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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  • Hi there, I see the new MP has only X options. I'm flying a Hex, using APM, jDrones motors 850Kv and escs etc, but on a Droidworx AD-6 frame. I don't see frame holes to allow an X setup with the landing gear on this rig. Any advice for a noob?


  • Problems with the Git Repo?  

    martinb$ git clone
    Cloning into ardupilot-mega...
    remote: Counting objects: 28404, done.
    remote: Finding sources: 100% (28404/28404), done.
    remote: Total 28404 (delta 18652)
    remote: Error: internal server error
    error: RPC failed; result=18, HTTP code = 200
    fatal: The remote end hung up unexpectedly
    fatal: early EOF
    fatal: index-pack failed
    warning: https unexpectedly said: '0000'

  • This's loiter perfect in 2.1 , But now i don't fininsh about tuning ALT Hold.

  • Today I finished building my 3dr frame, set up the props and did check the prop directions 3 times before going outside.

    Compared to my last arducopter(the one that went missing with 2.0.38 firmware) this felt like i had to give a lot of throttle before it took off. It takes off good but drifts forward then drifts too much forward until it dives into the ground. Was just 0.5-1m up so nothing bad happend really..

    What could be wrong here?

    No sonar, gps was connected but not activated in firmware.

    Firmware: 2.1 uploaded on dec.17th with missionplanner 2.1.8. 3dr frame,standard esc and motors.

  • Thanks for this release. I have been flying with it the last few days and it seems great. I plan to integrate (Hardware) my optical flow sensor on the arducopter this weekend. I see that there is an option to enable 'optflow'. Could I know what I should expect performance wise from the Optical Flow sensor integration in ver 2.1? Does it work with waypoints , Loiter , stabilize etc?

    PS: I see Jason Short mentions in the post, "We need one more pass to finalize the Optical flow integration." Hence I want to confirm before I set my expectations?

    Thank you again!

  • Is it possible to reverse the Yaw output (APM not RC) from the MP? 

    RC 4= -1 reverse only the RC not the correction.

  • I just loaded 2.1 release, tried ALT_HOLD (Baro only, no sonar) and my quad leaped for the sky.   Managed to wrestle control back and land it safely.

    Does ALT_HOLD only work if there is a sonar installed?   I'm using a quad with APM2.


  • Hi all,

    I've tried the 2.1 AF02 on my Y6, in stabilize and alt hold, and it worked prety well, although I found the stabilize to very stable, but a bit wanderer.. yaw reacted a bit crisp, with quite a yaw jump after turning.

    Then I added those 3º on the motors, and it really made a HUGE difference in the yaw response, now it reacts softly and quick, and yaw jump is practically gone.

    I already had those 3º on my Octo, and it was great,  so as has been said before, I would make those 3º a MUST for all kind of multicopters.

    Merry xmas.


  • ***NOTE***  

    I have done some bench testing and have come to the conclusion that with dev 2.1.0 AF2 Mod, after a couple mins, I loose sensitivity and responsivness in pitch and roll.  More noticable with roll and motor 1 in quad x setup.  AFter uploading Off 2.1, responsivness stays the same no matter how long I test.  This explains my sudden left bank and crash since motor 1 was less responsive and my input to go right did almost nothing to trajectory change.

  • Developer

    At this moment, I really prefer to fly with the firmware ArduCopter v2.1 + AF02 mod... It is really quiet and stable in light wind conditions in LOITER or ALT_HOLD mode as shown in the video above.

    Regards, Jean-Louis

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