Arducopter 2.1 release

Ardupilot 2.1 is out and can be downloaded by the mission planner (or with Git). You must have the latest version of MP to be compatible. If you're compiling with Arduino, you must use the "mrelax" version of Arduino that is in our downloads section. This is because Arduino was never tested with code larger than 128K. And since our code is probably the most complex Arduino project ever, we found the issue. This altered version of Arduino allows you to specify a special compiler flag that makes it work again. Otherwise it's functionally identical to version 22. When we transition to 1.0 of Arduino, you won't need to use a modified version, since they have patched it for us.


This version has a few new features, but is mostly a bug fixes and compatibility with APM2.  The nav routines have been updated and well tested. I'm getting very reliable results now. 

One new feature that I snuck in was SuperSimple mode, which re-calibrates simple mode when you are flying with GPS > 20m from home. It allows you to fly in any direction in Simple outside of this radius. Check the wiki for more info.

Added Auto_land mode to help with Failsafe implementations.


Here's a video I took flying WPs using CH 7 to toggle record them. I flew back and forth over the park to se how straight a line I could maintain and how repeatable it was, then I recorded a few waypoints to the left and right, then I recorded a landing wp by toggling CH7 when the copter was on the ground. The landing could be improved, it was trying to maintain a location and didn't level out in the last meter to the ground as it should. I was missing the screw holding my Arm in place so it folded in just a bit, no real damage done. BTW, this video is W/O a sonar.


The next video is of the Loiter control. I improved loiter a bit with a bug fix and the stability patch from the stabilization. Wind was mild. Could be tuned just a little higher.



Here's a video from Dec 17 showing WP recording. The radio was on the ground the entire video. The 3DR frame did not have a sonar on it. The landing was recorded as well.



Tridge wrote a Geo - fence routine to restrict flight within a certain area for Arduplane. We'll port that over to AC. You'll be able to fly acro inside a safe area and have it go into AP if you loose control!

We need one more pass to finalize the Optical flow integration.

Finalization of the Z Accel code.


Have fun and fly safe,




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  • 3D Robotics

    I'm delighted that ArduCopter had reached the level of sophistication that people are now benchmarking it against the leading closed-source commercial multicopter controllers. And with the progress that Jason and the rest of the dev team has made in the 18 months that ArduCopter had been in development, I'm sure that it will equal their performance, especially with the new APM 2 board. 

    But I wanted to point out this it's a little bit of an apples-to-oranges comparison when you take into consideration price, real UAV mission planning, and hackability. Quite surprisingly, with the exception of Mikrokopter, the closed-source multicopter controllers aren't capable of real UAV missions, since they don't allow waypoint mission planning and scripting like ArduCopter. That's one of the huge advantages ArduCopter has: it's built on a real UAV platform (APM/ArduPlane) that has years of mission planning development and experience with many thousands of users. 

    Closed Source:

    Hoverfly Pro with GPS: $900    (just GPS hold and RTL: no waypoint missions)

    DJI Wookong with GPS: $1,100 (just GPS hold and RTL: no waypoint missions)

    Mikrokopter with GPS:  $900 for all three boards required (rises to $2,400 if you want waypoints with 500m distance)

    Open Source:

    ArduCopter with GPS: $200 (GPS hold, RTL and unlimited waypoints at unlimited distance) 

  • Developer

    Hi all! I decided to launch my metaphorical "N" bomb! :-)
    This is the video (at the end) about loiter  test with my heavy octo and V2.1 software release.
    Maybe someone watching the video will think "but it is still building!", unfortunately if you think this has no terms of comparison or has not looked the second and third parts.
    I state that my hover in STABILIZE is at 50% of the throttle stick and that in the stabilize flight the drone behaves quite well.
    But back to the question loiter: in the absence of wind does not behave badly, unfortunately it seems very simplistic to decide whether to use ArduCopter because it does not move a leaf or Mikrokopter/DJI because there is a tornado (LOL).
    ArduCopter is not use the accelerometer for mantain the position in loiter mode, disabled by default because does not work properly, so the error doing by a errors caused by abnormal or intermittent readings of the GPS are not managed as well as the annoying circle effect.
    Also there are strange variations of the engines on my system when i correct the position of loiter with ALE, dunno why, i just put  a little "left ALE" correction (see video for this at 1:39)... in loiter with 2.0.49<->55  the problem is absent.
    I know there's two loiter mode in this release but this one is the default, if the other is better do not understand why not enter it as primary.
    The variations in speed of the engines are too dry issue on my system (read if you want to some of my previous posts about this), not smoother, and causing continuous little wobbling.
    Concluding, IMHO about the loiter in 2.1: is not an upgrade but a downgrade if my drone goes too loud from the recorded position.
    Want some parameters can be modified in order to adapt the pwm rate corrections (logaritmics, not linear, and too smoother) for fine tuning the motors rpm according to the size of the drone, props and motors, i'm not talking about PID, and the accelerometers are managed to anticipate the drift errors generated by the GPS/wind... enough of these circles, we want some square! :P
    Besides, we do not have all the original ArduCopter DIY Quad, and the dear Jason can not do miracles testing its release only on his standard DYI drone.
    The alternative would be to make buyers aware that the system works properly if installed on DYI configurations.
    I hope these problems will be  solved seriously, significantly considering the advice of users with a "non standard configuration" because i believe that exceed those that use a lot of DYI kits, or i will have to selling out or giving away my APM and sonar with displeasure.
    I think it's useless to fly the drone automatically if first you do not have acceptable stability in the management of the precise position with gps (i mean no more than 3 meters in the absence of wind without circle effect)... the others additional features are negligible if the primary does not work well.
    And if can not possible thanks anyway to all the developer team, it was nice to test the world's most popular free Arduino flight system, sin not wanting to use it to play does not make my case (as it does now).
    Follow with interest your comments / criticisms, thanks!

    Best to all!


  • Alt_Hold

    I´m having this sonar-baro offset. Is that normal?

    3692320283?profile=originalAttached is the log file


    2011-12-18 05-49 3.log

  • I found this in Wikipedia, I thought it might be of interests in this context.

  • The last thing you want to do is enable the brake. The Prop. slows down quite fast enough with aerodynamic drag. The reason for descent wobble is down to the fact that the angle of attack creates a partially stalled blade. Less pitch angle and wider blades that are much lighter confirms this fact beyond any doubt. You can create more stability with prop tuning than PID settings. All you can do with the PID is try to tune the response signal to match the characteristics of the motor prop. combination whereas you should first look at the prop. Put a heavy large dia. prop. with too much pitch angle on a wookgong and it also becomes  unstable. Whatever reasoning you may have regarding linear response curves it becomes less the faster you can make your mechanical thrust change.

  • Developer

    I tried 2.1 in loiter with soft wind, is better but there's many motor speed variation TOO HARD, with fine pid tuning it's the same.
    And there's a lot of difference with front and rear wind.
    Please Jason you must intruce in the code a new parameter called "motors smooth" like Mikrokopter, with the same functionality i've write and explain on my post yestarday.
    Some hours and i post here a new video with loiter (with baro enabled) and you can see what i mean.

  • What rz_ten described above is exactly the same issue I've reported on page 17 and no one replied. After a couple of seconds flying I need to hold my stick on bottom right for my copter to keep position. After landing and start flying again the process restarts.

  • Developer


    Congratulations to Jason and  to All the DIY Drones Dev Team...

    Regards, Jean-Louis

  • This's my logs. But , I don't understand is about is have little noise sonar in begin Code .50 to 2.1. Even though , I used cable and RC filter but it have noise. And I will back to upload .49 my sonar is normally haven't noise.  

    2554-12-18 12-11 1.log
  • I'm having serious issues with 2.1.  Loiter seems broken.  When I enter loiter, the quad will oddly circle the loiter point a couple of times, and then suddenly decide that the loiter point is somewhere behind it and will take off in a random direction with a 10 degree tilt.  I've let it get about 30 ft away from the loiter point before resuming manual control, but it does it every time I've tried it.

    The new version of the code doesn't seem to correct yaw nearly as well, and I've seen it frequently drifting out of alignment.

    I've also had about 6 crashes today with 2.1 (I switched back to 2.0.55 and it seems to be fine).  After flying around a bit, the quad will suddenly decide level flight is tilted 30 degrees along one axis (it's not always the same axis, so I don't think it's a bad gyro).  Needless to say, it's quite difficult to level it again when it's constantly fighting me, and I've ended up cutting the motors every time its occurred.

    PIDs are default.  Sonar is disabled.

    2011-12-17 05-17

    2011-12-17 05-18

This reply was deleted.