The last week was epic. We had 3 days of our online conference, the BAM days – I’m sure you’ve heard of them by now.
We are really happy with how everything went down. During those 3 days, 142 people attended, which is a highest number than we could have expected. The Welkom platform we used was stellar, allowing us to use Mibo rooms for very fruitful discussions after each talk.
Quiz and community Q&A
We took the opportunity to talk to our community, which is something we didn’t have the opportunity to do in a long time. Your insights and feedback were greatly appreciated and we have a lot to think about in the next coming weeks on how to best use all the remarks we got.
We also had a short quiz about Bitcraze, and we were quite impressed with how you performed ! And interesting to note that the hardest question for you was how many decks we sell (it’s 16, if you want to cheat on our hypothetical next quiz)
As I’ve mentioned, after each event we gathered in Mibo rooms. Even though attendance there was not as high as we would have liked, we still got quality time with community members, speakers, collaborators, even first-timers that were interested in the Crazyflie. We really love this platform, making us feel almost like meeting in real life. We even had some karaoke in Mibo during the closing party (which MAY be a good excuse to end the day for those who listened)
Content
Our external speakers presented a lot of interesting work. It was a great pleasure and honor to welcome every one of them as they explained their latest work. I have to admit that it’s rewarding to see such smart people doing awesome and cool research with our products.
We did our share too, with workshops and demos. Kristoffer’s autonomous demo using distributed consensus required a lot of work but worked perfectly in the end. Here is a small excerpt:
What now?
Now, we’re feeling as everyone is feeling the day after a party: exhausted, happy, and wondering what to do next. Hopefully we have some plans for that !
If you missed the conference, we created a Youtube playlist where you can watch everything that you missed. During the next few days, we’ll update the event page with BAM’s presentations too so you will have the opportunity to catch up. Some of our workshops will also turn into tutorials or documentations of some kind, but we’re still just cleaning up.
We are so happy with how everything went that we are already thinking about a future BAM. This one was exceptional, of course, since it was at first to celebrate our 10 year anniversary (and I have to admit that we’re all a little bit tired after 3 intense days), so we’re not going to be able to top that. But we are considering making BAM a fixed point in our agenda (and yours, let’s hope). We don’t how, we don’t know when, but one thing is sure: BAM is just beginning.
Kimberly on a different continent
On a totally different note, Kimberly is flying to the US this week: if any of you America-based wants to grab the occasion to have a more time-zone appropriate conversation with one of us, you will have a few weeks to make it possible!
I’m sure you know about it by now, but as a reminder, the BAM days are this week ! We’re all are really excited about it – and, let’s be honest, a little nervous too as the day grows nearer.
We are really happy to see that so many of you plan on joining us. We have more than 100 people registered to the event, which is actually the highest estimate we were hoping for. By the way, if you are registered to the event, dismiss the Event Brite email you got on Sunday and prefer the direct Welkom link you’ve been sent: the process is much easier if you use the latest. If you did sign up, but haven’t received an email with any link (even after checking your spamfolder) , please send us an email at contact@bitcraze.io!
Our workshops are all ready and we’re proud to present you our selected subjects. Each one of us will get the opportunity to talk about an area he cares about, so if you attend the whole event you will get also the chance to meet all of us. Of course, the social fika will also be the perfect place to meet us, so don’t hesitate to jump in the Mibo room we’ve set up!
There are also keynote speakers that we’re honored to host, close collaborators whose work we admire. It will be really interesting to hear from them, whether about Motion Capture or swarms.
There are been a few changes on the agenda:
On Wednesday morning, we’ll have a second session of the quiz. Those that missed it on Tuesday evening can then also get a chance of winning the one and only Goldenflie. It will be followed by a community Q&A: if you have any questions unanswered, it will be the time to ask them! In the afternoon, Arnaud will talk about Rust and the App layer after Greenwaves’s talk (and not on the morning as announced before).
If you’re interested in swarms, Friday morning will be perfect for you as we have a double feature: Wolfgang will present his CrazySwarm and Jonas will follow with a presentation about using the CFlib to fly a swarm. Afterwards, they will have a panel discussion on swarm management.
There is also a demo programmed on Friday. We haven’t told much about it yet because we wanted to be sure it was possible to do before we promised anything, but I can tell now that on Friday, you will be able to see an autonomous swarm making distributed decisions. It’s the first time we’re trying something like that and you don’t want to miss it !
Just be aware that during the BAM days, we won’t be as reactive on answering our emails or the forum, as most of us will be on the platform, but we’ll still be shipping orders.
Only 8 days left before the first Bitcraze-organized conference ever. We are really excited about it, and this coming week is pretty much dedicated to organize the conference. We’re working hard on getting the best experience possible for there 3 days, both for us and for you. That means collaborating with great speakers, creating awesome workshops, but also think about the best way to come together – one of the main purpose behind the BAM days.
It’s been a couple of months since we decided that we wanted to organize our own conference. The main idea behind it was that we missed going to conferences, meeting people and talking with a lot of interesting persons.
Expression of the BAMdays
Bitcraze turning 10 felt like a big occasion that we wanted to celebrate. And indeed we did, internally, but we wanted to share this accomplishment with you too. An online conference seemed like the best idea. So when time came to choose a platform for it, we looked for something which put emphasis on social experience. We finally went with the Welkom platform, from the Netherlands. It’s easy and natural to use, with a simple interface, and lots of options for us to organize different activities.
The event platform
The Welkom platform we’ll use hosts two different Mibo rooms. It’s a spatial chat, where your avatar can run around a 3D world, discovering different environments. Your camera is your head, so you’ll need a webcam to join. There are some fun activities around, plenty interactive stuff, from chairs to basketballs. We have used it to for our coffee breaks when we were working from home, and had fun using this world: we’ll be happy to meet you there and hope you’ll find it fun too.
Bitcraze goofing around in Mibo
The plan is to have between each talk or workshop at least 30 minutes in Mibo to talk to the speakers, take a coffee break, discuss the exciting things that’s been happening, and generally catch up in ways we haven’t be able to the past year.
At the end of each day, we’ve programmed social events to gather together. On Tuesday, we’ll host a special quizz. Telling you its content may be a bit cheating, but if we’ve read our blogposts regularly, the questions should not seem hard to you. For the winner, a once-in-a-lifetime reward: a GoldenFlie ! You will be able to put it in your chimney mantle with your others awards, or actually use it – because, yes, it flies!
The GoldenFlie!
The second day, Wednesday, we’ll have a roundtable with Q&A. A perfect occasion for us to get feedback from you, and for you to ask us all the questions you have been burning to ask us.
The last day (Thursday), we’ll talk a little about Bitcraze and its future: where it is headed. We’ll then have a last party – in Mibo of course.
All the program and other useful information is in our event page. We really hope you’ll take some time to come by and say hello !
Last week it was time for the International Conference on Intelligent Robots and Systems (IROS), which is one of the biggest yearly robotics conferences! In previous editions (see 2018 blog post, 2019 event page), we joined IROS’ exhibition and showed an autonomous demos for everybody to enjoy during the coffee breaks. Then… as everybody knows… the Covid-19 pandamic hit and we had to cancel our plans to go to the 2020’s Las Vegas edition. This year’s IROS was supposed to be held in Prague, but was very early announced that this was going to be an online edition.
Eventhough we considered joining IROS’s online exhibition, after our decision to organize the Bitcraze Awesome Meetup (BAM) days as a celebration to our 10 year anniversary (see this blo gpost), we wouldn’t have enough time to prepare for both. However, we still signed up for the conference itself, so we could see how and where the Crazyflie is used in the robotics community! So this blog post will give a list and small overview of the Crazyflie-fueled research with some highlights.
Crazyflie as a Demonstration Tool in Research
A common use-case that we saw is to use the Crazyflie as a research demonstration tool. In the case of designing algorithms for quadcopters, many of the researchers we heard from or talked to told us that there is significant added value to demonstrate their ideas on a real platform. Then it can be truly evaluated with real environmental issues and platform dynamics. For this, the majority of the papers have used the ROS package developed for the CrazySwarm project but some researchers has gone as far as implementing it fully on the Crazyflie’s MCU [6, 8]!
We also noticed the large spread of the Crazyflie-featured papers throughout the sessions of the conference. A bunch of the papers could obviously be found in Aerial System sub-sessions as in ‘Perception and Autonomy’ [1], ‘Applications’ [3], ‘Mechanics and Control’ [4 , 5], but many were spread out in areas like Reinforcement Learning [2], Localization [6] and Collision avoidance [7]. There were also some papers to be found in the Swarm Robotics session [8, 9], as well as in Distributed Robot Systems [10].
Note that there is usually quite some overlap between the different sessions, but it is still very exciting to see that the Crazyflie being used in so many fields!
Highlights and the Community
We saw lots of awesome applications but there are a few that we really like to highlight! There was a presentation of an actual solar-powered Crazyflie [2] which can literally fly forever. This research was done by the same group at the University of Washington that also was featured in a blog post last year, and who is responsible for the Smellicopter. Also, our jaw literally dropped at the sight of the 4 Crazyflie-fueled mega-copter by the University of California, Los Angeles [4, 5]. Last but not least, the fully onboard autonomous gas-seeking swarm, Sniffybug [8], from the MAVLab (TU Delft), never stops to amaze us. They wrote a blog post about their work on our website this summer!
We are hoping for more interesting blog posts related to the papers in the list below in the future. We also would like to invite all the researchers, who have been working with the Crazyflie, to join us for discussions at the Community Q&A at the BAMdays. Most of the amazing aspects of the Crazyflie in terms of autonomy, localization and swarming have all been contributions of the research community in the past. So join the discussion to continue that path in order to bring the Crazyflie to a new level!
List of IROS 2021 Papers featuring the Crazyflie
Here is a list of all the Crazyflie-related papers we could find, but please let us know if we are missing any!
[1] Target-Visible Polynomial Trajectory Generation within an MAV Team Yunwoo Lee, Jungwon Park, Boseong Jeon and H. Jin Kim
Lab for Autonomous Robotic Research (LARR), Seoul National University
[3] Toward battery-free flight: Duty cycled recharging of small drones Nishant Elkunchwar, Suvesha Chandrasekaran, Vikram Iyer and Sawyer B. Fuller
Department of Mechanical Engineering, University of Washington
[4] An Over-Actuated Multi-Rotor Aerial Vehicle with Unconstrained Attitude Angles and High Thrust Efficiencies Pengkang Yu, Yao Su , Matthew J. Gerber, Lecheng Ruan and Tsu-Chin Tsao
[6] A Computationally Efficient Moving Horizon Estimator for Ultra-Wideband Localization on Small Quadrotors Sven Pfeiffer, Christophe de Wagter and Guido C.H.E. de Croon
[9] micROS.BT: An Event-Driven Behavior Tree Framework for Swarm Robots Yunlong Wu, Jinghua Li, Huadong Dai, Xiaodong Yi, Yanzhen Wang and Xuejun Yang
Artificial Intelligence Research Center, National Innovation Institute of Defense Technology, Beijing
[10] Neural Tree Expansion for Multi-Robot Planning in Non-Cooperative Environments Benjamin Riviere, Wolfgang Honig, Matthew Anderson and Soon-Jo Chung
[11] Trust your supervisor: quadrotor obstacle avoidance using controlled invariant sets Luigi Pannocchi, Tzanis Anevlavis, Paulo Tabuada
University of California, Los Angeles
[12] Continuous-time Gaussian Process Trajectory Generation for Multi-robot Formation via Probabilistic Inference Shuang Guo , Bo Liu , Shen Zhan , Jifeng Guo and Changhong Wang
Harbin institute of Technology
[13] Non-Prehensile Manipulation of Cuboid Objects Using a Catenary Robot Gustavo A. Cardona , Diego S. D’Antonio , Cristian-Ioan Vasile and David Saldana
Hello everyone, my name is Rik and I’m Bitcraze’s new intern. I took up this internship as part of my MSc studies at the faculty of Aerospace Engineering at the Delft University of Technology. Over the past year I have worked with the AI-deck as part of my thesis work at the MAVLab, and I’m looking to contribute to Bitcraze with my practical knowledge of the platform.
For my MSc thesis I have primarily worked on the design of very small optical flow CNNs, capable of running on the GAP8 SoC, using a neural architecture search (NAS). I have implemented a pipeline on the AI-deck, feeding a stream of camera images into the CNN to determine optical flow on-board. One of the last remaining goals of my thesis work is to design an application which utilizes the resulting dense optical flow. In the meantime, the NAS is ever running to find the best possible architecture.
Image 1
Image 2
Optical flow color coding
Resulting optical flow
On-board optical flow estimation on the AI-deck. A copy of The Hitchhiker’s Guide to the Galaxy, a DS-2Turbo Distortion guitar effects pedal, and a water bottle that moves in the top-left direction between image captures.
With my practical knowledge I hope to contribute to making the AI-deck an easier platform to work with. Of course, working at Bitcraze is a great learning opportunity, too. I’m already learning a lot about embedded systems and programming. After several years of studying, it’s great to get my first relevant working experience. And maybe most important of all, so far it has been a lot of fun working at Bitcraze and I expect to have a lot more of it. And yes, the falafel is really good.
The AI-decks are back in stock! Also, last week we had our quarterly meeting, where we plan our focus for the next quarter. As it is also the start of the fiscal year, we also take this opportunity to update our 1 year and 3 year plans as well. We have a big plans coming up, but one of the important focuses that we will have this year, is to get the AI-deck out of early-access!
But what would be necessary for such a task? The AI-deck is one of the most complicated boards we have worked with, so do we have to evaluate its ‘out-of-readiness’ along the same standards than any of our other products.
Mega AIdeck Tutorial
So one of our idea is to be able to achieve a state of the AIdeck in order to write a mega AIdeck tutorial series. This implies that we are able to show how somebody could go from a datasets all the way to a flying aideck-crazyflie combo. Such a series could consist of the following topics:
How to go from a dataset of images to a (Deep) Neural Network
Testing the DNN on the computer with the Image WiFi examples
Converting the neural network to Tensorflow Light (with basics on Edge AI and quantizing neural networks)
AIdeck basics (How to access the camera, how to add the network to the cluster, how to send commands)
Build and flashing the AIdeck and testing it out in the hand
Attach the AIdeck to the crazyflie, make an app-layer application to fly and react on the image input.
From the first look of it, this sounds like it should be easy to do right? Actually, there are still much to be done in order to make this tutorial possible.
Replumbing the Communication
One of the more challenging aspects of the AIdeck as it now is, is that users need to buy a JTAG-enabled programmer in order to flash the GAP8 and the NINA module of the AI-deck. That is the reason why currently the AIdeck has these 2 x 10 pin jtag connectors attached, but ideally we would want to get rid of it completely. This means is that we need to have over air flashing of the GAP8’s binary and that the intercommunication of the NINA and AIdeck will become even more important.
Moreover, the communication protocol from the GAP8 to the STM32 of the Crazyflie is currently very basic, as of right now, it is only possible to send single characters. It might work in some situations, but what if you would like to send an array of values back to the Crazyflie, like the collision probability & steering angle like in PULP platform’s implementation of Dronet? And, would we like to keep on using two UART serial ports or perhaps just relay both NINA and GAP8 communication all through one? The later will make it easier for us to maintain the crazyflie-aideck communication but can perhaps introduce communication delays.
These are just a slice of the type of re-plumbing work for the AIdeck before we can even start our dream tutorial series, but at least it will give you an idea of what we are dealing with :)
Rik the Intern
From this week we have the honor of hosting Rik Bouwmeester for a couple of months. He is currently doing his Master Thesis at the MAVlab from the faculty of Aerospace Engineering of the TU Delft. Since he has experience of working the AIdeck before, he will be able to provide us with some user perspective and help us with the above mentioned issues. You can expect a blogpost from him soon!
The Crazyflie firmware is the result of a lot of engineering (Making It Work) effort over a long period of time, the first commit in the GitHub repository is from 2013.
There are issues, inconsistencies and pain points in our firmware that have been found along the way, things that are difficult to fix because they have, in some sense, become load-bearing.
An examples of an issue like this is our inconsistency in what units are used in the Crazyflie firmware, we would like to use SI units everywhere but today that is not the case. And converting everything is proving to be tough.
We would like to fix all of these, but, the problem is that we have APIs to consider. There are programs written that assume that the data received from the Crazyflie is in a certain way. If we were to switch to the, more correct, aerospace axes these programs might break. And worse, they might break silently, meaning there will be no error message.
Our APIs constitute some kind of promise between the Crazyflie ecosystem (firmware, python library, documentation) and our users.
Examples include the parameter- and logging API which today has ideas about which way the coordinate system points and what units are used for values. As well as the Commander Framework / API, since this API has opinions regarding what way X, Y or Z grows in relation to reality.
Our APIs exists both between the Crazyflie firmware and our Python library code and between our Python library code and our users programs, as visualized in the diagram below.
If we were to implement solutions to the known issues we need to take these API into consideration. There are applications, demos, scripts and research code out there that rely on these APIs to behave a certain way.
So what can we do? What are our options? We have tried to enumerate them below.
1. Go Ahead And Change Units and Coordinates – But Do Not Update APIs
We fix as much as we can of the unit, correctness and conventions bugs in the firmware, but we leave the APIs as they are. This means that we keep the name of the parameter- and logging variables and we keep the name of all Python classes and functions. This is the less amount of work, it only needs updates to the crazyflie-firmware repository.
All examples and programs will continue to run. But they might now operate under false pretenses, perhaps with no error messages. The programs might stop working because of the implicit change of API.
We will have to communicate loud and clear that this will happen beforehand.
2. Go Ahead And Change Units and Coordinates – And Update the APIs
We fix as much as we can of the unit, correctness and conventions bugs in the firmware, and we also rework our APIs! We will gather learnings from our years with the current CRTP and Python API and we update them to be more developer ergonomic as well as update the parameter- and logging variables to be more consistent in naming and SI units.
A big benefit of this would be that we are then open to change where the boundaries for our API lies, what we provide as libraries and what is applications responsibility. And we can address pain points that are deep and structural to todays APIs.
This will break all existing programs out there, they will no longer run. They will get error messages and will need to be updated to the new APIs. We might also get weird issues and scenarios where old library code try to interface with newer firmware. We could create policys on for how long we maintain the old API and try to have them side-by-side for a bit.
3. Go Ahead And Change Units and Coordinates – Keep Old API Forever and Add a New One
We fix as much as we can of the unit, correctness and conventions bugs in the firmware, and we also rework our APIs! We will gather learnings from our years with the current CRTP and Python API and we update them to be more developer ergonomic as well as update the parameter- and logging variables to be more consistent in naming and SI units. And! We will also keep the old API as a legacy API.
It is unclear if this is possible, if we have enough memory in the firmware as well as enough bandwidth to maintain two APIs.
We could in theory keep all of the user-facing Python API and attempt to translate between the old and new one in Python code. This might take a lot of work and effort to do, but it might be possible.
But. Fixing all the correctness, convention and units in the firmware might make it very difficult to support both APIs. It might also limit how creative and how different a new API could be, while still being translatable to the old API.
We could also investigate if it would be possible to keep the API between the firmware and the libraries (CRTP and paramter- and logging variables) but translate to be more correct in regards to Units and Conventions in our library.
Even if this was deemed possible it would not help anyone developing directly against the firmware, without using a Bitcraze library.
4. Do Not Change Units and Coordinates – Keep Old API
Accept that the crazyflie-firmware will not reach correctness in respect to units and conventions and close the issues above. We can make sure all new features going in respect SI units and convention, but consider what we have as a legacy. This is by far the one that requires the less work. zero. But it will keep the pain points and inconsistencies of the Crazyflie platform.
Conclusions
There are trade offs between all solutions. We need to decide what our current APIs are worth to us. And how painful it would be for our users to handle an API break.
Maintaining multiple APIs might be to big of an burden for both us and our code base though. This is very very tricky.
It would help us a lot to hear from our users!
If you are someone who develops or have developed against the Crazyflie ecosystem please get in touch, we have created an GitHub issue here. Tell us if you have hit any of the pain-points described in this post or how an API break would affect you.
As you maybe remember, we decided to celebrate our 10 years anniversary with our very own conference. It’s going to be 3 days of online meeting, sharing and generally awesome meetups to connect, learn, and hopefully develop new knowledges and acquaintances.
We are working hard on creating the best experience possible for you ! The program is still only a skeleton with some very interesting bones, and we add more and more flesh to it as the dates grow nearer.
As you can see from the program below, each day is organized around a global theme. Let’s break them down:
The first day, Tuesday, is going to be dedicated to navigation systems. Guest speakers Klaus Kefferputz from Hochscule Auburg and Joseph La Delfa (the man behind Drone Chi). will each talk about how they use positioning systems, in two very different ways. We’ll also have a workshop about the different positioning systems we support, to get into the more nitty gritty side of things.
The next day, we’ll talk about the AI deck ! Our collaborators at PULP-platform and Greenwaves Technologies are the perfect guests to talk about our newest deck. The talks will be followed by a workshop about app layers and a general panel discussion about Bitcraze – and more particularly its future. We want to hear from you, so don’t hesitate to join us as we try to determine a way forward (for the next 10 years, we have some ideas but we’re curious what you think)!
And finally, the last day will revolve around swarms. It’s Wolfgang‘s specialization, so he is of course the first guest we turned to. Bart Duisterhof and Guido de Croon from Delft University of Technology will also talk about their autonomous swarm, (they are the team behind the sniffy bug!). A swarm workshop will follow, and we will close the conference with some fun surprises!
We’re really excited and lucky to welcome all those speakers to talk about drone development. The program is not entirely fixed yet, some surprise guests should turn up. You can also still add your input by filling out this short survey.
And last, but not least : you can register to the event here on EventBrite. You will be able to add it to your calendar and finally mark the dates ! Also checkout the BAM days event page occasionally for updates.
On September, 1st of 2011, Arnaud, Marcus and Tobias signed a paper in Lund registering their brand-new company: Bitcraze. We’re here, now, 10 years later, hardly believing this gamble paid off so greatly.
Bitcraze’s story actually begins in 2009, when the 3 met in their day job and started dreaming about what will become the Crazyflie. For a long time, they combined a 9-to-5 job with the development of the nanodrone. Monday meetings run from the end of the workday until 2am, and they were exhausted, but the hard work paid off when we know now how many Crazyflies took off after that!
Some things have been added since 2011, of course! For starters, 4 more people joined the team, each changing the face of the company, making it evolve. Lean and self-organized was the way to go, the more people there was. The product itself changed and grew: from the first batch of Crazyflies, that had to be soldered out of the box, we’re now at the 2.1 version. And as years flew by, Bitcraze added to its backpack with new decks and extensions, always wanting to test new things and generally make awesome stuff. From its first flight, we’re now at impressive autonomous swarm flights!
The Crazyflie celebrating its first year in 2012! (and yes, it flew with the candle on it)
In 10 years, we’ve also done things we would never have thought of. Did you know Marcus gave a 15 minutes speech at a conference … entirely in French ? Or that 3 different employees got a cut on their finger for the exact same reason (we’ll let you guess why!) ? We’re still amazed at how much we discovered, learned and shared in those 10 years.
For us, it’s a special moment, looking back at 10 years of awesome things, of hard work, and of passion. We plan on celebrating, of course! First with a few days’ getaway, the first occasion we’ve had in a while to be actually together and enjoy. But this milestone would not be happening without all the support of those around us: our family and friends of course, but also our contributors and our customers. That’s why we’ve decided to organize our own conference, to gather everyone for awesome days of meetup and celebrate with you!
Keep an eye out on our social media too, as this September we’ll look back a little down the road. We’ll post some fond memories (and maybe, just maybe, some embarrassing photos too!) and see how much we’ve accomplished in 10 years.
Previously we have been using off the shelf scales and other methods to measure characteristics, such as thrust or efficiency, of the Crazyflie products. We thought it was time to build something that is easier to use, more repeatable and tailored to our needs. Well, this has been on our wanted list for a long time, already back from when we did the RPM-deck. It was however first when Wolfgang visited us this winter that he nudged us over the edge so we finally allocated some time for it. We started off by buying some load cells and breakout boards to do something simple as a start, so we could at least measure thrust more easily. We actually started looking for off the shelf thrust stands but could not find anything suitable for the Crazyflie’s size. As is often the case here at Bitcraze, the project grew. Already before we had any load cells up and running I was designing a deck with RPM sensors, load cell amplifier and power meter. Now with the objective to easily do system identification. Therefor we named the deck the system-id deck.
For the RPM sensors we used the same as on the RPM-deck, the QRD1114. They are not great as they need a reflective surface, this means adding white stickers or paint to black propellers, but they work well enough. The load cell amplifiers ended up to be the NAU7802 as it has a high accuracy and sample rate. For power metering we chose the new ACS37800 power monitoring IC that can handle up to 30A, this looked exiting.
The QRD1114 we wired the same way as previously done on the RPM-deck:
The NAU7802 was configured as per the datasheet suggestion and similarly to other open designs out there:
The ACS37800 was very new so the datasheet had to be used as the main information source. A bit tricky as this chip is mainly intended to measure mains supply, and we wanted to measure low voltage DC, which it said it could do…and in the end we managed to get it working.
We also added a buck/boost DC/DC that could provide a stable 3.3V from 2-5V input, just in case, as the ACS37800 is specified for this voltage and not the 3.0V the Crazyflie can supply.
The outcome
The PCB was designed as small as possible so it could be mounted on a Crazyflie 2.X and used while flying. A bonus would be if it could be used on a Bolt as well.
Here it is mounted on a Crazyflie 2.1 together with a 3D printed stand and load cell.
The load cell would then be mounted to a desk or similar so the the Crazyflie is mounted up-side down, pushing down on the load cell.
Software
The software, as often, took most of the time to make. Three major deck driver files was created, rpm.c, acs37800.c and loadcell_nau7802.c. Aside from these there where only small changes to make, like making it work when being up-side-down. The modifications have all been pushed to the dev-systemid branch for those that are interested. As for now we are mainly using the logging framework to transfer the data to the PC, which is quick and easy to setup and use, but writing to SD-card is also possible. The scripts for this can be found in the tools/sytem_id folder.
Remaining work is to test, gather and analyse more data. When we have done so, we will post more. Until then below is a sample of what it can measure. The data is taken with a ramping PWM from 0% – 100% – 0%. The added resistance of the extra wires and connectors are not taken into account, but the estimated efficiency of 4g/W is probably not that far off.
