Category: Crazyflie

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Pre-series ordered!

  2012-10-08  |     |    29 Comments

We just finished the top level BOM, test plan, fabrication files, etc… which mean everything required to order the pre-series of the Crazyflie. The pre-series  is meant to be last version before the first real production batch and the idea of it is so that we can test the manufacturing and verify that it is manufactured with good quality.

One of the last minute changes we made for the pre-series has been to power the motors directly from the battery instead of through the power management chip. This should gives us up to 8% more power and efficiency due to power management mosfet on-resistance losses. It should also reducing the voltage drop which causes disturbances to the other circuits. The only drawback is that the Crazyflie consume a bit more power when OFF, because of the leakage current through the motor mosfets, but it is still within acceptable limits (a full battery will still take more than 2 years to be depleted by our electronics). Also the battery can now be swapped/disconnected for storage as we have added a connector.

Our target is to have the Crazyflie DIY kit availible for X-mas. It is very tight and it will be hard but what would life be without challenges :-)

Tools

  2012-10-01  |     |    4 Comments

One of the goals during this project has been to only use open-source tools for development. The main incentive for this is that we want everyone to be able to take part in the development and look at the all the parts of it once it has has been released. Also it was a great opportunity to see how far we could push open source free development software in a non-trivial embedded project.

Some of the tool has worked great and some has caused us some headaches since we have worked with the proprietary alternatives during the daytime. Our conclusion is that a project like this is definitely doable, but some parts does still require more work (and some frustration). The open-source tools for firmware development and PC client are state of the art and could be used instead of there proprietary counterpart (of course most of the time there is no GUI and some more setup or manual job might be required, but this comes with the benefits of a greater flexibility). However the hardware design tolls are still behind there (expensive!) proprietary counterparts and often requires a great deal of efforts to reach the wanted result.

Of course it’s great that these open-source alternative exists and that a lot of great developers puts time into making them. Without them this project would not have been possible!

The firmware – For firmware development we use a wide number of applications: gedit, Eclipse, Mercurial, gcc, make, openOCD and gdb. On Crazyflie we run  FreeRTOS. As we built the development environment with cross platform tools the development can be done seamlessly on Linux or Windows, on the console or with Eclipe. The radio dongle has been developed from scratch (ie, just from the datasheet) with the help of sdcc to compile for the 8051 contained in the nordic chip.

The client software – For the client side software we use Python, libusb, pyusb, QT/PyQt. Even though there was a lot of discussion within the group (Ruby vs Python, qt vs gtk) we landed on Python due to all the bindings that works out of the box on Linux and Windows. This enables you to quickly create applications. Combining this with QT/QTDesigner and you get a nice GUI application.

The hardware – Since the very first prototype we switched from Eagle CAD to Kicad to use a fully open source e-cad program. It does the job perfectly fine but the routing part requires a lot more time as many of the time reducing functions are still lacking compared to proprietary programs.  For complex boards, if time is an issue, Kicad is not the e-cad to use, but for simple board and typical DIY boards it does the job fine (ie. our experience of kicad is a lot smoother for the radio dongle than for the copter).

The mechanics – For the mechanics we have used freeCAD which is one of the few open-source 3D CADs tools that we have found. When we started out we had a lot of problems with this software because it keep crashing during the design. After the stable release of the 0.12 branch it’s gotten better but we’ve still had some problems with crashes. Over all we managed to design and 3D print many revision of the motors holder with freeCAD.

The website – On our server we are running WordPress, Mercurial and Redmine, all these on a Linux and Apache. We will probably also run phpBB later on.

 

Sensor poll

Waiting another week did not make things clearer whether to mount all sensors or not, but the quotation to buy and mount them did. The $20 we estimated was too low, depending on the amount of boards we make of course, but we would probably have to add another $10 to that which made the decision simple. It is mainly the barometer that is very expensive so we might still decide to mount the magnetometer. First we will do some tests though to find out how much “value” it really adds. For people that wants the barometer it will still be possible to manually mount it afterwards making it a win-win decision.

Inductive charging hack

  2012-09-24  |     |    21 Comments

After the LED hack we are back with an inductive charging hack!

The idea of charging Crazyflie inductively is almost as old as the copter itself. Last week we received a Palm Touchstone charging kit that we ordered. Like many phone hacks using this inductive charger we dismounted the receiving coil and electronic and attach it to the Crazyflie:

As the Crazyflie has a power-management circuit, any supplied voltage above ~4.5V will make it charge, and as we have made some soldering pads available for things like this it was a simple task. The coil is very thin and light (about 3g) so the flight performance are not affected a lot by the change. The charger is working very well and provides enough current for charging. We charge with a little less then 500mA and we think the Touchstone can supply up to 1A. One possible problem though is that the copter has to be placed exactly in the middle of the charging station to be able to charge. The phone has magnets to align it to the charge station and on top of that the charge station is not straight but tilted. The magnets are way to strong to let the Crazyflie take off so we are trying to find a landing area design that would permit the copter to land in the right spot and still be able to take off again without the magnets, any ideas?

LED hack

  2012-09-17  |     |    3 Comments

When I was shopping for some ink-cartridge at this Swedish accessory store named Kjell&Co I also bought one of these 12V LED lamps. I didn’t buy it to actually use it instead I bought it to have a look inside. I cracked it open when I came home and found, not so surprisingly,  a lot of LEDs and a step up converter with a current sensing mode. Since it was made for 12V AC I removed the rectifier bridge and a large cap to get it as light as possible. Testing it with a power supply reviled that it worked all the way down to 2.2V and at 3.7V it consumed about 0.5A. A bit to much for the Crazyflie so I doubled the current sensor resistors to get it down to 0.25A. Some soldering and some double sided foam tape and we suddenly have  a pretty bright lamp hooked up to the Crazyflie. Now we have a search&rescue device :-) or maybe just an UFO…

Let’s not forget the sensor poll. It’s a very close encounter with 55% wanting the extra sensors. We will keep the poll open until next week to see if it gets any clearer.

Sensor poll

  2012-09-10  |     |    12 Comments

If you have been reading our previous blog post you know that we redesigned the Crazyflie to use the MPU6050 instead of the IDG500-ISZ500-BMA145 combo. This was done because the IDG500 became obsolete, recently we found out it was because Invensens had production problems with this sensor, anyway when redesigning we managed to squeeze in a HMC5883l magnetometer and a MS5611 pressure sensor.  Now when we are getting close to actually making some kits we have to take some decisions and one of them is if we should build the Crazyflies with the HMC5883l magnetometer and the MS5611 pressure sensor mounted. This will of course increase the price which we have estimated to be about $20. Currently we do not use neither the magnetometer nor the pressure sensor. The yaw drift is so low that when you pilot the Crazyflie it isn’t noticeable and therefore we do not use the magnetometer. The pressure sensor we have just tested briefly and we do not really know how well it would work. Altitude hold might not be so useful inside but maybe outside.

Because of this little decision whether to mount the magnetometer and pressure sensor or not we would like to make a poll so please give us your thoughts.

 

 

Should we mount the pressure sensor and the magnetometer?

View Results

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Board outline

  2012-08-27  |     |    5 Comments

The coming week we are reviewing the new revision of the hardware before we press the order button. With the previous prototype we had a few violent incidents where one of the arms broke off. Fixing it wasn’t to hard. We used an aluminium tube we cut to the right size and glued over the arm and it holds up well. For this next revision we have changed the board outline around the arm joint to be smoother as this seams to be the weakest point. If everything goes according to plan the next prototype should be the last before we can order a larger batch.

During the last week we also did a little test making an small Android app and plugging the radio dongle in one of our Galaxy Nexus. It’s detected and can be used via the USB API.  It’s nothing that we are planning on spending any time on right now but in the future…

 

 

 

Vacation is over, now we’re getting back to work!

  2012-08-20  |   

We’re all back from vacations and now it’s time to focus and ramp up the work again. After syncing what we have been doing during the summer (and doing some catching up) we think that we are in good shape. There’s still lots to do but now we have re-charged our batteries!

Since the weather is nice we decided to do some flying outside and at the same time do some range testing. Unfortunently we waited a bit too long so it was pretty dark outside. The Crazyflie is normally hard to see when you get too far away and when it’s dark it’s even harder… So the range test was done by flying slowly forward until the radio connection watchdog kicks in and the motors are cut. We then used MyTracks on Android to measure the distance to where we found it in the grass :-D We only did two tests but the best one was 55m.

Here’s some images of the test and the flying:

Crazyflies at night

Crazyflie at night (far away)

Crazyflie range test

Logging and parameters

  2012-08-13  |     |    3 Comments

One of the things that we’ve been working on for the last week is the parameter and logging systems.

Since the start of this project we’ve had a protocol in place for logging data from the Crazyflie but it’s been a bit hackish. It has relied on that the client/Crazyflie has been in sync regarding what to log and how to log it. The problem that we had was that as we start development on a new feature our logging needs change and we start tweaking what we log. Sometimes we change the size of variables to fit more data in or we switch them out completely. This has resulted in the logging breaking frequently which has been a pain…the three of us was hardly ever in sync :-D The solution that we have been working on now is more dynamic.

At start-up the client will download a TOC (table of contents) of loggable variables. By using macros when defining a variable in the Crazyflie code the variable will automatically be included in the TOC and will be loggable. It is then possible to setup a log configuration where a number of variables are pushed over the radio at a specific interval. Multiple configurations can be added so one usage is to log the battery voltage every second but to log the roll/pitch/yaw 100 times per second.

We have also been developing a similar system for getting/setting parameters. Like the logging there’s been a hackish system in place until now that’s been used to set regulation parameters during tuning. With the new system it’s possible to declare a variable using macros so it will be automatically included in the param TOC and will be gettable/settable from the client. One typical use is for tuning the regulation but it could also be used to switch between flying configurations (normal/X).

The biggest reason for implementing these systems is to make it easier for other people to tune and modify the program of the Crazyflie (also it’s a lot of fun :-D).

Still summer

  2012-07-30  |     |    5 Comments

We are still mostly on vacation but we are continuing the development but not as actively. Like we wrote last time we compiled a list of tasks that has to be finished in order for us to release the project so that’s what we are working on :-D

Apart from that we are also working on some mandatory IT-stuff, like deciding what forum/SCM/VPS provider to use etc.