INAV can do automated landing on fixed wing?

Those of you how subscribed to my YouTube channel should have noticed, that I got an interest in automated landing of fixed wings after RTH in INAV. And the sad truth was that, well, INAV up to 1.7 was unable to do it right. When landing after RTH was enabled (nav_rth_allow_landing = ON) and it was enabled by default, airplane usually started a 20 degrees dive to the ground. One does not has to be a prophet to figure out how it ended.

For example like this:

If not manual override, that would end up in a beautiful crash and probable full rebuild of an airplane.

Luckily, that motivated DigitalEntity enough to something about that, and yesterday I was able to perform (probably the first one ever) a controlled descend after RTH that ended up with an airplane on the ground without any damage. With enough optimism one can call it even a landing. This is how it looked like:

Current implementation is still far from perfect. Although it does not crash, it has a few small problems:

  • No disarm. Throttle is open all the time
  • It happily ignores speed. Both ground and airspeed
  • It also ignores wind, heading and so on

But, to be honest, this is a nice progress. Stay tuned for more changes here, since I’m planning to work on it in the near future.

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FS1000A and XY-MK-5V 433MHz RF modules: overview

One of the cheapest (but not the best) solutions for DIY wireless data transmission between different devices (Arduino and other microcontrollers) is a pair of 433MHz modules: FS1000A and XY-MK-5V. A set of them (you will need one transmitter and one receiver) costs about $1. Pretty cheap, right?

FS1000A and XY-MK-5V

Of course, there is a price to pay. Those modules are as simple as possible. They do not offer anything like error correction, RSSI, frequency hopping, or even two directional transmission. They offer only basic functionality: receiver reports digital ONE when transmitter detects ONE on the input (if in range, of course). Everything above that has to be done in the software. Continue reading “FS1000A and XY-MK-5V 433MHz RF modules: overview” »

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AnyFC F7 output mapping for INAV

AnyFC F7 when running INAV, is not using standard output mapping. That means, that M1 output is not where you should connect Motor 1 and M2 is not where Motor 2 should be connected. It’s a little complicated, but with following table it should be pretty easy to connect any possible configuration to AnyFC F7 and INAV.

Multirotors

Output number No LED Strip With LED Strip
1 Motor 4 Motor 4
2 Motor 5 LED Strip
3 Motor 6 Motor 5
4 Motor 7 Motor 6
5 Motor 3 Motor 3
6 Motor 2 Motor 2
7 Motor 8
8 Motor 7
9 Motor 8
10 Motor 1 Motor 1
Input Function
1 PPM
2
3 Servo 1
4 Servo 2
5 Servo 3
6 Servo 4

Airplanes

Output number Function
1 Motor 1
2 Motor 2
3 Servo 4
4 Servo 5
5 Servo 3
6 Servo 2
7 Servo 6
8 Servo 7
9 Servo 8
10 Servo 1

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Using FET transistors as switches

When over a year ago I published this post about using transistors as switches, I described only how to do it with bipolar transistors. And bipolar (NPN and PNP) transistors have a small problem: they are current driven, so they consume current when they are switched on. They consume much less than they drive, but still…

Field Effect Transistors (FET), and especially the ones from MOSFET family, work in a slightly different way. Instead being current driven, they are voltage driven. Than means, to conduct between Source and Drain terminals, specific voltage has to be applied to Gate terminal. More than that, FET transistor consumes current only during switching. It works kind of like a capacitor. When Gate is charged, it stops conducting electricity.

And that, in case of low voltages and low currents (3.3V – 5V logic level and few hundred miliamps), removes the requirement of Gate resistor. Small MOSFETs like 2N7000, BS250 and other, can be directly connected to microcontroller outputs. Cool!

Switch with N-channel MOSFET

N-channel MOSFET is ON when positive voltage (comparing to Source) is applied to Gate. So, Load will be powered when HIGH state is applied.

N-channel MOSFET as switch

Switch with P-channel MOSFET

P-channel MOSFET is ON when negative voltage (comparing to Source) is applied to Gate. So, Load will be powered when LOW state is applied. It acts like an inverter.

N-channel MOSFET as switch

Gate resistor

In case of bigger currents and voltages, gate resistor might be required since FET gate acts like a capacitor and passes electricity until charged. Consult transistor data sheet.

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Scarab Knife 200 finally in the air

It took me much more time to put my Scarab Knife 200 4″ from CarbonBird.com into the air and actually fly it. First try that happened 2 weeks ago failed due to beginner mistake: too long motor screw caused one of the motors to overheat. I had to order shorter M2 screws and redo some other things: add 1000uF 36V low-ESR capacitor to power rail, relocate VTX and X4RSB RX. Nothing super fancy. Final effect looks like this:

Scarab Knife 200 racing quad

Scarab Knife 200 racing quad

Scarab Knife 200 racing quad

There are a few problems that I hope proper tuning will solve. One of them, is strange wobble, or low frequency oscillation, on full throttle. I’m not sure what is the source of it. It might be from quite soft props. I will try replacing stock HQProp 4×4.5″ with DAL T4045. But second problem is that probably 4″ props do not match my flying style. Those small props just do not gip so much air as 5-inchers and do not keep flying path as good as I’m used to. I had similar feelings when testing JJPro P175, so that might be the case.

Next tries in 2 weeks…

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AnyFC F7 Pinout

There is still very little about AnyFC F7 on the internet. Especially pinout is kept secret. Without sambas official GitHub repository for hardware projects, there would be nothing at all. I’ve decided to close that gap a little and prepared full pinout for AnyFCF7.

AnyFC F7 Pinout - Top Side

AnyFC F7 Pinout - Bottom Side

Yes, I know they are hand drawn and scanned, but I have a strong aversion for computer graphics software. I can move a slider left and right, but every time I have to do some creative photoshopping, my head starts to hurt. This is extremely ironic, since my major at university was computer graphics. Heh…

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FrSky SmartPort Telemetry on AnyFC F7

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.

How to connect F7 flight controller to SmartPort

Continue reading “FrSky SmartPort Telemetry on AnyFC F7” »

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Marabou Stork reborn

It took me quite some time, but I've finally rebuilt my Depron FPV airplane Marabout Stork after last year's crash.

In theory, all I had to do, was to replace nose section. At the end, it turned out, that I should also reinforce wing mount, redo FPV system and replace flight controller. So, full list of changes:

  • Rebuilt nose section that is longer than original by 30mm
  • Full sized MinimOSD was replaced with Micro MinimOSD to save some space
  • Flip32 flight controller was replaced by SP Racing F3 and external BMP280 barometer
  • INAV 1.7 baby!
  • Various reinforcements, mainly around wing mount

Weather conditions in above video were far from perfect. Wind speed around 50km/h made everything hard.

It still awaits for new GPS module, since Ublox Neo-6M is really, really, really crappy solution…

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Hands on: AnyFC F7 from Banggood

Before we proceed, short clarification. Legal background of AnyFC F7 flight controller from Banggood is iffy. It’s not that BG ripped the design from Sami Korhonen (sambas). Sambas published design of his AnyFC under Creative Commons BY-SA. So, it’s free to copy this design as long as Sambas is referenced as author, and license is not changed. The problem is that “by attribution” part is not met. Sambas is not referenced as author on BG. Still, Sami wrote that he is fine with it, as long as boards quality is good enough.

Today I have something brand new to write about. Probably the first commercially available flight controller based on STM32F7 CPU: AnyFC F7 from Banggood.

AnyFC F7 STM32F745 flight controller

Continue reading “Hands on: AnyFC F7 from Banggood” »

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