3D printed racing drone, part 2

January 4, 2018January 11, 2018 Dziku 1 Comment

My 3D printed racing drone is done. More or less. I was able to finish it a few weeks ago and even perform a maiden flight. It survived the experience, but I also discovered few problems I will have to solve before officially calling this project a success.

First of all, the decision about hard mounting a flight controller and not installing a capacitor on mains was a bad one. Not only motors are "twitching" from time to time, a video is very noisy. I hope big low ESR capacitor will solve that, since there is no way for soft mounting for this frame.

Besides that, it worked just fine. I will try to prepare a video from the maiden flight in a few day, for now only a few pictures and final specification:

Frame: PLA 3D Printed, 220mm motor-to-motor diagonal
Motors: EMAX RS2205S 2300KV
ESC: Racestar RS30A BLHeli_S
Flight controller: FrSky XSRF3O running Betaflight 3.2
VTX: TS5823 200mW
Camera: RunCam Swift
Total weight, no battery: 380g

Total build is, of course, heavy, but not that heavy as I feared. I was expecting something way above 400g. The frame is also quite stiff. I wonder how much beating it will be able to take….

DIY RC radio link: the problem of protocols

November 2, 2017 Dziku Leave a comment

So, you want to build your own RC radio system? Long range maybe? Cool, I want to do it too. Since I'm pretty deep in that topic now, I can give you a hint or two. For example, have you thought about a protocol your radio system will implement?

Or rather should I say: protocols? Why plural? If you want to do a RC link that talks with popular radios like FrSky Taranis on TX side and servos or flight controllers on the RX side, it will have to implement at least 2 different protocols. More likely 3. And if you will want to add telemetry downlink, 4 or even 5…

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Hands on: FrSky XSRF3O flight controller

October 30, 2017 Dziku Leave a comment

Since I just started to add support for "old" FrSky XSRF3O flight controller to INAV (expect this in a release after 1.8) it might be a good idea to share few words about it.

First of all, it comes in a box. Why am I mentioning this? Because none of my flight controllers, and I own at least more than a dozen, came in box. C'mon, this is huge! I'm not joking, this is really a nice touch.

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Generate S.Bus with Arduino in a simple way

October 25, 2017 Dziku 12 Comments

Did you noticed that lately I write about radios quite often? Well, I do and it's not a coincidence. Proper introduction for what I'm working on will happen in a next few days, but now I will only write that this will be a mid-range, cheap, DIY radio link for UAVs. By mid-range I mean up to 5km. So, it will be positioned somewhere between 2.4GHz systems and full sale LRSes like DragonLink or TBS Crossfire.

Back to business. I've discovered, that there is very little in The Internet how to generate S.Bus with Arduino. OK, there are few libraries for reading Futaba S.Bus protocol like mikeshub/FUTABA_SBUS or zendes/SBUS but the only library made simple I've found is bolderflight/SBUS. Too bad it works only with Teensy devices. So, after a few hours of hard work, reading code of OpenTX, MultiWii, INAV, reading RcGroups and final help of Konstantin Sharlaimov (Digital Entity of INAV), I give you:

Generate S.Bus packets with Arduino in a simple way

But first, few simple facts:

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Hands on: Tiny Frsky 8CH Receiver from Banggood

September 19, 2017 Dziku 3 Comments

I have a nasty habit of buying things and then forgetting about them. Something like that happened to Tiny Frsky 8CH Receiver (Wolfbox F802 software compatible) from Banggood I’ve purchased last year. For some time I used it in JJPro P175 quadcopter, but then it landed in a box and I forgot about until last week.

So, let’s do overdue “hands on” on Tiny Frsky 8CH Receiver from Banggood… (more…)

FrSky SmartPort Telemetry on AnyFC F7

May 4, 2017 Dziku Leave a comment

STM32F7 CPU family present in newest, experimental, flight controllers like AnyFC F7 (as well as upcoming AnyFC M7 with smaller STM32F722) simplifies many things. For example, comparing to F4 boards, SmartPort or S.Bus connection is extremely simple and can be done on any free UART. No more hardware hacks, external inverters and other “special” ways of doing things.

It’s super simple again, and here is how to do it in Betaflight (Cleanflight 2.x) and INAV

Hardware

The only required hardware is a cable to connect SmartPort enabled receiver with free UART port on F7 board. This will work on X8R, X6R, X4R, X4RSB, XSR and any other. The trick is to connect S.Port pin with UART TX pin only.

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Talking Taranis – teach FrSky Taranis to talk to you

April 13, 2017 Dziku Leave a comment

One of the most important features of modern, computerized, radios is that you can make them talk to you. After all, with setup telemetry link from UAV, radio should “know” things. Things like battery voltage for example. Why not make FrSky Taranis (or Horus or Taranis X Q7) talk to you and report LiPo voltage in a smart way?

Before we proceed, you have to setup SmartPort telemetry or “legacy” FrSky telemetry. This post does not covers this topic. You might want to take a look here and here.

Let’s go

In OpenTX menu navigate to last page called Telemetry and check if VFAS is reporting proper value.

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Mini Flying Wing: MiniWing v2

March 31, 2017June 15, 2017 Dziku 2 Comments

Miniquads are fun, right? After all, there is a reasons most uf us flies 210-250 quadcopters. If so, small flying wings should be fun too! I tried that already in late 2015 and failed miserably! My design did not survived maiden flight. Well, things like that happens from time to time, so few months ago, after learning few new things, I’ve made a second attempt. And this time I’ve succeeded.

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Hardware SmartPort Inverter using BC547 bipolar transistors

February 4, 2017 Dziku 2 Comments

This post is only a short update for SmartPort inverter for F4 flight controllers. Here is alternative SmartPort inverter circuit using bipolar BC547 instead of unipolar 2N7000. All other aspects of operations are the same like in MOSFET version.

SmartPort inverter for F4 flight controllers

January 3, 2017January 15, 2017 Dziku 7 Comments

While STM32F4 family processors installed in newest flight controllers are superior to STM32F3 (and F1 of course) in terms of raw speed, they are inferior to F3 family in terms of IO handling capabilities. For example, F4 family is not equipped with UART port inverters. And that creates a series of problems when it comes to connecting various serial RX receivers and telemetry systems.

The most popular FrSky (Futaba) S.Bus serial RX protocol and FrSky SmartPort telemetry require inverted UART signal. If there is no hardware inverter on hardware UART port, they will not work. While S.Bus requires only one data line, external inverter is not a big issue. Some time ago I’ve published The Simplest Harware Inverter. One MOSFET transistor, one resistor and that’s all.

In case of SmartPort, it’s slightly more complicated. Not only signal is inverted, SmartPort also combines TX and RX UART line into single wire. That means the following:

More complicated inverter is required
Software has to support this case and fallback to unidirectional UART mode

Hardware

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