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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Sad to see APM dropped.

First rc1 flight behind and quad still in one piece. No errors in the log. I'm seeing quite a lot altitude surfing which is visible in log too. Also baro and gps altitudes are not in par. Barometer seems to show higher alt than it actually was. I did autotune in around 4 meters and raised during it meter or two because of surfing. Baro shows 8 meters :|.

Tested autotune, result wasn't best possible. Quad is barely flyable and has quite strong wobble if sharp commands are given. Earlier version did rock solid settings.

PIDs, earlier and now:

stab 8.5, 6.2


P 0.26, 0.13

I 0.26, 0.32

D 0.018, 0.002

IMAX 500, 50


P 0.35, 0.08

I 0.35, 0.21

D 0.02, 0.002

IMAX 500, 50

New yaw values seemed to work fine.


Thank's Randy, no Pixhawk for the moment but in wish list for this year :) :I think I find an issue in land mode but I have to do another check and post in the correct post (3.2.1) during next week with logs.

Great to see this, Randy. We, like everyone else, are now firmly in the 32-bit era, so it was time to take advantage of that power and leave 8-bit (APM 2.6) behind for new development. 

That said, the Copter 3.2 code, which runs great on APM 2.6, will continue to be available forever and will be supported (critical bug fixes, if needed) for a long time.  So for all of you with APM 2.6, no need to fear. Your copters will fly great and the mobile/desktop/cloud apps that work with them will continue to improve, bringing new functionality outside of the autopilot itself. 

Is it still possible to use DCM? I don't have much faith in EKF currently given the number of EKF_CHECK errors I still get on a fairly regular basis.


Will one of the releases allow remapping channels so that we can utilize different inputs for mode changes. 



Thank's Chris, shure it's time to update harware; we have to give many thank's that we have a high mature code to still enjoy flying with our old APM, mine is only a minor issue but I begin with this only for work (crop monitoring) and now it's a hobby too so follow updates and find issues is part of it :)  .

Oooh, Alexmos support...to do what exactly?

to do what it says in 8 c I would imagine :)...to send demands to it.

So i just maidened ac:3.3 on my Y6. Flew great! Except for one exception, well two really. But the second one is not an ac3.3 issue, just a satellite issue. 

First issue: It seems as though every time i plug in my birds I get BAD AHRS errors. This has been happening since 3.2 for me on 4 separate frames and configs.

Second issue: Seems like I was about to have a flyaway when about 3 feet off the ground. I was between my car, and my house, and a big building, so that is to be expected. But i thought EKF would catch that before it happens? It started flying off at about 30 degrees when i hit stabilize and full throttle to get it out of danger. It went about 30 feet horizontal before i hit stabilize.

When is UAV/CAN going to be enabled? I really want to try this zubax that has been sitting on my shelf for 6 months.

Cheers! And thanks for all your hard work and efforts! I appreciate it!

Have you the logs of the second issue?

Just uploaded 3.3 rc1 and reset to default. Followed by a complete setup.

At the moment i have only one error saying something like "EKF Variance" (LED is flashing blue/yellow)

Apart of that it's flying ok so i decided to go in the garage and run AutoTune.

here is the result compared to previous version :

                           AC3.3rc1       Old AC3.2.1
RATE_PIT_P        0.07585344    0.1249999
RATE_PIT_I         0.1896336      0.1249999
RATE_PIT_D        0.004598       0.006499999
RATE_PIT_IMAX   2000             1000

RATE_RLL_P        0.04932502     0.12
RATE_RLL_I         0.1233125       0.12
RATE_RLL_D        0.00255887     0.006999999
RATE_RLL_IMAX   2000              1000

RATE_YAW_D      0                    0.004
RATE_YAW_I        0.04019607    0.04
RATE_YAW_P      0.4019607       0.4

STB_PIT_P          10.82979         10.59375
STB_RLL_P         7.311701          10.94531
STB_YAW_P        4.477529         6

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