BrainFPV Radix Flight Controller and Power Board

When I first saw the Radix on BrainFPV’s website, I was immensely impressed with the specs and the design that went into both boards.  The Radix combo really put off a vibe of being well engineered for use in freestyle, racing, and even endurance multirotors.  While the two Radix boards don’t come as a combo, they are designed to be paired together.  However, the BrainFPV Radix FC will also work very well independent of the PB.  As such, let’s look at them separately first, then together, as they are truly meant to be.

BrainFPV Radix Power Board

BrainFPV Radix Power Board Specs

• Battery Voltage: 3S to 8S (9V to 35V)
• Maximum Current: 100A constant, 160A burst.
• Voltage Regulator: Integrated 5V, 2A.
• Noise Filter: Integrated LC filter for clean video.
• Current Measurement: Up to 160A (20mV/A).
• Motor Outputs: Solder pads for motor signals (DSHOT) for clean and simple wiring.
• ESC Telemetry: Solder pads for ESC telemetry signals.
• LEDs: Four integrated programmable RGB LEDs. Output for additional LEDs.
• Stacking height: 5.5mm (space between RADIX FC and RADIX PB).
• PCB: 4 layer, 4oz (170um) copper per layer. HASL plating (lead-free).
• Dimensions: 36mm x 38.5mm.
• Weight: 8g

Initial Thoughts on the BrainFPV Radix Power Distribution Board

Looking at the stats for the Radix PB, I was pretty impressed and was eager for a clean build using this along with the Radix FC.  Once I got the package open, I gave it a good once over.  BrainFPV packed quite a big punch in such a small space, and were able to do that without having to jam both sides of the board with components.  In fact, only five small components are on the underside of the board, and are flush mounted pretty tight under there.  However, you will still need to raise the board off your carbon frame due to this, but only about the height of one nylon nut.

There are multiple options for soldering your ESC’s and XT-60 pigtail available.  You can solder either to the top of the board, or to the underside, or a combination of the two.  ESC power terminals are pads, however the signal, ground, and telemetry nodes are all through hole, which give you a measure of security for those wires.

BrainFPV also provides two versions of power that you can provide for your VTX. Radix PB supports high voltage options like the Immersion RC Tramp, the TBS Unify HV, or the Lumenier TX5GX, just to name a few.  If you’re not using those, and have a 5v VTX, or if you are plan on pushing the PB to its 8S range, you can use the 5v option.  For accessories, a harness cable that links the PB directly into the Radix FC, eliminating the need for messy wiring.  All in all, pretty impressive.

Wiring the BrainFPV Radix Power Distribution Board

First off, BrainFPV has really great support documentation available for the Radix line of products in the form of the Radix Hardware Manual and the effort putinto the manual to make it easy for pilots to get started. , I had the guide pulled up on my tablet, and gave it a once over before getting started.

First, I prepped my ESC’s, Then I started by tinning the pads on the Radix PB.   Here, my first real complaint about the board.  Solder had some difficulties penetrating the plating, and refused to layer on nicely due to the HASL plating used.  Thus, after the first pad, I stopped and cleaned the board with electronics parts cleaner.  I had hopes that it would help, however it made little impact.  Eventually, I was able to power through it and get everything tinned.

The layout of the board in regards to the signal, ground, and telemetry wires was also a little awkward, and because of this, caused the ESC wires to crisscross, which seemed a little odd to me.  Even so, not a deal breaker, but something that I wasn’t used to. The last issue I had was minor.  The XT-60 terminals are pads, instead of through hole.  Probably more personal preference than anything, however I do prefer the security of through holes on the pigtail connections as it just seems more solid overall.

Overall, was I happy with the Radix PB?  Yes.  I think it’s a very solid design, with great stats to back it up.  However, is there room for improvement?  Absolutely.

Pros:

• Great power handling capabilities
• Integrated LC Filters
• Integrated LED’s light up the heart of your multirotor (way cool in my book)
• Clean wiring between PB and FC
• Stack can be made very tight for space critical builds.
• Pricing is good for a PB with these capabilities.

Cons:

• HASL plating made initial tinning process difficult
• Signal, ground, and telemetry wiring is a little awkward
• No through hole for XT-60 pigtail

BrainFPV Radix Flight Controller

BrainFPV Radix Flight Controller Specs

• Processor: STM32F446RET6, Coretx-M4, 32bit, 180MHz, 128kB RAM, 512kB Flash.
• IMU: Bosch Sensortec BMI160 running at 3.2kHz, connected using SPI.
• Baro: Bosch Sensortec BMP280 connected using SPI.
• OSD: Full-graphic, PAL/NTSC auto detect, adjustable black and white levels. Full Betaflight OSD support with extra graphical features. Support for side-by-side 3D when used with a 3D FPV camera.
• Memory: MicroSD card slot for logging.
• Motor Outputs: 6 outputs with full DSHOT (150/300/600/1200) and OneShot support.
• Receiver Support: PPM, S.Bus (inverter built-in), DSM, HoTT, SRXL, CSRF, FPort ready. 5V or 3.3V supply for receiver. Receiver gets power from USB for easy and safe setup.
• Telemetry Support: FrSKY Smart Port, FrSKY Sensor Hub, HoTT Telemetry, SRXL, CSRF, FPort ready. Built-in inverter for FrSKY telemetry.
• Serial Ports: 4 full serial ports (UARTs). UART3 and UART6 have inverters for S.Bus and SmartPort telemetry. The inverters are automatically enabled/disabled for maximum flexibility.
• RGB LEDs: Dedicated RGB LED output.
• Camera Control: Dedicated output for accessing the camera menu to change camera settings.
• IR Emitter: Dedicated output for infrared based lap timing with multi-protocol support (I-Lap, Trackmate). Needs external IR LED and driver.
• Buzzer Port: Dedicated port for 5V (100mA max) buzzers.
• Analog Inputs: Voltage sensing up to 35V, current and RSSI inputs (3.3V max).
• Power: 4.5V to 5.5V, 120mA.
• Dimensions: 37mm x 37mm, 30.5mm hole spacing. 4.1mm holes for anti-vibration grommets.
• Weight: 6g

Initial Thoughts on the BrainFPV Radix Flight Controller

Again, like the Radix PB, I was pretty pumped about getting my hands on the Radix flight controller, as it has a lot of great features.  BrainFPV is really standing behind their product with some unique customization options and support.  First off, the Radix has one the best integrations of the Betaflight OSD of any flight controller on the market.  BrainFPV gives the pilot the option to use their “Logo Customizer” to add a pilot and team logo to the OSD.  Downloads several popular logos are possible, with an option to  upload a picture of your own using the directions and the logo customizer will kick out a compatible image.

The Radix FC also comes standard with a barometer built onto the board, thus giving the pilot feedback on altitude in flight, with a full graphic overlay on the OSD.  BrainFPV also built in a MicroSD card slot built in for black box logging, providing ample storage space to dial in the PID tune.  Radix FC joins the ranks of the very small group of flight controllers with a dedicated camera control pad that gives the pilot control over the settings of their FPV camera on the fly.

Radix has an F4 Bosch processor running at 180MHz, providing fast processing times, and plenty of processing power to spare and four UARTS for all peripherals and control options.  For accessories, a silicone wiring connector for pairing with the Hobbywing 4-in-1 ESC, which for this application I did not use. Five silicone vibration dampening grommets are also in the package.

Consequently, be it racing, freestyle, or endurance, the BrainFPV Radix FC should have you covered.  Overall, with these features, the Radix is a well rounded and feature rich offering from BrainFPV.

Wiring the BrainFPV Radix Flight Controller

First, I installed the included silicone grommets giving the board some vibration isolation from the rest of the multirotor.  The grommets, paired with a nylon nut, are also the only height you need to separate the flight controller from the PB.  The Radix FC did not have the same HASL plating as the Radix PB, which made soldering a much easier affair.

Second, I with soldered the connector for my FrSky XSR, connecting the power, ground, SBUS, and SmartPort wires to the through hole pads on the rear of the board.  Likewise, wiring  up the Immersion RC TrampHV connector to the front of the board  was just as easy, connecting the video out and telemetry cables.  Finally, also on the front of the board, I connected the video in and OSD connectors from the FPV camera.  I opted to power the FPV camera from the TrampHV directly to avoid any potential ground loop issues.  I’m not saying that the on board power filtering on the BrainFPV Radix FC isn’t adequate, however I always opt for the safer route.

While wiring up the Radix FC, I did notice that the pads are very well laid out, putting them exactly where they need to be.  From there, all that was left was connecting the Radix PB to the flight controller with the silicone wire connector that came with the PB.  Because of the limited wiring, the build went incredibly quick, and made the margin for error much smaller.

On a side note, the BrainFPV Radix FC can be used as a standalone flight controller, separate from the Radix PB or Hobbywing 4-in-1 ESC.  There are pads on the bottom of the board that will replace the connector for those that would like to use a different PB.

Betaflight Setup

Before starting, I wanted to know that I had the latest release of Betaflight available for the BrainFPV Radix FC.  However, being that the Radix is so new, there isn’t a built in hex target for the FC yet.  A quick RCGroups search did bring up a link to the BrainFPV GitHub page where they have the newest releases.  I’m sure that the Radix will integrate into Betaflight fairly quickly.  Though marked in pre-release, I flashed the firmware to the v3.3.0-Brain-2 release, which went smoothly and had no issues.

From there, it was a simple setup of the ports to accommodate the TrampHV, ESC Telemetry, and my FrSky receiver.  I also modified the OSD to clear up my screen a lot, and played around with the LED’s on the Radix PB.  There was no special CLI modifications necessary to get the FPV camera control working, as was my VTX settings and PID control through the Betaflight OSD.

Flight Testing

During flight testing, the BrainFPV Radix FC and PB performed wonderfully.  The flight on stock Betaflight settings was smooth, and didn’t throw up any issues.  I did conduct a little PID tuning after the first few packs to get the flight characteristics that I prefer, which was easy through the Betaflight OSD.  I was also able to use the camera control out in the field to adjust my settings a little as my flying was near dusk.

Pros:

• Board layout is perfect, putting the right pads in the right places in relation to components
• Inclusion of the barometer is fun for knowing how high the multirotor is
• Lots of UARTS for peripherals
• MicroSD card slot for logging
• Excellent documentation support
• Logo Customizer is unique
• Clean wiring

Cons

• None

Overall Thoughts

Despite some of the small issues with the PB, I would say the BrainFPV Radix FC coupled with the Radix PB is a keeper.  I can appreciate all the engineering that Martin Luessi and BrainFPV has put into this tiny package.  Because it is feature rich, clean, and packs power, it lends itself to whatever uses pilots have in mind.  Furthermore, I would consider this combo as a go-to for my future builds, and look forward to more exciting releases from BrainFPV.