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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Very gusty wind here in Detroit.  15-30 mph easy... took off in alt hold. VERY impressed, Pos hold too,,, very impressed. Rock solid it just hangs there like it's on a rail!!!!!!!!!!!!!!  

The only thing I notice is my throttle stick seems different. %50 holds fine but it seems different somehow. Was there a default something  with 3.3 and throttle settings??? It's like the dead band got bigger? Is it just me? Is it intentional?   But wow!!! Is the major improvement because of EKF???  I have turned that on and off before.... but this flight characteristics now are way better. Love it... thx devs!!!


Txs for the feedback.  Maybe the EKF helped but my guess is much of it is Leonard's work on the attitude controllers and also the improved thrust curve (it was a set of three lines but now it's a smooth curve).

We did resolve a small bug in the throttle input code which we never noticed until more people started flying with sprung throttles (in particular the Solo).  Fixing that did slightly adjust where mid throttle and the deadband are.

3.3 and 3.3.1 have no changes in that area.  This version uses EKF and has checks now to see if the two gyro's are outputting somewhat the same values.  If not then you get the BAD GYRO HEALTH.  Others have reported the accelerometer calibration failing but after repowering and running the setup again it would work.  Flying without calibration is a bad idea.

Hi Randy! I think its a big bug... My Quadcopter does take off in stabilize with ca 45%, and in loiter or alt hold with ca 80%. Why?


ca? What is that?


Nathaniel ~KD2DEY

*with about 45%

Hello! I would like to share with you the altitude controller's amazing performance when powered with XL-EZ4 rangefinder.

It is extraordinary how precisely it can control the altitude, even in extreme low height flight.

Thanks Arducopter team!!!


Frame: Tarot 680 Pro with 4.4Kg auw weight


Hi Richard, I live in the thumb. Nice to see a fellow Michigander. Go Lions! Meow!

wow your kidding.. I have a place by lexington. Looking forward to 3.4 and 'boat mode' for some killer lake Huron footage :] 

Hi! I did another test flight with my tbs discovery. I was a bit windy last day. but everything went fine. I raised my quad to 60m without problem, then raised it up to 100-120m and held it there for a few seconds then returned down and landed safely. I reviewed my logs after finding out a very surprising info. My current draw peaked to almost 60A

my setup is this:

sunnysky 900kv 2216

gemfan 1045 carbon nylon mix

DYS 30A V2 esc (blue)

5200mah 10C multistar 4s

normally I see my current draw below 30A. I was bothered after I found out about the current draw. Can somebody analyze my log? I will attach the file. thanks!

I have been playing with the lidar lite and am very impressed with how well it makes my quad hold altitude. It make arducopter still more fun to use!

I am really looking forward to fuller integration of range finders,(during auto missions)and the potential for obsticale avoidance by adding a second forward facing range finder. 3.4 maybe?

Dreaming I know, but 10 years ago who have ever imagined civilians drone in the hands of hobbist running auto missions?

Please Randy, and rest of the development team, tell us how we can help to move development forward!

Thank you again!

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