Category: Electronic

For a while now we have been selling the BigQuad deck which makes it possible to transform the CF2 to control a bigger sized drone. It does so by becoming the quadrotor control board, controlling external brushless motor controllers, which allows to scale up the size. This can be very convenient when trying out/developing new things as it first can be tested on the small CF2 and later scaled up by attaching it to a bigger quad. However for a more permanent setup it is a bit bulky, so we have been playing around a bit and designed something in the middle. The result is a stand alone control board targeting quads around 0.1 – 0.5kg.

We call it the CF-RZR as it is inspired by the smaller sized racers with some fundamental differences. It is designed with a higher level of autonomous functionality in mind and being easy to repair while still being fully compatible with the CF2 firmware and decks. Listing the biggest features of the current prototype:

  • Fully compatible with the CF2 firmware, expansion decks as well as radio.
  • Connectors to attach motor controllers (still possible to solder though) so it is easy to build and repair.
  • Power distributions built into controller board. (Max ~8A per motor controller though)
  • Motor controllers can be switched of by the system so the system can go into deep sleep and consume around 50uA.
  • Voltage input 1S-4S (3V to 17V)
  • Standard mounting (M3 mounting holes placed 30.5mm square)
  • External antenna for increased range

To summarize, the strength of the CF2 but in a little bit bigger package :-). Last week we got a chance to test fly it for the first time. We used a off the shelf racer frame, ESC and motors. At first it did not fly that well at all but after some PID tuning it became pretty stable and we had a lot of fun :-).

We would love your feedback, good/bad idea, what do you like/dislike etc!

Link to video

Ever since we released the Alpha round of the Loco positioning system we’ve been talking about designing a more generic tag that could be used together with other robotics platforms for local positioning. We did a quick design of a prototype that we tested, but with the workload involved in bringing the LPS out of Early Access, finishing the Z-ranger and lots of other stuff , it’s remained on the shelf. But recently we’ve been getting more and more requests for this kind of hardware, so we thought it might be time to dust off the prototype and try to release it. One of the blockers (except workload) has been that we’re not sure how the tag should look mechanically and how to interface it electrically for it to be as useful as possible for our community. This post is for detailing the current status of the hardware/firmware and to see if we can get some feedback on what our community would like the finished product to look like.

The hardware

To make use of the firmware that’s been developed so far for the Crazyflie and the Loco positioning we aimed at making something similar to what we already have but with another form factor and slightly different requirements. As you might know the Loco positioning node can be configured as a tag, but there’s two drawbacks that we wanted to fix. First of all the Loco positioning node might be a bit big to put on smaller robots. Secondly the Loco positioning node can only measure the distances to the anchors, it doesn’t have an IMU to get attitude of the board and doesn’t have the processing power to run the same algorithms we have on the Crazyflie 2.0.

So for our Loco positioning tag prototype we decided to fix these. The prototype has the same sensors as the Crazyflie 2.0: Gyro, accelerometer, magnetometer and pressure sensor. It also has the same MCU as the Crazyflie 2.0: STM32F405. In addition to this it has the DWM1000 module for the ultra wide-band radio (used for positioning). We’ve also added the interfaces we have on the Crazyflie 2.0: SWD debugging, micro-USB for communication and power as well as a button. Looking at the pictures below you might also notice that we’ve added the Crazyflie 2.0 deck connector. So does this mean you can connect it to the Crazyflie 2.0? No, well not this prototype at least. The reason for adding it was we wanted to be able to use the same expansion decks as for the Crazyflie 2.0. So it’s possible to add the breakout deck for breadboard prototyping or the LED-ring for visual feedback.

So what’s the status of the hardware? Even though it’s the first prototype it’s fully functional and will give you positioning and attitude. What’s left is defining the electrical interfaces and the form-factor of the board so it can easily be attached to what ever you might want to track. The images below shows a side-by-side comparison with the current Loco positioning deck.

Loco positioning tag (on the right) compared to Loco positioning deck (on the left) (FRONT)

Loco positioning tag (on the right) compared to Loco positioning deck (on the left) (BACK)

The firmware/software

Like I wrote above we wanted to reuse as much of the firmware and software as possible. So the firmware running on the prototype is just a scaled down version of the Crazyflie 2.0 firmware. As you might have noticed the prototype looks a lot like the Crazyflie 2.0, except that it’s not a quadcopter and doesn’t have the nRF51 radio. So by “scaled down” I mean we’ve removed the motor and radio drivers, that’s about it. So how do you communicate with it? Well you can use one of the protocol available on the deck connector: SPI, I2C or UART. But the currently implemented way is using USB. Since it’s basically a Crazyflie you can use our client and python libraries to set parameters and log data values from it.


The current prototype is basically a USB dongle where you get position and attitude. It could easily be connected via USB to a Raspberry Pi, Beaglebone or any other SoC based platform or a computer. You can also interface it from an Arduino using the peripherals on the deck connector. The firmware is working and using the python library (or any other of our community supported libraries) you can easily get the position and attitude of the board. But to be able to take the next step and make something our community could make the most of we would love some feedback on the prototype. What kind of electrical interfaces and form-factor would you like?

The past

The Crazyradio has been designed as a radio dongle to control the original Crazyflie 1. It is based on a Nordic Semiconductor nRF24LU1. It is basically the radio from Crazyflie 1, the nRF24L01, with a microcontroller and a USB device peripheral. Crazyradio has been designed from the beginning to be extended for other used: the code is completely open-source, can be powered with 12V and has an expansion port with possibility of implementing a serial port to communicate with the radio.

When we designed Crazyflie 2.0, we extended Crazyradio to make Crazyradio PA. It is basically the same hardware but we just added a power amplifier to make sure Crazyradio is transmitting with the same power as competing radio in the same 2.4GHz band: Wifi and Bluetooth. Crazyflie 2.0 is not using an nRF24 chip anymore but an nRF51822 which integrates a microcontroller and implements bluetooth low energy as well as nRF24 compatible radio.


The present

The Crazyradio (PA) has been used for a couple of hack like our glove controller. Another popular use has been by security researcher to experiment with the security of wireless mouse and keyboard. Indeed the nRF24 serie of chip is extensively used in wireless mouse, keyboard and even quadcopters ;).

We are often very quiet about the Crazyradio since ‘it just works’. It does not means that it is finished or perfect, there is actually a lot that was planned to make the radio link more efficient, to be able to control more Crazyflie per Crazyradio, etc… Some of this work has been done in the context of the Crazyswarm project by Wolfgang from USC but a lot more could be done. One of the main blockers for Crazyradio development is that it is based on a very old microcontroller, an 8051, and that it does not have a safe bootloader or (open) debugging access. It means that each modification is potentially a big commitment in time and since the radio already work quite well it is hard to put much time in it.

The absence of a safe bootloader means that if you flash a firmware that crashes, you will need an SPI programmer to recover the radio in working mode. This makes it quite stressful to work with the radio. However there are a couple of programmers made for this and we recently published a Hackster project about using a Raspberry Pi to recover the bootloader:

The future

We have been looking at making a Crazyradio with an nRF51-series chip, these chips have a Cortex-M0 CPU which means that they are much easier to program using a modern development environment. However none of the chip in the nRF51 series have USB which forced us to prototype the concept with an added microcontroller for USB. This creates a bigger and more populated Crazyradio:

We did not like this design very much since having 2 microcontrollers is always much more haste to program, debug and maintain. Thankfully Nordic semiconductor will release a nRF52 chip with USB support. Adding to that a powerful Cortex-M4 microcontroller, a lot of ram, still Bluetooth low energy and nRF24 radio compatibility but they also added iEEE802.15.4 2.4GHz (ie. the protocol used by Zigbee). This new chip is a very good candidate for the next Crazyradio.

We are very much in the pre-study phase for the next Crazyradio (and mass production for the new nRF52 is planned for Q4 2017 anyway…), so if there is functionality that you would like to see in a future Crazyradio it is time to speak up! Please tell us in the comment section bellow or in the forum ;-).

For those of you out there that are new to flying drones the height is often the most difficult thing to control. One solution to that problem is our newly released Z-ranger deck that can precisely measure the distance to the ground. Using this information the drone itself can stabilize on a desired target high and therefore become much easier to control. The Crazyflie 2.0 will then behave similar to a hovercraft sweeping over the ground or climbing stairs which is a ton of fun. As an in-action example please check out the video below where a Crazyfie 2.0 with a Z-ranger e.g. follows a flight of stairs :-).

For information of how to activate the height hold mode have a look at the getting started guide and for further details please check out the Z-ranger wiki page.

In this beginning of 2017 we are proud to announce that there are two new decks for the Crazyflie 2.0.

The first one has been in the works for quite some time, it is the Micro SD card deck. It enables read and write access to a SD-Card from the Crazyflie firmware (where we have also implemented FAT filesystem support). Our first use case for this deck has been to implement high speed logging of the IMU sensors: the SD-Card has much higher bandwidth than the radio so it allowed us to log all the sensor values for later analysis. Another use-case could be to read an autonomous sequence from a file on the SD-Card and implement fully autonomous sequencing in the Crazyflie when used in the Loco Positioning System for example. The SD-Card deck is already available on Bitcraze web-shop.

The Second deck is the Z-Ranger deck, it is a laser time-of-flight ranging deck that measures the distance to the ground. We talked about this deck in a previous post. The manufacturing of the deck should be finished soon and so it will be available in our shop shortly. When using this new deck, the altitude hold stability between 0 and 1.5 to 2m height is greatly improved.

On a final note, FOSDEM 2017 is this coming up this weekend and we are looking forward to meet you there. There will be two presentations related to the Crazyflie, if you want to meet us come at these presentations or get in touch in the comment or by mail. The two presentations are:

We hope to see you there!

At FOSDEM 2016 we met someone from Bosch Sensortec, he was very interested by the Crazyflie and got one. Apparently his college liked the Crazyflie too because soon later we where contacted by Bosch that wanted to make a deck for the Crazyflie containing a brunch of there sensor. We have been tweeting about this board before and now we just pushed the drivers for some of the sensors into the Crazyflie main branch.

The deck has an impressive list of sensor onboard:

  • BMI055: 6 Axis gyro and accelerometer, with closed loop technology gyroscope
  • BMI160: 6 Axis gyro and accelerometer
  • BMM150: 3 Axis magnetometer
  • BMP285: Pressure sensor
  • BME680: Environmental sensor (air, pressure, humidity, temperature).

Thats a lot of data, and there is also an non-populated footprint for a BMF055 which is a BMI055 and an Atmel ARM Cortex-M0 in the same package, this is something that could be very interesting to play with in the future. The drivers and the integration are still in early stage but what has been pushed so far is support for the BMI055 and BMI160. We look forward to tuning those sensors and testing the others as well!

Bosch has made most of the work with this deck them selves and we have provided mainly guidance and support, a big benefit of open source! That has been working great and it has been very fun working with them. We are not sure if this is going to be part of a product yet, as in releasing a deck full of sensors. Please tell us what you think and if anyone would have use for such deck.

Most of the time we have a few prototypes lying around that we’re working more or less on. Sometimes some of these make it into a product if we feel that they might be useful or fun for the community, like for instance the SD-card. Now it’s time for another prototype to be moved to manufacturing, a deck with VL53L0x laser ToF distance sensor.

On the Crazyflie 2.0 (and Crazyflie 1.0 10-DOF) we have a pressure sensor mounted to help control the altitude of the platform. Since air pressure is moving around a lot and the measurement is noisy it’s been very hard to get a rock-solid altitude hold working (although it’s getting closer). Already back when ST released the VL6180X we were looking at it, but the range was too short (10cm max). So when ST released the VL53L0x which has longer range (200cm max) we though this might be a good deck for the Crazyflie 2.0.

So we have a working prototype and thanks to stephanbro and Marcus Grieff we also have the firmware to use it with the Kalman filter. We are currently working at making it work together with the pressure sensor with the current altitude-hold mode.

Currently we’re working on verifying the hardware to make sure the power supply is good enough for it, but then the next step is production. Hopefully it will be available in a couple of months 🙂 Below is a picture of the current prototype.


The logging subsystem of the Crazyflie 2.0 is fairly flexible and easy to use, but despite its nice properties it may still be limiting in some scenarios. Two areas where it is lacking are offline- and high-speed logging. As a step towards solving these problems we are happy to announce support for micro SD-cards in the Crazyflie 2.0 firmware.


We have had a prototype for a micro SD-card expansion deck lying around in the office for a long time but have not had time to write any code for it. Finally we decided to go ahead an fix it and now there is a first basic version in the master branch of the firmware. What we have added so far is a driver for communicating with the deck and support for the FAT file system and that means that it is possible to read or write files to/from a SD-card. We have not yet implemented any means for configuring parameter logging to file but that is something we would like to do in the near future.


The hardware design for the expansion deck is very simple.


If you are eagerly waiting for this functionality it should not be too hard to create your own deck, otherwise we plan to release one sometime in the near future. We can not promise when, but if you need it please let us know as it might change our priorities when deciding what to do.

When the deck is installed all you have to do is build the firmware with 


in the tools/make/ file to enable the SD-card functionality and add your own code in src/deck/drivers/src/usddeck.c to read or write to your SD-card.

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


The first boards to be produced are the Loco Nodes:


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


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

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

As we already talked before in a couple of post, we are currently developping a local positioning system for the Crazyflie based on ultra-wide-band radio DWM1000. This is one of our main focus currently so we wanted to post a short update on our progress.

We have assembled and shipped a couple of LPS system already and so far the performance and progress are great. We now think that we have the copter flying as good as we can have it without running sensor fusion and the control loop in the Crazyflie microcontroller. Next step is to integrate algorithms in the Crazyflie.

We are currently working hard at finishing the design to make it ready for production. We will write more updates about that so stay tuned :).

We have shot a short video demonstrating the current state, see after the video for more information about the setup:

To make this video we have installed 6 anchors. 3 are above the room and 3 at about 50cm from the ground. The Crazyflie has a LPS deck and ranges in a round-robing fashion with all 6 anchors. The ROS driver pulls the ranging, estimate the Crazyflie position, and calculate a corrected roll/pitch/thrust in order to keep it at the pre-defined setpoint. The Yaw is not controlled externally, it is kept by the Crazyflie internal gyroscope only.

The ROS computer was setup according to the instruction on our wiki, and by launching the pf_hover launch file:

roslaunch bitcraze_lps_estimator dwm_loc_pf_hover.launch uri:=radio://0/110/2M x:=1.5 y:=5 z:=1.2