Category: Random stuff

As noted in a previous post, Mike Hamer from ETH Zurich has been implementing an Extended Kalman Filter (EKF) for the Crazyflie. The beginning of this week I am visiting Michael at ETH and we have now pushed the EKF to the Crazyflie master branch!

Visiting ETH is really nice, and it is very impressive to see the Flying Machine Arena in real life. Though, owing to the Crazyflie’s size, we do not need such a big space and can work in a more regular-sized room.

The EKF has now been added to the master branch but is not enabled by default. It is currently intended to be used with the Loco positioning system (although it should be easy enough to integrate with onboard GPS, or potentially offboard motion capture measurements). While it does fly better than the currently used, offboard particle filter for autonomous flight, it requires some care to work properly. I am going to update the wiki description for the loco positioning to document how to get started with the EKF during the week. Our hope is that through community engagement and feedback, we can continue to improve and tune the filter, now that Mike has put the basic functionality in place.

The greatest enhancement is that the Crazyflie is now able to estimate its own position, without the help of an external computer. Coupled with the onboard controller, the Crazyflie can now fly fully autonomously. I have also pushed a new example in the Crazyflie python lib that shows how to send an X/Y/Z set-point to fly the Crazyflie, allowing it to fly through waypoints.

In the near future we (Bitcraze, and hopefully, the community!) need to work on a couple of more things to make it fly even better

  • Revamp of the controller: the current controller is a position controller, splitting it in two controllers, one for position and one for velocity, would allow for a more stable flight and to finally use TheSeanKelly new PID settings!
  • Implementing TDOA positioning on the LPS would allow more than one Crazyflie to fly at the same time
  • Implementing the new commander packet in the Crazyflie, python lib and ROS driver. This will allow us to stop hacking the current commander each time we need a new functionality (such as onboard position control) — and since I have push rights, only my hacks get pushed, which is unfair ;-).

Mike will describe the Kalman filter in greater details in a future post. In the mean time we will update on the progress in the Loco Positioning mailing list.

Controlling the Crazyflie from the PC client through the Crazyradio gives you a lot of flexibility and power when it comes to coding and scripting. The drawback is that you need a computer and Crazyradio which is fine in the office, but not as convenient when flying on the go. As a part of our Friday-Fun hacks we have been working on a standalone controller with everything included to solve that problem.

I finished the first working basic prototype a few weeks ago and have done some test flying during my vacation. I (and the son of a friend) am very happy with the performance end ease of use, so I think it is time to move on and create a usable product.


So far the controller is very basic, it is only two joysticks, an Arduino and a radio. All it does is to scan the joysticks and send controller packets on a fixed radio channel. Even though it is super simple I like that it is possible to just turn it on and fly, no other actions are required!

The product will have (many) more features, the question is what to add? This is your chance to be a product designer, if you have any input or wishes let us know!

Some ideas that we have so far:

  • Support other protocols to control other copters or robots
  • Arduino compatibility to make it simple to alter the functionality and behaviour
  • Expansion ports, maybe compatible with Crazyflie decks
  • USB and bluetooth low energy to use it as a generic game controller
  • A mode to use it as a Crazyradio connected to a computer over USB

We also need to come up with a name, please share your ideas!

Up until now, we’ve made our products available to customers through Seeedstudio and a number of distributors around the world. This has been a great solution since we’ve been able to focus on development of products instead of shipping packages and maintaining our own e-shop. When customers contact us and want to buy, we’ve been directing them towards local distributors where they can buy in local currency and with faster delivery times. But the last year more and more customers wanted to buy products directly from us and this has been taking up more and more of our time. The main reason has been complex purchasing procedures or local distributors not carrying the hardware the customer wants. Also if a customer starts discussing with us about what to buy, they tend to want to buy directly from us instead. Since we haven’t had a good set-up for this, we’ve been shipping packets on a case-to-case basis from our office basement (yes, the same basement where we fly with the Loco positioning). This has been very time consuming.

So, in order to optimize the sales and shipping, we’ve decided to launch our own e-shop. Our idea is that it is a complement to other distributors and the Seeedstudio Bazaar. Buying from local distributors will result in lower shipping costs and faster delivery. So we’re not aiming at replacing this, instead our goals are:

  • Have one place where we offer a full assortment of our products
  • Take responsibility for the end-to-end experience (both the purchasing and product support)

In order to service the e-shop, we’ve set up warehousing in Hong Kong, close to Shenzhen were the Seeedstudio manufacture is located. Aside from servicing the e-shop, this solution will also be used for drop-shipping custom orders, so replacing our basement packaging system.

As with most things, the more you know about something, the more you understand how complex it is. When we first started thinking about setting up our own e-shop/warehouse solution, we thought that this would probably take about a week: we evaluate a couple of solutions, select one and then just start selling/shipping. Turns out that things are more complex and this has caused a few weeks delay for the Loco positioning products since they will only be available through our shop. Now we’re hoping everything is on track, but we’re very new at this so please bare with us if there’s any hickups along the way when starting this up.

We’re opening up the store today, so you can have a look. Any feedback and comments are welcome! But as you might quickly notice, all the products are out of stock. The Loco positioning hardware as well as the other products are on their way to the warehouse, but they got a bit delayed along the way. Our best estimate is that the products are stocked at the end of the week or beginning of next week. The link to the e-shop is


Here’s a photo of some of the boxes. Looks a lot like normal boxes, but these contain the Loco positioning hardware 🙂


As summer is here, in the northern part of the hemisphere, in Sweden we like to have a bit of vacation to charge up with new energy. Thus the forward momentum will decline a bit but it also means less distraction from email requests, meetings etc. We take this opportunity to switch focus a bit and just as last year, we will put our effort in cleaning up. That means fixing bugs, improving documentation etc, things that normally doesn’t get prioritized enough.

Along with the cleanup, the Loco positioning system is still our highest priority and we work full thrust to get it in the hands of users. Hopefully we will be able to start shipping the first systems in the beginning of next week and more widely the week after that so make sure to stay tuned and sign up for the newsletter if you are interested! Have a great summer everyone!

Upcomming loco positioning indoor explorer bundle

The upcomming early access loco positioning indoor explorer bundle

We are excited to announce that we have just started the production of the first boards for the Loco Positioning system!
Since this is the first batch of a complex new product, we thought we should be there in person. This time, Tobias and Kristoffer went to visit Seeedstudio, our product manufacturer. It is always very nice to meet them in person and to visit the factory.
Also visiting the factory is always an opportunity to discover a new fashion style!


The first boards to be produced are the Loco Nodes:


After a minor problem: we specified the LEDs to be mounted reversed, quickly found and fixed for this first batch by the Seeedstudios engineers, the production of the nodes is looking good and the first 8 pieces are flawless!


To go with the nodes, we need to have the Loco decks. Like for the other decks we have implemented the test rig based on a Crazyflie 2.0 programmed with special flags for the test. We found some issues with the rig software but it has been quickly sorted out. So the launch of the deck production, tomorrow Tuesday, should be without any hick-ups. This is what a deck test rig looks like (note the Crazyflie 2.0 being attached on the bottom):

In other news we’re welcoming Aman in the Bitcraze team for the summer. Aman is flying straight from Kiruna at the very north of Sweden (before that from Germany and even before from his university in the US). He will be looking at improving control and stability of the Crazyflie. The fist step today was to learn how to fly it manually :-).

At Lund University PhD student Kenneth Bastone and professor Kalle Åström are currently using the Crazyflie and the Bitcraze ultra-wide band based Loco Positioning system as part of their research involving local positioning systems at Centre for Mathematical Sciences. We visited them a couple of week ago and though we would write a blog post to explains a bit how they use Crazyflie and the Loco positioning system.


A local positioning system creates a number of interesting mathematical problems that PhD student Kenneth Bastone and professor Kalle Åström have decided to focus their current research on.

By experimenting with different technologies to create position estimations in 3D space they have come across a variety of different ways to explore indoor localization using a local positioning system. The origin of this work area was with optical tracking and localisation, it has since grown to include any technologies and configuration capable to be used for local positioning like radio and sound.

One focus area for instance is how to estimate transceiver node positions from measured transceiver distances, this is a key issue concerning for example radio antenna array calibration or mapping and positioning using ultra-wide band. Another problem is how to determine how many nodes the system needs to generate sufficient information and to understand how often the system needs to make estimations to work sufficiently well.

According to Kalle Åström solving this kind of problems regarding local positioning systems is one step closer to a whole new area of future applications. In particular it is a technology enabler that opens up the possibilities for new ways to study motion and/or behavior, for instance in healthcare or for analyzing performance in sports.

Recently Kalle and his team has had access to an Alpha Loco Positioning System, this has allowed them to apply their algorithm more specifically to ultra-wide-band based localisation. The algorithm is able to estimate the position of the anchors and of the Crazyflie from a set of distance measurements only. Using the local positioning system the Crazyflie can estimate its position by using the distances to the anchors and the position of the anchors in space. Here we have visualized the idea in 2D:

anchors1In this diagram the red point is the Crazyflie and the green and blue points are the anchors. We will look more at the anchor A3. If we see things the other way around, from the Crazyflie point of view, all we know about anchor A3 is how far away it is. So it could be anywhere on a circle:


Now if we decide to go forward a little bit, the possible positions of A3 is reduced to 2 locations:


As you can see in the figure, it is not enough to only go forward, we still have two intersection for the possible positions of A3. We need to make a turn:


Now we have reduced the possible positions down to 1. We are not done yet because in reality the Crazyflie position is not known but by applying the same idea to anchor 1 and 2 the system is constrained so that the positions of all 3 anchors and of the Crazyflie can be found over time.

The algorithm is already working with the Crazyflie and the Loco Positioning system and allows the system to find the position of the anchors and the Crazyflie using a couple of seconds of data while the Crazyflie is moving around.

According to Kalle using the Crazyflie and the Loco Positioning system has proved to have some benefits. It is open-source which means that it can be modified easily to fit the research purpose. It is also safe and very practical to work with: a test system can easily and quickly be set-up as the Crazyflie does not require specific protection for people or equipment around it.

Like we announced last week we will be releasing the Loco Positioning system in a couple of weeks. Last week, we added product pages for the Loco Positioning boards on our website. We have also made a new short video explaining a bit on how it works with a demo:

Early access means that we have tested the hardware and are pretty confident it performs well. Though the software is still in a beta stage and requires some more love and will be evolving a lot over time. Right now we made sure that the ranging is working and we have some software, based on ROS, to fly the Crazyflie autonomously. We will make sure to document carefully the steps so that you can get started with the system quickly. We see two big functionalities that will be worked-on first: making the system able to control much more Crazyflies at once (right now the software is designed to handle only one Crazyflie), and moving positioning and controller into the Crazyflie which has the potential to enhance the flight performance a lot. More on that later.

If you want to receive information as the system evolves, sign up to our mailing list (we have added everyone that mailed us last week ;-). If you want to talk to us directly do not hesitate to comment or send us a mail at

As early as when the first Crazyflie prototype did it’s first flight back in 2009, we where dreaming about a local positioning system that would allow our future micro quadcopter to fly autonomously indoor. This dream is now becoming a reality with the development of the Ultra Wide Band radio that we have been using the last months to develop our own local positioning system for the Crazyflie 2.0. We are now reaching a very important milestone: the first early access production batch has been ordered!

We sat down to find a name for the system and since ‘Crazy’ is kind of a theme for our products here at Bitcraze we settled for “Loco Positioning”. So the two products we are about to launch are the Loco Positioning Node and the Loco Positioning Deck.

If you want to receive information as the system evolves, sign up to our mailing list. If you want to talk to us directly do not hesitate to comment or send us a mail at

The positioning system is based on the Decawave DW1000 Ultra Wide Band radio chip. These radios work by transmitting very short pulses instead of full sinus waves the way a standard radio would, and the advantage for positioning is that it is possible to measure the time at which these short pulses are received very precisely. By using clever algorithms it is possible to measure the time it took for the radio signal to “fly” from one radio to another and from that we can calculate the distance between the radios.

A basic system is composed from a number of Anchors (Loco Positioning Nodes) at fixed positions and a Tag on the Crazyflie 2.0 (the Loco Positioning Deck). The system continuously measures the distances from the Tag to the Anchors and calculates the position of the Tag from that information. The concept is similar to GPS where the Anchors represent the satellites and the Tag the GPS-receiver. 4 Anchors is the theoretical minimum required to calculate a 3D position, but 6 has turned out to be more realistic number.

We have designed the Loco Positioning Nodes as standalone boards containing a micro controller and the DWM1000 UWB radio module. The nodes are intended to act as Anchors: they are setup at fix positions in the room and will serve as references for the system.


The Loco Positioning Deck, also based on theDWM1000 module, acts as a Tag and plugs into the Crazyflie 2.0 expansion port. It allows the Crazyflie 2.0 to calculate its absolute position in space and this is all we need to start flying it autonomously in the room. In this case the Crazyflie 2.0 acts as a Tag, but since we are always striving for flexibility, the nodes can also act as Tags for example for other robotic application.


We consider the first batch to be an early access release. This means that the hardware is finished and tested but the software is still very much work in progress. Currently the Crazyflie ranges with the Anchors, while a PC running ROS interprets the ranges and calculates the estimated position. More in depth information will come if future blog-posts and e-mails on the list. For a video and some more information see our previous post “Update on Local Positioning System“.

Two weeks ago we had the opportunity to make a field trip to Gothenburg (Sweden) where we visited the students and teachers at Chalmers University of Technology.


The Crazyflie 2.0 is used by the students as a development platform for the course “Embedded control systems“, which makes us all very happy since we are passionate about education. I mean how cool is it not to see how students use your product to gain new knowledge!

While visiting Kristoffer held a guest lecture to the students and we also took the opportunity to discuss with Associate Professor Knut Åkesson about why and how the Crazyflie 2.0 is part of the course.


A few of the topics that were mentioned was the big benefit with Crazyflie 2.0 being open and how that enabled the students to easily getting started implementing their own code.

If you want to read more about why the teachers at Chalmers choosed the Crazyflie 2.0 and how they use it for education, visit our newly added web section “Used in education”.

We have just released a new version 2016.04.1 of the Crazyflie client.


The biggest change is actually not so visible but very important: we have now separated the GUI client from the Crazyflie lib. The great advantage is that the lib became a small project and could be pushed to pypi. This means that if you want to control Crazyflie from your own Python program all you have to do is to “pip install cflib” and you are ready to “import cflib” in your program to control the Crazyflie.

For the new release of the client we also pushed the client in pypi as well. This will be mainly useful in Linux and Mac where you are now able to install the client with “pip3 install cfclient”. One little drawback however: since the GUI lib we are using, pyqt, is not in pypi it has to be installed on the side. This can be done in Ubuntu with something like “sudo apt-get python3-pyqt4 install python3-pyqtgraph” or on Mac with homebrew or MacPorts.

Last but not least we have enabled Windows continuous integration with appveyor and fixed the Windows build. This means that a Windows build and installer are going to be generated for every commit in the Crazyflie client repos. Maintaining the Windows client has always been a challenge to us since we are mainly Linux users, so the this will help a lot to keep good Windows support. We still consider this Windows build to be somewhat experimental so please test it and report any bug you are hitting.

The last system to support for executable distribution is Mac. We did put some time trying to generate a mac app out of the client without any success. If anyone wants to give it a try or have some tips please head to the ticket on github.