguments. For example, to take off, the command is AT*REF=1,290718208 where AT*REF is the command, 1 is the sequence number (always the first argument) and 290718208 is a bitmask that means take off. I created a SendCommand routine that looks like:

procedure TARDrone.SendCommand(cmd, arg: string);
  full: string;
  if not udp.Active then Connect;

  full := Format('%s=%d,%s' + Chr(13), [Cmd, Seq, arg]);
  Seq := Seq + 1;

Notice the command is terminated with a carriage return (#13). The documentation says line-feed (#10), it is wrong. Supposedly you can send multiple commands in the same message, if they are separated by the carriage return. I haven’t tested that. Then I can send the some common commands like this:

  SendCommand('AT*REF','290718208'); // Takeoff
  SendCommand('AT*REF','290717696'); // Land
  SendCommand('AT*CONFIG', '"control:altitude_max","10000"'); // unlimited altitude
  SendCommand('AT*CONFIG', '"control:altitude_max","5000"'); // restrituded altitude - unsure what units 500-5000.
  SendCommand('AT*PCMD','1,0,0,0,0'); // Hover (stop movement)

PCMD is the move command. It takes 5 arguments (after the sequence number.) The first is the controller type, which we are leaving 1 for now. The next 4 are phi, theta, gaz, yaw and they are floating point numbers in an integer representation. This is where it gets interesting. The documentation says:

The number –0.8 is stored in memory as a 32-bit word whose value is BF4CCCCD(base 16), according to the IEEE-754 format. This 32-bit word can be considered as holding the 32-bit integer value –1085485875(base 10).

The first way I thought of to access the same memory as two different types is a variant record. So I came up with the following helper routine:

function IEEEFloat(const aFloat: Single): Integer;
  TIEEEFloat = record
    case Boolean of
      True: (Float: Single);
      False: (Int: Integer);
  Convert: TIEEEFloat;
  Convert.Float := aFloat;
  Result := Convert.Int;

Using that I built a move routine that takes 4 singles (32-bit floats) and sends them as integers:

procedure TARDrone.Move(const phi, theta, gaz, yaw: Single);
    [IEEEFloat(phi), IEEEFloat(theta), IEEEFloat(gaz), IEEEFloat(yaw)]));

Now if I want the drone to go up I can call:

  Move(0,0,5.6,0); // positive gaz is upward acceleration

Now it is just a matter of figuring out how to the rest of the movements map to the physical worked and building a user interface on Android, iOS, Windows or Mac. Maybe all 4! Once I build up the API a little bit more I’ll share some full working apps and libraries. Let me know if you are interested in collaborating on such.

Audio podCast

51 – Nick Hodges

Talking with Nick Hodges, former Delphi product manager, Spirit of Delphi award winner, development manager at Gateway Ticketing, and all around great guy. This was originally going to be part of a series of pre-release podcasts highlighting XE3, but that didn’t work out. Before talking with Nick I did a little coverage on XE3 and Oxygene 5.2, including the new Nougat flavor. I’ll have more coverage on XE3 and Oxygene 5.2 in future podcasts.

Nick and I discuss unit testing, development methodology, the Spring Framework and other interesting topics on Delphi development.

[Fixed the audio!]

Audio podCast Conferences podcast

Delphi Tage 2010

Recorded live and in person at Delphi Tage in Berlin (I’m still here for 2 more weeks for EKON too). The Delphi Tage (“Delphi Days”) was a short (3-day) conference organized by the German Delphi PRAXiS community forums, alongside Embacrdero and Developer Experts.  It provided two days of preconference workshops, and a day with 3 tracks of conference-style talks on various topics surrounding Delphi and Delphi Prism . Our podcast is basically a roundtable discussion with a bunch of people involved in the conference, including the organizers (Daniel Wolf and Daniel Magin), some RemObjects folks, David I from Embarcadero and Uwe Schuster (the guy behind the SVN integration in Delphi/Win32 XE) and Arvid Winkelsdorf of Indy fame.

Since this was so much fun, we decided to share this episode between here and RemObjects Radio.

Update: The organizers of the Delphi-Tage is the German Delphi community represented through Delphi-Praxis, Delphi-Treff and Entwickler-Ecke supported by Embarcadero Germany and Developer Experts.  — Thanks to Martin for clarifying that for me.

Audio podCast podcast

42 – David I

Today we talk with David I, chief Developer Evangelist and VP of Developer Relations from Embarcadero Technologies.

We talk about

Audio podCast News podcast

41 – Primoz Gabrijelcic – OmniThreadLibrary

Primoz is a long time Delphi developer as well as writer for The Delphi Magazine, Monitor and Blaise Pascal magazines.  You may know him from his blog or his OmniThreadLibrary for threading in Delphi.  You can also find his articles at 17th Elephant and he is on Stack Overflow.

  • We discuss Delphi Mac support
  • Delphi Garbage Collection
  • 64-Bit Delphi
  • The OmniThreadLibrary
  • and more!

Questions for Nick Hodges

I need your questions for an upcoming interview with Nick Hodges, the Delphi & RAD Studio R&D Manager with Embarcadero Technologies. Leave them as a comment to this message and then listen to his answers in our next episode.

Comments closed in preparation for interview.  Thanks to all who commented!

Audio podCast podcast

39 – marc hoffman on Prism and Mac

Talking with marc hoffman of RemObjects talks with us about what is new in the Oxygene compiler in Delphi Prism and what to expect when developing applications on the Mac.

I remixed the audio to remove the 5 minute gap.

Audio podCast podcast

38 – Marco & Cary

Visiting with Marco Cantu and Cary Jensen.

If you have any other questions or comments for Marco or Cary you can leave them here, or catch them online:

Marco Cantu

Cary Jensen


Delphi Live! Date Updated

Kind of expected this to happen due to all the conflicts, but I just received an update for the Delphi Live! 2010 dates.

Due to the rather short notice of the date, which gave some other potential speakers a bit of a hard time and because we have received quite a few emails from the community, we have decided to shift the dates to August 23-26. The location will still be San Jose, this time the Crowne Plaza in downtown.

Hopefully this date works for more people.

The Crowne Plaza looks really nice, although I am not sure where the new Embarcadero office is located in relation to it.

It is however right next to the Tech Museum, which we have had conference evening events at in the past.

Still no update on the Delphi Live! website, and I don’t know if there is an extension on the Call for Papers or not.


Marco Cantu’s REST Webinar

I didn’t get the episode with Marco and Cary edited and posted yet (came close – might still get it posted tonight when I get home).  In that episode Marco mentioned his free REST webinar which occurs at three different times tomorrow (March 3rd).  So sign-up to attend one of those sessions and download the white paper, it will be really good.
Marco Cantù presents REST in Delphi and RAD Studio 2010

Let Marco Cantù show you how to get the most from RAD Studio 2010 with Representational State Transfer (REST) – a new architecture for Web services that is having a significant impact on the industry. Join Marco as he delves into the technologies involved in REST from the Delphi perspective.

Register now for
March 3 6:00 AM PST / 3:00 PM CET

March 3 11:00 AM PST / 2:00 PM EST

March 3 8:00 PM PST / March 4 3:00 PM AEST

Topics covered in this webinar will include:

  • The Concepts Behind Representational State Transfer
  • REST technologies and Delphi
  • Creating Delphi REST clients that interface with RSS feeds, maps, and Twitter
  • Data-Oriented REST Servers