FrSky R-XSR pinout

FrSky R-XSR Pinout

  • GND – ground wire
  • +3,5-10V – positive voltage supply. R-XSR is rated up to 10V and powering it from 5V is the best option
  • SmartPort – inverted S.Port pin (standard) – can be used directly with STM32F3 and F7 series
  • SBUS – SBUS protocol output
  • SBUS Input – for redundancy function only
  • Uninverted SmartPort – uninverted S.Port pin (standard is inverted) – can be used directly all flight controllers on any serial port
  • Uninverted SBUS – uninverted SBUS protocol output (standard is inverted)

FrSky Taranis Q X7 and X7S – is it still worthy?

FrSky Taranis QX7 appeared on the market a few years ago and got quite a lot of popularity in its time. There were reasons for that:

  • much cheaper than Taranis X9D
  • still with full-size JR bay,* a lot of switches – less than on X9D, but who uses all the switches on X9D?
  • the same radio link as on the bigger brother means it has the same range and reliability as well proven radio link of a bigger Taranis

Thanks to all of that, not only Q X7 became a very popular entry-level radio transmitter for new people in the hobby, a substantial amount of pilots migrated from X9D to Q X7 as it’s lighter, cheaper, and work as well full-size Taranis.

The situation was even better when FrSky showed Q X7S with incorporated great Hall-effect gimbals and some extra features like wireless trainer port, etc.

FrSky Taranis Q X7S Carbon Edition ACCESS

Now, the question is: is Q X7 still worth buying in 2020 or should new and existing users be rather interested in other radios like X9 Lite, Jumper T16 or similar?

The answer is as follows: the Q X7 is still one of the most interesting radio transmitters on the market. You might say, that it’s aging well. Not only it works as great as when it was introduced, but it also is not as much “castrated” product as X9 Lite for example. This is why, my verdict is: if you like how it looks (not everybody does) and look for a higher entry-level device, Taranis Q X7 is for you. It’s not so obvious with Q X7S as it’s much more expensive and then Jumper T16 Pro becomes a valid competition, but the cheaper version is probably the cheapest FrSky radio worth getting!

NEJELaser Master Driver and Software

NEJE Master aka NEJELaser Master aka KKmoon Laser Engraver is a family of cheap laser engravers/cutters. They come in a variety of laser powers, from 3500mW, by 7000mW up to 20W. Bear in mind, this is the electrical input power, not real optical output power. The 20W module has a real power of around 5.5W optical. Still, it's enough to cut through 3mm plywood in 2 or 3 passes.

Anyhow… NEJE made it extremely hard to download their software. The web server where they store ( it is extremely slow! The transfer is well below 3kB/s and breaks very often. This is why I've prepared a small package. It contains Windows driver for NEJE Laser Master and version 4.7 of NEJE software. You are welcome!

Download NEJE 4.7 and NEJE windows driver here

Dalprop Nepal N1 5″ propellers

This weekend, thanks to Foxeer, I had an opportunity to test flight new Dalprop freestyle props: Nepal N1. Although the name is a puzzle for me, I’m pretty sure Dalprop Nepal N1 might make some stirr!

Dalprop Nepal N1

Anyhow, Nepal series is intended for freestyle although I’m pretty sure you can do some relaxed, non-competitive FPV racing with them as well.

  • diameter: 5,1″
  • pitch: 4,35″
  • weight: 3,7g
  • PoPo compatible
  • material: polycarbonate

Dalprop Nepal N1

The most visible feature of Nepal N1 is that they have heavily swept-back blades. The resemblance to Azure Power propellers is obvious, but they are far from being identical. Blade shape and curvature are different.

Dalprop Nepal N1

After flying a few LiPo packs with those propellers, all I can say is that I like for they perform and for sure will use them a lot.

  • The prop wash is very gentle and easy to tune out. The marketing slogan for Nepal N1 is “No prop wash” but it’s only a slogan. Prop wash is there, but it’s not big and simple to avoid
  • Yaw is responsive but not over-responsive like some heavy pitched props
  • They seem like a nice compromise between very gentle and power lacking props like Ethix S3 and the previous generation of Dalprop propellers know as Cyclone.
  • Nepal N1 feel very precise in flight and I was kind of surprised how easily I was able to navigate between trees and fit into small holes
  • I have no idea what exactly they used to make Nepal N1, but they are bloody tough props! After a few at least moderate crashes, there is still not a single scratch on them and I did not have to replace even a single propeller. All are straight and you can see some evidence of being in use only after a close examination. Very durable indeed
  • Powerlooping is easy again as they do not lack power at the high end and I had no problems to travel back far enough to have enough time and space to hit the gate again. Very nice!

Dalprop Nepal N1

INAV and DJI HD FPV system – there is a light at the end of the tunnel

When DJI did not decide to add INAV and Ardupilot to the list of the supported flight controller for the HD FPV system, some people were, at least, disappointed. Long story short: DJI OSD works only with Betaflight. Period.

DJI HD FPV system

Until today, DJI avoids the answer to the question if INAV and Ardupilot will be supported. I know there are some talks and there is a chance for native support for INAV and Ardupilot, but the timeline is not revealed.

In the meantime, there is a solution. It's based on, dadam, Arduino! Yeap, Arduino to the rescue! Thanks to Mavlink to MSP bridge DJI AirUnit thinks it's talking to the Betaflight flight controller, while indeed it is talking to any flight controller software that supports Mavlink! Since INAV supports Mavlink, you are golden! Enable Mavlink on one of the ports, connect DJI AirUnit via the Arduino and that's all!

It might not be the perfect solution to the problem, but it is a solution that seems to be working!

Drone and RC airplane motors – everything you wanted to know but you were afraid to ask!

Today, let's have a nice talk about brushless electic motors we use in the RC hobby. Both on airplanes, as well as on drones. In this video we will discuss:

  • motor size
  • motor KV and rotation speed
  • KV versus KT as motor constants
  • stator and rotor
  • number of coils and poles
  • winding
  • phases
  • airflow and cooling
  • does a motor care about rotation direction
  • how to change the rotation direction of a motor
  • shaft and hub
  • mounting holes spacing
  • how not to fry your motor right away

DJI FPV System & INAV – current situation

DJI FPV System

When DJI released updated firmware for their DJI FPV system with improved OSD, Betaflight users started cheering. The move to add OSD with elements like GPS position, the artificial horizon, etc is kind of puzzling. It works only with Betaflight flight controllers and a typical user of Betaflight does not really need it. After all, Betaflight concentrates on racing and freestyle on 5-inch mini-quads, not long-range.

On the other hand, users INAV, that concentrate on airplanes and long-range flights, can not use new DJI FPV OSD. Pilots immediately started to ask INAV developers to implement DJI FPV support. The problem is, that it's not working like that.

  • Support for Betaflight is built-in into DJI Air Unit, not another way around.
  • DJI FPV seems to be actively checking if the flight controller it talks to is Betaflight or not
    INAV and Betaflight support the same serial protocol: MSP. This means DJI FPV is capable of talking to INAV, it just refuses to do so
  • INAV and Betaflight use the same OSD positioning protocol using the same MSP frames. Still, DJI FPV refuses to talk to INAV
  • We have no idea what DJI Air Unit expects from a flight controller since it is the closed source!

All of that means that INAV developers can not fix something that is not within the code of INAV. For INAV support, DJI has to implement it. Not the other way around.

Pirx Seven – The ultimate custom 7-inch FPV frame, part 1

Do you know this old saying “If you want something done right, do it yourself”? I do and sometimes I just live according to it. Not always, I’m not crazy, but at least from time to time!

I fly 7-inch FPV drones a lot. To be honest, they are my favorite flying devices. There are a few good 7-inch frames, like TBS Source One for example. There is a difference between good and great tho. I do think that Source One is a good frame, there are a lot of things on it that do not make me very happy tho! The list might not be very long, but it is relevant:

  • props in the view
  • limited space to install split-like hybrid cameras
  • no very convinient place to install VTX
  • it’s not that big inside as one might imagine…

Because of that, and because I think I know how to do it (I’m an engineer) I’ve devided to design and manufacture my of 7-inch FPV drone frame that would fix what I do not like in Source One.

This is how Pirx Seven was born!

Pirx Seven - 7-inch FPV drone frame

  • Dead Cat configuration
  • Plenty of space inside for everything you want! There is even a place in the back to fit the whole 30x30mm stack!
  • Place for Split-like hybrid camera in the front
  • Attachable mounts for antennas, GPS and other accessories
  • Clear, unobstructed view for HD camera like GoPro on the front deck

So far, I was able to mill a prototype unit to test it in flight. So far so good, I really have to say that I like what I designed.

Pirx Seven - 7-inch FPV drone frame

Fully assembled frame weight 205g with steel screws and aluminium standoffs.

Pirx Seven - 7-inch FPV drone frame

What next? Test flight and some changes. The full list consists of 12 points in total and basically means that I will have to redesign almost everything…

If you want to know why the name and what does Pirx stands for, here is the answer. It’s a tribute to Polish writer StanisÅ‚aw Lem and his book Tales of Pirx the Pilot.

Your first 7-inch FPV drone

I love 7-inch FPV drones and during the last year, they were my most used FPV gear. For freestyle, cinematic, cruising and long-range. I currently own 3 7-inch FPV drones and 4th one in the assembly process.
I think of myself as a 7-inch expert. I’ve wasted enough money and equipment to know what works and what does not work well with 7-inch propellers.

TBS Source One 7-inch FPV drone

If you are thinking about building your own 7-inch FPV drone, here are some tips that might save you a lot of time and a lot of money on wrongly chosen equipment.

The Frame

Of course, the frame is the most important part of a build. No matter if you will be building a freestyle or long-range rig, there is one thing that you have to know: Horizontally scaling 5-inch frame by making arms longer is a no-go. Longer arms require more stiffness and they also have to be thicker! The sweet spot is 6mm thick good quality carbon fiber. 5mm thick might work too but forget about 4mm or thinner arms. They will be too flexible and the whole quad will be in a state of a constant wobble!

Alfa Monster 7-inch FPV Frame

If you are looking for 7-inch frame recommendations, here are my choices: Team BlackSheep Source One with 7-inch arms, Alfa Monster and AlfaRC Fighter.


Kind of obvious, right? The choice of good 7-inch propellers is not that big as one might imagine. Sure, you can buy some “inventions from 4 years ago for cheap” but believe me, they are not worth it. There are 3 types of modern 7-inch propellers that I find worth looking at in late 2019:

  • DAL T7056C – good for freestyle and thanks to aggressive pitch they are very dynamic. Can be used no longer flight, but this is not where they really shine.
  • HQProp Durable 7x4x3 V1S – a more aggressive version of 7×3.5×3 that in my opinion works much better than original. Slightly more pitch only helps during steady flight. They are rather for cruising than for freestyle.
  • GemFan FLASH 7042 – kind of good propeller, but don’t get me wrong, you should try 7042 only if DAL or HQProp are too heavy for your motors. So if you have 2207 or 2306 you might try FLASH. If you have bigger motors, just go with DAL or HQProp.


Brotherhobby Avenger V2 2507

Probably the most often made mistake by the “7-inch virgins” are too small motors. Beginners think that putting the same motors that work great with 5-inch propellers on a 7-inch frame is a good idea. OK, maybe sometimes they lower the KV. This will not work. I know. I tried that by myself and only wasted some money and a lot of time and nerves.

What you need are big motors. In a size of 2506-2507. 2208 might work as well and 2508 is rather the max size that makes sense.

On the KV size, the rule of thumb is that on 4S you should aim at 1500-1500KV and on 6S at 1200KV. Those values give a nice compromise between efficiency and raw power. Of course, this is only a rule of thumb and when needed you might choose higher KV. For example, my 7-inch freestyle drone uses 1700KV on 4S motors.

My recommendation is rather simple: for now, there is only one motor that comes is wide enough KV range and it’s called BrotherHobby Avenger v2 2507.

Everything else

For the rest of the equipment, you can choose whatever you want. Any equipment will work and you do not have to match it to the propeller size. My choices are: