We kicked off the Crazyflie 2.0 production about one week ago and we are still working hard on ensuring the best possible quality of the production. To do so we have a test specification/plan that is executed on all the produced units. Making test protocols is something we have had some experience of in our former day-jobs, but it is always a challenging and time consuming task. However the reward is great, good tests ensure good quality to the end user. The higher the production quality is, the happier everyone is, and the more time we have to do other things like developing new features :-).

The tests runs on an assembled PCB and first thing to verify is an electric test checking that voltages and current consumption are normal. Then the board gets programmed.

For the original Crazyflie, the testing was heavily based on the power on self-test. This is still the case with the Crazyflie 2.0 which allows to make sure that everything is working in factory as well as every time a Crazyflie gets powered (this power-on-self-test is the first thing to run before assembling the Crazyflie).

For Crazyflie 2.0 we also needed to create new tests for the expansion port. First of all we needed to check that the connector is mounted properly and that the pins for the expansion port are able to pass though the PCB. Secondly we also have to test the electrical connectivity. For this we have created a special expansion test board which, allows the Crazyflie to self test all expansion connections. This board is detected by the 1-wire memory which is mounted on the test board. When it is inserted it will automatically trigger the test code which checks all connections.

To do tests on a limited budget you will have to get creative. E.g. to do output power and frequency test for the radio communication on the Crazyflie and Crazyradio we are using the rfExplorer. It is a neat cheap 2.4GHz spectrum analyzer that we control from Python which can measure the radio frequency and output power. ICT or bed of nail tests are also very expensive and instead we use test fixtures with pogo-pins to test the electronics. It doesn’t get as extensive as a net checking ICT but with some clever testing using the software most components can be tested anyway. We have added some photos of the original Crazyflie test rig to this post. We will soon travel to the Seeedstudio office in Shenzhen in China and we will take photos of the new production and test equipment.

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First of all, thanks to everyone that helped us out during the pre-order. Today we are finishing the last details and tomorrow Seeedstudio will launch the production of the first Crazyflie 2.0 batch! It’s been a hectic couple of months here at Bitcraze and it feels great to finally have reached this point. For the first batch we will manufacture more units than were pre-ordered. So from now up until the units are ready we will continue the pre-order, but without the discounted prices. The first batch is planing to start shipping mid-December. We are prioritizing the discounted pre-order but will ship everything as soon as possible.

Last week we published the iOS prototype code for controlling the Crazyflie 2.0. This week we are publishing the Crazyflie 2.0 expansion board template project. The project is done using KiCad and includes the schematics, the footprint mapping and an initial layout with the connectors in the correct place. The license of the template project is CC-BY 4.0. In order for users to more easily see what their expansion board will look like and how it will fit, we have included the Crazyflie 2.0 board outline as well as some key components that might interfere.

We are really excited to see if any cool expansion board projects will come out of this template. So if you feel like giving it a try then head over to GitHub, clone the repository and add some cool stuff. Any ideas of what to do?

This weekend we spent at the Maker Faire in Rome and got to meet lots of fellow geeks and makers. Even though it was busy times at the Bitcraze booth, we got a chance to walk around a bit and see other projects. It’s really inspiring to see what people come up with! It was also the first time we got the chance to show off the new Crazyflie 2.0 to the public and the feedback was really positive. We have realized that we might be a bit wide in our description of the new platform. There’s lots of new features that we are very eager to talk about, but maybe we should focus a bit more on the biggest improvements. With two weeks left on the pre-order we have been trying really hard to get some extra attention for the new platform, but haven’t really succeeded yet. This might be one of the reasons.

So even though there’s lots of new features we would really like to highlight the new expansion port. It’s been something that we have been talking about internally for a while now and we are really excited that we managed to fit it in. Like we wrote in an earlier post we used some exotic use-cases to figure out what to include in the expansion header. For example this resulted in the ability to charge the battery from the expansion board, like we are doing with the Qi wireless charging expansion board. Since the Crazyflie 2.0 has the ability to connect multiple expansion boards (both on top and bottom) we also needed some way to determine what boards are added. So one of the pins in the port is used as a 1-wire memory buss. Each expansion board has a 1-wire memory that allows identification of the board, it’s revision and what resources it uses. This way we can adapt the features available from the computer client or mobile device when the platform is connected.

Below is an overview of what’s available in the expansion port:

For the pre-order we have managed to include 4 expansion boards: the LED-expansion, the Qi wireless charging expansion, the breakout expansion and the prototyping expansion. Aside from these boards we also have some prototypes of more expansions. Before the pre-order we were working really hard on a GPS expansion board, but in the end we didn’t think the current prototype had enough precision to launch. We reached about 10-20 meters accuracy with locking times of about 2-3 minutes and didn’t have time to spin another prototype. During the fall we will work on perfecting the design so we reach a level of performance that we feel is good enough.

We also have a prototype for a distance sensor to be used for precision landing. After looking for a solution for a while we finally found the VL6180, a time of flight sensor from ST. The range is not very long, but combined with the high precision pressure sensor mounted on the Crazyflie 2.0 we think the result can be very good. We also have an uSD expansion that we are currently testing.

After getting feedback from the visitors we met at the Maker Faire we have also decided that we will be designing an Edison adapter expansion for the Crazyflie 2.0. The Edison board is fairly small and light, so it should be possible to design an expansion board that has the 70-pin expansion connector featured on the Edison. Our plan is to use some of the interfaces in our expansion board to connect to the Edison, like I2C, UART and SPI.

Last but not least we are also working on an analog FPV expansion board. It’s still just an early prototype, but we think it’s something that a lot of users might be interested in.

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As we will continue making more and more boards we also hope the community will take the opportunity to do so as well. We will soon release templates for KiCad making it really quick to get started. What board would you like to make? Let us know what you think about the new expansion port. Do you have any ideas for boards or any comments about our planned ones? We would love to get some feedback!

We would also like to say congratulations to Mihir Garimella on being one of the winners of the Google Science Faire 2014 with his project the Flybot! He used the Crazyflie to work on escape maneuvers similar to those of fruit flies. Really great work!

As you might already know we have added a 20dBm RF amplifier to the Crazyflie 2.0 as well as to the Crazyradio PA. We have had high hopes of getting a more stable link and much better range with this. We have done a lot of tests in the building we are sitting in and already experienced a big improvement in range. However radio range is a tricky thing as it depends on so many things and when we have tested it outside of the office we could only get a stable link for about 80m. This is very different from the documents we read where we could expect up to a kilometer of range! Maybe the fifteen wifi networks that where present outside our office played an effect.

So this weekend I set out to do some test on the country side. I packed my bag and mounted the Crazyradio PA on a 1m stick which I put in my bag so it could reach higher than my head. Then I took the bike to get to the country side. I got a lot of strange looks while bicycling. It was first when I reached the country side, it came to me that bicycling around with an antenna sticking out your backpack might be interpreted the wrong way :-o. After a while I reached a good spot and decided to put the Crazyflie still somewhere and instead take the computer with me so I could see what was happening. As the nRF51822 can take RSSI measurements we made a simple python program where the computer pings the Crazyflie and the Crazyflie responds with the RSSI measurement. We save the data in a CVS file which can be plotted in real time. I hang the Crazyflie in a bush, started the Crazyflie 2.0 at channel 10 and 250k air data rate, fired up the plot and took the bicycle and started pedaling.

After 100m I still had a solid connection, very good sign. After 500m the RSSI had dropped to about -80dBm but still a stable connection. After 1300m it got really shaky, about -100dBm, as the line of sight was obstructed by some trees and the road turned as well, 1.3km, LOS, that’s a huge improvement from the 80m we got back at the office. We know these circumstances are very optimal but at least it shows us we are not way off and hopefully we can expect half of that range in a more real situation. We have still not tuned the matching network for the antenna, which we will do soon, so hopefully we can expect yet another improvement. I also did a test with a hacked Crazyflie 2.0 with a duck antenna. With this one I got about -70dBm at the same 1.3km spot. This could be a great hack for special applications that require long radio distance as it could probably go beyond 2km range LOS, both up- and downlink.

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