Flight Controller Defined: How you can Select the Greatest FC for FPV Drone

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A flight controller is without doubt one of the most essential parts in a FPV drone. It’s liable for stabilizing the plane, guaranteeing exact flight manoeuvres, and offering information to the pilot. On this article, we’ll clarify intimately what a flight controller is, the way it works, and why it’s such a essential a part of any drone. Whether or not you’re a newbie or a seasoned pilot, understanding the fundamentals of flight controllers is essential for getting essentially the most out of your flying expertise.

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If you’re new to the passion, try our FPV drones inexperienced persons information to be taught extra.

The Greatest FC Suggestions

Flight Controller: What it’s and The way it Works

A flight controller, or “FC”, is just like the mind of an FPV drone. It’s a circuit board outfitted with sensors that detect the drone’s actions and consumer instructions. With this data, the FC adjusts the velocity of the motors to maneuver the drone within the desired course.

All flight controllers have primary sensors like gyroscope and accelerometer, whereas others could embrace different sensors corresponding to barometric strain sensors (barometer) and compasses (magnetometer).

The FC can even function a hub for different drone peripherals like ESC, GPS, LED, servos, radio receiver FPV digicam and VTX.

As expertise advances, flight controllers are getting smaller, extra feature-packed, and utilizing higher processors and {hardware}.

FC Varieties

There are two principal sorts of flight controllers: one is extra plane-oriented, whereas the opposite is extra multirotor-oriented. This doesn’t imply you should use a airplane FC on a multirotor or vice versa, however you’ll seemingly face extra challenges. It’s finest to decide on the right kind of FC for a smoother expertise.

Aircraft/Wing Oriented FC	Multirotor Oriented FC/ESC Stack

Throughout the multirotor FC, you’ll discover common FC and AIO (All-in-One) FC.

An AIO FC integrates the ESC onto the identical board, which makes for a compact setup. Nevertheless, they aren’t as strong as ESCs on separate boards, as present in common FC/ESC stacks (two separate boards). The selection relies on your necessities—if house and weight are priorities, you in all probability need to go along with an AIO FC. In any other case, an everyday FC/ESC stack is often most popular for its reliability.

Common FC/ESC Stack (2 boards)	AIO FC (1 board)

FC Connection

Right here is an instance wiring diagram how parts in a FPV drone are related to the flight controller. Every FC has a unique wiring diagram attributable to variations in solder pad layouts, however the idea stays the identical—you simply must establish the suitable pads in your FC.

Flight Controller Firmware

Relating to flight controllers, you could have a selection not solely in {hardware} but in addition in firmware. Totally different firmware choices supply totally different options and specializations for numerous functions. For instance, iNav is designed with GPS and autonomous flight in thoughts, whereas Betaflight is extra centered on flight efficiency.

Listed here are a checklist of well-liked FC firmware choices for FPV drones: https://oscarliang.com/fc-firmware/

Nevertheless, I might personally suggest selecting between these two:

• Betaflight: This open-source firmware focuses on flight efficiency. It has the biggest consumer base, which makes beginning out simpler because of the abundance of tutorials. It additionally means assist is available while you encounter points. Moreover, Betaflight helps the widest vary of flight controllers. Right here’s a tutorial to get you began: https://oscarliang.com/betaflight-firmware-setup/
• iNav: If you’re extra curious about automated flying and GPS waypoint mission, iNav is the way in which to go.

When you’ve chosen your firmware, you may then search for a suitable flight controller board.

Configuration and Tuning

Flight controller firmware may be configured utilizing a pc, smartphone, or radio controller. Every firmware has its personal consumer interface (UI) and parameters that may be modified. Nevertheless, even similar-looking UIs can produce totally different flight traits relying on the firmware, so it takes time to be taught and modify to a brand new one.

“Tuning” is the time period we use within the passion to explain the method of adjusting parameters like PID, charges/expo, and others to attain desired flight traits. This is a vital step in optimizing your FPV drone’s efficiency and getting essentially the most out of your flight controller. I’ve a tutorial on how one can tune your FPV drone in a couple of easy steps.

Processor

FC Processors: from left to proper: STM32 F1, F3, F4

A flight controller makes use of microcontroller models (MCUs) to retailer firmware codes and carry out complicated calculations.

At present, STM32 MCUs corresponding to F4, F7, and H7 are supported by Betaflight, whereas F1 and F3 are not supported attributable to inadequate reminiscence for the increasing firmware necessities. Due to this fact, it’s essential to concentrate to the reminiscence obtainable on totally different processors – it’s simply as essential as velocity, if no more. As an example, though the most recent Betaflight lets you choose which options to make use of and maintain the code measurement small for processors with much less reminiscence, in the long term, the slower F405 may even have a bonus over the quicker F722 attributable to its bigger reminiscence capability.

This text supplies a extra detailed clarification of the variations between all of the MCU for a greater understanding of FC processors: https://oscarliang.com/f1-f3-f4-flight-controller/

Traditionally, STM32 chips have dominated the FPV drone flight controller market. Nevertheless, in recent times, AT32 is shortly turning into a viable various to STM32 chips attributable to its availability and affordability. Be taught extra right here: https://oscarliang.com/at32-flight-controllers/

Gyro

The flight controller on an FPV drone makes use of a variety of sensors to detect motion and orientation. The primary sensor used for this goal is named an Inertial Measurement Unit (IMU). An IMU incorporates each an accelerometer and a gyroscope, however within the passion, the time period “gyro” is commonly used to confer with the IMU sensor.

The gyro can measure angular velocity whereas the accelerometer measures linear acceleration. When flying an FPV drone in full guide mode (aka acro mode), it makes use of solely the Gyro, whereas in self stage modes corresponding to Angle mode, it requires each the Gyro and Accelerometer to work.

Gyro Overview

The most well-liked sorts of gyro for FPV drone FCs are made by two producers: InvenSense (now a part of TDK) and Bosch Sensortec.

Right here’s an inventory of frequent gyro fashions, together with the communication protocols they assist and their most efficient sampling frequency:

* MPU9150 is successfully MPU6050 with an built-in AK8975 magnetometer, whereas MPU9250 is MPU6500 with the identical magnetometer

There are two sorts of communication between the gyro and processor: SPI and i2c. SPI is the popular communication protocol between the IMU and processor as a result of it permits for a a lot increased gyro refresh fee than I2C (which has a restrict of 4KHz). Nearly all fashionable FCs at this time use SPI connection for the gyro. We need to keep away from MPU6050 and 9150 as a result of they solely assist i2c and never SPI.

How you can Discover Out What Gyro FC Is Utilizing

To seek out out which gyro your FC has yow will discover the IMU mannequin quantity printed on the chip, for instance that is the favored Invensense MPU-6000.

Gyro and Accelerometer on a flight controller

Or you may enter the “standing” command within the Betaflight Configurator CLI and search for the identify of the IMU below Gyro/ACC. Some FC could have a couple of Gyro onboard, and you’ll select which one to make use of within the CLI with the command “set gyro_to_use=0 or 1”.

Which Gyro Is Greatest?

Flight controllers don’t supply Gyro choices, however typically, if you happen to select a good model that features a gyro with observe report, it shouldn’t pose any points. Right here’s a quick historical past of gyros utilized in flight controllers.

The selection of gyro relies on its max sampling fee and susceptibility to electrical and mechanical noise. Earlier than 2022, essentially the most extensively used gyro was MPU6000 due to its robustness in opposition to noise. The overall consensus is to keep away from MPU6500 and MPU9250 regardless of their increased sampling velocity. The ICM20689 can be an honest gyro when it comes to efficiency however allegedly has the next failure fee. The ICM20602 is one other well-liked selection, nevertheless it’s extra inclined to noise and tougher to tune. Since Betaflight 4.1 (Oct 2019), 32KHz gyro sampling fee has been faraway from Betaflight, so there isn’t any benefit utilizing gyro with 32KHz sampling fee.

In 2022, FC producers shifted from MPU6000 in direction of BMI270 attributable to price and availability. Whereas its max sampling frequency is simply 6.4KHz, Betaflight forces it to enter OSR4 mode (with a cutoff frequency of 300Hz), leading to a good decrease sampling fee of three.2KHz. Which may sound suboptimal, however as I’ve examined it myself personally, the precise efficiency of BMI270 is corresponding to MPU6000 (in Betaflight 4.3/4.4). The primary draw back might be the additional filtering that’s generally required because the cut-off frequency is increased within the built-in low cross filter with the BMI270 gyro.

In 2023, increasingly more producers are once more shifting from BMI270 to ICM42688P attributable to availability and price. The ICM-42688P Gyro has been the topic of debate attributable to perceived noise and tuning points. Nevertheless, investigations reveal that the gyro itself isn’t the issue; quite, it’s the design of the flight controllers it’s built-in into. Particularly, the gyro requires a clear energy provide for optimum efficiency, which was missed by some early FC designs in 2022 and early 2023, resulting in poor efficiency. For customers contemplating buying a flight controller that includes this gyro, thorough analysis into product opinions specializing in noise efficiency is essential.

Structure

FC format refers back to the association of pins and solder pads on a flight controller board, which may significantly have an effect on how simple it’s to attach numerous parts. Many individuals solely care in regards to the specs of a flight controller, and infrequently overlook the significance of the format.

As an example, evaluating the next two flight controllers, you may see the primary one has a superior format with all of the pads grouped by operate and situated all the sides.

ESC Compatibility

4in1 ESC’s are sometimes offered along with flight controllers these days as a stack, and they’re designed to be plug and play.

Nevertheless, when utilizing ESC and FC from totally different manufacturers, whereas they need to be suitable, the pinouts could be totally different, requiring rearrangement of the wires within the harness, which could be a large trouble. If that is what you need to do, guarantee to double-check the pinout earlier than connecting the FC and ESC collectively, flawed wiring might fry your FC upon powering up.

Solder Pads Defined

Right here, I’ll checklist a few of the essential solder pads typically wanted on a flight controller and clarify what they imply.

Voltage Pads

VBAT, 3.3V, 5V, 9V

These pads are used to energy exterior gadgets. VBAT is the direct voltage from the LiPo battery, whereas all different voltages are generally known as BEC (Battery Eliminating Circuit). Nearly all FCs have VBAT, 3.3V, and 5V pads; some bigger FCs supply different voltages corresponding to 9V and 12V to energy video transmitters. Word that each one BECs have an amp ranking, so keep away from overloading them to keep away from harm.

UART

UART (Common Asynchronous Receiver/Transmitter) is an important connection on a flight controller. It’s a {hardware} serial port used to attach exterior parts corresponding to radio receivers, video transmitters, GPS, and so on.

Every UART has two pins: one for transmitting information (TX pin) and one for receiving information (RX pin). It’s essential to do not forget that the TX on the peripheral gadget connects to the RX on the FC, and vice versa. It’s important to join TX and RX of the identical quantity for a tool. Some gadgets solely require connecting both TX or RX if two-way communication isn’t wanted.

As proven within the following instance, UART3 (R3 and T3 pins) and UART6 (R6 and T6 pins) on a flight controller may be assigned totally different duties within the ports tab of the Betaflight configurator.

Flight controllers have a restricted variety of UARTs; some have as much as 6, whereas smaller FC’s could solely have 2. It relies on the processor and house obtainable. Guarantee there are sufficient UARTs for the gadgets you intend to make use of earlier than buying.

For those who want extra UART ports, Betaflight has a characteristic known as SoftSerial, which converts sure solder pads into “digital serial ports.” These are just like UARTs however have a a lot slower replace fee, making them unsuitable for time-critical functions corresponding to receivers and GPS. They can be utilized for analog VTX management but in addition improve CPU load, making them not beneficial for slower processors otherwise you may must decrease the PID Loop Frequency.

Digital camera Pad

Vin or Cam

For those who run analog FPV system, that is the place you join the FPV digicam. The flight controller will then overlay the OSD to the video feed earlier than it outputs it to the VTX.

VTX Pad

Vout or VTX

That is the place you join the VTX if you happen to run an analog FPV system.

i2C Pads

SDA and SCL

For connecting gadgets like a GPS compass and barometer.

Buzzer Pads

BZ+ and BZ-.

For beepers.

LED Pad

For connecting RGB LED strips.

Mounting Sample

The mounting sample refers back to the distance between the adjoining mounting holes on a flight controller. Frequent patterns embrace 30.5×30.5mm, 25.5×25.5mm, 20×20mm, and 16×16mm.

For five″ FPV drones or bigger, FC with 30.5×30.5mm mounting sample is commonly used, whereas smaller drones typically use 25.5×25.5mm or 20×20mm.

Different Options

Flight controllers include a variety of options that may improve your flying expertise. Let’s check out a few of them.

Blackbox

Blackbox is helpful for tuning and troubleshooting. You’ll be able to report your flight information in two methods – utilizing built-in flash reminiscence or storing it on an SD card if there’s an onboard SD card logger.

I’ve a tutorial explaining how one can use Blackbox: https://oscarliang.com/blackbox/.

Flash reminiscence is cheaper however has restricted storage capability, usually 16MB which provides round 5 to 10 minutes of flight information. Downloading information from it can be gradual. Utilizing an SD card reader in your flight controller, you may maintain recording all 12 months lengthy with out emptying the storage, and it offers you entry to the logs immediately by inserting the SD card in a card reader.

Blackbox logs is a must have for knowledgeable pilots. It offers you the flexibility to squeeze each little bit of efficiency out of the drone and diagnose points intimately. I’ve a tutorial explaining how one can tune your FPV drone: https://oscarliang.com/pid-filter-tuning-blackbox/

In case your flight controller doesn’t have an SD card slot or flash reminiscence, you too can join an exterior SD card reader to the FC by way of UART.

Connector Varieties

The three principal sorts of connectors on a flight controller are

• Plastic JST connectors
• Solder pads
• Via holes

Plastic connectors are much less sturdy however handy to make use of, whereas solder pads are extra strong however requires soldering. Via holes provide the possibility of direct soldering or utilizing header pins.

BEC

BEC (battery eliminator circuit) is simply what we name voltage regulators on a flight controller.

Nearly all flight controllers have a 5V BEC for powering radio receiver, GPS and so on, whereas some additionally supply 9V or 12V BEC devoted for powering the video transmitter. Though you may energy FPV gear straight from the LiPo battery, powering them from a regulated energy supply can produce higher outcomes.

Study how one can wire analogue FPV setup for finest end result.

It’s essential to decide on the fitting voltage supply based mostly on the gadget you’re powering. Some gadgets may be powered straight from the LiPo battery e.g. the video transmitter. Nevertheless the ability supply from LiPo tends to be noisy, voltage spikes may even harm your gadgets if there isn’t sufficient filtering. A BEC acts as an influence filter and is normally a greater energy supply, however you have to test if it meets the voltage and present necessities of your gadget.

Barometer

Having a barometer constructed into your flight controller could make GPS-assisted flight extra correct (corresponding to GPS Rescue Mode), however it’s not obligatory.

OSD Chip

For analog FPV system, be certain your flight controller has an OSD chip (AT7456E) obtainable, or Betaflight OSD gained’t work. Nevertheless, it’s not mandatory for digital FPV methods corresponding to DJI, HDZero and Walksnail, all they want for OSD to work is only a spare UART .

Comfortable Mounting

Comfortable mounting the flight controller is essential for optimum efficiency, it reduces the noise/vibration from the body attending to the gyro.

Nearly all FC lately have M4 holes, which let you insert rubber gummies (grommets) so you should use M3 {hardware} to safe the board in a body.

There are FC with the Gyro “mushy mounted” on a chunk of froth for decreasing vibrations attending to the gyro. This isn’t a extremely popular strategy, because it’s been confirmed pointless so long as the flight controller itself is satisfactorily soft-mounted. Listed here are some tips about soft-mounting and filtering capacitors to cut back noise.

Comfortable mounted Gyro – Kakute F4

A Little Historical past

The historical past of FPV drone flight controller may be traced again to 2009, when a maker used the Wii Movement Plus Accent with an Arduino board to regulate a drone. This led to the event of the Multiwii venture, which ultimately created its personal flight controller board that labored on an 8-bit Atmel processor.

In 2013, one other developer named “timecop” created a flight controller board with an ARM 32-bit processor, Naze32,  and ported the Multiwii supply code to it, known as “Baseflight.” This board established the 35x35mm kind issue (with 30x30mm mounting) and remains to be related until this present day.

In 2014, “Hydra” modified Baseflight and created Cleanflight, resulting in an explosion within the 32-bit flight controller market, with producers growing their very own FC variants.

Betaflight was created in 2015 by “BorisB”, utilizing Cleanflight’s supply code and making vital modifications to it. When Betaflight was first launched, it was primarily centered on enhancing the efficiency of Cleanflight, whereas additionally including new options and capabilities. Over time, Betaflight has diverged considerably from Cleanflight, and is now thought-about a separate and distinct firmware. Betaflight is presently the most well-liked flight controller firmware for FPV drones, and remains to be being frequent up to date.

Edit Historical past

• 2014 – Article created
• 2016 – Added decisions of flight controller firmware, up to date FC options
• 2017 – Up to date Processor and Gyro sorts, Added “FC Evolution” infographics, Up to date MPU sorts
• 2018 – Up to date data about FC integration, Added data about mounting sample
• 2020 – URL Modified; Up to date: FC Firmware, Gyro Data; Added: connection diagram/instance, AIO FC & Characteristic integrations defined, format, digicam management
• 2022 – Added data about BMI270 gyro
• 2023 – Tutorial revised, Added data about ICM42688P Gyro
• Could 2024 – Up to date tutorial, added FC suggestions.