If you have been reading our previous blog post you know that we redesigned the Crazyflie to use the MPU6050 instead of the IDG500-ISZ500-BMA145 combo. This was done because the IDG500 became obsolete, recently we found out it was because Invensens had production problems with this sensor, anyway when redesigning we managed to squeeze in a HMC5883l magnetometer and a MS5611 pressure sensor.  Now when we are getting close to actually making some kits we have to take some decisions and one of them is if we should build the Crazyflies with the HMC5883l magnetometer and the MS5611 pressure sensor mounted. This will of course increase the price which we have estimated to be about $20. Currently we do not use neither the magnetometer nor the pressure sensor. The yaw drift is so low that when you pilot the Crazyflie it isn’t noticeable and therefore we do not use the magnetometer. The pressure sensor we have just tested briefly and we do not really know how well it would work. Altitude hold might not be so useful inside but maybe outside.

Because of this little decision whether to mount the magnetometer and pressure sensor or not we would like to make a poll so please give us your thoughts.



Should we mount the pressure sensor and the magnetometer?

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Last summer we were sitting in a meeting room after office hours discussing how we should react to the fact that a lot of people seemed to want to buy a Crazyflie. After having a bit of down time in the project we finally posted a video, that was already about 6 months old, on Youtube.  It was during the spring 2011 showing us flying the first prototype Crazyflie. After getting picked up by Hackaday it got a lot more attention that we originally thought and a lot of people wanted to buy one which was great! The only problem was that we only had three of them and at this time there where already obsolete components. Another problem was that the motors/propellers were scavenged from toy airplanes (they had a sale and we got them cheep) which was not a scalable sourcing solution.

So sitting in this meeting room we decided to give this project a shot by trying to release a kit that could be sold. Back then the development was funded by Epsilon, the consulting company that we are working for, which was not optimal if we wanted to commercialize the Crazyflie. So we decided (after a lot of discussions) to form a company which became Bitcraze AB (the name came after even more discussions). We needed a company to make manufactures and distributors take us seriously and for import and tax reasons. It is also pretty satisfactory to be on the board of director of our own company :-).

At this time the Crazyflie was already flying but it had to be redesigned, parts sourced and we needed to find someone to manufacture it for us. Since we didn’t (and still don’t) have that much capital this wasn’t something that we could leave our day-jobs for so the development continued on weeknights and weekends. As anyone working with product development (specially if it includes any type of hardware), going from a prototype that is working to a final product requires a lot of work.

A big obstacle for us was sourcing the mechanical parts: Motors, propellers, motor mounts and battery. Some of these can be found and some are harder. And even if you find something that looks good on paper there’s no guarantee that it’s very good or working at all. We got some motors that seemed like they were scavenged from the junkyard (and probably were), we got batteries that didn’t meet the specification and propellers that were unbalanced. All this takes a lot of time. Finally we had to design a motor mount ourselves since we couldn’t find anything that suited our purpose. After a lot of searching/testing we finally found good batteries and motors. The propellers are still a bit hard to find a reliable source for but we think that we have it sorted out.

Even though it’s been very frustrating at times, like when the Invensense gyros we were using went out of production, we have a lot of fun when we work (which you can hear in the videos). Also we have been challenged to learn new stuff and got to try things that we normally would’t do at work. One of the reasons we started the project at all back in the fall of 2009 was that we wanted to do something more challenging and we think that we achieved that :-)

So what’s the plan for the upcoming year? Well, the main plan is to release the kit soon of course! After that there’s a lot of ideas of what we want to do so we will have to see how things go. Also we would like to thank everyone that’s been following our progress and supporting the project!

No, the candle isn’t burning when we are flying…although we did try to…

The coming week we are reviewing the new revision of the hardware before we press the order button. With the previous prototype we had a few violent incidents where one of the arms broke off. Fixing it wasn’t to hard. We used an aluminium tube we cut to the right size and glued over the arm and it holds up well. For this next revision we have changed the board outline around the arm joint to be smoother as this seams to be the weakest point. If everything goes according to plan the next prototype should be the last before we can order a larger batch.

During the last week we also did a little test making an small Android app and plugging the radio dongle in one of our Galaxy Nexus. It’s detected and can be used via the USB API.  It’s nothing that we are planning on spending any time on right now but in the future…




We’re all back from vacations and now it’s time to focus and ramp up the work again. After syncing what we have been doing during the summer (and doing some catching up) we think that we are in good shape. There’s still lots to do but now we have re-charged our batteries!

Since the weather is nice we decided to do some flying outside and at the same time do some range testing. Unfortunently we waited a bit too long so it was pretty dark outside. The Crazyflie is normally hard to see when you get too far away and when it’s dark it’s even harder… So the range test was done by flying slowly forward until the radio connection watchdog kicks in and the motors are cut. We then used MyTracks on Android to measure the distance to where we found it in the grass :-D We only did two tests but the best one was 55m.

Here’s some images of the test and the flying:

Crazyflies at night

Crazyflie at night (far away)

Crazyflie range test

One of the things that we’ve been working on for the last week is the parameter and logging systems.

Since the start of this project we’ve had a protocol in place for logging data from the Crazyflie but it’s been a bit hackish. It has relied on that the client/Crazyflie has been in sync regarding what to log and how to log it. The problem that we had was that as we start development on a new feature our logging needs change and we start tweaking what we log. Sometimes we change the size of variables to fit more data in or we switch them out completely. This has resulted in the logging breaking frequently which has been a pain…the three of us was hardly ever in sync :-D The solution that we have been working on now is more dynamic.

At start-up the client will download a TOC (table of contents) of loggable variables. By using macros when defining a variable in the Crazyflie code the variable will automatically be included in the TOC and will be loggable. It is then possible to setup a log configuration where a number of variables are pushed over the radio at a specific interval. Multiple configurations can be added so one usage is to log the battery voltage every second but to log the roll/pitch/yaw 100 times per second.

We have also been developing a similar system for getting/setting parameters. Like the logging there’s been a hackish system in place until now that’s been used to set regulation parameters during tuning. With the new system it’s possible to declare a variable using macros so it will be automatically included in the param TOC and will be gettable/settable from the client. One typical use is for tuning the regulation but it could also be used to switch between flying configurations (normal/X).

The biggest reason for implementing these systems is to make it easier for other people to tune and modify the program of the Crazyflie (also it’s a lot of fun :-D).

We have noticed that there’s a lot more work to be done in this project than only designing hardware and developing software :-) It’s now about 14 months ago that we decided to make a Crazyflie kit that we would try to sell. At that point we had already had the first version of the Crazyflie flying for about 1 year. The list of things that we have done since then is pretty long…a lot longer that we first thought it would be. But let’s save that list for another post…

One of the things that we’ve had to spend some time on is setting up our IT environment and now we are trying to make the final push. Up until now we have been using Mercurial/Redmine hosted on our own VPS. Here’s a list of what we are thinking about using in the future:

  • CM for code and schematics: Bitbucket
  • Issue handling: Bitbucket
  • Wiki: Dokuwiki
  • Forum: phpBB
  • Blog: WordPress :-D

Any thoughts or ideas about these? Any services that’s missing? Anyone that has good/bad experience with Bitbucket?

We are still mostly on vacation but we are continuing the development but not as actively. Like we wrote last time we compiled a list of tasks that has to be finished in order for us to release the project so that’s what we are working on :-D

Apart from that we are also working on some mandatory IT-stuff, like deciding what forum/SCM/VPS provider to use etc.

We haven’t seen any more problems with the prototypes since we exchanged the MPU-6050. All of the changes for the new prototype has now been tested and we are currently modifying the board design to fix the bugs that we have found. Then it’s time to order a new batch of prototypes. Our hope is that this will be our last round and that the next order will be a bit bigger!

The last couple of months we have re-designed large parts of the code to be more modular and easier to maintain and at the same time we have added more features such as rate controlled PID and flexible logging and parameter system. The UI has been slightly re-designed and the PyQwt dependency has been removed.

During the summertime we are a bit split up since we are going on vacation and are actually trying to go outside! So we have tried to define the features and tasks that are left until the first release of the project so we can focus our efforts on the right things.

We feel that we have never been this close to the release so we are really looking forward to this autumn :-D



One Sunday in March when we met up to work on the Crazyflie we suddenly realized that we do a lot of developing and discussing when we meet, but we don’t actually do that much flying. After realizing this we spent most of the Sunday just flying and playing around with the quadcopters.

So what could we try that we haden’t tried before…well we could try to crash each other while we are flying around: Crazyflie dogfight! The idea is that you should try to push the opponent out of the air without being dragged with him/her. This is easiest done by flying above the opponent making his/her crazyflie unstable and crash, however it is easier said then done!

This is not the first time two Crazyflies crash into each other in the air, but it’s the first time it’s actually intentional! It was a lot of fun but it can quickly end if something breaks. This dogfight however ended up with nothing to repair :-)