Setting up iNav on 250 class racer

Although iNav (iNavFlight) with advanced GPS and navigation support is best suited for larger, GPS equipped drones, there is absolutely no reason not to use it on something smaller like 250 racer. Why? Well, why not? Basic flight mechanics is the same like in Cleanflight or Betaflight. FP-PID is brand new PID controller, not very popular and not very well documented, but in many ways superior to LuxFloat. The way it handles D term is just outstanding. It can be pushed very, very high without introducing noise.

OK, it has a drawback. High computational requirements and floating point logic causes users of STM32F1 based flight controllers like Naze32 or CC3D can forget about looptime 1000us. 1400us is all those boards can do. On the other hand, looptime 1000us (or even 500) is quite new thing introduced and made popular only about half year ago. And people were racing before that somehow… So, 2000 is not that bad after all. Good thing SMT32F3 board are strong enough not to have to worry about this issue. So, let’s go!

iNav can be configured with Cleanflight Configuator. In almost exactly the same as regular Cleanflight/Betaflight setup. With one very important difference I will describe in next paragraphs.

First important Configurator’s tab is “Ports”.

ports setup

My 250 quad uses 2 extra feature: Blackbox logging and OSD and has 3 hardware UART ports. So, MSP protocol is enabled on UART1 for USB access, and on UART2 for OSD. Blackbox is enabled on UART1. It can be shared with MSP: when unarmed MSP is used, after arming port is going into Blackbox mode.

Next important tab is “Configuration”, specially section “Board and Sensor Alignment”.

general configuration 1

If your flight controller is rotated in any axis, software has to know about it. This is specially useful if you want to have easy access to USB port. Degree is counted clockwise. So, if board is rotated 90 degrees right, yaw rotation should be 90. If it is rotated 90 degrees left (counter clockwise), yaw rotation is 270 degrees. Unfortunately, Cleanflight Configurator is not compatible with iNav on that matter. Configurator sets degrees, iNav expects decidegrees. So, instead to using input field, CLI modes has to be used:

set align_board_yaw=9000

Just multiply board rotation by 10 and done.

Next, since we will not be using GPS, Current Meter or any advanced features, most of this tab will be unchanged comparing to defaults.

general configuration 2

general configuration 3

In my case the only differences are enabled PPM radio and Blackbox logging.

“Radio” tab is also more less unchanged. The only difference is RSSI value reported on channel 6 for OSD. If your radio can not inject RSSI into on of RC channels, just ignore it.

Radio configuration

Radio tab is also useful for checking if radio trims are OK. With radio on, Roll, Pitch and Yaw should show 1500. If not, do trim corrections in transmitter so they are at 1500 (or very close)

Second incompatibility between iNav and Cleanflight Configurator is visible in “PID Tuning” tab. Configurator states that you can choose between 3 PID controllers. This is not true. There is only one, FP-PID and it’s used no matter what you choose here.

PID tuning

Default PID gains should be flyable, but you have to tune to work well with your hardware. This is highly individual.

Setup of flight modes is also individual. My setup looks like this:

Flight modes configuration

I’m using one of 3 position switches for both arming and enabling Air Mode. Switch on Low disarms, Middle arms, High arms and enables Air Mode.

Last thing is gyro filtering. iNav is much more “conservative” by default than Betaflight for example. While for bigger drones this is fine, small racers will suffer from low pass filters set too low. If you are interested in all the details of why gyro_lpf can and should be pushed up, you can read this thread. If not, and you do not have excess vibrations from motors, just move it it from default 98Hz to 188Hz:

set gyro_lpf = 188Hz

Also additional software low pass filters for gyroscope readouts and PID D-term can be increased from default values. Recently I’m using the following:

set gyro_soft_lpf_hz = 90

set dterm_lpf_hz = 42

And this is all. Flash, setup and go flying!

5 thoughts on “Setting up iNav on 250 class racer

    1. Building a QAV 250r and QAV x can I just download Inav firmware to Flight controlled and not have to have a GPS antenna and say aDJI nav trying to understand this new to fpv never built drones or flown and building two right now one for me and one for son. Please explain as for my 250r for my son I just ordered a DJI Nav from getfpv so he could have the return home feature which will add weight that I would like to get rid of. If I understand this correctly I would just purchase say a KISS flight controller and download the Inav firmware which is free and I could eliminate the GPS antenna and return the DJI nav system to getfpv? and I could do the same for the QAVX that I am building which is too small to add a gps Flight controller this way the QAVx would have a return to home feature as well with no added weight? or am I way off here someone please help me understand. Thanks very nice QAV by the way

      Kevin
      [email protected]

      I have also been looking for some help with these QAV builds and have posted below what I could use help with on some FPV forums with no luck so if someone could assist I would surely be grateful!

      New to this sport, never flown or built before, I am sparing no expense in building two drones so I want to get this right. I am currently ordering parts to build my son a QAV 250r and I ordered a QAV x for myself. Below is what I have ordered for parts and I need some help with eCalc configurations to give me some specs on what I am building. I am looking for optimal prop size and pitch with the motor and size I chose along with optimal ESC to handle the motors on a 4s 95c 1300MAH Luminier battery.
      OEM Lumenier QAV X and QAV 250r will have PRO Tmotor F40 2600KV motors, Kiss 30 AMP ESC, 4s 1300 MAH 95c Batteries, 5045/3 Props. I seeking to get out of the 250r to 80-90 MPH and my QAV X to 95-100 MPH if not faster with decent fly time!
      My eCalc configurator shows that I am not even close to desired MPH and fly time for both QAV X and QAV 250r and shows my ESC’s, (KISS 30 AMP) are too small and I, need a bigger AMP ESC’s, it also shows my Pitch is way off and shows low MPH for both QAV’s. (I could be entering the wrong information based on lack of experience which is why I need your help)
      Can someone configure both QAV’s for me and let me know the following
      a) What optimal ESC and Prop size/Pitch would be for both build configurations and what prop would you suggest?
      b) What Max Speed will be for both QAV’s QAV 250r for my son and QAV X for myself?
      c)What is the fly time for each?
      d) What is your experienced opinion about the Motors ESC, Battery and Prop selection I choose for each the QAV 250r and the QAV X builds. Is there a more efficient, more powerful lighter better combination you would have gone with to make each QAV sick performing drones? if so what would you have chosen? Please email me product info and why you would have gone that route so I can research and change products before I build.
      e) What is it you would do to maximize each QAV with the Motor, ESC, Battery and Prop to get the most out of each QAV.
      You can email me at [email protected] or text me at 989-359-1026 I will be building these QAV’s this week and parts are arriving daily so time is off the essence and I need an experienced FPV Drone builder to help. Best regards,

      [email protected]

  1. i flashed inav on naze32 rev 6. this board have onboard flash to store the blackbox but when i access with cleanflight configurator the option is not available and its not record any data to internal flash. do you know about this issue? thanks

    1. I do not own Naze32 rev.6, but have you enabled blackbox storage to internal flash with `set blackbox_device = SPIFLASH` ?

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