Category: Electronic

During the fall we did two blog-posts (12) about a new prototype named Obstacle Avoidance/SLAM deck, but since then it’s been a bit quiet about it. So we thought it was due for an update! First of all, after a lot of discussions, we decided to rename the deck to Multi-ranger. It better describes what the board does and matches the naming of the Z-ranger. We’ve sent out some samples to customers and so far the response has been great. So we’re pushing forward and preparing for production that’s estimated to begin in March. Below is a picture of the latest prototype.

The biggest change for the final prototype is adding a LDO regulator to power the sensors. We’ve seen that depending on the settings for the sensors they might consume a lot more than when we initially tested. Using the same settings as for the Z-ranger brings the consumption to 90 mA, which together with the Crazyflie 2.0 electronics, comes close to filling the power budget for the Crazyflie 2.0 VCC LDO regulator. Aside from that we’re making some minor changes to simplify production and testing.

We’ll keep you updated on the progress!

It is now the first day in 2018 and a good day to look back at 2017. Its been a busy year as always and we have had a lot of fun during the year. One of the first things popping up is that things takes so much longer then we think. Luckily we are working with open source and the progression is not only dependent on us as we have awesome help from the community. We are already really excited about what’s coming in 2018, looking forward to working together with so many great people!  


The Crazyflie 2.0 is still gaining attention and are becoming more and more popular among universities around the world. We see interest from researchers working with autonomous systems, control theory, multi-agent systems, swarm flight, robotics and all kinds of research fields, which is really great. This means that a lot of exciting work have been contributed by the community, so here is a small summary of what has happened in the community during the year.

In the beginning of the year the Multi-Agent Autonomous Systems Lab at Intel Labs shared how the Crazyflie 2.0 is used in their research for trajectory planning in cluttered environments. We wrote a blog post about this if you want learn more about their work. The Crazyflie showed up on the catwalk of Berlin Fashion week being part of fashion designer Maartje Dijkstras futuristic creation TranSwarm Entities”, a dress made out of 3D prints accompanied by autonomously flying Crazyflies.

For the third year Bitcraze visited Fosdem. We had a good time and got to hang out with community members like Fred how did a great presentation about what’s new in the Crazyflie galaxy. During the conference we took the opportunity to present the Loco positioning system and demo autonomous flight with the Crazyflie controlled by the Loco positioning system. In the demo we flew with the non-linear controller from Mike Hammer using trajectory generation from Marcus Greiff

We have had a few interesting blog post contributions during the year from major universities. Including a guest post written by researchers at Carnegie Mellon University. The researchers are using the Crazyflie 2.0 drone to create an adaptive multi-robot system. Similar work has been done by the researchers at the Computer Science and Artificial Intelligence Lab at MIT were they have been studying coordination of multiple robots, developing multi-robot path planning for a swarm of robots that can both fly and drive.

We have also had two interesting guest blog post from the GRASP Laboratory at University of Pennsylvania, the “A Flying Gripper based on Modular Robots” and “ModQuad – Self-Assemble Flying Structures“. Inspired by swarm behavior in nature, for instance how ants solve collective tasks, both projects explore the possibilities of how multiple Crazyflies can work together to perform different missions.

During the fall Fred took the time to pay us a visit at the office in Sweden and worked together with us. He is making great progress on the Java Crazyflie lib that is going to be used in the Android client as well as in PC clients. It will allow to connect and use a Crazyflie from any Java program, there has already been some successful experimentation done using it from Processing

Some other great news is that thanks to Sean Kelly the Crazyflie 2.0 is now officially supported by the Betaflight flight controller firmware. Betaflight is a flight controller firmware used a lot in the FPV and drone racing community.

Thanks to denis on the forum, there is now support for Crazyflie 2.0 in the PX4 flight controller firmware. PX4 is a comprehensive flight controller firmware used in research and by the industry.

Finally The Crazyswarm project, by Wolfgang Hoenig and James A. Preiss from USC ACTlab has been presented at ICRA 2017. It is a framework that allows to fly swarms of Crazyflie 2.0 using a motion capture system.  There is currently some work done on merging the Crazyswarm project into the Crazyflie master branch, this will make it even easier to fly a swarm of Crazyflie. In the meantime the project is well documented and can be used by anyone that has a couple of Crazyflies and a motion capture system.


During 2017 we released four new products. Beginning with the Micro SD-card deck which e.g. makes high speed logging possible. Then the Z-ranger that enables a height hold flight mode up to 1m above ground. We like to call it drone surfing as that is very much what it feels like when flying. We ended by releasing two boards, Flow deck and Flow breakout, in collaboration with Pixart containing their new PMW3901 optical flow sensor. The Flow deck enables scriptable flight which is very exiting. That lead us to release the STEM drone bundle which we hope will inspire people to learn more about flying robotics.

Hardware prototypes, our favorite sub-category, are something we have plenty of lying around here at the office. To name a few, a possible Crazyradio 2, the Loco positioning tag, the Crazyflie RZR, the Glow deck or Obstacle avoidance/SLAM deck. It takes a long time making a finished product… Hopefully we will see more of these during 2018!


At the same time we released the Flow deck we also released the latest official Crazyflie 2.0 FW and client (2017.06). This enables autonomous capabilities as soon as the Flow deck is inserted by automatically turning on the corresponding functionality. Just before that, the loco positioning was brought out of early access with improved documentation and simplified setup. Since then a lot of work has been put into making a release of TDoA and improving overall easy of use. With the TDoA2 and automatic anchor estimation starting to work pretty well we should not be far from a new official release!

We would like to end 2017 with a big thank you to our users and community with this compilation video. Make sure to pump up the volume!

video link

We’ve been seeing an increase in the demand for a “programmable drone”, where users can easily give simple commands though scripting and the Crazyflie 2.0 following them. In order for this to work well you need a closed-loop control, i.e you need a reference system to see how you’re moving. Previously this was only possible using external camera systems or bulky on-board cameras. But a while ago we released the Flow deck which solves this problem. Thanks to the mouse-like sensor the deck contains it enables the Crazyflie 2.0 to see how it’s moving along the floor. Suddenly it’s possible to give commands like “move 1 m forward” or “fly in a clock wise circle with the radius of 1 m”.

To make it easier for users to pick out the parts needed we’ve put together a discounted STEM drone bundle. It contains all the parts needed for scripting the flight. If you have a gamed-pad or a Bluetooth LE enabled phone you can of course fly it manually as well :-)

To quickly get up and running, we have written a getting started guide. There is also a great hackster project, Beginner’s Guide to Autonomous Quadcopters by community member Chathuranga Liyanage, containing more details.

So we are now back in the cold and dark Sweden after about a weeks visit to a warm and nice Shenzhen, China. Every time we go there something major has happened. When we visited last time, about a year ago, cash was king. Now apparently payments are done with QR codes, even in small lunch restaurants. And I was kind of proud about the BankID and Swish payments we have here is Sweden, until now… Another observation we did was that there are now a lot of colorful rental bikes which can be found about everywhere and which can be rented for around 1 RMB/hour. A great way of resource sharing and pushing Eco-friendly transportation. It has it downside though as piles of bikes could be commonly found and e.g. written about by theguardian.

Aside from the above observations the Maker Faire Shenzhen was one of the reasons we came to visit. As Shenzhen is called the “the silicon valley for hardware” we had pretty high expectations when coming to the Maker Faire. Even though it was a great Faire it did not really reach our high expectations but it is growing fast and I’m pretty sure in a couple of years it is the Maker Faire to be at. A quick summarize, robotics was one of the top categories of products on the faire. 3D printers which are popular on European and US faires was not that common which surprised us. Now let the pictures do the talking:


We exhibited on the faire sharing booth with Seeedstudio where we showed an autonomous sequence on top of a table using the flow deck. By pressing a button, the Crazyflie 2.0 would take of, fly in a circle, come back and land roughly in the same spot. It was a very engaging demo catching many peoples attention and especially the kids. The kids constantly wanted to press the button and interact with the Crazyflie.

All the interaction made us very happy and next time we will try to add the obstacle avoidance deck to make it even more engaging.


Unfortunately the Crazyradio PA is out of stock in our store and is estimated back around December 1. Until then please checkout our distributors for availability.


A few weeks ago we wrote about a new prototype that we call “the obstacle avoidance deck”. Basically it’s a deck fitted with multiple VL53L0x ToF distance sensors that measures the distance front/back, right/left and up of the Crazyflie 2.0. Combined with the Flow deck this gives you an X/Y/Z robot that you can program fly around avoiding obstacles which doesn’t need any external positioning system.

After implementing firmware support for the deck (see #253 and #254) we’ve finally had a chance to do some initial testing, see the video below. In the current implementation we’re doing the measurements in the firmware but using the logging framework to get all the distances into a Python script which does the movement control. Since we have the Flow deck attached we can control the Crazyflie 2.0 in velocity mode, which means we can say things like “Go forward with 0.5 m/s until the forward sensor shows a distance lower than 50cm” or “Go forward 1 m/s for 1s and rotate to measure the distance to all objects”. Since there’s no real-time requirements we can move the complexity of the algorithm from the firmware into external scripting which makes it a lot easier to develop. Now we’re really eager to start setting up obstacle courses and time how fast we can move though them :-)

The results from the testing shows that our two main concerns aren’t an issue: The sensors doesn’t seem to interfere with each other and we can sample them all at high-enough frequency without occupying the bus too heavily (currently we’re doing 20Hz). The next step is figuring out the requirements (i.e how many VL53L0x sensors are needed, do we really need the back one?) and a mechanical solution for attaching the sensors in production. If there’s any feedback let us know now and we’ll try to get it into the design. Also, we really need a new name for the board. Any suggestions?

A long time ago we got a request for a bright LED deck from a community member. When working with high powered leds heat becomes a problem that needs to be taken into account. From the community member we got suggestions of using one of the luxeon rebel leds and so we did. We designed a prototype pretty quickly but also realized that it is a bit harder than we first thought. If using a simple control scheme such as PWM and a mosfet the circuit is simple but brightness will be effected by battery voltage. Using a dedicated LED driver the brightness would be stable but the circuit more complicated and expensive. Trying to list the pros and cons:

+ Low complexity
+ Low cost
+ High efficiency
– varying brightness depending on battery voltage
– Might stress LED (could be solved with low ohm resistor)

LED driver
+ Stable brightness
+ Not as high efficiency (~80%)
– Higher cost
– Higher complexity

We ended up trying booth. The LED driver design failed due to that the battery voltage needed to be lower than the LED voltage + schottky and it is just in the middle. The PWM design half failed since the LED anode and cathode was swapped in the design but was possible to patch afterward. So at least we got something up and running.

The effect is very nice and it is what we used for the wedding show. The question now is, is this something we should finish and put in the store?

At any given time we have a bunch of deck ideas floating around. Some of them might not be doable (or very hard), but still fun to discuss. Other we just never get around to since we’re always pressed for time. The “obstacle avoidance” deck is one of the latter ones.

The idea with the “obstacle avoidance” deck (current working name in lack of imagination) is to mount one of the VL53L0x ToF distance sensors, the same we have on the Z-ranger and the Flow deck, in each direction. This would allow you to keep a distance to the ground, avoid the walls (or any other obstacles you might fly into) and also keep away from the ceiling. Basically you could do a “turtle bot” that just flies around randomly without crashing. Another fun idea we’ve been discussing is being able to SLAM the room you’re flying in. If you can keep track of how you are moving around (with the Flow deck, Loco positioning system or any other means) while you’re measuring the distance on all sides you could make a map of the room.

After discussing this on and off for a some time, mainly focusing on mechanical and production issues of the design, we decided to just try out the concept with a simple prototype. The prototype, named “OA”, has daughter boards with VL53L0x sensors mounted front/back, left/right as well as one sensor facing up. It’s designed to be mounted on the top of the Crazyflie 2.0 and combined with the Flow deck which will give relative movement and also the sixth direction, distance to the floor. One of the issues with the design is that all the VL53L0x sensors are on the same I2C bus with the same address. To work around this the sensor has a nifty feature where you can re-program the I2C address. For this to work you need to release the reset of the sensors one by one: release the first reset, reprogram the address and then release the reset of the next sensor. The reset for the VL53L0x is not cabled on the Flow deck, so this is the first to be re-programmed. Then the reset will be released one-by-one for the sensors on the OA deck. In order to control the reset pins on the deck there’s a 8bit I2C GPIO expander. The reason for the GPIO expander is to use as few GPIOs on the deck connector as possible to keep the compatibility with other decks high. For instance the deck will work fine with the Loco positioning deck.


The goal with the prototype is to try out the concept of the deck and to see if it’s feasible. A few of the things we need to sort out is:

  • Mechanical solution for side senors (front, back, left and right)
  • Interference between sensors
  • Update rate when we have 6 sensors on the same bus which we might have to run one-by-one to avoid interference

The current status is that we’ve verified the electronics and written the I2C GPIO expander drivers to test all the sensors. The next step is to work on a new VL53L0x driver to allow multiple sensors running at the same time, which will force some refactoring of the firmware.  Once we’ve made some more progress we’ll do another post and report the results. If you have any feedback on the design/concept or have any ideas of what the deck could be useful for, don’t hesitate to drop a comment below.

Last week we released the Flow deck, it enables you to get really stable autonomous flight with the Crazyflie without requiring an external positioning system. We have been lucky to get access to the brand new Pixart PMW3901 optical flow sensor, the core of the Flow deck, very early and we wanted to bring this awesome functionality to everyone, including those without a Crazyflie. The solution is the Flow breakout board, it enables anyone to use this new optical flow sensor for any kind of motion tracking.

The flow breakout contains a PMW3901 optical flow sensor and a VL53L0x time of flight ranging sensor, the same sensors that are mounted on the flow deck. We have also added voltage translation logic that allows you to use the flow breakout with a system voltage of 3 to 5V that makes it possible to use it directly with any Arduino board and most embedded system. Further more we have written an Arduino driver for the PMW3901 optical flow sensor to make it easy to use the breakout deck. For the VL53L0x there are already a couple of drivers available out there.

The flow breakout is currently being manufactured and will be available in our shop in a couple of weeks. If you want to be notified of the Flow breakout board availability, please sign up in the shop or follow us on twitter.

There have been a few requests from the community for a brushless Crazyflie and we blogged about a prototype we are working on a few weeks ago. The most common reason for wanting brushless motors is to be able to carry more load, in most cases a camera. A camera could be used for FPV flying or open up various image processing use cases like understanding the would around the drone using SLAM. Image processing on-board requires quite a lot of processing power and the CPU in the Crazyflie could not handle that, so more processing power would be required for a scenario like that. It is summer time (with a slight touch of play time) so we wanted to see what we could do with the CF Rzr and if it would be a useful platform for these types of applications. We hope that we might get some insights on the way as well.

We set the goal to try to add a camera, a small “computer”, the Flow deck for assisted flying, FPV capabilities and support for a standard RC controller.

We chose the Raspberry pi zero-w in order to get video processing and video streaming from the quad as well as more computing power. The Raspberry pi zero is not the most powerful board our there but it has a couple of advantage for our prototype:

  • It has a readily available, good quality camera and good software support for it
  • It has an analog video output and hardware streaming support, which means that the quad could be flown FPV using the Raspberry pi camera
  • It has hardware JPEG and H264 encoders that will enable us to save and stream images and videos if we want to

Raspberry pi and camera mounted on the top part of the frame

For assisted flight and improved stability, the XY-part of the Flow deck works fine outdoors but the laser height sensor on the deck has a maximum limit of 1-2 meters, and further more it does not go well with direct sunlight. We decided to add an ultrasound sonar distance sensor to measure the height instead. The ultrasound sonar connects via I2C and was simply soldered to a breakout deck that plugs into the CF Rzr.

Crazyflie Rzr with ultrasonic sonar, breakout deck and flow deck mounted on the lower part of the frame

The first step is to see if we can physically fit everything on the frame. With some 3D printed mounts for the camera and the Raspberry pi, we think it starts to look pretty good. Next step will be to squeeze in the FPV video transmitter board, the RC receiver board and finally connect everything together.

The current setup with everything mounted

We are far from done but it is a good start, and it is fun.

We are pleased to announce the release of a new expansion deck for Crazyflie 2.0: the Flow deck. The flow deck is a new expansion board for Crazyflie 2.0 that contains an optical flow sensor from Pixart and a ranging sensor. These two sensors allows the Crazyflie to understand how it is moving above the floor and using this information the Crazyflie can fly itself.

The Flow deck can be used for manual flight where it allows to super easily fly the Crazyflie: if you realease all joystick the Crazyflie just stays there and hovers! The flow deck is even more interesting when used in combination with scripting: it is now possible to script the Crazyflie movement to achieve autonomous flight without needing any external positioning system.

Link to video

The Flow deck is available in the Bitcraze shop and at Seeedstudio.