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 necessary elements 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 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 probably the most out of your flying expertise.

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If you’re new to the pastime, try our FPV drones inexperienced persons information to study 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 path.

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

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

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

FC Sorts

There are two essential sorts of flight controllers: one is extra plane-oriented, whereas the opposite is extra multirotor-oriented. This doesn’t imply you need to use a aircraft FC on a multirotor or vice versa, however you’ll doubtless face extra challenges. It’s greatest to decide on the proper kind of FC for a smoother expertise.

Airplane/Wing Oriented FC	Multirotor Oriented FC/ESC Stack

Inside the multirotor FC, one can find 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). The selection depends upon 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 generally 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 elements in a FPV drone are related to the flight controller. Every FC has a special wiring diagram attributable to 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 the case of flight controllers, you might have a selection not solely in {hardware} but additionally in firmware. Completely different firmware choices provide totally different options and specializations for varied functions. For instance, iNav is designed with GPS and autonomous flight in thoughts, whereas Betaflight is extra targeted on flight efficiency.

Listed here are a record of in style 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: If you’re extra serious about 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 suitable flight controller board.

Configuration and Tuning

Flight controller firmware could 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 attain desired flight traits. This is a crucial step in optimizing your FPV drone’s efficiency and getting probably the most out of your flight controller. I’ve a tutorial on easy methods to tune your FPV drone in just a few easy steps.

Processor

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

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

Presently, STM32 MCUs resembling F4, F7, and H7 are supported by Betaflight, whereas F1 and F3 are now not supported attributable to inadequate reminiscence for the increasing firmware necessities. Subsequently, it’s necessary to concentrate to the reminiscence out there on totally different processors – it’s simply as necessary as velocity, if no more. As an illustration, though the most recent Betaflight lets you 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 would possibly even have a bonus over the sooner F722 attributable to its bigger reminiscence capability.

This text gives 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, in recent times, AT32 is shortly changing into a viable different 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 objective known as an Inertial Measurement Unit (IMU). An IMU accommodates each an accelerometer and a gyroscope, however within the pastime, the time period “gyro” is commonly used to consult 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 resembling 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 a listing 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). Virtually all trendy FCs as we speak 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 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’ll be able to enter the “standing” command within the Betaflight Configurator CLI and search for the identify of the IMU underneath Gyro/ACC. Some FC could 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 Greatest?

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

The selection of gyro depends upon its max sampling fee and susceptibility to electrical and mechanical noise. Earlier than 2022, probably 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 by way of efficiency however allegedly has the next failure fee. The ICM20602 is one other in style selection, nevertheless it’s extra prone to noise and tougher to tune. Since Betaflight 4.1 (Oct 2019), 32KHz gyro sampling fee has been faraway from Betaflight, so there is no such thing as a benefit utilizing gyro with 32KHz sampling fee.

In 2022, FC producers shifted from MPU6000 in direction of BMI270 attributable to value and availability. Whereas its max sampling frequency is just 6.4KHz, Betaflight forces it to enter OSR4 mode (with a cutoff frequency of 300Hz), leading to an excellent decrease sampling fee of three.2KHz. That 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 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. Nonetheless, investigations reveal that the gyro itself isn’t the issue; reasonably, 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 ignored 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.

Structure

FC structure refers back to the association of pins and solder pads on a flight controller board, which might tremendously have an effect on how simple it’s to attach varied elements. Many individuals solely care concerning the specs of a flight controller, and infrequently overlook the significance of the structure.

As an illustration, evaluating the next two flight controllers, you’ll be able to see the primary one has a superior structure with all of the pads grouped by operate and positioned 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 suitable, the pinouts could be totally different, requiring rearrangement of the wires within the harness, which generally is a large problem. If that is what you need to do, guarantee to double-check the pinout earlier than connecting the FC and ESC collectively, mistaken wiring may fry your FC upon powering up.

Solder Pads Defined

Right here, I’ll record among the necessary 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 often called BEC (Battery Eliminating Circuit). Virtually all FCs have VBAT, 3.3V, and 5V pads; some bigger FCs provide different voltages resembling 9V and 12V to energy video transmitters. Word that every one BECs have an amp ranking, 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 elements resembling 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 necessary to do not forget that the TX on the peripheral gadget 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 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 could 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 depends upon the processor and area out there. Guarantee there are sufficient UARTs for the gadgets you intend to make use of earlier than buying.

In the event you 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 fee, making them unsuitable for time-critical functions resembling receivers and GPS. They can be utilized for analog VTX management but additionally enhance CPU load, making them not beneficial for slower processors otherwise you would possibly must decrease the PID Loop Frequency.

Digicam Pad

Vin or Cam

In the event 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 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 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 beneficial 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 easy methods to 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 will also be gradual. Utilizing an SD card reader in your flight controller, you’ll be able to hold recording all 12 months 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 knowledgeable pilots. It provides you the power to squeeze each little bit of efficiency out of the drone and diagnose points intimately. I’ve a tutorial explaining easy methods to 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 even join an exterior SD card reader to the FC through UART.

Connector Sorts

The three essential sorts of connectors on a flight controller are

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

Plastic connectors are much less sturdy however handy to make use of, whereas solder pads are extra strong however requires soldering. By way 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 many others, whereas some additionally provide 9V or 12V BEC devoted for powering the video transmitter. Though you’ll be able to energy FPV gear immediately from the LiPo battery, powering them from a regulated energy supply can produce higher outcomes.

Find out about easy methods to wire analogue FPV setup for greatest consequence.

It’s necessary to decide on the proper voltage supply primarily based on the gadget you’re powering. Some gadgets could be powered immediately 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 gadget.

Barometer

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

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 vital for digital FPV programs resembling DJI, HDZero and Walksnail, all they want for OSD to work is only a spare UART .

Delicate Mounting

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

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

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

Delicate mounted Gyro – Kakute F4

A Little Historical past

The historical past of FPV drone flight controller could 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 mission, which finally 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 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 vital modifications to it. When Betaflight was first launched, it was primarily targeted on bettering 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 at present 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 varieties, Added “FC Evolution” infographics, Up to date MPU varieties
• 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, structure, digital camera management
• 2022 – Added information about BMI270 gyro
• 2023 – Tutorial revised, Added information about ICM42688P Gyro
• Might 2024 – Up to date tutorial, added FC suggestions.