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

34.2K

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

A number of the hyperlinks on this web page are affiliate hyperlinks. I obtain a fee (at no further price to you) if you happen to make a purchase order after clicking on considered one of these affiliate hyperlinks. This helps assist the free content material for the group on this web site. Please learn our Affiliate Hyperlink Coverage for extra data.

In case you are new to the pastime, take a look at our FPV drones novices 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 person instructions. With this data, the FC adjusts the velocity of the motors to maneuver the drone within the desired route.

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

The FC also can 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 foremost forms of flight controllers: one is extra plane-oriented, whereas the opposite is extra multirotor-oriented. This doesn’t imply you should utilize a airplane FC on a multirotor or vice versa, however you’ll probably face extra challenges. It’s greatest to decide on the proper sort of FC for a smoother expertise.

Aircraft/Wing Oriented FC	Multirotor Oriented FC/ESC Stack

Throughout the multirotor FC, you’ll 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 relies on your necessities—if area and weight are priorities, you most likely wish to go along 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 elements in a FPV drone are related to the flight controller. Every FC has a unique wiring diagram because of variations in solder pad layouts, however the idea stays the identical—you simply have to determine the suitable pads in your FC.

Flight Controller Firmware

In relation to flight controllers, you’ve gotten a selection not solely in {hardware} but additionally in firmware. Totally different firmware choices supply completely different options and specializations for numerous 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 checklist of widespread 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 most important person base, which makes beginning out simpler as a result of abundance of tutorials. It additionally means assist is available whenever 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 focused on 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 could be configured utilizing a pc, smartphone, or radio controller. Every firmware has its personal person 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 study and regulate 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 learn how to 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 advanced calculations.

At present, STM32 MCUs comparable to F4, F7, and H7 are supported by Betaflight, whereas F1 and F3 are not supported because of inadequate reminiscence for the increasing firmware necessities. Due to this fact, it’s essential to concentrate to the reminiscence out there on completely different processors – it’s simply as essential as velocity, if no more. As an example, though the newest 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 because of its bigger reminiscence capability.

This text offers 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 because of 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 variety of sensors to detect motion and orientation. The primary sensor used for this objective is named an Inertial Measurement Unit (IMU). An IMU accommodates each an accelerometer and a gyroscope, however within the pastime, the time period “gyro” is usually 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 guide mode (aka acro mode), it makes use of solely the Gyro, whereas in self degree modes comparable to Angle mode, it requires each the Gyro and Accelerometer to work.

Gyro Overview

The most well-liked forms 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 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 forms 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 fashionable FCs as we speak 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.

How one 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 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, if you happen to select a good model that features a gyro with an excellent observe document, 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 in opposition to noise. The final consensus is to keep away from MPU6500 and MPU9250 regardless of their larger sampling velocity. The ICM20689 can also be a good gyro by way of efficiency however allegedly has the next failure charge. The ICM20602 is one other widespread 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 isn’t any benefit utilizing gyro with 32KHz sampling charge.

In 2022, FC producers shifted from MPU6000 in the direction of BMI270 because of price and availability. Whereas its max sampling frequency is barely 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 akin to MPU6000 (in Betaflight 4.3/4.4). The primary draw back might be the additional filtering that’s typically required because the cut-off frequency is larger within the built-in low go filter with the BMI270 gyro.

In 2023, an increasing number of producers are once more shifting from BMI270 to ICM42688P because of availability and value. The ICM-42688P Gyro has been the topic of debate because of perceived noise and tuning points. Nonetheless, investigations reveal that the gyro itself just 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 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 vastly have an effect on how simple it’s to attach numerous elements. Many individuals solely care concerning the specs of a flight controller, and infrequently 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 perform and situated all the sides.

ESC Compatibility

4in1 ESC’s are sometimes bought 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 is likely to be completely different, requiring rearrangement of the wires within the harness, which is usually a big trouble. If that is what you wish to do, guarantee to double-check the pinout earlier than connecting the FC and ESC collectively, incorrect wiring may 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 units. VBAT is the direct voltage from the LiPo battery, whereas all different voltages are often known as BEC (Battery Eliminating Circuit). Nearly all FCs have VBAT, 3.3V, and 5V pads; some bigger FCs supply different voltages comparable to 9V and 12V to energy video transmitters. Be aware 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 a very powerful connection on a flight controller. It’s a {hardware} serial port used to attach exterior elements comparable 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. 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 could 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 relies on the processor and area out there. Guarantee there are sufficient UARTs for the units you intend 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 functions comparable to receivers and GPS. They can be utilized for analog VTX management but additionally enhance CPU load, making them not advisable for slower processors otherwise you may have to decrease the PID Loop Frequency.

Digital camera 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 if you happen to 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 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 may document 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 learn how to 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 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 learn how 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 may as well join an exterior SD card reader to the FC through UART.

Connector Sorts

The three foremost forms 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 strong 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.

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’ll be able to energy FPV gear straight from the LiPo battery, powering them from a regulated energy supply can produce higher outcomes.

Study learn how to wire analogue FPV setup for greatest consequence.

It’s essential to decide on the appropriate voltage supply based mostly on the gadget you’re powering. Some units could 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 often a greater energy supply, however you should 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 (comparable to GPS Rescue Mode), however it’s not obligatory.

OSD Chip

For analog FPV system, ensure your flight controller has an OSD chip (AT7456E) out there, or Betaflight OSD gained’t work. Nonetheless, it’s not vital for digital FPV techniques comparable 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 nowadays 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 “mushy mounted” on a chunk of froth for lowering 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 recommendations on 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 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, referred to as “Baseflight.” This board established the 35x35mm type issue (with 30x30mm mounting) and continues to be related until today.

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 targeted 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 preferred 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 & Characteristic integrations defined, format, digital camera management
• 2022 – Added information about BMI270 gyro
• 2023 – Tutorial revised, Added information about ICM42688P Gyro
• Could 2024 – Up to date tutorial, added FC suggestions.