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Looking forward to 2025

  2024-12-30  |     |    Leave a comment

2024 is almost over and 2025 is coming fast so it is a good time for us to think about what is coming for Bitcraze in 2025.

Projects

2025 will be the year of the Crazyflie 2.1 Brushless! We are finally releasing it early January. The end of the development phase was longer that expected (who would have thought manufacturing would be hard … :-), but it is now ready and we are very excited to see what awesome projects the community will come up with using the Crazyflie Brushless.

With the Crazyflie 2.1 Brushless released, we will have more time to dedicate to other projects. Following is a list of fields we think we might look at, no strong promises here though and if you think we should focus on anything specific do not hesitate to drop a comment under this post, a post on github discussions or just send us an email. We have way too many ideas, but we are always open to more :-).

We still have the Lighthouse deck V2 in the back-burner, this is likely something we will look more at soon. As a reminder, the new deck is going to support lighthouse systems with 16 base-stations which will increase the space that can be covered by a lighthouse system

We also have a Wifi camera deck in early prototype, we have been showing it at various conferences in the last years. We are still working on trying to find the perfect Wifi-chip/processor/Camera combo to make it a reality.

We (ie. I) also have a lot of ideas on how to improve the communication with the Crazyflie. Crazyradio 2.0 has a lot of untaped capabilities that we can use to implement better, easier to use and more reliable communication protocols so this is definitely something we want to have a look at.

Finally, I apparently managed to sell the Rust programming language a bit too well to the team. Some of us are even more enthusiastic than I am about it! This together with an increased frustration with Python and PyQT6 distribution to various platform will likely make us experimenting even more in Rust in the future. The first target in sight is to write a Rust lib for the Crazyflie together with binding for various languages including Python and C/C++. This means that would be able to have only one lib for most use case of the Crazyflie both in Python and in ROS.

Conferences

Arnaud is part of the organizing committee of the FOSDEM Robotics and Simulation devroom at Fosdem. Fosdem is one of the biggest open source conferences in Europe. It is an awesome community-driven conference, so if you are not too far and are interested in open-source please join us in Brussels the 1st and 2nd of February 2025!

As usual we will likely participate to a couple of robotic conferences during the year. We are not yet sure which one though so stay tuned for more information on this blog.

Team

The team has been evolving in 2024, we are now 6 in the Malmö office, Mandy is working from Shenzhen in China handling the production and Joe is doing a post-doc in Stockholm in close collaboration with us.

We are actively looking at hiring 2 more team members, one in technical support and one in Sales. Our goal is to build a team where all of us can focus on our strengths to develop even further and faster the Crazyflie ecosystem.

We wish you a great new year filled with hacking and exciting new discoveries!

Looking back at 2024

  2024-12-23  |     |    Leave a comment

As 2024 comes to an end, it’s the perfect time to reflect on what we’ve accomplished over the past year. A major highlight has been our work on the Crazyflie 2.1 Brushless. We’re thrilled that it will be available early in the new year! While much of our efforts focused on refining and preparing the platform as a whole, we also introduced some standout features like support for contact charging on a charging pad, perfecting the specially optimized motors, and propeller guards to enhance safety for both users and the drone.

The Crazyflie 2.1 Brushless with propeller guards on a prototype charging pad
The optimized brushless motor

Finalizing the integration of the Crazyflie 2.1 Brushless into our software ecosystem and expanding its documentation were key steps in preparing for its launch. These efforts ensure compatibility, improve the user experience, and make the platform more accessible to the community. We’re looking forward to a smooth launch and to seeing how the community will utilize the new platform!

This year, we introduced updates to the Crazyflie 2.1 kit, making the 47-17 propellers the new default and including an improved battery. These upgrades enhance flight performance and endurance, culminating in the release of the Crazyflie 2.1+—an optimized iteration of our established platform.

The Crazyflie 2.1 Brushless featured on the cover of Science Robotics vol. 9, no. 92

Community

In 2024, Bitcraze had an action-packed year, engaging with the robotics community through numerous conferences, workshops, and live events.

In May, we attended ICRA 2024 in Yokohama. We collected several research posters that now proudly feature at the office. Kimberly presented at the Robotics Developer Day, where she won Best Speaker Award for her impressive live hardware demos with ROS2. We co-organized the ‘Aerial Swarm Tools and Applications’ workshop at RSS 2024 in Delft. Arnaud and Kimberly shared insights on demo-driven development on an episode of OpenCV Live!. Additionally, we had a booth at ROSCon ’24 in Odense, connecting with the vibrant ROS community and showcasing our latest developments.

ROSCon
ICRA

And don’t forget the developer meetings, where we shared some more behind the scenes information and collected invaluable feedback from the community.

We also released a new edition of our research compilation video, showcasing some of the coolest projects from 2023 and 2024 that highlight the versatility and impact of the Crazyflie platform in research.

Team

In the past year, Bitcraze saw significant changes within the team. in February, Rik rejoined the team. Tove started at Bitcraze in April. Mandy, with whom we’ve already worked extensively over the years, joined as our production representative in Shenzen. At the end of the year, we said goodbye to Kimberly, whose contributions will be deeply missed. Additionally, we had Björn with us for a few months, working on his master’s thesis on fault detection, and Joe continued his industrial postdoc at Bitcraze that began in December 2023. Looking ahead, Bitcraze is hiring for two new roles: a Technical Sales Lead and a Technical Success Engineer, to support our ongoing projects and customer collaborations.

Midsummer lunch with the team
Christmas-themed Bitcraze office

As we close the chapter on 2024, we’re proud of the progress we’ve made, the connections we’ve strengthened, and the milestones we’ve reached. With exciting launches, new faces on the team, and continued collaboration with our community, we’re ready to soar to even greater heights in 2025. Thank you for being part of our journey!

A Brushless Christmas dream

  2024-12-16  |     |    Leave a comment

This Christmas, Bitcraze is sending out a callout to Santa. As it turns out, one of our Brushless prototypes has a lifelong dream of becoming one of Santa’s reindeer. In a hopeful attempt to fulfill its wishes, we shot a video to prove that it’s ready for Santa’s most elite aerial team!

Imagine a tiny, determined drone with big dreams, practicing its sleigh route moves with the intensity of an Olympic athlete. Our little Brushless is proving it has what it takes to join the North Pole’s premier delivery squad.

Going through small openings, avoiding obstacles, and flying in perfect precision are skills that any good reindeer should have – but here, the Brushless accomplish this in an autonomous flight, and in a much smaller and more practical package than Rudolph and consorts.

Of course, there’s some technical magic behind this Christmas miracle. For this project, we relied on stock firmware and Python library, taking advantage of the new spiral and constant velocity features (check out the GitHub PR here). These features added variety and fluidity to the maneuvers, moving beyond straight lines and making the flight more interesting. By using the high-level commander, we took a simpler approach compared to trajectory optimization, which we’ve used in past Christmas videos. Trajectory optimization would have been far more difficult for this project due to the unique challenges of the flight path—namely its length and the need for pinpoint accuracy near obstacles and through gates.

Positioning relied on four Lighthouse base stations, which we used to manually locate the Christmas wreaths by holding the drone within each one to log their exact coordinates. This project also gave us the opportunity to further integrate the Brushless into our firmware and Python libraries, setting the stage for a smoother launch in the new year. The Brushless impressed us yet again during this project. Even though we’ve tested it extensively in the past, seeing it navigate tight gates with such precision and handle the demanding flight path reinforced just how capable it is. Working with it in this setting has made us even more excited to release it soon and share its potential with everyone.

Santa, if you’re reading this, we think we’ve found your next top reindeer recruit. You can watch the full audition tape here or below:

And if you think what you just saw is a pretty straight-forward and easy path, think again! This year’s blooper video highlights the resilience of the Crazyflie 2.1 Brushless and the fast, iterative workflow we used for this project. Since testing reliability and resilience was a key goal, we adopted a workflow that allowed for quick scripting, flying, and adjusting—often completing the cycle in just minutes. This approach made crashes more likely, especially during the spiral sections where the drone struggled to keep up and started cutting corners. While we resolved the issue by slowing those sections down, we suspect that more aggressive tuning of the Mellinger controller could have helped the drone maintain speed without cutting corners. The Brushless managed some impressive recoveries, but even minor collisions usually meant it couldn’t keep pace with the rest of the trajectory. After all the trial and error, we had a stable and reliable setup that not only performed well for the demo but also flew beautifully when we showed it to our families at the Christmas party.

Here is what our Brushless could endure during training:


Merry Christmas from all of us at Bitcraze – where even our prototypes have holiday dreams!

Dr. Kim’s last Fun Friday Project

  2024-12-09  |     |    Leave a comment

Hi everyone! I have a bit of news to share… I’ve decided to leave Bitcraze at the end of 2024. But not before I share with you my latest Fun Friday project that I’ve tried my best to finish up before I leave before my Christmas holiday in December.

Frankensteining the Pololu Robot with the Crazyflie Bolt

During the ROSCon talk about the lighthouse system (see the recording here), I’ve already shown a small example of how the lighthouse system could be used on other robots as well. Here you see a Pololu RPI 2040 (the hyper edition of course), with a slimmed down Crazyflie Bolt and a Lighthouse deck. The UART2 port on the Bolt (pinout is the same as Crazyflie) is interfacing with the UART0 connection on the Pololu (pinout). Then the Pololu’s 3v3 is connected to the vUSB and GND to GND (obviously), so 4 wires in total. Technically, the 3v3 port is not supplying enough power for the Crazyflie on paper, but it seemed to be enough as long as the Crazyflie Bolt doesn’t have motors connected it should be fine. But if anyone would like to do a driving-flying hybrid with this combo, you might need to check the specifications a bit closer. For now, just ignore the red low-battery LED on the Bolt, but if you see it restarting then perhaps give the Pololu a fresh set of batteries.

Since the Pololu RPI 2040 doesn’t have any wireless communication, this can be done through the Crazyflie Bolt and the Crazyradio. I’ve made an app layer variant for the Bolt to forward state estimates and velocity commands; however, it did require a bit of an extra logging variable in the firmware itself. But this allows me to control the Pololu through the CFclient! Since it’s using velocity commands, this means that the mobile app is out though, but perhaps if anyone is interested in getting this rolling, let me know. Also, the screen shows the current X, Y, Z, and yaw estimate of the Bolt transferred to the Pololu with the commands that I’ve given it.

I’d like to have connected this to a differential drive controller to make use of the position setpoints, but unfortunately the AA batteries ran out at the office and I was unable to complete this by the last day. It would have been great to use the Lighthouse positioning for this. Perhaps in the next coming months, I can try to continue with it and have my cats chase an autonomous robot around the house, who knows! If anyone is interested in playing around with this, these are the repositories/branches for both the Bolt and the Pololu:

What is next?

First of all, I’ll take a long holiday in the US, first visiting New York (first time) before I hop over to Tulsa and Santa Barbara to visit family. Early 2025 I’ll be taking a long break, or a mini sabbatical of sorts, where I plan to work on some personal projects but mostly have a breather. I haven’t had a break like this in over 15 years, and given a tough 2023, I can definitely say that I’ve deserved some time off. What will happen after, I will hopefully figure out then, but for sure I will be continuing to co-lead the Aerial Robotics Interest Group at ROS and helping out in support of the Crazyswarm2 project.

I’d like to thank my colleagues at Bitcraze for an amazing 5 years here in Malmö, Sweden, and everyone that I was able to meet through them. I’ve learned a lot in terms of joint software development, code maintenance, community interaction, and, most importantly, having fun during work. I also will never forget the support I received while I was going through cancer treatment, and for that I’m very grateful. I wish you all the best and I hope the Crazyflie continues to thrive, saving more PhD projects as it did mine. Thank you.

Crazyflie 2.1 Brushless release update

  2024-12-03  |     |    Leave a comment

The last couple of months we have been working really hard on finalizing the Crazyflie 2.1 Brushless and we’re happy to say that we’re finally nearing the release date! The first units are scheduled to be finished during December with shipping in January. Make sure so sign up for the Crazyflie 2.1 brushless product notifications to not miss out once it’s available!

We’re also working hard to offer everything that complements the Brushless. You’ll have access to spare parts and the option to choose your platform for some bundles. Hopefully, the charger will also been available soon, to allow you to charge the Brushless effortlessly!

It’s beginning to look like Christmas

  2024-11-25  |     |    Leave a comment

November is always a tough month in Sweden, when the darkness deepens and the cold begins to bite. We had our first snow last week, a sudden reminder that winter has arrived. So instead of letting the gloom settle in, we decided to turn to what makes us feel good: pretty lights, pretty trees, and pepparkakor!

I realized that, although we talked about it last year, we never fully showed our big new flight arena once it was up and running. It made an appearance in our latest Christmas video, but was actually never fully revealed before. Capturing a 110square meters space in a single photo is no small feat, but here is my best shot:

It felt the right time to make the office feel a little more wintery. It may be a little early, but we couldn’t resist the charm of festive decorations and a cozy atmosphere to brighten up the dark days. Especially now that we’re more settled into our massive flight arena – a space this large calls for many more Christmas lights! Of course, there’s more to it than just creating a Netflix-Christmas-movie vibe—we’re also gearing up for two big events: our annual Christmas party, which will be hosted here, and the filming of our newest Christmas video!

Speaking of Christmas video, that’s exactly what we’ll be diving into during our next dev meeting! We recently had a great time revisiting how we’ve used demos to guide development – if you missed that particular dev meeting, you can see it here. We thought it would be a great idea to dedicate our next session to exploring all the Christmas videos we’ve created over the years. It’s fascinating to see how our Christmas projects have evolved over time and we hope you’ll join us to reminisce about it Wednesday 11th of December at 15.00 (CET). You’ll find all the info here.

New recruitment at Bitcraze

  2024-11-18  |     |    Leave a comment

It’s been a while since I last talked about hiring! We successfully onboarded our most recent recruit, and now it’s time to start planning for the future.

One of our challenges as a team is that we’re very heavy on engineers and developers. While that’s fantastic for building products, it means we lack expertise in other important areas. That’s why we’re now shifting our focus to bringing in talent to help fill those gaps. We’ve partnered with a recruitment agency once again to help us find the right people for the job.
We’re currently hiring for two distinct roles—here’s what we’re looking for!

Technical sales lead

You will be responsible for developing and implementing sales strategies while exploring both new and existing markets. You’ll take the lead in driving sales and acquiring new customers, becoming the company’s go-to expert on marketing and sales tactics. Your day-to-day tasks will include supporting business development, optimizing sales processes, and proposing effective marketing strategies. This role is perfect for someone with a background in technical sales with a strong strategic mindset and a sense of responsibility.

You can read more about it here.

Technical success engineer

We’re looking for a Technical Success Engineer to provide our customers with technical guidance and product expertise. This role involves offering first-line support, creating documentation and tutorials, and assisting with tech-focused sales efforts. The goal is to ensure a smooth and seamless customer experience while building strong client relationships. It’s an ideal position for a “social developer”—someone with a solid technical background who also excels in communication and enjoys engaging with others.

You can read more about it here.

Both positions are full-time and based at our office in Malmö, Sweden. If you’re curious about why you should join our team, I’ve already shared some of the many reasons why I love being part of Bitcraze.

If you’re interested or have any questions, please send an email to fredric.vernqvist@techtalents.se or contact us at contact@bitcraze.se.

From Shadows to Light: A swarm robotics approach with onboard control for seeking dynamic sources in constrained environments

  2024-11-11  |     |    Leave a comment

Today, we’re excited to share research from Vrije Universiteit Amsterdam, ‘From Shadows to Light,’ which presents an innovative swarm robotics approach where nano-drones autonomously track dynamic sources indoors.

Motivation

In dynamic and unpredictable indoor environments, locating moving sources—such as heat, gas, or light—presents unique challenges. GPS-denied settings, in particular, demand innovative and efficient onboard solutions for both control and sensing. Our research demonstrates how small drones, like Crazyflies, can be organized into a coordinated swarm to autonomously locate and follow these sources indoors, relying solely on onboard sensing and communication capabilities. Without sharing individual measurements, each drone adapts its behavior in response to its own sensor readings, allowing the swarm to collectively converge on the center of a light source through modified interactions with nearby agents.

Tugay Alperen (right) and Victor Retamal (left) during ICRA 2024 poster session

Method

Our approach enables each Crazyflie to function autonomously, using onboard sensing combined with continuous inter-agent communication at a frequency of 20 Hz. This methodology is structured around three core components:

Proximal Control and Collective Motion

Each drone broadcasts its position to nearby agents, enabling the calculation of relative positions to maintain safe distances. This proximal control ensures cohesive group movement by computing virtual force vectors for velocity commands, which are sent to onboard controllers operating at 20 Hz.

Source Seeking Through Adaptive Social Proximity

Drones use custom light sensors to detect local light intensity. Instead of directly adjusting positions based on this measurement, each drone modifies its social proximity to neighbors according to the sensed intensity without broadcasting this information. This adaptation allows the swarm to collectively follow the light gradient toward the source in a decentralized manner.

Obstacle Avoidance

Equipped with time-of-flight sensors, each drone independently detects obstacles and adjusts its trajectory to maintain safety. This ensures the swarm remains intact while navigating toward the source.

By combining continuous relative positioning, virtual force-based control, individual sensing, and adaptive social behavior, our methodology provides a robust framework for efficient source seeking in GPS-denied indoor environments.

Experimental Setup

Crazyflie equipped with Flow Deck v2, UWB Deck, Multi-Ranger Deck, and a custom-made deck that produces an analog voltage reading from an LDR for light intensity measurements.

The system architecture allowing us to achieve autonomous flocking and source localization with a swarm of Crazyflie

Our experiments take place in a 7×4.75-meter indoor arena with remotely controlled overhead light bulbs. These bulbs, activated individually or in pairs, create a moving light gradient. We tested our flocking swarm by initially positioning them at the edge of an illuminated area. As the light source shifted, we assessed the swarm’s performance by comparing their trajectories with the known centers of the illuminated areas without waiting for full convergence at each step. We also mapped our environment’s light intensity by moving a single Crazyflie randomly around the flight arena and recording the measurements to later merge on a single map to generate this light intensity heatmap.

The brightness values around the test environments, measured for each light source when only it was active.

Results

The flock flies as an ordered swarm, successfully localizing around the source with the swarm’s centroid positioned at the source center. (The centroid appears as a point without an arrow in the video.)

Even with an obstacle present within or between the illuminated regions, the flock successfully localizes around the center, avoiding the obstacle and maintaining order and cohesion within the swarm. The Multi-Ranger deck provides distance measurements for obstacle detection.

Future Directions

As the next step, we plan to apply our highly generalizable algorithm to various source types, including gas sources, radio signals, and similar sources that provide only scalar strength measurements rather than directional cues. Additionally, we have demonstrated that our flocking and source localization algorithms work effectively in 3D. We aim to showcase a fully functional application with a 3D-localized source and a flocking swarm operating in 3D space. Finally, we are working toward achieving fully onboard relative localization, which would eliminate the need for any indoor positioning system. This advancement would allow our swarm to operate autonomously in any environment, replicating the same behavior wherever it is deployed.

Links

The authors were with the Vrije Universiteit Amsterdam.

Please feel free to contact us with any questions or ideas: t.a.karaguzel@vu.nl

Please cite this as:

@ARTICLE{10314746,
  author={Karagüzel, Tugay Alperen and Retamal, Victor and Cambier, Nicolas and Ferrante, Eliseo},
  journal={IEEE Robotics and Automation Letters}, 
  title={From Shadows to Light: A Swarm Robotics Approach With Onboard Control for Seeking Dynamic Sources in Constrained Environments}, 
  year={2024},
  volume={9},
  number={1},
  pages={127-134},
  keywords={Robot sensing systems;Autonomous aerial vehicles;Position measurement;Vehicle dynamics;Sensors;Location awareness;Drones;Swarm robotics;aerial systems: perception and autonomy;multi-robot systems},
  doi={10.1109/LRA.2023.3331897}}

ROSCon ’24 Recap

  2024-11-04  |     |    Leave a comment

It’s been 2 weeks ago that we went to ROSCon ’24 in Odense Denmark as exhibitor and silver sponsor! Since it was a 2-hour train ride for us, it made much sense for us to attend this as a company and we are very happy we did. In this blog post we are sharing our experiences of the event.

The Booth Build-up and Demo

We made some changes to our well-known cage that is a must at every conference we have exhibited. Usually, it would take us a good few hours just to set up the cage alone, but we have improved the corners which improved our build-up experience quite a lot and we were done within an hour! Just in time for us to join the tours and bird of feather sessions with no stress!

All done before 11 am!

For ROSCon we prepared a more ROSflavored demo that enabled full demo control from ROS, which was based on the swarming mapping demo shown in this tutorial and the robotics developer day (see this video). Here we already hit a couple of issues that all had to do with the differences between demos for exhibitions versus one-time talk demos (see OpenCV! Live episode where we talked about demo driven development). We switched back to our usual fully decentralized autonomous swarm demo (see this blog post). Luckily, the Crazyflie could still communicate at the same time to give through the multiranger values, such that the computer could still generate the Swarm merging map while the Crazyflies were flying around avoiding each other.

Exhibition Booth

Tuesday and Wednesday were the actually exhibition days so that is when we talked with most of the people. It was a bit slow in the beginning as we were located at the end of the hall, but luckily the ROSCon passport game motivated people to go by each of the booth to get a stamp. We went a bit rogue and made our own much bigger stamp ;) but luckily it still fit as long as we aligned properly. We donated a STEM Ranging bundle as one of the prizes to congratulate whoever won this! And now they can try out this ROS tutorial ;)

Talking to people outside and inside the cage

We noticed that the Crazyflie Brushless got a lot of attention. The ability to carry more than a regular Crazyflie seemed of great interest to many of the ROSCon attendees. Moreover, the prototype of the forward-facing expansion connector (a.k.a. the Camera deck) was also a well-requested feature of the Crazyflie and has solidified our belief that the community needs something like this as well. In general, the lighthouse positioning system and the stand-alone lighthouse node were also quite well received. Luckily we were able to forward people to our accepted talk about the Lighthouse position system on Thursday

Lighthouse Positioning Talk

One of the reasons we were present at ROSCon 2024 was to gauge the interest of the general robotics community in the lighthouse positioning system. We have been using it for years for the Crazyflies, but we’d like to also evangelize its submillimeter and cost-effective awesomeness for any other platform. And there seems to be quite some interest for it! We gave a short presentation on Thursday Afternoon during the ‘ROS Tooling & Testing’ session (we will share the recording once it becomes available).

Talk about Lighthouse Positioning – Taken by Dharini Dutia from Women in Robotics

We also send out some polls just to see what kind of positioning systems are used and for what purpose. It was evident that there are many outdoor roboticists that also use onboard-sensing based state-estimation like SLAM, but there was still a significant portion of people that used indoor positioning systems for the actual positioning replacement and/or Ground truth. And also we got some valuable feedback, like if it would still work out with a Lidar or Kinect, or if it is suitable for a 12-meter size robot (wow). We will take this all in for improvements for any new upgrades to the lighthouse deck and stand-alone nodes for it. Thanks to you all for providing all the feedback and the interest!

Side-events

We also attended a couple of events related to ROSCon 2024. Marcus and Kimberly both attended tours of Odense Robotics, Universal robots and Teradyne facilities. The tour of the SDU Drone Center was particularly impressive. Moreover, we also attended the Aerial Robotics Meetup, who attracted about 90-100 people at the max, with drinks and snacks provided by Dronecode Foundation. It was great to see such a big aerial presence at ROSCon. There was also the Karaoke meetup, the ROSCon afterparty by Odense Robotics with a beer-serving robot arm, the Women in Robotics lunch… there was just too much to attend to but it all was a great success!

Check out the ROSCon 2024 event page on our website of what we have shown at ROSCon 2024 and see more information about the demos/products we had there.

Link performance metrics

  2024-10-28  |     |    Leave a comment

We are excited to announce that we are working on several new link performance metrics for the Crazyflie that will simplify the troubleshooting of communication issues. Until now, users have had access to very limited information about communication links, relying primarily on a “link quality” statistic based on packet retries (when we have to re-send data) and an RSSI channel scan. Our nightly tests have been limited to basic bandwidth and latency testing. With this update, we aim to expose richer data that not only enables users to make more informed decisions regarding communication links but also enhances the effectiveness of our nightly testing process. In this blog post, we will explore the new metrics, the rationale behind their introduction, and how they will improve your interaction with the Crazyflie. Additionally, we will be holding a developer meeting on Wednesday November 13th to discuss these updates in more detail, and we encourage you to join us!

“Link Quality”—All or Nothing

Until now, users of the Crazyflie have had access to a single link quality metric. Implemented in the Python library, this metric is based on packet retries—instances when data packets need to be re-sent due to communication issues. This metric indicates that for every retry, the link quality drops by 10%, with a maximum of 3 retries allowed. As a result, the link quality score usually ranges from 70% to 100%, with a drop to 0% when communication is completely lost. However, as packet loss occurs, users often experience a steep decline, commonly seeing 100% when packets are successfully acknowledged or dropping to 0% when communication is completely lost.

Client representation of link quality; no link, yes link

The current link quality metric has served as a basic indicator but provides limited insight, often making it difficult to gauge communication reliability accurately. Recognizing these limitations, we’re introducing several new link performance metrics to the Crazyflie Python library, designed to provide a far more detailed and actionable view of communication performance.

What’s Coming in the Upcoming Update

The first metric we are adding is latency. We measure the full link latency, capturing the round-trip time through the library, to the Crazyflie, and back. This latency measurement is link-independent, meaning it applies to both radio and USB connections. The latency metric exposed to users will reflect the 95th percentile—a commonly used measure for capturing typical latency under normal conditions.

Next are several metrics that (currently) only support the radio link. For these, we distinguish between uplink (from the radio to the Crazyflie) and downlink (from the Crazyflie to the radio).

The first is packet rate, which simply measures the number of packets sent and received per second.

More interestingly, we are introducing a link congestion metric. Whenever there is no data to send, both the radio and the Crazyflie send “null” packets. By calculating the ratio of null packets to the total packets sent or received, we can estimate congestion. This is particularly useful for users who rely heavily on logging parameters or, for example, stream mocap positioning data to the Crazyflie.

The Received Signal Strength Indicator (RSSI) measures the quality of signal reception. Unlike our current “link quality” metric, we hope that a poor RSSI will serve as an early warning signal for potential communication loss. While RSSI tracking has been possible before with the channel scan example, this update will monitor RSSI in the library by default, and expose it to the user. The nRF firmware will also be updated to report RSSI by default. Currently, we only receive uplink RSSI, that is, RSSI measured on the Crazyflie side.

Work in progress client representation of new link performance metrics

We’ve already found these new metrics invaluable at Bitcraze. While we have, of course, measured various parameters throughout development, it was easy to lose track of the precise status of the communication stack. In the past, we relied more on general impressions of performance, but with these new metrics, we’ve gained a clearer picture. They’ve already shed light on areas like swarm latency, helping us fine-tune and understand performance far better than before.

You can follow progress on GitHub, and we invite you to try out these metrics for yourself. If there’s anything you feel is missing, or if you have feedback on what would make these tools even more helpful, we’d love to hear from you. Hit us up over on GitHub or join the developer meeting on Wednesday the 13th of November (see the join information on discussions).