Blog

Home / Blog

Playing outside

  2012-05-08  |     |    15 Comments

While we are waiting for our prototypes to arrive, the ETA is the 18th of may which is a looong wait, we thought we would play around with the Crazyflie outside now when spring has finally reached the south of Sweden. The drawback with a quadcopter this small is that it doesn’t work that well when it is windy outside but the upside is that it is pretty durable which makes great for some crazy testing :-). This Monday it was very calm outside and we got the idea to throw it in the air and try to make a “throwing start”. From the beginning we thought, no way, but it actually worked better then we thought. Here are some of the clips of  the more successful attempts :-)

We also bought one of these very popular key chain spy cameras to try and get some on-board action footage. We removed the electronics from the casing, removed the battery and connected it to our battery instead. We even removed the mini-USB connector to save weight. It all ended up in about 25g including the Crazyflie which is OK. Now it is really starting to look as an insect of some sort…

Frame from onboard video footage

We managed to take a short on-board video but the camera doesn’t handle the battery voltage drop and resets pretty easily as soon as you hit the thrust. Maybe it is possible to power it from our stable 2.8V instead because now it is pretty useless. Also the view-angle is to narrow as well as the framerate being too low to get any good footage. We seem to have gotten the 808 #14 model which isn’t supposed to be the best. At least the Crazyflie is looking pretty mean with it attached :-). Further investigations will be done when we have some time left over.

Further work on Crazyradio

  2012-05-01  |     |    4 Comments

We are still working hard on the Crazyflie code while we are waiting for the new prototypes. We are also working on finalizing the Crazyradio, the radio dongle we are making to communicate with Crazyflie.

In order for us to test the radio hardware performance we brought a RFExplorer:

The radio chip (nRF24U1) is put in continuous carrier mode, which makes it emit constantly at a single frequency. Below is a screenshot of the measured frequency and power from the radio dongle:

This measurement is not that useful as an absolute value (for one we do not have a RF test chamber) but it will give us the opportunity to compare the next prototype with this one. Our next radio prototype uses smaller SMD component for the RF parts which is supposed to give better performance. We already compared it with another dev board and our radio seems to have similar performance :).

Teaser video

  2012-04-23  |     |    8 Comments

We wish we had something interesting to write about, but recently we have just been cleaning up and reorganizing the Crazyflie firmware. We are doing this so it would be simpler to further develop the software when it is released. We have also been preparing the new drivers for the digital sensors so they will be ready when the next version of prototypes arrives within the next two weeks.

One funny thing we have though is this little teaser video we put together while testing the speed of the Crazyflie. It is not recommended crashing into something hard at this speed 8O

Some progress on the software side

  2012-04-17  |     |    7 Comments

While waiting for our next round of prototypes we are continuing the work on the software. As we feel that the copter is now stable enough for release we are concentrating on making the software easier to use and better organized.

We have also run a little profiling test on the Crazyflie firmware to see how much CPU was used by the current stabilisation algorithm. We use FreeRTOS and added some functionality to log all the task transitions.  The first result was quite worrying as it seems that we where using about 90% of the avaliable CPU. After further investigation is appeared that the problem came from the fact that we where testing Debug buils. When optimizing for size (-Os of GCC) it brings us back to 70% cpu usage and optimisation for speed (-O3) to 65%:

We are currently running two sensor fusion algorithms in parallel and have a lot of room for improvement for the code efficiency but we believe that would be good enough.

There has also been some work done on the PC GUI, there are now more flight settings and it is easier to use. We are currently adding a Joystick configuration window to be able to add support for new joysticks/gamepads more easily:

Crazyflie GUI: Flight data tab

Controlling Crazyflie with RC remote

  2012-04-10  |     |    12 Comments

To begin with, we have just created a Bitcraze Announcement google-group that we will use as a very-low-volume mailing list to make big announcements like the release of Crazyflie. So if you are interested by buying Crazyflie just subscribe to the list and you will receive a mail as soon as it becomes available.

 

As for the project, we are now waiting for the next (and hopefully last) prototype run. In the mean time we are trying to fix everything from the todo-list. One item was to verify that the radio dongle can receive PPM signal from a RC remote, as it was designed for. This is what I  have been working on last week and the result hardware-wise is this kind of hacked programming/RC-training cable attached to our radio dongle:

The idea is to be able to control Crazyflie using a RC transmitter only (without a computer) so that the radio dongle would be powered and controlled by the RC transmitter. This kind of transmitter generates a PPM (Pulse Position Modulated) signal which is acquired from the training jack of our ‘Turnigy 9X’ transmitter. We do not plan to manufacture such cables right now as there are too much kind of RC transmitter around there  and we believe that you will be able to hook the Crazyradio dongle to your transmitter without problem :-).

As the cotper firmware can not fly easily without the PC yet (most of the settings are still sent from the PC software before flight) we decided, as a first step, to use the PC anyway but by using the radio dongle for the PPM acquisition:

A HID USB joystick mode has been added to the radio dongle so that it is now recognized as a joystick by the PC (in addition to the radio endpoints) and transmits the axis position of the RC transmitter to the PC. By mapping the axis the same way a Plastation3 gamepad is mapped we could fly Crazyflie with the RC remote and with an unmodified version of our PC software. This permitted to verify that the radio dongle can acquire PPM signals (with a little hardware change that has been sent just-in-time to our manufacturer for the next prototype) and so Crazyflie will also be able to fly without PC :-). In the case of our radio transmitter however we will have to connect the radio dongle to the TX module port instead of the training jack as the training jack does not provide power.

This is still work in progress and it is unlikely the ‘pc-free’ functionality will be finished before the copter release but at least now we know that the hardware can do it.

Crazyflie with digital sensors ready for prototyping

  2012-04-03  |     |    15 Comments

The last week we have been working hard on finishing the Crazyflie with the digital sensors, MPU-6050, HMC5883L and MS5611-01BA03. We are not so sure that the magnetometer,  HMC5883L, will work that well due to the strongly magnetized motors just a few centimeters from the sensor. That will be one of the upcoming tasks to find out.

Within 3-4 weeks we will receive what will hopefully be the final prototype version which later can be used for the first batch of Crazyflies. Until then we have plenty of work with software both on the PC side and the firmware. Now it is pretty late, the clock just passed 00:00 and writing at this hour is hard. We will post some video to compensate for this short post later this week :-)

Testing new sensors using the expansion connector

  2012-03-26  |     |    7 Comments

Due to the IDG/ISZ-500 gyros EOL problem we are removing the  IDG/ISZ-500/BMA145 and going for the MPU-6050 instead. We where pretty certain the gyro part of the MPU-6050 would work but not so sure about the accelerometer.

To minimize the risk we wanted to try it out with our design before pushing the order button. We looked around for small IMUs with this chip and found that the FreeIMU uses the sensors that we are interested in testing. So we bought one and attached to the Crazyflie using the expansion connector. Here’s a image of what it looks like:

Since we now free up some space by replacing three sensor ICs with one we added a HMC5883L magnetometer and MS5611 pressure sensor which are the most common IMU sensors right now. If they will be mounted or not in the final version depends on cost and possible performance increase. If we don’t mount them there is always the possibility to do this yourself. Actually, as of this writing, we just made a virgin flight using the MPU-6050 data from the FreeIMU with good results.

Flight training

  2012-03-21  |     |    11 Comments

We realized the other day that we have spent a lot of time discussing issues and developing stuff and not so much actual flying. We haven’t even left the rockie piloting stage… So when we met up on Sunday we spent a lot of time just flying around and having some fun :)

Here’s a first cut from some of the video we shot.

Sensor troubles…

  2012-03-20  |     |    10 Comments

So as we were putting the finishing touches on what we hoped would be our last prototype before the final production version we noticed something rather serious on the InvenSense webpage. The IDG500/650 (and the ISZ-500/650) that we are using are EOL (and the LTB has passed). So this puts us in a rather tight spot where we have a couple of alternatives:

Stay with the IDG/ISZ 500/650 – We could stay with the sensors we have and try to source as many as possible but this would leave us in an awkward position if we get more demand than we can source gyros.

Analogue replacement – We could find an analogue replacement that would replace the X/Y and Z gyros we have today (that are analogue). The best candidate for this is currently the new ST gyro L3G462A but it is still under Evaluation and we don’t know if and when it will be available. It’s easy to put in our current design but we are unsure about the performance and immunity to vibrations.

Going digital – The most attractive option but the option that requires most work is switching from analogue to digital sensors. This is a step that we wanted to take eventually but taking it now delays everything but we do get a chance to get a bit more up to date by putting in a MPU-6050 and maybe a pressure sensor. But we are not sure how the sensors will respond to the vibrations and ripples on the supply voltage.

Our current plan is to drop the old analogue sensors from InvenSense and start on the digital design using the MPU-6050. We will keep the analogue ST gyro as a backup plan just in case we hit into any problems with the digital version.

Do you have any other ideas for sensors or comments about the performance of the MPU-6050 or L3G462A (if you managed to get a sample)?

Testing sensors

  2012-03-13  |     |    6 Comments

When we built the latest prototypes we built two different versions. One with the ST accelerometer LIS344ALH and with the ISZ-IDG650 gyros. The other one with BOSH accelerometer BMA145 and with the ISZ-IDG500 gyros. It turned out that the LIS344ALH accelerometer is very vibration sensitive and doesn’t work that well for an application as this. If we would just have spent some time on the Internet we could have found this information in before hand… luckily we made the hardware design work with both and the BMA145 is working pretty well, however now we no longer have an alternative :-(.

The ISZ650 and IDG650 works pretty well even though they are less sensitive with their ±2000deg/s output. We can’t see any direct stability issues compared to the IXX500 versions with ±500deg/s output. Maybe we will stick with the IXX650, that way  we don’t limit the flip and loop speed to much. Not that the Crazyflie can do flips/rolls right now but we are very confident it will be able to in the future, judging from its agility.

We have also been working on getting the Crazyflie easier to control for beginners. With some slew rate limiting and thrust control we seem to be getting there. Now even Marcus can fly it without any problem. He used to hit the wall or ceiling all the time before :-).