Copter-3.3 beta testing

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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      • You should take of in LOITER when you use Optical Flow. And NOT in STABILIZE.
        Or at least, I remember this.
        I think is written in the wiki, but right now the wiki is off line (503 error) and I can not link here the page about the Optical Flow.
        By the way, when the wiki is up again I read twice the process, maybe I have done something wrong =P

        Thank you very much fort the issues about the Optical Flow (=
        I will give a try (=
        But the developer team have in mind to fix this issue, am I right?

      • I used to never take off in loiter for mapping missions.  I'd always lift off in stabilized, the auto and finally auto.  That got old.  Now I arm in loiter and all my checks are good, switch to auto and throttle up.  Of course always keeping a safe distance : )

      • Developer

        I also think taking off and landing in Loiter is fine.  I also do this all the time and have never had problems.  GPS glitches can happen at any time so best not to be silly and get too close to the vehicle but with all the pre-arm checks we do I think it's pretty safe.

        • I also think the same way of Randy.
          A lot of time I take off and land in LOITER.

          By the way, I was using Optical Flow with LOITER.

          If I do not remeber wrong, with Optical Flow you have to take off in LOITER and NOT in STABILIZE.
          Do I remember wrong?

          By the way, I can not control in a correct way my multicopter during OF LOITER.
          Here it is the log con Google Drive/Docs:

        • Can I ask why is there loiter and pos hold? I know loiter was pre 3.2 aka before pos hold was created. But isn't pos hold simply loiter with more maneuverability? Is there some advantage to loiter over pos hold? 

          • Yes that's the difference Richard. Position Hold is basically a Loiter mode with pitch/roll control response similar to that of a stabilize mode. In Loiter mode, the stick input tells the FC how fast the vehicle needs to move proportional to control input. And I think the max speed is limited to 5m per second. Not that much. So no matter how powerful your motors are, the FC will limit your speed. If you have a very under-powered copter, you will move at 5m/s or if you have super powerful copter, you will still move at around 5m/s. This means your lean angle will be very limited; It will be controlled by the FC not by your stick deflection. Your copter will never reach 45 degree (which is the default max lean angle in stabilize mode) unless you are flying into the wind maybe.

            My understanding is that in Position hold mode, developers incorporated the stabilize roll/pitch controller where the roll/pitch stick input directly changes the lean angle. FC doesn't try to maintain or limit your speed. So in this mode, full stick deflection corresponds to 45 degree angle in the desired direction. With this, you will fly as fast as your propulsion system lets you. You won't be limited to 5m per second speed. So your vehicle will feel much more responsive.

            Other than the roll/pitch control, I don't think there is a difference between the two modes. So the altitude and the yaw control remained the same between the two.

            Technically both flight modes do the same thing which is to maintain the vehicle's orientation, attitude and altitude; only one will feel more maneuverable as you stated.

            As far as if both modes needed or if one should take off in any of these modes, I think this depends on the pilot's taste. Personally, I always take off in Stabilize and then switch to Loiter but it is good to know that the code improved enough to let us directly take off in any of these modes.

            If one just needs a stable hover over a certain location, Loiter mode will suit him. But sometimes you may need to move around fast and/or move to another hold location much quicker. So if this is the case, you will not want to do this in Loiter mode because it will take too long. Prior to Position Hold mode, people would switch to stabilize, move to desired position and then switch to Loiter mode again. Now the position hold mode will let you do this without switching between loiter and stabilize flight modes. So in that sense, I favor of having both of the flight modes and let the pilots decide which one to use. It is very easy to disable one of them in your flight mode screen.

            My only complaint would be the naming of of these two. Loiter and Position hold aren't really telling me the difference and when you hear them first; it is confusing. But it is at least better than the previous name "Hybrid". That name was throwing me all over the place:)))

            One last comment about DJI flight modes. I also fly DJI Naza FC. DJI has 3 basic flight modes: Manual (Acro in AC), Attitude (Stabilize in AC) and GPS (Position Hold in AC). In GPS mode, you can move around pretty quickly but I almost always observe that it is not as fast as Attitude mode. When I switch to Attitude mode in NAZA, I feel the vehicle becomes more maneuverable than the GPS mode.

            Here is how AC wiki explains the above flight modes:

            Loiter Mode

            Position Hold Mode


            • Thanks Alex!! Perhaps they should have named pos hold 'speed loiter'. I usually take off in alt hold. Once you get the MR dialed in and well balanced props there's no surprises. Not always the case in a gps mode. 

      • I take off almost exclusively in Loiter and PosHold. Both work great. I also fly almost exclusively using these modes - I have never had an issue. So your definition of fly mode is clearly different to mine - if these are not suitable for takeoff then Pixhawk is not the FC it purports to be.

      • >1st off Loiter is not a mode you should be taking off in. Loiter is meant to plant the MR in the sky and keep

        >it there. It's NOT a fly mode

        It is an interesting comment indeed as there are 2 modes now that are 'loiterish' - old loiter and a 'position hold'.

        Both are armable and flyable from the initial power up.

        Statement 'it`s not a fly mode' is also a bit off - it is indeed a fly mode and it is configured as such. Should it not be one and be more of a switch flag on top of a fly mode - is a different question, but right now it is a selectable regular fly mode.

        I presume right now if you choose 'loiter' fly mode it first engages 'alt hold' and then engages 'loiter' on top of it.

        • It was a poor choice of words on my part. Yes it is a "flight mode" but stand by the issue that you should not "fly" in Loiter mode, and you should not arm or take off in Loiter. PosHold [Hybrid] is there for the DJI mentality that thinks it's ok to fly around in GPS mode, but Loiter is meant to plant your MR in 1 place and keep it there. Up till recently you could not arm in Loiter mode at all and I think it needs to go back that way.

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