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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Randy, any ideas what is it?


thanks a lot for testing! 

I just had a very short look. It seems you enabled IMU_FAST instead of IMU_RAW (because I could not run an FFT in MissionPlanner).

What is really interesting is that the Vibes closely follow vehicle movement - although the idea behind is to "remove the vehicle’s movement and create a “accel_vibe_floor”. This is visible in my logs as well to some degree but your flight was longer and maybe much more aggressive.

Could you please try again with raw IMU logging? 

Thanks again!



Same here.. Mine was about a year old with 100s of cycles.. Just worn out?

This one was brand new lol. Only had 1 flight on it. But no worries, I'll get it sorted eventually :)

Did you try on another pc?

Didn't Rob explain its supposed to be like that? They are accelerometers after all and I really pushed the hexa to the limits so they are measuring the actual aceleration during maneuvers. The "grass" height is actually very consistent and within the range.

I had both enabled. Fast and raw. Tomorrow I'll give it another try if the weather allows it. It's night atm.

Yup. but no worries. I tried the SD card out of my other hawk. I tried booting holding the safety switch. I tried different computers, different usb cables, and different hubs and what not. Just waiting on the RMA to send it back and be done with it and will start again when he replacement gets here.

Ups!! , it's horrible when you can't find a solution; at first I reset to default as you, but what I do now when I want to reset settings, I use reset to default button as Randy recommends; first i save old settings and them I use compare button and check only modes, batteries and that standard settings not to have to program all again...vague woman ;) , perhaps this helps  the following time you want to reset settings.


I've had a look at the compass and compared to my IRIS.  The graph's for both vehicles are below with the magfield (in red) vs the throttle out (in blue).  There's certainly a lot more variation in your vehicle's log (top) but it doesn't seem very correlated with the throttle output (or current which is not shown) and only somewhat related to lean angle.

I'm not seeing errors on the I2C bus, the compass remains healthy for the whole flight.  So I'm really not sure what's causing the extra noise.

We have a slight weakness in the software in that we rely on the compass hardware's vector scaling which we know is not perfectly accurate.  We have an improved compass calibration routine coming in AC3.4 (already in Solo) that improves this.  Without this improved scaling you may find the mag-field length changes as you lean the vehicle.  You can test this by connecting with the MP, then check the Flight Data screen's Status tab, look for magfield and see if it changes as you tilt the vehicle.

My guess is that it's ok, especially if you're not seeing any kind of problems in flight although I suppose it would be nice to get to the bottom of the noise.


Great, thanks.  If it's not too late, could you check the LOG_BITMASK's IMU_FAST bit is checked?

In -rc7 this was forced on but I forgot to apply that change to -rc8.  The IMU_FAST is helpful to Paul Riseborough because it gives the 400hz IMU logging so we can run Replay on the log.  It's not critical but it would help, thanks!

It should be possible to get the firmware uploaded on it using mission planner, I think it's just about getting the timing right so that MP recognises it's a Pixhawk and is also able to catch the board in the first few seconds of being plugged in (or rebooted) because during that period it's in bootloader mode and will accept new firmware.

The PX4 guys also have a much simpler tool, QUpgrade that can be used (I can't immediately find a link to that applicatoin).  it might work better in this particular case because the user tells the program what board is being used (while MP has to figure it out).


Thanks for the report.  I've reproduced the issue so we should be able to come up with a fix.  I think what's happening is the output of the "Overtime .." message is interrupting the input of the message to the ardupilot firmware.  It's not clear to me yet whether it's a mission planner issue or an ardupilot firmware issue.

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