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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Trying to use photoscan, so hopefully there's a fix in MPs geo-ref tool soon!

I tried to manually pull the CAM lines from the rc7 log into their own file and format them the same as a 3.2 log, so that the tool would accept them, but didn't have any luck. There ended up being 300 CAM lines for the 170 images that were taken, so I'm not even sure what's going on there...

I was facing the same problem as you, Glenn. My workaround was to export the log's GPS info into a GPX file using MP, then use ExifTool to to add the GPS tags to the JPEGs from the GPX file. I then used Agribotix to make the mosaic, which worked perfectly. Let me know if you need details.


Yes please Fred, do you mind posting the exiftool command you used? Also if there are any other steps to get the tags into the images that info would be appreciated!

I have created the KMZ + GPX from the log, and have exiftool.exe and the gpx in the folder of the images to geotag.


Glenn, assuming 3 things: that the GPX file and the JPEGs are in the same folder, that you are located in that folder with the command line tool (whether Mac or PC), and that the time in the images and the time in the log are in sync, then the ExifTool command is "exiftool -geotag NameOfFile.gpx *.JPG" (match the case of the extension of your images). You'll get a bunch of error messages, but they have no consequences (anyway, they did not for me). Sample check the exif info by looking into one of the images: you should see the five newly added GPS tags. If you need to deal with a timezone or other time difference between images and GPX, you'll need to use the Geosync tag in the exiftool command: find out more about that here: http://www.sno.phy.queensu.ca/~phil/exiftool/geotag.html. I hope this helps. Let me know. Fred


Sorry for your crash. Catastrophic failure is the right term.  The MPU6k was unhealthy right from the beginning and some very bad data was returned by the barometer.  I think if you'd had telemetry attached you would have seen a "Bad Gyro Health" and/or "Bad Accel Health" warning.  My guess is it's a hardware failure, if this was a board purchased from 3DR between June 2014 and Feb 2015 you could likely request an RMA of the board and have it replaced.

There's a couple of things we need to do as a result of this:

1. add an arming check that the IMUs are healthy.  There's a pre-arm check but apparently the IMU went bad sometime after boot-up but before arming.  So we could have prevented the vehicle from even taking off.

2. ensure the EKF baro glitch protection is working and that the system can deal with this crazy data.  In this case NaNs appear in the logs which means that the system tried to consume the bad data.  NaNs are extremely bad because they spread like a disease if any part of the system tries to consume them.

Thanks for the report, there will be some additional protections in -rc9 to catch these failures.

One last question, you rebooted the board after uploading the firmware of course?


If you have Tower connected it should tell you but also when arming, try arming in Loiter,  It won't let you arm unless it has a good lock and position estimate.


No, we don't support the graupner hott protocol.  The link you've got there is for the px4 stack and although we share many drivers, this particular one would require using the px4 flight controller stack.

I don't think you'll see any improvement by going back in beta versions.  -rc8 is the best version we have so far.

The compass variance is a warning which is shown by the mission planner for a full 30 seconds in case the EKF reports, even for a short time, that the compass data didn't match the rest of the sensor data (gyros, etc).

AC3.2.1 uses DCM+InertialNav and doesn't have a way to recognise the compass is bad unless the vehicle is moving so this is a new protection in AC3.3.

I just did a quick test and found I was able to rotate the compass up to 35deg before I saw this error.  At the same time I've heard a few others (including RobL from the dev team) say they see this error often.

I found that if I left the compass in it's new orientation, after about 15 seconds the EKF would start adjusting it's orientation to match the compass and then the warning goes away.

Anyway, I can ask Paul Riseborough (EKF master) to look into whether it's too sensitive.  If others could test approximately how much they can move he compass before it appears, whether the messages clears and whether the vehicle's heading on the HUD eventually rotates around to the new heading that might clear up if people have different behaviour.

Thank you for your reply Randy.

Very kind and veri technical.

I have done some test. That's the results:
If the veichle is disarmed and i move it on Yaw axis, after little time "compass variance" pop-up on mission planner.

By the way, if I power up the copter, and I be very careful to not touch anything, to not move anything I can arm it correctly.
But I repat myself: I need to not move anthing, because if I move the copter too much the "compass variance" pop-up.
If i do not move nothing and I'll be veri careful I can arm.

This with rc8.

In the next days I do some other test.


I use this occasion to ask a thing/sugges a thing: in Italy there is a new law that is about the UAV with MTOM less than 300grams. So I'm working on a little UAV that have less than 300g of MTOM.
I need to get start the autotune, but I can mount on my UAV only a 6channel PPM receiver.
There is a way to start autotune with CH6 (or with ground station)?
unfortunately I can not mount a 7 channel rx.
If there is not, it can be added?

For less than 300g UAV's that can be very useful, since there can be more than one case with only 6ch receiver.


Thanks for the tests, it does sound like the EKF is having problems here so I'll ask Paul if he can have a look.

It's possible to invoke AutoTune by setting up one of the flight modes to AutoTune.  Remember you can only enter it from AltHold so another flight mode switch position will need to be set to AltHold as well.

I don't understand how it happens, that two accels placed on the same board have such different vibrations.

And I have one more question. The same copter flies on AC3.2.1 perfectly, as I understand EKF instead of correcting a non-conformity of sensors, it strengthens them and makes flight impossible.

I uploaded the firmware at home and was powered off for the trip to the field. Could this also be the cause of the board seemingly not booting up sometimes? I power it on and the minimOSD either has no display, or does not come out of the "No Mav Data" stage, even after pushing OSD restart button. The board was purchased in Aug 2014, so I will contact 3DR. Thanks for your help, Randy.

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