Review: BrainFPV RE1 F4 OSD Flight Controller

by Oscar

Recently I tested the RE1 F4 FC and mPB (PDB) from BrainFPV. When I looked up the FC/PDB combo, I found several ads stating that the RE1 is the most advanced racing flight controller ever made! Wow that’s a big statement, guess we will find out in this review.

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The BrainFPV RE1 FC is available at (link). This review is written by Justin Nishida.

With all the new products hitting the market on an almost daily basis, its certainly an exciting time to be in this hobby/industry. Each new product brings a lot of expectations with the various vendors/developers/manufacturers pushing this hobby into overdrive .

Close Look at RE1 FC and mPB


The BrainFPV RE1 is made up of a 6 layer PCB which allows the power rail traces and other components to run completely separately from the sensors circuits, which means less electrical interference to the gyro.

I’ve been running very high quality PDB’s lately and can appreciate having this level of quality components. I used to run external caps to clean up the power to reduce video interference with cheap PDB’s. No longer are these steps necessary with good filtering on high quality PDB’s which the mPB does exceptionally well. The mPB (mini power board) has 3oZ of copper, built in current sensor and is designed to stack under the RE1.

Great Customer Support

The manual for the RE1/mPB is awesome. It has detailed info and diagrams walking you through how to build and setup your gear with these components. Technical support is excellent with Martin, the owner of BrainFPV providing much of the support directly to the end users along with the rest of the community.


Software – dRonin

The RE1 initially only supports dRonin, but later on also supports Betaflight. The configurator for dRonin is based off the OpenPilot platform which I was never a big fan of.

Setting Up Feels Easy

After playing around with the configurator I was reminded how easy it is to setup a new quad due to the wizards. The setup wizard walks you through setting up the basic configuration of the FC and then the transmitter wizard walks you through setting up the transmitter channels and switches. As long as you have everything connected properly, you will almost be ready to get airborne once your finished with the wizards.

Learning Curve Of Getting Into New Software

Now coming from Clean/Betaflight and KISS, it took me some time to get used to the tuning part of dRonin. There are 3 tabs for PID tuning, basic, advanced and expert. Depending on your technical skill set and understanding of PID’s, you pick the one that suits your needs the best.

Terminology and features are also different, and it takes time to learn them and get used to. For example, there is no “Airmode” like in Betaflight, rather it’s a setting in the expert tab called “Hangtime”. Hangtime can only be activated for up to 4.5 seconds so that means you will only be able to retain full control inverted for up to 4.5 sec. For 2D flight, this is a descent amount of time while inverted but I’m still not sure why this is limited.

One of the neatest features of dRonin is the functional Autotune. Unlike other firmware, dRonin actually got Autotune to work for mini quads. This may not sound like a big deal but with the ever increasing popularity of FPV mini quads, tuning becomes a huge roadblock for many to fully enjoy there machines. I was told that the Autotune feature would give me a tune that I could go race with. So I tried it to see if it was really that good. Unfortunately the frame I chose to try the FC on at first didn’t play well with the Autotune (DMC Whippet I frame, bottom mounted LiPo). The Autotune didn’t like this layout and failed to produce a flyable tune regardless of what I tried and I had a lot of help from the community on this to try and figure out why it wasn’t working with this frame. I ended up manually tuning the quad and was able to get some good runs in with this quad.


I decided to go a step further and test the Autotune with several other frames, QAV210/Armattan F1-5/QAV-R 5″/Alien 5″ and LRC Race X 5″. The other frames were a mix of traditional H’s and X frames, all of which the Autotune feature worked great on. I still had to make a few tweaks with the filters but it got me close enough that I was able to get a great flying tune within minutes of finishing the Autotune on each frame. There’ also a feature to share your Autotune so that the rest of the community can see your setup and compare/try with others. This also helps the development work on any issues or bugs and to help improve the firmware.

Betaflight Support

The original choice of software was one of the reasons that were holding people back from using the BrainFPV boards. Now there is officially Betaflight support for the RE1 and I’m sure more and more Cleanflight and Betaflight forks will follow suit.

Gyro Noise Spectrum in OSD!

Betaflight still utilizes the RE1 OSD and configurable features. One of the neatest features is the live spectrograph which is super handy for setting notch filters on the field. Betaflight 3.0 and on now has OSD support for FC’s with built-in OSD hardware (not sure if external OSD is supported).


How To Flash Betaflight on RE1

To flash Betaflight on the RE1:

  • open the dRonin GCS
  • Go to the firmware tab, click Rescue and connect the RE1 to USB
  • Then click on Open file and pick the firmware file you downloaded for beta

The motor output has been changed to match the Clean/Betaflight motor layout in the official release so watch this if switching back to dRonin or vice versa. All regular features such as LED programming, buzzer, ESC Passthrough, RSSI/ADC inputs (voltage, current) and lap timing (configure through OSD menu) should be working.

There Is No MAX Chip on the RE1 to get OSD working! :)

Normally, a MAX chip is required for OSD in MinimOSD and many OSD integrated FC boards (for example the Skyline32+OSD). However in the RE1, all the OSD hard work is done in the powerful F4 processor, and there is no additional OSD chips.

In order for Betaflight to work on the RE1, a real-time OS (chibiOS/RT – also in dRonin) was used to run Betaflight and the OSD “in parallel”. Well, not really in parallel in a strict sense since there is only 1 processor, the OSD is being drawn while Betaflight is not calculating PID numbers.

However Betaflight tasks have higher priority and runs whenever there is a gyro sample (uses an interrupt from the gyro to wake up task). When Betaflight is idle, the OSD code is drawing the OSD. Switching between the 2 tasks is very fast at about 500nSec (0.0005mSec) so there is no noticeable delay. Also be sure to use the latest version of the Betaflight configurator (Chrome App) to ensure proper function of all the features.

There are already some Betaflight flight controllers with OSD coming out, but they use a character based OSD, not a graphical one like RE1 has.

So What Happens to dRonin?

Don’t worry, for the dRonin fans, the RE1 will continue to be supported and further developments are underway to increase the RE1’s features and performance. I hear there’s an upcoming option to add an additional serial port so it will be fully GPS capable. As well, a new feature called expoM.



Back to the RE1 fc, some of the features I really liked are the built in multi protocol transponder. It works with iLaps and Easylaptimer systems with IR bulbs.

Another feature is the built in OSD which is actually part of the F4 processor and is setup in the dRonin and Betaflight configurators. It has full graphical support and can be used with 3d cameras like the Nerdcam. No more flashing MWOSD and having separate software to control everything, the OSD is right in the main processor. This also allows the RE1 to control a TBS Unify Pro VTX directly thought the OSD menu. Not only can you set your PID/Rates and other setting for the FC through the OSD but you also get access to changing VTX power output and band/channels selections.

The board also has the capacity controlling up to 2000 separate programmable LED’s. The mPB has a built in current sensor so the OSD displays true mAh consumption, amp draw and other readings that are true readings rather than virtual sensors giving calculated readings.

The whole Betaflight support addition will no doubt turn many more pilots to the RE1 as it is truly a piece of work. The guys at BrainFPV are on point with the new RE1 flight controller.

I’d like to thank Martin Luessi, CEO of BrainFPV and Oscar Liang for the opportunity to test this top notch product and to the countless others who helped develop and support the firmware/hardware. While these parts may not be cheap, the quality surpasses any advantage saving money may have had. There is no doubt that the RE1 really is at the current moment one of the most sophisticated, high end FC’s out there that performs as designed and expected. Is this enough for you to try it out? I’d say yes but that’s up to you to decide.

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Jason Hitesman 27th October 2016 - 5:32 pm

Regarding Hangtime in dRonin. The approach is fundamentally different than airmode – hangtime is a function of “Actuator clipping management” but “hangtime” is a bit less of a mouthfull ;) The important point is that it’s not just enabling the PID controller at zero throttle like airmode. It actually deals with what happens when user input results in a request that requires more or less power than is available at both extremes. So at zero throttle it gives extra power to keep things stabilized and at full throttle it makes it possible to maintain control and stability in situations where your motors are already at full throttle but more is needed to achieve the commanded inputs by lowering power to the other motors. Kind of like the inverse of what happens at low throttle. The reason for the time limit is that if someone were to set their power add too high this could easily result in a situation where the vehicle just keeps adding power at zero throttle (or max throttle) and could result in a flyaway – so it’s a safety feature.

However, the 4.5 seconds is NOT a hard limit. It’s a safety limit imposed by the GUI. Using the UAVO browser you can set the hangtime limit manually without the safety limit imposed by the GUI. (Same for the power add percentage – though increasing beyond the GUI imposed max on that is much riskier as it doesn’t take a lot of power add to make a difference.)

Think of the UAVO browser as dRonin’s version of the CLI in that it lets you access settings that aren’t exposed in the GUI – though it’s more structured, organized, searchable, and also goes further allowing you to view the status of internal variables in real time. The UAVO’s also provide a structured backup mechanism which is why dRonin can automatically adjust settings when you upgrade to a new version since chances in the structure can be easily tracked by the developers.

In the UAVO browser you can adjust the hangtime time limit by going to Settings->ActuatorSettings->LowPowerStabilizationMaxTime

The UAVO browser is a bit intimidating at first, but once you get the hang of it can give a much faster and complete way to interact with the settings and data on your FC. It’s worth getting to know since when new features are added to dRonin they’re often only accessible/configurable through the UAVO browser for a release cycle or two while the features mature. For example the latest Quixote release of dRonin now includes support for spi attached MAX based character OSD’s such as on the airbot f4 omnibus, being a new feature that’s still being rolled out there is no UI for configuring the OSD yet – but in the UAVO browser you can access all of the settings for it and make changes.

Finally ExpoM is already available on the latest Quixote release. It’s a great improvement over standard expo, instead of just setting a percentage it allows much finer control over the expo curve and lets you change the shape of the curve to get an extended flat section near center stick for more smooth flight stick range while still having high rates at full stick for acro flying.

What is new and not yet in a release build is an exciting new flight mode “acrodyne”. Acrodyne is an attempt to achieve the goals of Acro+ in a more controlled manner. While Acro+ basically suppresses the PID controller at high stick positions giving direct manual control acrodyne instead dynamically increases the rates at high stick positions. This lets you run a lower max rate to get even more smooth lower rate controls at low stick positions – but as you stay at higher stick positions the dynamic rate increases over time allowing you to achieve extremely high rates despite the lower max rate. The combination of ExpoM and acrodyne makes it very easy to achieve a setup which is tame and smooth around center stick through mid stick but still lets you do really fast multiple flips at full stick.

Glad to hear your enjoying your Brain RE1 and were able to get past the initial issues with autotune on your Whippet. There’s actually a whole new autotune system being worked on which will take an even better approach towards autotune and will hopefully work on most of those builds that the current system has issues with making the speed ease of autotune accessible to more users and giving even better initial tunes.

Mike 28th October 2016 - 2:07 am

AJ– We’ll all defer to your expertise in controls. No one can know better than the guy who hacked up acroplus to have no integral term, and flew it for 6 months insisting it was great, and then eventually left our community after making a mockery of himself in many similar situations. :D