The Crazyflie 10DOF has a pressure sensor that can be used as an altimeter. This sensors was waiting to be used and we had many contributors implementing altitude hold/hover mode for it. We recently merged one of the best working contributions to the main branch of both the Crazyflie client and firmware so that it is now a bit easier to experiment with it. The current code is based on the work done by omwdunkley who did a great initial job and you can read more about it in his post.

The altitude-hold is another control-loop that will try to keep the copter at the same altitude by using the altimeter and the accelerometer to sense the altitude and vertical speed. This is controlled by keeping a button pressed on the game-pad. When altitude hold is activated the thrust joystick axis controls the altitude set-point and thus are used to make the copter rise or fall.

Foam on the Crazyflie 10DOF pressure sensor

From our test in a calm pressure stable room the altitude is held at roughly ±15cm. However we had some problems when we where moving around. The Crazyflie sometimes suddenly rose and went to the ceiling. After some debugging we found that the problem was mainly physical, the pressure sensor is exposed of dynamic pressure when flying. To fix that we cut some of the foam we have in the Crazyflie box (yes that was planed all along ;-), and we stuck it on top of the pressure sensor. Doing so greatly improve the stability when flying more aggressively! (Something we kind of knew from peoples suggestions but it is nice to see it working in reality)

This functionality still require some debugging, tuning and code clean-up, but if you want to test it just grab the latest version of the firmware and client from Bitbucket. To begin with check that the altitude hold function is well configured for you joystick mapping (we found that it is best set on the shoulder button of the thrust hand). The altitude lock will be activated as long as the button is pressed. It can be pressed while the copter is flying or while it is in the ground. If pressed when the copter is in the ground, you will have to press the thrust joystick up a bit to make the copter fly higher. We also recommend to be a bit experienced with flying the Crazyflie as the altitude hold sometimes requires a quick recovery manoeuvre ;-).

Last year we quickly hacked together a client for Android to show that it was technically possible to use the Crazyflie/Crazyradio on the platform. It worked, but it wasn’t very good. After that not much has happened, until now. Thanks to contributions being made by fredg02, Sebastian Sams and bug tickets from Sascha Heymann, the hackish prototype we did is now turning into something that is actually usable. It’s still under heavy development but there’s already some new features. Here’s a quick run-down of what’s been added:

• An external controller can be used instead of on-screen thumb sticks
• You can scan for Crazyflies
• The same flight control settings that are in the cfclient are now available (i.e advanced mode, X-mode, max roll/pitch/yaw and thrust)

So the Android client works with phones and tables that support USB host or OTG. Anything else? Well, there just happens to be an Android platform that even comes shipped with an external controller…the Ouya! So if you have an Ouya and a Crazyflie you can just side-load and you are ready to go! Since we are used to the PS3 gamepad we had some issues getting used to the Ouya controller. If you have the same issue you can pair your PS3 controller with your Ouya and use it instead!

Once the software becomes more stable an APK will be released, but until then the repository with the code and issue tracker can be found here.

In order for users to be able to pilot the Crazyflie from platforms without a graphical user interface there’s now a headless client in the repository named cfheadless. It’s intended to be run the command-line and is still under development, but working.

The main reason it was made in the first place was to enable flying from the Raspberry Pi. The QT interface was very sluggish and it required all the QT dependencies to be installed. So the cfheadless client doesn’t depend on QT and doesn’t have a graphical user interface at all. For users to quickly get something working with the Raspberry Pi we prepared a pre-configured SD-card image that is based on the Raspian Wheezy. We didn’t remove anything from the image, we just added the things needed to fly the Crazyflie. It works out of the box with the Crazyradio and a PS3 controller. In order to switch to anther controller you will have to connect to the Pi and edit the configuration.

To use the image you have to edit the configuration if needed and then just connect your controller, power on the Crazyflie and lastly connect the Crazyradio. The cfheadless client will now automatically start and connect to the Crazyflie.

The image can be downloaded using this torrent or via direct download. The torrent is preferred since the direct download is limited to 6 simultaneous downloads. For more information on how to use the image have a look at the wiki page and if there’s any issues or suggestions drop by the project tracker at Bitbucker and add them. If you already have a Raspian image downloaded and running and you want to be able to use it with the Crazyflie then have a look at how we made the image or the hacks page with the original instructions.

It’s been another week with lots of stuff going on. Shortly after the Crazyflies were delivered things really started to accelerate. Now there’s lots of cool stuff going on and we are trying to keep up :-) Here’s a few things from the last week.

• People have started looking at the pressure sensor that is mounted on the 10-DOF version. phiamo is working on a hover-mode using the pressure sensor. There’s more information and code in this post.
• Contributions to the Mac OSX install instructions have been made and they are now usable.
• Another frame has been designed by bscott and is uploaded on Thingiverse. No doubt, next on the Bitcraze shopping list is a 3D printer.
• The USB3 issue on the Crazyradio has been fixed so there’s a new version of the firmware. If you don’t have any problems with this then don’t update, because there’s a slim chance of bricking the radio (see the wiki page). The firmware is available here and instruction on how to update it are here.
• A nasty bug on Mac OSX has been reported. When loosing connection to the input-device the output will become 100% thrust and it will not stop until the radio looses connection. This issue has been fixed in the latest version from the repository.

The Crazyflie Nano Quadcopter kit 10-DOF is out of stock again but there’s still some 6-DOF units left. We are currently planning the next batch but until then there will be a few more units (~50) that will drop into the Bazaar.

In order to have a better overview of which problems that have been solved and which still needs attention in the Support forums we are setting up some guidelines, which will be done during the week. So if you are hanging around in these forums or you want to get some support, then please have a look at the instructions.

If you live in the south of Sweden and you are interested in the Crazyflie drop by Javaforum next Tuesday (21/5) where we will be presenting.