Taranis

DIY RC radio link: the problem of protocols

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?

RC link simplified

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: Tiny Frsky 8CH Receiver from Banggood

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.

Tiny FrSky 8CH DIY Receiver Pinout

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

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FrSky SmartPort Telemetry on AnyFC F7

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.

How to connect F7 flight controller to SmartPort

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Talking Taranis – teach FrSky Taranis to talk to you

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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HC-12 433MHz RF serial module range test

Dziku 4 Comments

As I mentioned in my first post about HC-12 433MHz radio modules, I’ve put my interest in them for telemetry purposes. While S.Port telemetry I’m using in FrSky Taranis radio might have higher range than HC-12, it is closed environment. Since $10 for a pair of HC-12 is not much, I’ve decided for more open DIY solution.

Setup on a quadcopter consist of one HC-12 configured for FU3 mode and baud rate 9600bps connected to SPRacingF3 UART3 port and “air cooled” (shortened with a coil) 433MHz whip antenna. Well, to be precise, it’s 450MHz since I changed working frequency. Antenna is not tuned or scientifically computed. Just 433MHz version shortened a little using proportions. Antenna is mounted on GPS mast. In next version I will probably replace whip antenna with Vee antenna.

HC-12 Rf 433MHz module in quadcopter

"Air cooled" antenna on quadcopter

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Smartport telemetry for Cleanflight

Dziku 13 Comments

With their latest transmitters and receivers FrSky changed telemetry protocol. XJT module, Taranis radios, X8R, X4R and X4RSB are using SmartPort telemetry protocol. And that creates few problems. First of all, SmartPort is a serial protocol. That means, flight controller has to have free serial port to connect S.Port device. Second of all, TX and RX lines shares the same wire. The work in half-duplex mode. Third of all, SmartPort signal levels are inverted: logical 0 is in HIGH state, logical 1 is in high state. All of that combined, connecting SmartPort receiver to flight controller and sending telemetry data is not so easy to archive. Specially on FCs without hardware inverters. That applies to most popular STM32F1 devices like Naze32 and Flip32. Not only numer of UARTs there is limited, but also they lack hardare inverters. Of curse, everything is possible and hardware solution for Cleanflight, Naze32 and SmartPort telemetry can be found here.

Luckily, there is simpler solution for Cleanflight that uses SoftSerial and does not require any hardware hacks besides special wire. Requirements:

  • Cleanflight capable flight controller (STM32F1 or STM32F3),
  • SmartPort enabled receiver: FrSky X8R, X6R, X4R, X4RSB,
  • Possibility to enable SoftSerial. Depending on FC type, different fetures like Parallel PWM, Sonar, LED Strip or Current Meter collides with SoftSerial functionality. Check documentation first. In case of Naze32/Flip32 WS2812b LED strips and Parallel PWM can not be used.

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PPM output on FrSky X4R and X4R-SB receivers

Dziku 4 Comments

FrSky sells 2 small Taranis compatible receivers: X4R and X4RSB. By default, they offer only PWM signal. 4 channels on X4R and 3 channels plus S.Bus (16 channels over S.Bus) on X4RSB. And that is problematic. Many flight controllers does not support S.Bus very well (no inverters) or just does not offer enough UART ports. When speaking of small multirotors, PPM signal is often the best choice. That made X4R almost useless. For X4RSB additional S.Bus-PPM conversion cable had to be used.

Luckily, this has changed, since FrSky started offering custom X4R/X4RSB firmware that allows 8 channel PPM signal on receivers port 1. The only thing you have to do is to flash you receiver. And those are the steps to do it:

  1. Download CPPM firmware from this site. Remember that you need proper EU/non-EU version. It all depends if your Taranis and it’s built in XJT module has EU or non-EU firmware. How to determine EU/non-EU Taranis? If you are living outside EU you probably have non-EU firmware. If you are living in EU but bought from non-EU country (China probably) you have non-EU. Also, if in menu you can select D8 or LR12 internal radio mode, you have non-EU firmware. EU firmware allows only D16 mode,
  2. Follow those steps to flash X4R/X4RSB using Taranis built in port,
  3. Put a jumper on signal pins 2 and 3,
  4. Bind receiver with Taranis,
  5. Remove jumper.

From now on, pin 1 outputs PPM channels 1-8, pin 2 outputs PWM CH9, pin 3 outputs PWM CH 10, and pin 4 outputs either PWM CH11 in X4R or S.Bus on X4RSB. If you want to go back to non-PPM mode, bind receiver again, without jumper on pins 2 and 3.

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Multiple flight modes for Cleanflight with Taranis

Dziku 1 Comment

FrSky X9D Plus Taranis is incredible radio. But also can be intimidation when migrating from simpler radios. Great example is mixing multiple switches into 1 channel to pass flight mode to flight controller. Yes, you can do it, but it can be pain in the ass on a Mixer level. I’ve lost a lot of time trying to understand logic behind mixer weight and offset only to discover possibility to replace channel value, not add. And everything was simple again. So, here what I wanted, and what I did.

What I wanted

When I fly bigger FPV quadcopter, I want to use 7 different flight modes:

  • Angle without Altitude Hold (no BARO),
  • Horizon without Altitude Hold (no BARO),
  • Acro/Rate without Altitude Hold,
  • Angle with Altitude Hold (BARO),
  • Horizon with Altitude Hold (BARO),
  • Position Hold with Altitude Hold (BARO),
  • Return To Home with Altitude Hold (BARO)

And I’ve figured out, that 3 switches should be used to enable all the flight modes: SC, SD and SG. SC toggles Angle/Horizon/Acro. SD switches PosHold and RTH (as well as BARO and overrides SC and SG). SG enables Altitude Hold but only when SC is in up or middle position. 3 switches, 7 modes. I could do it with 3 radio channels, but that would have few flaws: would use 3 channels instead of one, and would allow for mistakes like no BARO with POSHOLD. So, advanced mixes and logical switches that is. (more…)

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RedCruiser – DIY Depron airplane for FPV

Dziku 2 Comments

Few months ago I’ve wrote about my first handmade Depron airplane. It was cool design. Super simple, with KFm-2 airfoil, durable and easy to fly. But it had few serious flaws:

  • motor mounted in front of fuselage is great for flight characteristics, but propellers breaks all the time. Even with prop savers,
  • big fuselage is not the same as fuselage with a lot of space inside.

Depron KFm-2 airplane with pusher propeller

That’s why, I have build a second Depron airplane. This time with pusher propeller mounted on a tower behind wing. Wing is almost the same design as in my first airplane. It is still an KFm-2 (Kline-Folgeman, modified) airfoil, 150mm chord, 12mm thick. But is a little shorter: 1200mm instead of 1250mm. The main difference is inside wing. Instead of carbon fiber spars I’ve used two carbon fiber 6mm pipes. That gives plenty of stiffness. Wing almost does not bend in flight, even during hard maneuvers. And generates more than enough lift to give nice, slow flying experience without danger of heavy stall. You really have to want to stall it. And event when it stalls, it recovers nicely: drops a nose, dives for a second or two, and you have lift again. No need to work with rudder, just let it dive and gain speed and then level.  (more…)

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