3D Printed HC-12 and HC-06 telemetry relay box

It’s a very nice feeling when people starts to create accessories for your inventions. OK, maybe “invention” is too strong word here, but still.

EduardoChamorro designed a 3D printed case for my HC-12 433MHz to HC-06 Bluetooth bridge that I published here last year.

LRS to Bluetooth 3D Printed case

It’s small, it has a switch and status LED. It also has integrated LiPo battery and a charger. Awesome!

Project can be downloaded from Thingiverse.

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Project “GPS Racer” – worklog #1

I know that I should not start new project when old one are still in progress. I really, really know that. But since I’ve somehow lost my interest in Project Dualcopter and I have a real need for a new quadcopter, Project “GPS Racer” has finally started.

What is GPS Racer? During my work as INAV developer, I’ve realized that I do not have a good platform for it. The only GPS enabled multirotor I own is Sparrow Hawk. And it has a gimbal, weight 2kg and is hard to transport. When Sparrow Hawk crashes, there is always something broken.

So, to be able to test navigation related features of INAV, and not have to rebuild every single crash, I’ve decided to build dedicated UAV. For most elements I will be using parts that I already have. I only had to order frame, propellers and GPS module. Continue reading “Project “GPS Racer” – worklog #1” »

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Cleanflight is still dead…

When week ago Dominic Clifton replaced all Cleanflight source code with Betaflight, I’ve written than Cleanflight is dead. Few people agreed, few (including Dominic himself) stated that it was a good idea. Main argument was that Cleanflight needed F4/F7, Dshot, CMS support and so on. Yes, CF needed that. This is true. In theory, with that one move Cleanflight got everything what it need. But also lost all it’s uniqueness. Further narration wast that all those things that only CF had will be readded on top of Betaflight code.

One week later I repeat: that was a bad move and here are my arguments:

  • All Open Source projects exists only thanks to The Community. The bigger the community, the better. I did not participated in Cleanflight development much. Only few really minor pull request. I joined the hobby too late. Many developers worked on CF code for months, maybe even years. Not only Dominic. If someones arbitrary decission would just “erase” my contribution (in both code and know-how) I would be pretty pissed off. Really, there was a reason all those people participated in CF. Now, all their work that was not present in Betaflight, is gone. That is not encouraging.
  • The same goes for 3rd party apps like EZ-GUI. All of them lost CF compatibility over the night. Will they be willing to adopt to the changes?
  • I’m really not sure is reimplementation of Cleanflight specific features on top new code will be simple enough to be done in reasonable period of time
  • The biggest programming problem I see are resources. Betaflight is in very comfortable situation: it, more less, can ignore the fact that servo and motor outputs can not share the same timers. After all, who uses servos on mini quads? And CF is (was) not only about mini quads. What about airplanes? Are resources ready to handle servos and motors at the same time and prevent all potential clashes? I doubt it
  • Changing codebase maybe looked like a best solution to get F4, Dshot and so on. But was not the only way. Somehow INAV got it after all. And Betaflight got it. How? Thanks to The Community

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STM32 F1 and F3 versus LRS 433MHz interference issue

This topic first appeared on my table few weeks ago. Can a flight controller interfere with long range system running on 433MHz band like openLRSng?

STM32 F1 and F3 based CPU running most flight controllers (Naze32, SPracingF3, Flip32, CC3D, etc.) run on 72MHz. Actually this is 8MHz of external clock and 9 multiplier. But still, CPU itself runs on 72MHz. Most LRS systems runs between 413MHz and 453MHz, with most channels grouped around 432 and 433MHz frequencies.

This might create a problem, since 432MHz is a 6th harmonic frequency of 72MHz. Theoretically, perfect square wave should have only odd-number harmonics, but in the real life, both even and odd harmonics are present.

Are those frequencies from flight controller "visible" in 433MHz band and can they affect LRS systems? I do not have LRS system yet, so I can not answer the second question. But I can answer the first one with the help of a small RTL-SDR radio dongle.

The test

Tests were performed with a RTL-SDR and FM frequency antenna (I know, far from perfect) placed 20cm, 10cm and 5cm from running Flip32 10DOF flight controller (STM32F1 CPU at 72MHz).

According to SDR software, exact clock frequency was 72,MHz which was caught nicely on the radio spectrum.

Continue reading “STM32 F1 and F3 versus LRS 433MHz interference issue” »

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Cleanflight is dead…

Only 5 weeks ago I’ve written that Cleanflight has a problem. Looks like, the problem was much bigger than I expected. Today in the morning, Dominic Clifton aka. Hydra essentially killed the project by resetting GitHub repository to Betaflight 3.1.

It was announced on Facebook:

Cleanflight v2.0.0-RC1 is out now, with all the new features from Betaflight v3.1 – please share this post!

Thanks to the hard-working betaflight developers especially Boris B, Jason Blackman and Martin Budden who have been doing fantastic work for us all!

Also, all GitHub Issues and Pull Requests were deleted.

What does that means? More less the following:

  1. Cleanflight lost all it’s uniqueness and is Betaflight under different name
  2. Pilots that were using Cleanflight on airplanes or big multirotors are left alone. Betaflight aims on mini-quads, not airplanes!
  3. Why anyone would want to use CF when BF is there and this moment it offers better community support?

The way I see it, it was a nice ride, but now it is over and Cleanflight is dead. Too bad, since it had a huge impact on multirotor community over last few year…

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Fixed Wing 101 – Lift, Angle Of Attack and Stall

With this short article I would like to initiate new series: Fixed Wing 101 where I will describe some basic concepts connected with fixed wing airplanes that should help beginners to enter the hobby. Today: why airplanes fly and why, from time to time, they fall down from the sky…


Airplanes fly thanks to the lift. It is a force generated by wings (by the way, propeller thrust and wing lift are the same force. After all, propeller is a rotating wing) thanks to pressure difference. When air pressure below the wing is higher than above it, lift appears. To archive level flight, lift has to be big enough to counteract mass and gravity.

The most important condition for a wing to generate lift is: wing has to move though the air (or air has to move around the wing). If there is no movement, there is no lift.

When there is air movement, there are two factors responsible for lift:

Bernoulli’s principle

Bernoulli’s principle states:

when gas or liquid is moving faster, it has lower pressure.

Simple. To obtain lower pressure above the wing, we have to make air move faster over there. This is why wing has a shape (airfoil) it has: top side (above chord) of a wing is longer than the lower side. Wing splits air into 2 stream. Upper one has longer way to travel than lower one, so it has to move faster. If it moves faster, it has lower pressure. If it has lower pressure, lift appears.

Continue reading “Fixed Wing 101 – Lift, Angle Of Attack and Stall” »

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Review: BuildTak Printing Surface

For last few months I’ve been happily 3D printing PLA on glass. Prints were repeatable, initial adhesion was just fine, ready print was easy to remove after glass cooled down. But I wouldn’t be me if I did not wanted to try something new. So I tried “the ideal 3D printing surface” BuiltTak.

My initial impressions were very positive. Nice mate surface a little similar to fine grain sanding paper. I was a little afraid that adhesion will be even too good and it will be hard to remove the print. But hey, they had to think of it, right? After all, BuildTak is quite expensive after all. Continue reading “Review: BuildTak Printing Surface” »

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