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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Thanks Randy. It's the same one I provided Rob for my landing issues :)


I have more if you need them. Some with EKF_CHECK errors, others where EKF diverges from DCM to some degree.



WARNING to TradHeli users:

Do not attempt to fly AC3.3 until you hear otherwise from me.  I have not even bench tested it yet, let alone test flown it.  There are quite a lot of changes that have gone in that could be crash-o-matic for helicopters.

AC3.3 release for Tradheli is likely to be delayed.


Ok, so this vehicle is actually using DCM, not EKF.  The check is similar and the error that appears in the dataflash log may not be clear enough.  In AC3.3 there is only the EKF check so it's fixed in that way going foward.

There's certainly something bad going on with the vehicle's heading.  Below is a graph of the heading error (in red) vs the throttle (to show when you're flying).  In the first two flights we can see the heading error climbing past 0.8 which triggers the failsafe (which is better than a fly-away which is what would happen without the check).

A normal copter would normally have it's error below 0.2 for the entire flight so something is wrong.  It can only be the compass or the gyros.

Some ideas:

1. it could be interference on the compass from the power wires although it doesn't appear to be.  you could try turning off compass-mot by setting COMPASS_MOTCT to zero.

2. the compass could be affected by heat if it's in an enclosed space or is heating up a lot

3. the gyro calibration could be going bad if the vehicle is being moved during arming

1. it could be interference on the compass from the power wires although it doesn't appear to be.  you could try turning off compass-mot by setting COMPASS_MOTCT to zero.

I have subsequently rerun compass mot with the full props on upside down, one position round thing and MP shows little interference. So I agree I don't think this is it.

2. the compass could be affected by heat if it's in an enclosed space or is heating up a lot

This is an external 3DR uBlox compass on a mast - so seems unlikely. QUESTION: is the internal compass consulted at all? My internal compass has very high offsets but the external one is normal.

3. the gyro calibration could be going bad if the vehicle is being moved during arming

After Craig mentioned this some time back I have been very careful about not moving during arming. Could the issue actually be gyro failure?

Incidentally the flight appeared normal from the outside - no poor control or anything.

just a feedback...I flashed the firmware, I haven't changed anything on my setup, just the firmware. Upon flashing, I cannot control my Alexmos gimbal's pitch. The Alexmos board is connected to the Aux1  port of Pixhawk which is programmed for the tilt control. It was working on AC3.2.1 before, but after flashing, the problem was there. I reverted to AC3.2.1 and again I can control the pitch. I tried to reflash AC3.3rc1 afterwards, but the problem persists. I used to control the pitch via RC6, the Gimbal is configured before in AC3.2.1, Can you help me please?

perhaps I need to rewire my gimbal to pixhawk... Can somebody enlighten me about the serial interface? i believe I am using the PWM setup, with RC9 (Aux1) connected to the Alexmos gimbal RC_pitch.. 

Or it would be better if I can still use PWM for the RC pitch of the Alexmos BGC..

Hi Randy

If I graph ErrYaw against IMU->GyrX, I get this:

Lots of noise when the error is increasing. I've had a look at some other logs of mine and there is a definite pattern here. Is this normal? (I'm guessing not) Why would this be? I looked at AccX etc and all seems ok, so not clear that this is a vibration issue. I am NOT moving the copter when it is arming.



Tested 3.3 today using Stabilize, Position Hold, Auto and Guided.

Test was done in 20 to 25 mile per hour winds.

If it weren't for the new tones between modes and landing I wouldn't know the difference.

The Altitude is still moving around.

Loaded 3.3 today, previous 3.2.1 flies fine in PosHold but with 3.3 I got error (Flightmode err 16) and PosHold is not working
Loaded 3.2.1 back and it is rock solid in Poshold.
I did not change anything between the 2 versions
Did this (Note #1: because of the accelerometer range change (see 6b below) this upgrade will require the vehicle's accelerometer calibration to be done again.)
Log from 3.3 attached 2015-04-13 19-18-15.log
Log from 3.2.1 attached 2015-04-13 18-38-21.log

Logs zipped

I tried to upload the logs, zipped and plain but it will not work.

How to upload logs??

This is very interesting. We do use the 3 axis 32 bit Alexmos controller. on the Pixhawk, which serial port is the one driving the Alexmos board?

Did a first test with 3.3-rc1 today. The F450 flew quite nice with the default settings, did an Autotune and it is a little bit more rapid after the autotuning but is seems as it doesn't stabilize as quickly as before the autotune

PID settings before and after tuning are in the end of the video.


Hi Maciej,

Yeh, that is a bad tune. Can you provide a log file of the tune so I can have a look.

I have made some improvements to Autotune that will be out in the next release candidate. It would be great if you could redo your tune then and let me know how it goes.


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