Flight Controller Defined: The best way to Select the Greatest FC for FPV Drone

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A flight controller is among the most vital parts in a FPV drone. It’s answerable for stabilizing the plane, making certain 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 important 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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In case you are 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 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 info, 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 some even embody elective sensors equivalent to barometric strain sensors (barometer) and compasses (magnetometer) to help in autonomous flights.

The FC also can function a hub for different drone peripherals (exterior parts) like ESC, GPS, LED, servos, radio receiver FPV digicam and VTX.

FC Sorts

There are two important sorts of flight controllers: one is extra plane-oriented, whereas the opposite is extra multirotor-oriented. This doesn’t imply you may’t 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 sort of FC for a smoother expertise.

Aircraft/Wing Oriented FC	Multirotor Oriented FC/ESC Stack

Throughout the multirotor FC, you can see common FC and AIO (All-in-One) FC.

An AIO FC integrates the ESC onto the identical board, which makes for a compact setup. Nonetheless, they aren’t as strong as ESCs on separate boards, as present in common FC/ESC stacks (two separate boards), as a result of they’ve to make use of smaller FET’s and there’s much less warmth dissipation on account of area limitation. Be taught extra about ESC on this information: https://oscarliang.com/esc/

The selection is determined by your necessities—if area and weight are priorities, you in all probability need to go together with an AIO FC. In any other case, a daily 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 on account of variations in solder pad layouts, however the idea stays the identical—you simply must determine the suitable pads in your FC.

Flight Controller Firmware

In relation to flight controllers, you will have a selection not solely in {hardware} but in addition in firmware. Completely different firmware choices supply completely different options and specializations for varied 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 listing of well-liked FC firmware choices for FPV drones: https://oscarliang.com/fc-firmware/

Nonetheless, I might personally advocate selecting between these two:

• Betaflight: This open-source firmware focuses on flight efficiency. It has the biggest consumer base, which makes beginning out simpler as a result of abundance of tutorials. It additionally means assist is available if 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: In case you are extra eager about automated flying and GPS waypoint mission, iNav is the best way to go.

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

Configuration and Tuning

Flight controller firmware will be configured utilizing a pc, smartphone, or radio controller. Every firmware has its personal consumer interface (UI) and parameters that may be modified. Nonetheless, even similar-looking UIs can produce completely 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 number 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 the moment, STM32 MCUs equivalent to F4, F7, and H7 are supported by Betaflight, whereas F1 and F3 are now not supported on account of inadequate reminiscence for the increasing firmware necessities. Due to this fact, it’s vital to concentrate to the reminiscence out there on completely different processors – it’s simply as vital as velocity, if no more. For example, though the newest Betaflight permits you to choose which options to make use of and hold the code measurement small for processors with much less reminiscence, in the long term, the slower F405 may even have a bonus over the sooner F722 on account of 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. Nonetheless, lately, AT32 is shortly turning into a viable different to STM32 chips on account of 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 objective is known as an Inertial Measurement Unit (IMU). An IMU accommodates each an accelerometer and a gyroscope, however within the passion, the time period “gyro” is usually used to check with the IMU sensor.

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

Gyro Overview

The preferred 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 widespread 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 larger gyro refresh charge than I2C (which has a restrict of 4KHz). Nearly all trendy FCs immediately 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.

The best way to Discover Out What Gyro FC Is Utilizing

To search out out which gyro your FC has you’ll find 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 multiple Gyro onboard, and you may 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 usually, for those who select a good model that features a gyro with a superb observe report, it shouldn’t pose any points. Right here’s a short historical past of gyros utilized in flight controllers.

The selection of gyro is determined by its max sampling charge and susceptibility to electrical and mechanical noise. Earlier than 2022, essentially the most broadly used gyro was MPU6000 due to its robustness towards noise. The overall consensus is to keep away from MPU6500 and MPU9250 regardless of their larger sampling velocity. The ICM20689 can also be a good gyro when it comes to efficiency however allegedly has the next failure charge. The ICM20602 is one other well-liked selection, nonetheless it’s extra inclined to noise and more durable to tune. Since Betaflight 4.1 (Oct 2019), 32KHz gyro sampling charge has been faraway from Betaflight, so there isn’t a benefit utilizing gyro with 32KHz sampling charge.

In 2022, FC producers shifted from MPU6000 in direction of BMI270 on account of value 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 an excellent decrease sampling charge of three.2KHz. That may sound suboptimal, however as I’ve examined it myself personally, the precise efficiency of BMI270 is similar 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 larger within the built-in low cross filter with the BMI270 gyro.

In 2023, an increasing number of producers are once more shifting from BMI270 to ICM42688P on account of availability and price. The ICM-42688P Gyro has been the topic of debate on account of perceived noise and tuning points. Nonetheless, investigations reveal that the gyro itself will not be the issue; somewhat, 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 neglected 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 evaluations specializing in noise efficiency is essential.

Format

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 straightforward it’s to attach varied parts. Many individuals solely care in regards to the specs of a flight controller, and infrequently overlook the significance of the format.

For example, evaluating the next two flight controllers, you may see the primary one has a superior format with all of the pads grouped by perform and situated all the perimeters.

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.

Nonetheless, when utilizing ESC and FC from completely different manufacturers, whereas they need to be appropriate, the pinouts may be completely different, requiring rearrangement of the wires within the harness, which is usually a big problem. If that is what you need to do, guarantee to double-check the pinout earlier than connecting the FC and ESC collectively, fallacious wiring may fry your FC upon powering up.

Solder Pads Defined

Right here, I’ll listing among the vital solder pads usually 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 referred to as BEC (Battery Eliminating Circuit). Nearly all FCs have VBAT, 3.3V, and 5V pads; some bigger FCs supply different voltages equivalent to 9V and 12V to energy video transmitters. Notice that each one BECs have an amp score, so keep away from overloading them to keep away from harm.

UART

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

Every UART has two pins: one for transmitting information (TX pin) and one for receiving information (RX pin). It’s vital to keep in mind that the TX on the peripheral system connects to the RX on the FC, and vice versa. You must 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 will be assigned completely 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 is determined by the processor and area out there. Guarantee there are sufficient UARTs for the gadgets you propose to make use of earlier than buying.

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

Digicam Pad

Vin or Cam

If you happen to 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 for those who 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. Widespread patterns embody 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 usually used, whereas smaller drones usually 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, sometimes 16MB which presents round 5 to 10 minutes of flight information. Downloading information from it may also be sluggish. Utilizing an SD card reader in your flight controller, you may hold 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 can too join an exterior SD card reader to the FC through UART.

Connector Sorts

The three important 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 choice 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 many others, whereas some additionally supply 9V or 12V BEC devoted for powering the video transmitter. Though you may energy FPV gear instantly from the LiPo battery, powering them from a regulated energy supply can produce higher outcomes.

Find out about how one can wire analogue FPV setup for finest consequence.

It’s vital to decide on the suitable voltage supply primarily based on the system you’re powering. Some gadgets will be powered instantly from the LiPo battery e.g. the video transmitter. Nonetheless the facility 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 often a greater energy supply, however you could examine if it meets the voltage and present necessities of your system.

Barometer

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

OSD Chip

For analog FPV system, be sure that your flight controller has an OSD chip (AT7456E) out there, or Betaflight OSD received’t work. Nonetheless, it’s not mandatory for digital FPV methods equivalent to DJI, HDZero and Walksnail, all they want for OSD to work is only a spare UART .

Tender Mounting

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

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

There are FC with the Gyro “tender mounted” on a bit of froth for lowering vibrations attending to the gyro. This isn’t a very talked-about 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 scale back noise.

Tender mounted Gyro – Kakute F4

A Little Historical past

The historical past of FPV drone flight controller will be traced again to 2009, when a maker used the Wii Movement Plus Accent with an Arduino board to manage a drone. This led to the event of the Multiwii undertaking, 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 continues to be related until at the present time.

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 important 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 of a separate and distinct firmware. Betaflight is at present the most well-liked flight controller firmware for FPV drones, and continues to be being frequent up to date.

Edit Historical past

• 2014 – Article created
• 2016 – Added selections 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 information about FC integration, Added information about mounting sample
• 2020 – URL Modified; Up to date: FC Firmware, Gyro Information; Added: connection diagram/instance, AIO FC & Function integrations defined, format, digicam management
• 2022 – Added information about BMI270 gyro
• 2023 – Tutorial revised, Added information about ICM42688P Gyro
• Could 2024 – Up to date tutorial, added FC suggestions.