Category: Crazyflie

We have noticed some confusion about how we control the Crazyflie after our RC controller post. So just to clarify we are using a Playstation 3 gamepad to control the Crazyflie from the PC, this is the best we have but any gamepad or joystick would do. However there are other options.

The Crazyflie will be controllable from the CrazyRadio USB dongle. The dongle has a number of interfaces that can be used: USB, SPI/UART and PPM. A custom made controller could be connected to the SPI/UART or a RC remote to the PPM interface. If the dongle is connected to the computer using USB it can be interfaced using our Python library. Currently we are using a QT application together with a gamepad controller to interface the Python library but it’s also possible to do other stuff like one of our dreams: using openCV to track the Crazyflie and control it autonomously from a PC and a couple of webcams :)

Also we are still porting the code and testing the new prototypes. So far we haven’t fond any more problems than the JTAG reset.

A large part of this Monday was spent assembling and testing the new prototypes with the digital sensors which arrived today. Eager to try them out we pretty quickly got stuck when we tried to program them with the JTAG. The copter wouldn’t respond to any JTAG commands… After a long time of testing we found our rookie mistake: We have been moving around some of the signals now when we have digital sensors to make the expansion port use a dedicated SPI port and not share it with the radio, which is a great improvement. With this moving around we managed to put one of the motor outputs on the optional JTAG reset pin, NJTRST. The motors are pulled low so they don’t start unintentionally which then makes the JTAG go in constant reset :o This can be walked around by temporarily holding that pin low during the first programming of the boot loader which will then immediately remap the NJTRST pin to be unused by the JTAG. If the bootloader is never removed the problem is gone but if the boot loader is unintentionally overwritten then one have to do the “pull low” trick again. So now we have to decide whether to live with this flaw or do yet another board re-spin… :-( There are still plenty of sensor testing left to do that maybe need another re-spin.

Before we have any maiden flight video the show below is a photo of the new Rev.D PCB. There are more in this album.

Crazyflie Rev.D PCB

 

We don’t have that much new to write about this week. The software clean-up is slowly evolving and we have been working some more on the radio protocol and the ground station.

We hope that the new prototypes will be ready this week so maybe we could make a first flight with them in the beginning of next week :-)

A none return point has been passed as we have put in an order for a shit-load of motors. Now everything has to work out or we will be sitting with a hole bunch of motors and no money to do other fun stuff.

 

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.

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 :).

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

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.

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.

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)?

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 :-).