Warning #1: an issue has been found with Tower's Pause button which can cause the vehicle to fly to an old position if the vehicle has not sent a position update to Tower in some time.

Warning #2: Copter-3.3.2 fixes a bug found in Copter-3.3.1's desired climb rate initialisation which could lead to a sudden momentary drop when switching from Stabilize or Acro to AltHold, Loiter or PosHold.

Warning #3: Copter-3.3.2 fixes an issue found in Copter-3.3.1 which could lead to hard landings in RTL or AUTO if the WPNAV_SPEED_DN was set too high (i.e. >400 or 4m/s) and/or the WPNAV_ACCEL_Z was set too low (i.e. <100 or 1m/s/s).

Warning #4: a bug was found in Copter-3.3 which could cause a sudden crash if you abort a Take-off initiated from a ground station.  Video description is here.  The bug is fixed in Copter-3.3.1 so we recommend upgrading.

Note #1: AC3.3-rc8 corrected a long standing bug in the HDOP reporting.  HDOP values will appear about 40% lower than previously but this does not actually mean the GPS position is better than before.
Note #2: if upgrading from AC3.2.1 the vehicle's accelerometer calibration needs to be done again.
Note #3: set SERIAL2_PROTOCOL to "3" and reboot the board to enable FrSky telemetry like in previous versions.
Note #4: the wiki will be updated over the next few weeks to explain how to use the new features

Copter-3.3.1 is available through the mission planner.  The full list of changes vs AC3.2.1 can be see in the ReleaseNotes and below are the most recent changes since AC3.3.

Sadly this version (and all future versions) will not run on the APM2.x boards due to CPU speed, flash and RAM restrictions.

Changes from 3.3:

1) Bug fix to prevent potential crash if Follow-Me is used after an aborted takeoff

2) compiler upgraded to 4.9.3 (runs slightly faster than 4.7.2 which was used previously)

Changes from 3.3-rc11:

1) EKF recovers from pre-arm "Compass variance" failure if compasses are consistent

Changes from 3.3-rc10:

1) PreArm "Need 3D Fix" message replaced with detailed reason from EKF

Changes from 3.3-rc9
1) EKF improvements:
    a) simpler optical flow takeoff check
2) Bug Fixes/Minor enhancements:
    a) fix INS3_USE parameter eeprom location
    b) fix SToRM32 serial protocol driver to work with recent versions
    c) increase motor pwm->thrust conversion (aka MOT_THST_EXPO) to 0.65 (was 0.50)
    d) Firmware version sent to GCS in AUTOPILOT_VERSION message
3) Safety:
    a) pre-arm check of compass variance if arming in Loiter, PosHold, Guided
    b) always check GPS before arming in Loiter (previously could be disabled if ARMING_CHECK=0)
    c) sanity check locations received from GCS for follow-me, do-set-home, do-set-ROI
    d) fix optical flow failsafe (was not always triggering LAND when optical flow failed)
    e) failsafe RTL vs LAND decision based on hardcoded 5m from home check (previously used WPNAV_RADIUS parameter)

Thanks for your testing!

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Guys... I need some clarification on my vibration levels. 

Do I have vibration problems ??? I do not understand if my graphs are dangerous or ok!

If I look only at the "grass" height I'm ok but if I look at -+3 and -+15 range i'm not. The waves in the graph are me pushing my flying limits  ( lolololol ) and of my 680 pro.

Any enlightenment would be great because I worked very hard to remove motor / prop vibration and if I still have vibration problems I quit LOL and move on...  learn how to fish or something :S

 Btw, first flight with 3.3 - rc8. It worked perfectly. 

Thank you very much.


I saw that the 3.3rc8 was out this morning so I couldn't resist, I loaded it and went to my best testing grounds to see how it went.

I had just loaded 3.3rc7 a few days back and it worked well. On the rc 7 I was unable to test the GPS dependent modes but this tine I did.  

The wind wasn't bad but was gusting a bit and it happened to when I was arming it.  The props spin to fast when it arms.  I guess there is parameter to adjust for that, but when I arm, it is hard to keep it on the ground.  So, it tipped over.. Do damage, so I gave it a second try. As soon as I cleared the ground, it was flying very smooth and stabile.  I placed into Alt hold and it was only about 3 meters off the ground and it held it for a short time, then dropped and did a soft touchdown and then I too it back up and hovered a bit.  This time it held altitude well, so I took it up a bit higher and engaged poshold.  It was pure pleasure from that point on. It was smooth, locked in and I conservatively to simulate taking some camera shots.  In fact I was running my GoPro at 4k 15fps to explore the concept of shooting 4k to get lots of high res photos, that works well BTW!  I had one anomaly, the MinumOSD was telling me I was still in Althold, even though I was in PosHold for most of the ride.. perhaps MinumOSD needs an update..

I had no other issues, so I really like this release.. Tommorrow I will put on the googles and do some FPV..

attached is the Flash log


I finally got to testing the large quad again with 3.3 RC7 after changing mounting options and ensuring throttle min was set properly and we have the same issue with it flipping. It seems to always happen after yaw inputs.

I am completely clueless as to what could be causing the problem as when I look at the logs I don't see anything wrong and there was no mechanical failure.

Logs attached.


Having an unusual issue with all motors spiking in throttle after SECOND arming event. The problem goes as follows. 

-  Quad plugged in. 

-  All Pre-arm checks passed

-  Arm Safety switch depressed

-  Quad armed via Tx and flown with no issue

-  Land and disarm via Tx (Without depressing Arm safety switch. Switch remains illuminated as steady red)

-  Immediately after arming again all motors spike to 50% power.

-  When Tx throttle moved slightly above low point and quickly back to low all motors respond as expected and I am able to takeoff from there without any problems. 

Any subsequent attempts to takeoff following the above sequence repeats the problem continuously. If i unplug everything and then start from step 1, the first takeoff is always as expected. The problem only occurs on the second takeoff event as described. The included photo is from the log file showing a graph of my throttle input to capture the motor runaway and bring them back to low for normal takeoff. This problem presents itself regardless of the flight mode used during takeoff. Acro and Stabilize

Ps: Previous issue with stability solved. Quad gimbal flex was causing High frequency oscillations (above what pixhawk can measure?). Auotune did its job and provided the highest PID possible while minimizing issues. Once the Gimbal twisting issue was solved autotune PID's provide a rock solid multi-rotor. Excellent job guys.



Yes, that change came as a direct consequence of you crash.  So thanks very much for the report including logs.

The next step in this vibration protection programme is to make sure the GCSs are making the vibration levels easily accessible to people.  So perhaps a bit like how the GPS appears on the HUD, we'd like "EKF" and "VIBE" printed in green, amber or red depending upon the health or level of vibration.  Maybe allow the user to click on these strings and pull up a more detailed view of their status.

Darn.  It's suppose to be fixed.  So what we may have here is a failure of the fix and the dev testing of the fix.

I don't have a board myself but we will review the patch and see if we can spot the error.  A few people on the dev team have AUAV-X2 boards so we should be able to test and include in -rc9 and/or a patched -rc8 so you can test.

Thanks for the report!


Definitely best to include a dataflash log.  We can then compare the mag field length to the throttle or current draw and if it's motor interference (which it probably is) it'll be crystal clear.


Thanks for testing and providing the feedback.  Instead of backing out to DCM/InertialNav I'd really prefer to get the EKF improved.  Can you provide a dataflash log?


Thanks for the report.  It looks like you've downloaded the dataflash logs, could you post them here as well?

Ok, let me know if i can try to recompile or patch this code and try it out, i may have time for that next week.

I still saw same compass variance error trying to "fly by hand" with rc8. Also note hdop 0 issue - but, even with it, little drone behaved way better now than with rc7.

bin file from flight


The .bin file is included in the link. It is ~30mb since it was a 15min log. I went back to rc 3.7 and the issue is there as well. 


The vibe levels are a bit higher than my IRIS on the Z-axis but I don't think it should cause significant problems.  Most importantly there's no accel clipping which is really important.  By the way, the new VIBE message is better at giving an objective measure of vibration than looking at the IMU values directly.

So we can see that your vehicle's Z is spending a fair bit of time in the middle at 20 which is higher than my IRIS (the example on the Vibration page) is generally down below 15.  We don't have enough feedback from people to know when the vibration levels start affecting altitude and position estimates but I suspect you vehicle is ok.

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