Flight Controller Defined: Easy methods to Select the Finest FC for FPV Drone

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A flight controller is without doubt one of the most vital elements in a FPV drone. It’s accountable 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 vital 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.

In case you are new to the pastime, take a look at our FPV drones learners information to study extra.

The Finest 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 pace of the motors to maneuver the drone within the desired route.

All flight controllers have primary sensors like gyroscope and accelerometer, whereas some even embrace non-compulsory sensors equivalent to barometric stress sensors (barometer) and compasses (magnetometer) to assist in autonomous flights.

The FC may also function a hub for different drone peripherals (exterior elements) like ESC, GPS, LED, servos, radio receiver FPV digital camera and VTX.

FC Sorts

There are two primary varieties of flight controllers: one is extra plane-oriented, whereas the opposite is extra multirotor-oriented. This doesn’t imply you’ll be able to’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.

Airplane/Wing Oriented FC	Multirotor Oriented FC/ESC Stack

Inside the multirotor FC, you will 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. Nonetheless, they aren’t as sturdy 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 resulting from area limitation. Study extra about ESC on this information: https://oscarliang.com/esc/

The selection relies on your necessities—if area and weight are priorities, you in all probability wish to go together with an AIO FC. In any other case, a daily FC/ESC stack is generally most well-liked for its reliability.

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

FC Connection

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

Flight Controller Firmware

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

Listed below are a checklist of common FC firmware choices for FPV drones: https://oscarliang.com/fc-firmware/

Nonetheless, 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 as a result of abundance of tutorials. It additionally means assist is available once 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 fascinated with automated flying and GPS waypoint mission, iNav is the best way to go.

When you’ve chosen your firmware, you’ll be able to then search for a appropriate flight controller board.

Configuration and Tuning

Flight controller firmware might 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 totally different flight traits relying on the firmware, so it takes time to study and modify to a brand new one.

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

Processor

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

At present, STM32 MCUs equivalent to F4, F7, and H7 are supported by Betaflight, whereas F1 and F3 are now not supported resulting from inadequate reminiscence for the increasing firmware necessities. Due to this fact, it’s vital to concentrate to the reminiscence accessible on totally different processors – it’s simply as vital as pace, if no more. As an example, though the most recent Betaflight means that you can 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 quicker F722 resulting from its bigger reminiscence capability.

	F1	F3	F4	F7	H7
Velocity	72MHz	72MHz	168MHz	216MHz	480MHz
Reminiscence	128KB	256KB	512KB/1MB	512KB/1MB	1MB/2MB

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 rapidly turning into a viable different to STM32 chips resulting from its availability and affordability. Study extra right here: https://oscarliang.com/at32-flight-controllers/

Gyro

The flight controller on an FPV drone makes use of a spread of sensors to detect motion and orientation. The principle sensor used for this function is known as an Inertial Measurement Unit (IMU). An IMU comprises each an accelerometer and a gyroscope, however within the pastime, the time period “gyro” is commonly used to discuss 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 degree modes equivalent to Angle mode, it requires each the Gyro and Accelerometer to work.

Gyro Overview

The most well-liked varieties 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:

IMU	Attainable Communication Protocol (BUS)	Max. Efficient Gyro Sampling Frequency
MPU6000	SPI, i2c	8KHz
MPU6050	i2c	4KHz
MPU6500	SPI, i2c	32KHz
MPU9150*	i2c	4KHz
MPU9250*	SPI, i2c	32KHz
ICM20602	SPI, i2c	32KHz
ICM20608	SPI, i2c	32KHz
ICM20689	SPI, i2c	32KHz
ICM42688P	SPI, i2c	32KHz
BMI270	SPI, i2c	6.4KHz

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

There are two varieties 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 charge than I2C (which has a restrict of 4KHz). Virtually all fashionable FCs right this moment use SPI connection for the gyro. We wish to keep away from MPU6050 and 9150 as a result of they solely assist i2c and never SPI.

Easy methods to Discover Out What Gyro FC Is Utilizing

To search out out which gyro your FC has you could find the IMU mannequin quantity printed on the chip, for instance that is the favored Invensense MPU-6000.

Or you’ll be able to enter the “standing” command within the Betaflight Configurator CLI and search for the identify of the IMU beneath Gyro/ACC. Some FC might have multiple 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 Finest?

Flight controllers don’t provide Gyro choices, however typically, in the event you select a good model that features a gyro with a superb 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 charge and susceptibility to electrical and mechanical noise. Earlier than 2022, essentially the most extensively used gyro was MPU6000 due to its robustness towards noise. The overall consensus is to keep away from MPU6500 and MPU9250 regardless of their increased sampling pace. The ICM20689 can be a good gyro by way of efficiency however allegedly has a better failure charge. The ICM20602 is one other common selection, nonetheless it’s extra inclined to noise and tougher to tune. Since Betaflight 4.1 (Oct 2019), 32KHz gyro sampling charge has been faraway from Betaflight, so there is no such thing as a benefit utilizing gyro with 32KHz sampling charge.

In 2022, FC producers shifted from MPU6000 in direction of BMI270 resulting from 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. 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 principle draw back might be the additional filtering that’s typically required because the cut-off frequency is increased within the built-in low move filter with the BMI270 gyro.

In 2023, increasingly producers are once more shifting from BMI270 to ICM42688P resulting from availability and price. The ICM-42688P Gyro has been the topic of debate resulting from perceived noise and tuning points. Nonetheless, investigations reveal that the gyro itself will not be the issue; slightly, 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 critiques 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 numerous elements. Many individuals solely care concerning the specs of a flight controller, and sometimes overlook the significance of the format.

As an example, evaluating the next two flight controllers, you’ll be able to see the primary one has a superior format with all of the pads grouped by operate 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 totally different manufacturers, whereas they need to be appropriate, the pinouts is likely to be totally different, requiring rearrangement of the wires within the harness, which generally is a big problem. If that is what you wish to do, guarantee to double-check the pinout earlier than connecting the FC and ESC collectively, flawed wiring may fry your FC upon powering up.

Solder Pads Defined

Right here, I’ll checklist a number of 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 units. VBAT is the direct voltage from the LiPo battery, whereas all different voltages are referred to as BEC (Battery Eliminating Circuit). Virtually all FCs have VBAT, 3.3V, and 5V pads; some bigger FCs provide different voltages equivalent to 9V and 12V to energy video transmitters. Notice that every one BECs have an amp score, 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 elements equivalent to radio receivers, video transmitters, GPS, and so forth.

Every UART has two pins: one for transmitting information (TX pin) and one for receiving information (RX pin). It’s vital to do not forget that the TX on the peripheral system connects to the RX on the FC, and vice versa. You need to join TX and RX of the identical quantity for a tool. Some units 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 might 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 might solely have 2. It relies on the processor and area accessible. Guarantee there are sufficient UARTs for the units you propose to make use of earlier than buying.

When you want extra UART ports, Betaflight has a characteristic referred to 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 purposes equivalent to receivers and GPS. They can be utilized for analog VTX management but in addition improve CPU load, making them not really helpful for slower processors otherwise you may have to decrease the PID Loop Frequency.

Digicam Pad

Vin or Cam

When you run analog FPV system, that is the place you join the FPV digital camera. 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 in the event you run an analog FPV system.

i2C Pads

SDA and SCL

For connecting units 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 spread 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 may 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 use Blackbox: https://oscarliang.com/blackbox/.

Flash reminiscence is cheaper however has restricted storage capability, sometimes 16MB which affords round 5 to 10 minutes of flight information. Downloading information from it will also be gradual. Utilizing an SD card reader in your flight controller, you’ll be able to hold recording all yr lengthy with out emptying the storage, and it provides you entry to the logs immediately by inserting the SD card in a card reader.

Blackbox logs is a must have for skilled pilots. It provides you the flexibility to squeeze each little bit of efficiency out of the drone and diagnose points intimately. I’ve a tutorial explaining 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 through UART.

Connector Sorts

The three primary varieties of connectors on a flight controller are

• Plastic JST connectors
• Solder pads
• By means of holes

Plastic connectors are much less sturdy however handy to make use of, whereas solder pads are extra sturdy however requires soldering. By means of 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.

Virtually all flight controllers have a 5V BEC for powering radio receiver, GPS and so forth, whereas some additionally provide 9V or 12V BEC devoted for powering the video transmitter. Though you’ll be able to energy FPV gear straight from the LiPo battery, powering them from a regulated energy supply can produce higher outcomes.

Find out about wire analogue FPV setup for finest outcome.

It’s vital to decide on the appropriate voltage supply based mostly on the system you’re powering. Some units might be powered straight from the LiPo battery e.g. the video transmitter. Nonetheless the ability supply from LiPo tends to be noisy, voltage spikes may even harm your units if there isn’t sufficient filtering. A BEC acts as an influence filter and is normally a greater energy supply, however it’s good to 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 obligatory.

OSD Chip

For analog FPV system, make sure that your flight controller has an OSD chip (AT7456E) accessible, or Betaflight OSD gained’t work. Nonetheless, it’s not vital for digital FPV programs 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.

Virtually all FC today 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 “gentle mounted” on a chunk of froth for decreasing vibrations attending to the gyro. This isn’t a extremely popular method, because it’s been confirmed pointless so long as the flight controller itself is satisfactorily soft-mounted. Listed below are some tips about soft-mounting and filtering capacitors to scale back noise.

A Little Historical past

The historical past of FPV drone flight controller might 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, referred to as “Baseflight.” This board established the 35x35mm type 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 creating 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 presently 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 decisions of flight controller firmware, up to date FC options
• 2017 – Up to date Processor and Gyro varieties, Added “FC Evolution” infographics, Up to date MPU varieties
• 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 & Function integrations defined, format, digital camera management
• 2022 – Added data about BMI270 gyro
• 2023 – Tutorial revised, Added data about ICM42688P Gyro
• Could 2024 – Up to date tutorial, added FC suggestions.