How to choose fpv drone flight controller

Buy Best Flight Controller for FPV Racing

Choosing the right FPV drone flight controller for you requires consideration of the following six factors: processor performance, sensors, compatibility, functionality and scalability, programmability, brand and after-sales service. The processor determines the computing power and responsiveness, sensors are necessary to acquire and process aircraft data, compatibility is needed to ensure hardware and software compatibility, functionality and scalability affect the performance and scalability of the flight control, programmability is very useful for professional pilots and developers, and a well-known brand and good after-sales service can ensure quality and user experience. Make a wise choice according to your needs and budget to better enjoy the fun of flying.

Different flight controller sizes

Different sizes of racks need to be matched with different sizes of flight controls, and there are three mainstream sizes:

• Regular size: usually the standard for five-inch machines, but also commonly used in a variety of three-inch crossing machine.
• Mini size（25.5×25.5 mini drone flight controller）: commonly used in racks below three inches, many three inches or five inches of the rack will usually be compatible with mini size flight control
• AIO size（20×20 aio Flight Controller）: is the abbreviation of All-in-one（20×20 Flight Controller）, meaning that the flight control ESC and even remote receiver all-in-one. Commonly used in the smallest size of indoor traversing machine.

What is the MCU of F4, F7 ?

The microprocessor is the key to determine the performance of the flight control, the name of the flight control will generally be directly marked with the model number of F405, F722 and other microprocessors. The model number of the processor can be seen directly on the surface of the chip.

For example, the meanings of the ARM STM32F722 in the above figure are:

ARM: Based on the ARM architecture, it is a commonly used micro-single-chip instruction set.
STM32: 32-bit chip designed by STMicroelectronics (STM).
F722: The model of the chip is F722, which belongs to the F7 series.

The STM32 series chips of the ARM architecture have been developed since 2007, and the technology is very mature. The chips of this series are also updated and iterated year by year, and the F1~F7 series were born. This series is widely used in traversing machines, the specific parameters are as follows:

Taking the common F405 as an example, the meanings of the above parameters are as follows:

• Operation frequency: It is the key to determine the speed of the processor. It directly affects the speed of sampling and calculation of flight attitude. In theory, the faster the better, but 168MHz is basically enough.
• Number of serial ports: connect the maximum number of peripherals that support the UART protocol, and support various external modules such as remote control receivers, GPS modules, and flash memory cards. In theory, the more the better, but the size of the flight controller is limited, and more than five can basically meet the demand.
• Flash memory capacity: Determine the size of the firmware and configuration information allowed to occupy space, the larger the better. With the gradual improvement of Betaflight functions, the space occupied by the firmware is also increasing, and the chips before F3 are gradually being eliminated.

Generally speaking, after the development of the processor to the F4 series, it is no longer the main reason for limiting the performance of the traversing machine. When purchasing, usually choose a processor with higher compatibility and cost performance. For example, although the F745 is better than the F722 in terms of parameters, the latter is cheaper and can fully meet the needs of flight, so most of the current F7 series flight controllers will choose the F722.

Number of serial ports
The number of serial ports supported by the processor is not always the same as the actual number of serial ports that can be used. On some small flight controllers, only a portion of the serial port is drawn from the chip due to size. In addition, the F7 processor serial port has a signal inverter function, while the F4 does not. Inverters function as follows:

Serial port signal inverter (UART Signal Inverter)

F4 processor does not contain a signal inverter, SBUS must be connected to the RX pin with inverter, so the receiver must be connected according to the connection diagram included with the product. f7 processor has a built-in signal inverter, there is no such problem.

Number of serial ports

The number of serial ports supported by the processor is not always the same as the actual number of serial ports that can be used. On some small flight controllers, only a portion of the serial port is drawn from the chip due to size. In addition, the F7 processor serial port has a signal inverter function, while the F4 does not. Inverters function as follows:

Serial port signal inverter (UART Signal Inverter)

F4 processor does not contain a signal inverter, SBUS must be connected to the RX pin with inverter, so the receiver must be connected according to the connection diagram included with the product. f7 processor has a built-in signal inverter, there is no such problem.

IMU Sensor

The attitude sensor is a micro sensor chip based on micro-electromechanical system (MEMS). The common attitude sensor models include MPU6000, MPU6050, etc., which are connected to the processor through the SPI bus to detect the attitude of the traversing machine.

The attitude sensor usually integrates an acceleration sensor (Accelerometer) and a gyroscope (Gyroscope), and the functions are as follows:

• Acceleration sensor (Gyro): Detect the space tilt attitude of the traversing machine in three directions.
• Gyroscope (Acc): Detect the rotation speed of the traversing machine in three directions.

In addition, there are also sensors such as MPU6050 integrated with an electronic compass, which can be used to sense geographic directions. However, there are many electromagnetic devices on the traversing plane, and the electronic compass generally needs to be calibrated before it can be used.

MEMS sensors require strong physical and electronic anti-noise capabilities. MPU6000 is relatively excellent in both anti-noise indicators and is currently the most commonly used model.

• Physical anti-noise: It means that the traversing machine can still detect the attitude stably during the variable speed movement. The glue on the flight control studs can effectively reduce physical noise.
• Electronic noise resistance: refers to the ability to accurately output signals in circuit fluctuations. A flight controller with better performance usually uses a low dropout regulator circuit (Low Dropout Regulator) to isolate power supply for the sensor.

In addition, the sampling rate is another important indicator of the sensor. In theory, the higher the sampling rate, the better, but due to interference from circuit fluctuations, too high a sampling rate often has no effect. The 8KHz of the MPU6000 is a relatively compromised choice. The sampling rate in BF is this meaning

Black Box Flash

The flash memory in the processor is limited and can only be used to store firmware and parameters, so a flash memory chip is generally integrated on the flight controller to store flight data. At present, the size of flash memory generally ranges from a few megabytes (MB) to tens of megabytes, and can generally store tens of minutes of flight data.

Input Voltage

The input voltage refers to the voltage range of the flight control power supply. The power supply of the flight controller is divided into two types: ESC power supply and lithium battery power supply. The 3~6S Lipo (12.6~25.2V) in the typical parameter table means that the flight controller can be directly plugged into a 3~6S lithium battery, or connected to a 12.6~25.2V ESC for power supply. However, it is not ruled out that some flight controllers cannot be directly powered by lithium batteries. If the voltage is too high, it may cause the flight controller to burn out. When choosing and matching, you need to pay attention to the voltage range.

Output Voltage (BEC)

The on-board step-down circuit (Battery Eliminate Circuit) on the flight controller can reduce the input voltage to several levels to supply power to various components. The most conventional output voltages are 3.3V, 5V, 9V, etc. The uses can be divided into model voltage and driving voltage.

Signal voltage: usually 3.3V and 5V, used to power peripherals such as the remote control signal receiver of the traversing machine. Most of these components are used to send and receive signals, and the current is small.

Driving voltage: usually 5V and 9V, used to drive high-current devices, such as FPV cameras, image transmission, LED lights, etc.

When connecting devices, pay attention to whether the output voltage is within the rated range of the external components, and whether the current of the external devices is less than the maximum current of the BEC.

ESC protocol

DShot (Digital Shot) is currently the most mainstream digital ESC protocol for traversing aircraft. Compared with the traditional analog ESC protocol, DShot has stronger anti-interference ability. The number after DShot represents the frequency of data transmission. For example, the most common DShot600 represents the communication rate between the flight controller and the ESC is 600,000 bytes/second. Since the frequency of DShot is far beyond the perception range of most flight controllers, just pay attention to whether the protocol of the flight controller is compatible with the ESC.

OSD Flight Controller

The OSD chip is used to superimpose more information on the image signal captured by the camera. The early flight control software and hardware functions were not perfect, and the OSD module needed to be purchased additionally and manually soldered to the flight control. At present, the OSD chip is basically the standard configuration of the flight control.

LED

The flight controller of the traversing plane supports the connection of WS2812 series three-color (RGB) LED strips. In Betaflight, you can individually set the lighting effect for each lamp bead on the light strip. In addition, we can also set simple trigger conditions for these lights, such as increasing the throttle to show green, and showing red when the battery is too low.

The LED signal port on the flight controller determines the number of light strips that can be independently controlled. Several lamp beads can be connected in series on each light strip. When purchasing a flight controller, you need to pay attention to the 5V output current of the BED. A single lamp bead needs to be driven by a current of more than 0.3A.