Plane 3.9.9 release

I have just release plane 3.9.9beta1. I expect this to be a fairly short beta and I would really appreciate some testing feedback.
Key changes are:

  • learn EKF biases even for inactive IMUs, making IMU failover much more robust

  • EKF uses earth magnetic field model to reduce in-flight compass errors

  • EKF switches to first healthy IMU when disarmed

  • IMU fix for dropped samples during high CPU usage

  • added support for Ublox F9 GPS

  • switched to ChibiOS I/O firmware for ChibiOS builds to support Spektrum bind

  • CUAVv5 Nano LED fix

  • fixed watchdog trigger on simple accelcal

  • fixed drift of AMSL estimate when disarmed

  • fixed rate integrator buildup when rate control disabled

Happy flying!



I wanted to try your ArduPlane 3.9.9 beta 2 but had to give up since it still doesn’t implement (as also 3.9.8) the very useful serial options which allows to use the Frsky passthrough protocol without requiring any of those DIY/Propriatery external HW converter crutches .

As of now those serial options are only available when using V3.10.0-dev.
So ,when can one expect to have them implemented with a beta and ultimately a stable version ?

Thanks for any hint.


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I expect to start on a 3.10.x beta release in about a months time, which will include that feature

I have just done a Plane3.9.9beta3 release. Changes since beta1 are:

  • fixed issue with setting of EKF origin in GPS modes
  • added support for MS4525 on 4th I2C bus
  • added delay on LW20 I2C probe
  • added mRoControlZeroF7 support
  • enabled IO pass-thru on FMU failure on ChibiOS builds

Please let me know of testing results, positive or negative!


Sorry that I had not written anything about beta2: Several hours flight time with 3.9.9beta2 worked without any abnormalities (F405Wing: Manual, FBWA, CRUISE, AUTO).
I hope to be able to fly a lot with the 3.9.9beta3 at the weekend and will report.

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Thank you so much for all the time and effort you put into the project. I so appreciate all the work that goes into continued development of this open source project. It is at a level that I cannot begin to understand. I did, at least, want to thank you for your work


Thanks Rolf, much appreciated!

I posted some feedback on the u-blox F9P support in this thread.

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I’ve now released 3.9.9beta4, with two fixes:

  • fixed an issue with handling baro failure on CubeBlack
  • forced INS_USE3=1 on CubeBlack when first two IMUs are enabled

Today I completed a 35 minute flight without any abnormalities (3.9.9beta4, F405 Wing, Manual, FBWA, CRUISE, AUTO, ACRO).

Thanks for the good news :grinning:

Thanks Rolf! Can you upload a log for me?

Of course:

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I have now released the final version of plane 3.9.9. Many thanks to everyone who did testing!
The final release has two additional patches over beta4:

  • fixed setting file timestamps with u-blox F9 GPS (thanks to Martin Sollie)
  • fixed return value of LightWare serial rangefinder driver when out of range

Happy flying!

@tridge thanks again for all the effort and continuous improvement!
one thing i’ve been desperately waiting for in release type fwares for quite a while now is external baro support. imho it’s a neat feature with a lot of possible benefits.
your fabulous external baro support PR has been added to master a year ago and it’s been working flawlessly on all my setups ever since. honestly, i shed a couple of tears when i realized it hasn’t made it into plane once again. i’m not sure if adding crying face emojis is appropriate for people above 20 years of age in a technical context?

cheers, basti.

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sorry for not back-porting this. I was actually planning to start a beta soon based on master. It would be quite a long beta period, but I think we are long overdue for a release based on master

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