# crazyflie

Earlier this month, ICRA 2022 was in held in Philadelphia and in person this time! Unfortunately we were unable to attend ourselves but quite happy that there were still virtual attendance options available. So I followed quite some presentations and read through papers, trying to find out the latest in Aerial and Swarm robotics and if anybody was able to use the Crazyflie to good use for their research. I even had the opportunity to attend the Exhibition floor with a telepresence robot, which was a lot of fun!

We have covered IROS 2021 end of last year, and we even have started to publish Crazyflie related publications on social media to keep ourselves and the community up to date with any Crazyflie research work. So here we will list the ICRA 2022 papers we have found and write some observations.

## Crazy Platforms

What I really noticed this year is that the Crazyflie has been used in more unconventional configurations and new platforms! IROS 2021 ready amazed us by a solar-powered Crazyflie and the 4 times Crazyflie combined quadcopter (which continued this conference by UCLA in (2). But we haven’t seen yet that a Crazyflie can jump! The PogoDrone by the Swarmslab of Lehigh university turned the Crazyflie into an autonomous jumping pogo stick (5)! Moreover, wheels were added by the Institute For Systems and Robotics (TU Lisbon) for increasing the flight/autonomy durability (7).

We also noticed 3 ICRA 2022 papers with Bolt-powered platforms, which is a huge increase compared to IROS 2021 which only had 1 Bolt entry. The MAVlab of the TU Delft compared the Crazyflie against a Bolt-powered Flapper-drone for flying against wind (see the presentation of Flapperdrone in our last MiniBam). Moreover, remember that saw the Science Robotics paper using a Crazyflie board for a dual wing rotating platform. The Engineering product development of SUTD took a similar design to the next level, building a single controllable rotating wing with a Bolt platform (3). Two of these can even work together cooperatively and fly stability, so it is no wonder that they won the ICRA 2022 Outstanding Dynamics and Control Paper Award.

## List of ICRA 2022 Papers featuring the Crazyflie and Bolt

Here is a list of all the Crazyflie/Bolt papers featured in ICRA 2022 but let us know if we are missing any (⚡: Bolt, 🐝: Crazyflie). Mind that only Robotic and Automation Letter entries have been officially published on IEEE Xplore already, so from the proceeding papers I tried to share the ArXiv paper if available.

1. ⚡ ‘Passive Wall Tracking for a Rotorcraft with Tilted and Ducted Propellers using Proximity Effects’ Ding et al. from City University of Hong Kong & Massachusetts Institute of Technology
2. 🐝 ‘A Fast and Efficient Attitude Control Algorithm of a Tilt-Rotor Aerial Platform Using Inputs Redundancies’ Su et al. from UCLA
3. ⚡x2 ‘Cooperative Modular Single Actuator Monocopters Capable of Controlled Passive Separation’, Cai et al. from Singapore University of Technology & Design
• ICRA 2022 Outstanding Dynamics and Control Paper Winner!
4. 🐝’Optimal Inverted Landing in a Small Aerial Robot with Varied Approach Velocities and Landing Gear Designs’ Habas et al. from Penn State
5. 🐝 ‘PogoDrone: Design, Model, and Control of a Jumping Quadrotor’, Zhu et al from Lehigh U.
6. 🐝 ‘Clustering and Informative Path Planning for 3D Gas Distribution Mapping: Algorithms and Performance Evaluation’, Ercolani et al from EPFL
7. 🐝 ‘A Bimodal Rolling-Flying Robot for Micro Level Inspection of Flat and Inclined Surfaces’ , Pimentel et al from Instituto Superior Tecnico
8. 🐝x 2 ‘Collision Avoidance for Multiple Quadrotors Using Elastic Safety Clearance Based Model Predictive Control’, Jin et al. from USTC & Sina
9. 🐝 + ⚡🦋 ‘An Experimental Study of Wind Resistance and Power Consumption in MAVs with a Low-Speed Multi-Fan Wind System’, Olejnik et al. from TU Delft
10. 🐝x 6 ‘Formation-containment tracking and scaling for multiple quadcopters with an application to choke-point navigation’, Su et al. from The University of Manchester.

Update

11. 🐝x 6 ‘Nearest-Neighbor-Based Collision Avoidance for Quadrotors Via Reinforcement Learning’, Ourari et al. from TU Darmstadt
ArXiv

## Other Announcements: Bolt 1.1 and Dev meeting

Bolt 1.1

The Bolt is now back in stock and with two small updates making it the Bolt 1.1. Here are the changes listed:

1. The board thickness has been reduced from 1.6mm to 1.0mm to save some weight, roughly 2 grams. This is handy for the slimmest and most lightweight designs.
2. Motor signal output M4 has been moved from PB9 to PB10 to be able to support the DSHOT motor signal protocol in the future.

Other then that it is fully backwards compatible but make sure to use a recent enough firmware (2022.03) that has the Bolt 1.1 device support added.

Time and Date for Dev Meeting

In this blogpost we noted that we wanted to organize our first Developer meeting before the summer break. From this poll we saw that most of you that want to attend are currently located in Asia and Australia, so that is why this time we want to organize the meeting at:

13:00 CEST (Sweden time) on Wednesday 22th of June.

The topic will be about our new support platform and support handling in general, so I’m hoping for some fruitful discussions about that. Keep an eye on this discussion thread for any details for joining.

This week, we welcome Airi Lampinen from Stockholm University, to talk about the Crazyflie competition she’s organizing in Stockholm.

Welcome to our one-of-a-kind hackathon with Bitcraze’s Crazyflie in Stockholm, Sweden, on June 15-17, 2022! If you are curious about how technology and humans may play together, enthusiastic about the Crazyflie, or eager to learn how to use the Crazyflie, this event is for you.

What, where, when? The Inaugural Challenge at the Digital Futures Drone Arena takes place on June 15-17, 2022 at KTH’s Reactor Hall – a dismantled nuclear reactor hall – which – especially if you haven’t been to this cool space before – makes attending the event worthwhile in its own right. In 2016, the reactor hall was used to film the music video for Alan Walker’s song Faded (Restrung).

Who can join? Anyone irrespective of age, profession and past experience with drones is welcome to participate. We welcome up to 10 teams of 2-4 people. We provide all the necessary drone hardware to the participants. We use the Crazyflie 2.1 and the Lighthouse positioning system. All that a team needs to bring along is a computer. Registration is open, with a final deadline on June 5 – we encourage those interested to sign up as soon as possible to secure their spot!

Program & prizes? On the first day of the hackathon, we will run short tutorials for those with no or little previous drone experience. The teams will then have access to the Reactor Hall to work on the challenge and conduct trial runs with their drone – we offer long hours but each team is free to choose how much they want to work. (The goal here is to have a good time!) The competition itself takes place on the third and final day. We’ve got exciting prizes for the most successful teams!

The event is organized as a part of the Digital Futures demonstrator project Digital Futures Drone Arena led by Luca Mottola from RISE and Airi Lampinen from Stockholm University.

## Bitcraze Announcements

We have also some Bitcraze news to share with you:

Last wednesday, we had our very first mini BAM, and it led to 2 hours of interesting talks and exciting discissions ! If you’ve missed it, you can find the recordings in your Youtube Channel: here for Flapper Drones’ presentation, and here for Collmot‘s talk. We plan on having at least one another mini BAM before the end of the year, so stay tuned if you’re interested in those events.

Finally, as I talked about in this blogpost, we are looking for a new team mate to add to the Bitcraze crew. You’re interested? Check out our jobs page if you want to learn more !

Since the pandemic, having a close relationship with our contributors, partners, distributors and generally speaking, users, have been a challenge. We tried to keep in touch as much as possible, by organizing our own conference, visiting labs in Europe, or asking for feedback.

Now that it seems the situation has gone back to almost normal (and I’m crossing all my fingers as I’m writing that, which makes typing difficult), we have exciting plans for the coming months for getting closer to the community. Here are some of the things we are cooking up:

## Mini BAM

The closest one is actually next week ! We are hosting a short webinar where 2 of our close collaborators will present what they’ve been working on. Matěj Karásek from Flapper Drones will talk to us about his Bolt-based drone, that is set up with flapping wings. We got to try it out in our lab last week, and it looked amazing: we’re excited you’re getting a look too!

Matej will be followed by Gábor Vásárhelyi from Collmot that will introduce us to Skybrush, its platform for any kind of swarm/fleet/multi-UAV mission control.

We’re really grateful that Flapper Drones and Collmot will join us for our very first Mini Bam to talk about drones in show! Here are the details:

It starts at 15.00 CEST on May 18th.

You’ll get an invitation to join the webinar.

## IROS 2022

After 2 years of online or hybrid conferences, we’re really excited to join the next one. And it’s a big one: IROS 2022, which will be held 23-27 october in Kyoto, Japan. We’re actually so excited about it that the whole company should be joining, if logistics and Corona let us. The situation in Japan is still uncertain, the country being still closed for tourism, but we are optimistic and hope for a week full of conference, meeting new people, and of course discovering a beautiful city all together. We’re planning on having a booth there, so if you plan also on visiting IROS, be sure to pass by and say hello !

## We’re hiring

Of course, all of those plans take time… And we’re a little bit short on that, since (as I maybe mentioned before) we’re a little short handed right now. With only 6 people at Bitcraze, we’re getting frustrated: we have many projects, and too little time to work on them ! That’s why we have begun actively looking for a new Bitcrazer to add to our ranks. A job offer should be posted soon on our page: if you’re interested, keep an eye out for this, and be sure to let us know if you fill the profile (or someone who does!). We know it will be a long process to find the right fit for us, but we’re hopefully we will discover the person that will help us achieving all those plans – and even more!

I know a lot of you will be too distracted by chocolate to read this post, so I will make it short.

As I mentioned earlier, we’re a little under-staffed right now. Jonas left us for new adventures, and Arnaud is enjoying some time with his baby (here in Sweden parental leave is thankfully long for dads too). On top of that, Kimberly was away the last two weeks to visit various labs in Europe. She will talk to you about it once she’s back, I’m sure. But with just 4 people at the office, time is a valuable resource. So what are we doing with it?

Well, a lot of that has been dedicated to the AI deck, but that’s not the only thing we’ve been working on. Recently, we had the visit of one expert on dangerous goods shipment. During 2 days, we got to learn about how to properly send the batteries we have, the regulations that are involved and what we have to implement to ship them. It may sound boring… and honestly, it was not the most interesting. But we got a certification out of it, that now allows us to ship as many batteries as we want with your order ! The 2 batteries only restriction that we have on the shop should be lifted – but please be aware that if you exceed 2 batteries per Crazyflie, the shipping cost will be higher, because of the fee Fedex imposes on dangerous goods shipments.

And speaking of Fedex, there are some problems right now on their air routes. Avoiding Ukraine and dealing with some strikes for air traffic operators in Europe has not been easy on their infrastructure, and we have experienced some delays in deliveries unfortunately. It seems to go back to normal gradually, so let’s hope their usual speediness resumes soon.

We’re also working on the Mini BAMs, which is on the 18th of May and will talk about drones for aerial show. Our special guest speakers are from Collmot and Flapper Drones, make sure to answer this survey if you want to participate ! You will get more informations soon.

And if want to play around with the AI deck, you will have an interesting occasion in September. IMAV launched a competition, where the goal is to have the Crazyflie equipped with the AI deck perform vision-based obstacle avoidance at increasing speeds. Deadline for registering are Mid-May, you can find more informations here.

We are now enjoying a long Easter week-end, recharging our batteries with families (and chocolate!), hoping that the Swedish spring finally settles here. I hope you’re enjoying it too !

A lot has happened at Bitcraze over the last months, which left us quite short-staffed. Thankfully, Victor has joined us again for a while. He mainly works on finishing his thesis with us, and we all agree that having an extra person at the office feels nice – especially considering the exciting stuff he’s working on! But let’s hear it from him first:

“Hi! I’m Victor, 26 years old, and studying towards a bachelor’s degree in Computer Science and Computer Engineering at LTH. I worked at Bitcraze during the summers of 2019 and 2020 and I’m now doing my bachelor’s thesis here.
During this thesis I will make a prototype deck that combines multiple ToF solid state lidar’s (more specifically, the new VL53L5CX). While there exists the Multi-ranger deck today, this new sensor outputs a matrix of distances, which opens up new possibilities that the Multi-ranger can not. Onboard the deck, there will also be an ESP32-S3, which will collect the data from the sensors and then send it to the PC, either through the Crazyflie, or through WiFi. This is all super exciting stuff and has endless potential, so let’s see how far I will get!”

I’m sure you will hear more on his progress in the next months, so make sure to keep updated!

## Stock issues

We’ve been dealing with the component shortage as good as we can, but production is still unpredictable. Sadly, it means the impact on our stock is too. . The AI deck, the Bolt and the battery chargers are unfortunately out of stock right now. We had to change slightly the Swarm bundles to adjust to the lack of chargers. We’re also low on Multi Rangers, which are expected to run out of stock next week.

All those products are expected back by mid-May, if luck is on our side. It depends on our manufacturer in China, where there is sadly a new Corona outbreak, so it’s not easy to say for sure if this estimation is accurate. We hope that production and delivery stay unimpacted. Just know that we are working on getting everything back on stock as soon as possible. If you want to stay updated on the status of one of our out-of-stock product, you can choose to be informed by mail in our webshop. Just go to the product’s page, and put your email there: you’ll be the first one to know when it’s back in stock !

You surely remember that last fall, to celebrate our 10 year anniversary, we organized a 3 days online conference on our own. We actually loved it, and you seemed to like it to. So we’ve been contemplating the possibility of having another, on a smaller format.

And after some thoughts, we are glad to announce the Mini BAMs! As the name implies, they are shorter (maximum 3 hours if the discussions get lively), with a simplified platform (to be determined yet), but still with interesting talks, and a lot to discover from speakers and the community. Each Mini BAM will be dedicated to a specific subject, with one or two guest speakers, followed by discussions.

We already have a session programmed, so let’s see what we have in store for our very first Mini BAM!

When? The 18th of May, in the afternoon (CEST)(the exact time will be determined shortly)

What ? Our focus this time is shows in the sky! You surely couldn’t have missed that drones are getting more and more involved in shows and productions. But while aerial entertainment is getting popular, its implementation is not easy. At Bitcraze, we try to accompany artists to help them create a unique experience, but it’s not our main area of expertise. that’s why we’re turning to 2 close partners for those shows in the sky. Which lead me to….

Who ? We will have two distinguished speakers with us this afternoon.

Gábor Vásárhelyi was born in Budapest, Hungary, in 1979. He received his MSc in engineering-physics from the Technical University of Budapest, Hungary, in 2003, and his PhD in technical sciences (info-bionics) from Péter Pázmány Catholic University, Hungary, in 2007. Since 2009 he is with Eötvös University, Department of Biological Physics as leader of the Robotic Lab at Tamas Vicsek’s Research Group on collective motion. Since 2015, he is the CEO of CollMot Robotics Ltd., a spinoff dedicated to multi-drone services. His research fields are connected to the collective motion and collective behavior of animals and robots (drones). He received many awards, for exemple: Junior Prima Award, category of informatics (2007), Magyary Postdoctoral Grant (2013), Bolyai János Research Scholarship (2015), ELTE Innovative Researcher Award (2021).

You may recognize Gabor as the author of this post. For this Mini BAM, he will present us with Skybrush, his very clean platform for any kind of swarm/fleet/multi-UAV mission control.

We will also be joined by Matěj Karásek.

Matěj Karásek studied mechanical engineering and holds a PhD in engineering sciences. He spent 10 years in the academia (ULB Brussels, TU Delft) researching animal flight and developing bioinspired flying robots. He is a founder of Flapper Drones, a startup company developing bird-like robots for research and entertainment applications.

Matej will talk to us about his Bolt-based drone, that is set up with flapping wings!

You will have time to ask them questions, and be sure to stay afterwards for discussions about show drones, the Bolt, and Skybrush!

https://forms.gle/spDpKqhrus7WrHYJ8

## Batteries in the shop

And now, for something completely different: you may have noticed that it’s difficult to order batteries with us these past weeks. That’s due to a change in transport regulation for Lithium batteries. Thankfully, we got a certification last week that allows us to ship batteries without the limitations that we had to put in the shop. We’re working on getting everything up to par with the new regulations, and shipping only batteries should soon be possible. Finally, the Swarm bundles will be, for a short time, sold without any chargers as we’re out of stock for those. The prices have been regulated accordingly.

There is a new fresh release of both the firmware and the python library and client! The last release (2022.01) was from 2 months ago but we already added quite some extra functionality so we wanted to make a snapshot of this before continuing on other priorities.

## Kbuild on CF firmware

One of the biggest changes that you will notice, is that there is now a new way to configure your Crazyflie firmware before building it. The old config.mk is gone and you will now need to either automatically generate a config file or generate one with the menuconfig, of which kbuild is most known for. For more information, please read the blogpost about this latest change, for the exception that we do prefer the users to use ‘make cf2_config’ as instructed in the 2022.03 version of the repo documentation.

## Platform support for Bolt

We now defined the Bolt as a different platform. That means that for each release, there should now also be a bolt flavor zip file, next to the cf2 and tag zips, as you can see in the release page. Moreover, if you want to build the firmware to be Bolt compatible, you would first need to do ‘make bolt_defconfig’ to generate the needed configs with kbuild. For more information of how to add your own custom platform, please check out these instructions.

## 2+ Lighthouse base stations (experimental)

For those that feel constrained by the max 2 lighthouse base station support in the firmware and client, this functionality is now part of the release. This blogpost will explain more about this, and it is still experimental in nature, as you would need to reconfigure the firmware with… you guessed it: Kbuild! Also the geometry estimation needs to be done as a separate python script as well all from the Crazyflie python library. No worries, if you still prefer using the cfclient, it still uses the old way of estimating if you click the button, but just remember that you would need to do something extra in order to get 2+ base station support.

## New VM release

We were also made aware of a pretty big error in the bitcraze VM, namely that we still used the old git:// type url for github repositories. IN the new release of the bitcraze VM this should be fixed, so please download the new one, or fix it yourself in your current VM by changing the remote URLs of the github repos you are working on to https://.

In December we had a blogpost where we gave an overview of existing simulation models that were out there. In the mean time, I have done some work during my Fun Fridays to get this to work even further. Currently I moved the efforts from my personal Github repo to the Bitcraze organization github called crazyflie-simulation. It is all still very much work in progress but in this blogpost I will explain the content of the repository and what these elements can already do.

The first thing that you will need to have for any simulation, is a 3D model of the Crazyflie. There is of course already great models available from the CrazyS project, the sim_cf project and the multi_uav_simulator, which are completely fine to use as well. But since we have direct access to the exact geometries of the real crazyflie itself, I wanted to see if I could abstract the shapes myself. And also I would like to improve my Blender skills, so this seemed to be a nice project to work with! Moreover, it might be handy to have a central place if anybody is looking for a 3D simulation model of the Crazyflie.

For simulations with only one or a few Crazyflie, the higher resolution models from the other repository are absolutely sufficient, especially if you are not using a very complicated physics geometry model (because that is where most of the computation is). But if you would like to simulate very big swarms, then the polygon count will have more influences on the speed of the simulation. So I managed to make it to 1970 vertices with the below Crazyflie model, which is not too bad! I am sure that we can make it even with lesser polygons but this is perhaps a good place to start out with for now.

In the crazyflie-simulation, you can find the Blender, stl files and collada files under the folder ‘meshes’.

## Webots model

We implemented the above model in a Webots simulator, which was much easier to implement than I thought! The tutorials they provide are great so I was able to get the model flying within a day or two. By combining the propeller node and rotational motor, and adjusting the thrust and drag coefficient to be a bit more ‘Crazyflie like’, it was able to take off. It would be nice to perhaps base these coefficients on the system identification of the Crazyflie, like what was done for this bachelor thesis, but for now our goal is just to make it fly!

The webots model can found in the same simulation repository under /webots/. You can try out the model by

webots webots/world/crazyfly_world.wbt

It would then be possible to control the pitch and roll with the arrow keys of your keyboard while it is maintaining a current height of 1 meter. This is current state of the code as of commit 79640a.

## Ignition Gazebo model

Ignition will be the replacement for Gazebo Classic, which is already a well known simulator for many of you. Writing controllers and plugins is slightly more challenging as it is only in C++ but it is such a landmark in the world of simulation, it only makes sense that we will try to make a Gazebo model of the Crazyflie as well! In the previous blogpost I mentioned that I already experimented a bit with Ignition Gazebo, as it has the nice multicopter motor model plugin standard within the framework now. Then I tried to make it controllable with the intergrated multicopter velocity control plugin but I wasn’t super successful, probably because I didn’t have the right coefficients and gains! I will rekindle these efforts another time, but if anybody would like to try that out, please do so!

First I made my own controller plugin for the gazebo model, which can be found in the repository in a different branch under /gazebo-ignition/. This controller plugin needs to be built first and it’s bin file added to the path IGN_GAZEBO_SYSTEM_PLUGIN_PATH, and the Crazyflie model in IGN_GAZEBO_RESOURCE_PATH , but then if you try to fly the model with the following:

 ign gazebo crazyflie_world.sdf

It will take off and hover nicely. Unfortunately, if you try out the key publisher widget with the arrow keys, you see that the Crazyflie immediately crashes. So there is still something fishy there! Please check out the issue list of the repo to check the state on that.

## Controllers

So the reason why I made my own controller plugins for the above mentioned simulation models, is that I want to experiment with a way that we can separate the crazyflie firmware controllers, make a code wrapper for them, and use those controllers directly in the simulator. So this way it will become a hybrid software in the loop without having to compile the entire firmware that contains all kinds of extra things that the simulation probably does not need. We can’t do this hybrid SITL yet, but at least it would be nice to have the elements in place to make it possible.

Currently I’m only experimenting with a simple fixed height and attitude PID controller written in C, and some extra files to make it possible to make a python wrapper for those. The C-controller itself you can try out in Webots as of this commit 79640a, but hopefully we will have the python version of it working too.

## What is next?

As you probably noticed, the simulation work are still very much work in process and there is still a lot enhancements to add or fix. Currently this is only done on available Fridays so the progress is not super fast unfortunately, but at least there is one model flying.

Some other elements that we would like to work on:

• Velocity controller, so that the models are able to react on twist messages.
• Crazyflie firmware bindings of controllers
• Better system variables (at least so that the ign gazebo model and the webots model are more similar)
• CFlib integration
• Add a multiranger and/or camera.
• and more!

I might turn a couple of these into topics that would be good for contribution, so that any community members can help out with. Please keep an eye on the issue list, and we are communicating on the Crazyswarm2 Discussion page about simulations if you want to share your thoughts on this as well.

This week we merged a pretty big change in the Crazyflie firmware code repository. The change altered the way we configure and build what goes in to the drone. We now make use of the Kbuild build system.

The Kbuild build system is the build system used, foremost, by the Linux kernel, but is also used in other projects like Busybox, U-Boot and sort of Zephyr. It is mostly known from its terminal based configuration tool, menuconfig.

Kbuild leverages Kconfig files to build up an hierarchy of configuration options to use when building the software. It allows you to setup dependencies between your configuration, allowing us to do things like only enable the Kalman filter when there is a deck driver that needs it enabled.

This new way of building the firmware replaces the old way of using config.mk to set the build defines you need. Our hope is that Kbuild will make it easier to customize the Crazyflie firmware to fit the need of your department or project.

## What does this mean for you?

If you are not changing the firmware as part of your Crazyflie development this will not change anything for you. The Python library will continue to work just like before and Bitcraze will release official firmwares, just like before.

If you are in the habit of fetching and building the latest and greatest version of the Bitcraze firmware there will be some minor changes. This can be seen in our updated build documentation on the web. The biggest deal is that the firmware code needs a configuration file before building is possible. To get the default one you can go:

$make defconfig make[1]: Entering directory '/home/jonasdn/sandbox/kbuild-firmware/build' GEN ./Makefile scripts/kconfig/conf --defconfig Kconfig # # configuration written to .config # make[1]: Leaving directory '/home/jonasdn/sandbox/kbuild-firmware/build' The way to compile app-layer applications has changed a bit and you will need to adapt (sorry!) the new way of building your app-layer application can be seen in the updated documentation. If you make heavy use of config.mk and frequently change code in the firmware there are many new possibilities for you. Check the documentation and keep reading this blog. ## Making the firmware more modular With the new build systems help we hope to make it easier to enable and disable features and sub systems in the quad copter. In the default firmware all drivers for all expansion decks are included, as well as all estimators. If you are pushing a feature or experiment that need more RAM or flash, that might be inconvenient for you. As an experiment we can try building the current maximum-, minimum- and default configuration of the Crazyflie. We say current because the work to make the firmware more modular is ongoing. The default configuration, the official firmware, we can obtain by invoking the special make command defconfig. $ make defconfig

And building the maximum is done using allyesconfig this gives us configuration file with all options enabled.

$make allyesconfig And conversely the minimum configuration can be set using allnoconfig, which will disable all features that can be disabled. $ make allnoconfig

The resulting firmware sizes can seen in the table below:

This shows some of the potential of the modularization of the firmware. We hope it will make it easier for you to get your stuff to fit, without having to hack around in the code too much.

## Making it easier for us to merge your contributions

The new system makes it easier include code in the firmware repository without necessary needing to include it in the official firmware. This will make it easier for us to merge controllers, estimators, algorithms, deck drivers and other stuff from you.

We can include them in our Kconfig files, allowing people to select them and build firmware using them and we can make sure they get (at least compile) tested as part of our continuous integration. So you can sleep soundly knowing your code will not suddenly break with new versions of the firmware.

## Creating and distributing your own config

If you want to create your own configuration, and spread it around you can do so.

You can use:

$make menuconfig To create a base .config file with your special configuration. If you copy the file, or have us merge it, to the configs/ directory. $ cp build/.config configs/waggle-drone_defconfig

Then it will be possible for other people to build your configuration by going:

$make waggle-drone_defconfig make[1]: Entering directory '/home/jonasdn/sandbox/kbuild-firmware/build' GEN ./Makefile # # configuration written to .config # make[1]: Leaving directory '/home/jonasdn/sandbox/kbuild-firmware/build' But it would also be possible to just add the configuration that differ with the default configuration to your config file: $ echo CONFIG_PLATFORM_BOLT=y > configs/waggle-drone_defconfig

$make waggle-drone_defconfig$ grep PLATFORM build/.config
# CONFIG_PLATFORM_CF2 is not set
CONFIG_PLATFORM_BOLT=y
# CONFIG_PLATFORM_TAG is not set


## Help out and test it please!

This is quite a big change and we are still shaking out bugs. Please give it a test run and report any issues you find!

If you want to help out, there is a GitHub project that contain the issues we know about, feel free to grab one and contribute your solution!

Happy hacking!

You might, or might not have heard about a tool called Wireshark, it is quite popular in the software development world.

Wireshark is a free and open-source packet analyzer. It is used for network troubleshooting, analysis, communications protocol development and education. It makes analyzing what is going on with packet based protocols easier.

Most often Wireshark is used for network based protocols like TCP and UDP, to try to figure out what is happening with your networking code. But! Wireshark also allows you to write your own packet dissector plugin, this means that you can register some code to make Wireshark handle your custom packet based protocol.

For the latest release of the Crazyflie Python Library we added support for generating a log of the Crazy Real Time Protocol (CRTP) packets the library sends and receives. This is the (packet based) protocol that we use to communicate with the Crazyflie via radio and USB.

We generate this log in the special PCAP format that Wireshark expects. And we also created an initial version of a dissector plugin, written in the programming language LUA.

When we put this two things together it turns into a pretty cool way of debugging what goes on between your computer and the Crazyflie!

## What does it look like?

Wireshark gives you a graphical interface where you can view all the packets in a PCAP file. You will see the timestamps of when they arrived. Selecting a packet will give you the information that the dissector has managed to deduce as well as how the packet looked on the wire.

On top of that you get powerful filtering tools. In the below image we have set a filter to view only packets that are received or sent on the CRTP port 8, which is the port for the High level commander. This means that from a log file that contain 44393 packets we now only display 9. Which makes following what goes on with high level commands a bit easier.

The dissector knows about the different types of CRTP ports and channels and knows how to dissect an high level set-point, as seen by the image above.

## What can this be used for?

This functionality is, we think, most useful for when developing new functionality in the Crazyflie firmware, or in the library. You can easily inspect what the library receives or sends and make sure it matches what your code indented.

But it can also be useful when doing client type work! We recently located the source of a bug in the Crazyflie client with the use of this Wireshark plugin.

It was when updating the Parameter tab of the client to handle persistent parameters, and to use a sidebar for extra documentation and value control. As I was testing the code I noticed that every time I changed the value of ring.effect to a valid integer and then disconnected and reconnected, the value was set to 0. Regardless of the value I had set.

I recorded a session using the PCAP log functionality:

$CRTP_PCAP_LOG=ring.pcap cfclient  And the I fired up wireshark: $ wireshark ring.pcap


It was now possible for me to track what the library and firmware thought was going on with the ring.effect parameter, by tracking the crtp.parameter_varid field using Wireshark. Filtering down from from 3282 packets to 12 packets.

I had earlier figured out that the varid of the ring.effect variable was 183. This is a quasi-internal representation of a parameter that we do not expose in a good way. In the future we will try to make this Wireshark tracking work with the parameter name as well.

Looking at the write parameter packet from USB #3 to the Crazyflie I could see where I set the value of the parameter to 5, so far so good.

The surprising part however was seeing a write further down setting the parameter to 0! This mean that something in the client was actually setting this to zero!

After seeing this, locating the actual issue was trivial. I noticed that the Flight Control tab was setting the ring.effect parameter to the current index of the combo box in the UI. And when no LED-ring deck was attached, this amounted to always setting the value to zero.

But having confirmation that this was something happening on the client side, and not some kind of bug with the new persistent parameters was very helpful!

## How do you use this?

We have added documentation to the repository documentation for the library on how to generate the PCAP log and how install the Wireshark plugin.

But the quick-start guide is this:

• Copy the tools/crtp-dissector.lua script to the default Wireshark plugin folder
• Windows: %APPDATA%\Wireshark\plugin or WIRESHARK\plugins
• Linux: ~/.local/lib/wireshark/plugins
• Restart Wireshark or hit CTRL+SHIFT+L
• Set the environmental variable CRTP_PCAP_LOG to the filename of the PCAP log you want to generate
• Run Wireshark with the filename as an argument

And please report any issues you find!

Happy hacking!