KK 2.1 Flight Controller Review

February 23, 2014 14:42 | By | 11 Comments

The KK 2.1 is here! This incremental hardware update features new sensors and a beefier microcontroller, but does this improve performance? Read all about it in our review after the break!

Back before multicopters were all the rage, the KK flight controller boards were a trusty and proven solution to get hideous contraptions into the air. When the KK 2.0 was released, the initial firmware and the resulting flight performance was “good but not stellar”, though that was ok for the price it’s been sold for. A few months ago Hobbyking released the KK 2.1 board, which features a MPU6050, which is a very solid sensor that trades a bit of precision for high rotation rate support. Actually this is not entirely accurate, as you can select one of three supported sensitivity modes, choosing between a very high accuracy mode, a medium accuracy mode, and a low accuracy mode. The higher the accuracy, the less rotation degrees per second the sensor can sense. Which brings us to the big issue we had with the KK2.0: While pefectly fine for normal flying, during extreme maneuvers (especially extreme flips that did more than 5 or 6 complete 360-degree rolls per second) the older hardware simply could not keep up, and the flight controller was unable to recover from such a situation.

We have to stress one point here: This kind of maneuver is way past what, for example, the DJI NAZA v2 is designed for, which is limited to sensing 200 degrees/sec. As a matter of fact, the KK 2.0 autolevel function works much snappier than the NAZA V2. If you fear that the KK 2.0 is an unsafe board, fret not: It is a great flight controller and very safe to fly.

But for the same price as the initial KK2.0 you now get updated hardware that allegedly does away with this limitation, offering up to 2000 degrees/sec rotation sensing in addition to a beefier Atmel Mega644PA microcontroller. Let’s see how it performs in real life.


On the outside, the two boards are almost identical. What can be seen is that there’s an additional pin header, and the used chips are obviously different. You can now plug a 3W high power LED directly onto the board so you can see the currently active mode from afar. There’s still not barometer sensor, no GPS support, though there is now gimbal support included right out of the box.


The backside has changed a bit, but for all intents and purposes, this is very much a drop-in replacement for the KK 2.0

As for firmware, you CAN fly with the included v1.5 firmware. It features capable autolevel functionality and works quite well. There’s a bug that affects certain motor layouts, which is why Hobbyking urges users to flash v1.6 onto the flight controller as soon as possible. We have test flown both versions and to be perfectly honest, they work, but they’re not stellar. The most amazing functionality is missing: SL mixing.
SL mixing is a function that merges the best of acro mode and autolevel mode: Keep the sticks near the center, and the board is on full autolevel. Move the sticks to the outer limits and the autolevel percentage is smoothly scaled back. Depending on how agressive you set this up, you can make the boards do mind-blowingly agressive flips while recovering by just letting go of the sticks.

So when RC911 finally announced that his amazing “++” firmware is available for the KK2.1 now, we had to give it a go and include it in this review.


After flashing you have to set everything up from scratch. But with the KK 2.x it basically boils down to selecting your motor layout (Quad-X in our case), letting the board calibrate the horizontal position, and checking the control directions via the receiver test menu.  The menu structure is very easy to grasp, there are no multiple menu levels, everything is nicely laid out and logical.


Also relatively new (though also available for the KK 2.0) is the profile option to let you define multiple presets. That way you can set up profiles for a copter with and without heavy payload, or use one flight controller in multiple copters.


Quick tuning is a good way to change PI parameters without having to constantly go in and out of menus. You still have to arm and disarm the copter with the rudder stick of course.


One thing that always annoyed us was the ESCs beeping while in the menu. The latest firmware allows you to have the board send a valid signal to the ESCs and keep them quiet at all times. It’s a small detail, but a welcome addition.


The AUX channel now supports 5 positions, letting you freely assign different flight modes. The current position is indicated with a dot.


Flight Performance

After flashing and setup we immediately took to the sky. The board flew nicely on 250, 330 and 450 sized frames with default settings. Of course it wasn’t perfect yet, that’s why you can tweak the PI settings and the autolevel aggressiveness. But it has to be said, having a flight controller fly this nicely despite not having set up anything is fantastic.

We slowly dialed up the PI values, and then also cranked up the autolevel settings. Autolevel P was dialed up to 75 and Autolevel limit to 80, which allows the craft to straighten nice and level within a fraction of a second. In that regard, performance was near identical to the KK 2.0

We then performed multiple high rotation-rate flips. And lo and behold, we did not manage to get the KK 2.1 board into a situation where it failed to recover. The way SL mixing is handled in the latest RC911 firmware feels a bit more “tame” despite our settings, but as a whole the KK 2.1 feels rock solid and in control at all times. We tried flips with 6 and 7 full rotations per second, and the KK 2.1 recovered flawlessly where the KK 2.0 simply gave up before.

Aside from that, the KK2.1 just flies well, like it’s predecessor. During steady over, the new board is also just as stable as the old one. Rolf and Hobbyking didn’t fix what wasn’t broken, but instead tackled the two areas where the KK 2.0 was lacking: maximum rotation rate sensing and the limited microcontroller flash size.



If you have a KK 2.0 and you’re not doing crazy flips, there’s no need for you to upgrade. Instead, flash the latest RC911 firmware onto your KK 2.0 and enjoy. If you are still on the factory firmware, then yes, definitely update to the “++” firmware.

But if you don’t have a KK 2.0 yet, and you’re looking for an easy to use flight controller that doesn’t require a PC to set up but offers great performance, then you pretty much have no choice anyway since the KK 2.0 is being phased out. Luckily there’s no reason to choose a KK 2.0 over a KK 2.1.

This is the perfect flight controller for FPV flying, experimental multicopters, and generally any multicopter that doesn’t need GPS or altitude hold. It is cheaper, easier to set up and flies better than the AfroFlight Naze32 despite only having an 8-bit microcontroller. It’s also easier to set up than a NAZA v2. It will not do position hold, waypoint navigation, telemetry, bluetooth or any of that fancy stuff however. It is truly a beginner-friendly, cost-effective flight controller. If you just want to fly and have fun, the KK 2.1 comes highly recommended, especially with RC911’s fantastic firmware upgrade.

Order link: Hobbyking.com



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Category: Featured, Reviews

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Comments (11)

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  1. Alex Ellis says:

    I have a fly sky 6ch tx/rx, when I view the RC test view Elevator is +6-9 unless I move the trim almost always fully forward – then it goes between -1/0 constantly changing between the two. This results in the quad being aggressive in forward tilt and very unresponsive in backwards tilt. Can you help?

  2. loather says:

    Looks like the link for the RC911 firmware is busted. My google-fu is weak and I can’t seem to find it. Any thoughts on where it moved?

  3. tyler says:

    Where can I find the RC911 firmware. as the link has gone broken.

  4. oliver says:

    RC911 FW 1.6+++ R3 AIO for KK2.0 and KK2.15

    Stevies FW 1.19 [dont use older 1.9]
    is included in the flash tool.

    make sure you have the usbasp driver installed.

    • Francesco says:

      Ciao una piccola informazione io ho un KK 2.1.5 e non riesco a settare il sistema acro per flasharlo scaricato il programma è l’ultimo aggiornamento firmware l’uno. 19 ma nei profili non c’è nessun acro un aiutino grazie mille in anticipo

  5. Edoardo says:

    Hi,can i plug directly 11.1V in the voltage sense pin? Or i risk some smoke?

  6. cal says:

    where are the steps

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