Introduction

The F410 is a small-to-medium-sized UAV with a 410 mm wheelbase. It is equipped with a Pixhawk 6C/ICF5 flight controller, M8N GPS, brushless propulsion system, custom battery, LQ3 data link, optical flow and rangefinder module, and camera. Ready to fly out of the box, it supports stable indoor and outdoor flight as well as teaching and development applications.

Product Features

1. Open-source ecosystem support: Fully compatible with the FMT, PX4, and ArduPilot open-source platforms, with extensive code resources and community support for seamless integration into mainstream development frameworks.

2. Excellent software stability: Based on the official PX4 source code and refined through long-term testing and optimization, with validation by more than 500 users for stable operation and a beginner-friendly experience.

3. Extensive interfaces and strong expandability: Provides 8 power outputs (2 at 16 V, 4 at 5 V, and 2 at 12 V), a payload mounting plate, and a highly compatible design for adding sensors, onboard computers, and other payloads.

4. Multi-sensor positioning: Integrates optical flow and GPS positioning to support stable flight in both indoor and outdoor environments.

5. Rugged design: Critical areas use reinforced aluminum-alloy and carbon-fiber structures. The hard-case battery is easy to insert and remove and has an optimized mounting mechanism, providing durability in varied environments.

Legacy-version Wiring Diagram

RTK-version Wiring Diagram

New-version Wiring Diagram

LQ3 Data Link Wiring Diagram

Complete Aircraft Overview

Endurance Test

Flight Control Unit Hardware

Sensors

The flight controller mainly consists of the primary microcontroller, IMU sensors, power circuitry, and output I/O.

Processors:

The FMU processor is an STM32H743-series microcontroller. It provides 32-bit-wide Flash memory and an external memory interface, and supports multiple memory types, including SRAM, SDRAM, and NOR Flash. It also provides multiple communication interfaces, including SPI, I2C, UART, and USB, and supports Ethernet communication. In addition, the STM32H743 offers a wide range of peripheral functions, including analog-to-digital converters (ADCs), a digital power supply (DCD), timers and counters, and universal synchronous/asynchronous receiver-transmitters (USARTs). It supports multiple power modes to accommodate different application requirements.

The I/O processor is an STM32F103 with an Arm Cortex-M3 core running at up to 72 MHz, providing sufficient performance for most applications. Its integrated peripherals include analog-to-digital converters (ADCs), universal synchronous/asynchronous receiver-transmitters (USARTs), SPI, I2C, PWM, and timers. The STM32F103 also includes 128 KB of Flash memory and 20 KB of SRAM, supports USB connectivity and multiple power modes, and is well suited to cost-sensitive applications.

IMU (Inertial Measurement Unit):

An IMU integrates sensors such as accelerometers, gyroscopes, and magnetometers. It measures motion parameters including attitude, acceleration, and angular velocity. An accelerometer measures acceleration along three axes, which can be used to estimate displacement and velocity. A gyroscope measures angular velocity and helps determine the direction and rate of rotation. A magnetometer measures the Earth's magnetic field and provides directional information.

Processing and fusing IMU sensor data provides more accurate attitude and motion information. Common IMU processing and sensor-fusion methods include the following:

Attitude estimation: Accelerometer and gyroscope data can be fused to estimate an object's pitch, roll, and yaw. Common attitude-estimation algorithms include Kalman filters, complementary filters, and particle filters.

NOTE

A Kalman filter is a recursive algorithm for estimating the state of a system. It combines sensor measurements with a system model to provide an optimal estimate of the system state. A Kalman filter has two main steps: prediction and update. Based on Bayesian inference, it repeatedly updates the state estimate to progressively reduce estimation error.

Navigation: Combining an IMU with sensors such as GPS enables navigation. The IMU provides real-time attitude and motion information, while GPS provides absolute position information. Fusing this data with a Kalman filter or particle-filter algorithm can improve navigation accuracy and stability.

Attitude control: An IMU can be used to control the attitude of an object in applications such as flight control, robotics, and gaming. By monitoring attitude in real time, the control system can apply the appropriate strategy to adjust the object's attitude and motion.

Accelerometers and gyroscopes are commonly used together in flight control systems to provide more accurate and stable flight control.

A gyroscope primarily measures an aircraft's angular velocity or change in angle, thereby providing information about its rotation. However, accumulated error during prolonged operation can reduce the accuracy of attitude estimation.

An accelerometer is used to compensate for this accumulated gyroscope error and improve attitude-estimation accuracy. It measures the aircraft's linear acceleration, including gravitational and motion-induced acceleration. Combining gyroscope and accelerometer data enables more accurate attitude estimation.

In particular, when the aircraft is stationary, the accelerometer measures the effect of Earth's gravity and provides a reference direction. Fusing the accelerometer output with the gyroscope output corrects accumulated gyroscope error and produces a more accurate attitude estimate.

The accelerometer can also detect and compensate for aircraft acceleration and vibration. Filtering and signal-processing techniques can reduce accelerometer noise and interference, improving flight-control stability.

BMI055

The BMI055 is a multi-axis inertial measurement unit (IMU) that includes a three-axis accelerometer and a three-axis gyroscope. It can measure and detect aircraft attitude, motion, acceleration, and related information.

1. Attitude estimation: The gyroscope in the BMI055 measures the aircraft's rate of rotation along three axes, helping calculate its pitch, roll, and yaw. This is important for flight control and attitude stabilization.

2. Motion detection: The accelerometer in the BMI055 measures acceleration along three axes, including linear acceleration and static gravitational acceleration. By analyzing this data, the flight control system can detect motion states such as acceleration, deceleration, and turning.

3. Vibration compensation: External shock and vibration during flight can interfere with sensor measurements. BMI055 attitude information, particularly gyroscope data, can be used to compensate for this interference and improve attitude-estimation accuracy.

4. Attitude control: Based on the attitude and motion information provided by the BMI055, the flight control system can adjust motor output to maintain the desired aircraft attitude. This is essential for stable flight and precise control.

ICM-42688-P

The ICM-42688-P is a high-performance IMU integrating a 3-axis gyroscope and a 3-axis accelerometer. Its main functions in the aircraft include:

1. Providing accurate attitude information: The ICM-42688-P measures UAV acceleration and angular velocity, providing accurate attitude information. This information is essential for stable flight and precise positioning.

2. Improving navigation accuracy: Its high-performance gyroscope provides high-precision angular-velocity measurements, improving UAV navigation accuracy. When GPS signals are unreliable or subject to interference, gyroscope data can help the UAV maintain accurate positioning and navigation.

3. Improving stability: Its accelerometer senses UAV acceleration, allowing the UAV to adjust its attitude and maintain stable flight.

Compass: IST8310

The IST8310 measures the direction of Earth's magnetic field and provides an absolute directional reference.

The flight control system needs to know the UAV's pitch, roll, and heading in space. The geomagnetic sensor measures the direction of Earth's magnetic field and uses it to determine aircraft attitude. Used as an attitude sensor in a UAV, its magnetic-field measurements can help correct GPS-related errors and improve positioning accuracy.

The compass provides aircraft heading information to the flight control system, but it is susceptible to several sources of interference. Common interference sources and mitigation measures include the following:

Magnetic-field interference: External magnetic fields from power cables, motors, and other magnetic objects can interfere with the compass and cause inaccurate heading output.

Mitigation measures:

1. Installation location: Install the compass away from components that may cause interference and avoid strong magnetic objects.

2. Shielding: Protect the compass with a shield or magnetic shielding material to reduce interference from external magnetic fields.

3. Automatic calibration: Flight control systems commonly provide automatic calibration. Rotating the aircraft or using Earth's magnetic field for calibration can reduce the effects of magnetic interference.

Electronic-device interference: Electromagnetic emissions from other electronic devices in the flight control system may interfere with the compass. Interference signals can generate magnetic fields in wiring or on circuit boards.

Mitigation measures:

1. Optimized layout: Arrange internal flight-control-system wiring to reduce the transmission of interference through conductors.

2. Shielding: Isolate the compass and other sensitive devices with shielding enclosures or materials to reduce mutual interference between electronic devices.

3. Filtering: Add a magnetic-field filter to suppress high-frequency interference.

Environmental interference: Environmental conditions such as temperature and humidity changes can also affect the compass.

Mitigation measures:

1. Environmental control: Avoid flying in extreme environments, such as excessively cold or humid areas.

2. Temperature compensation: Some modern compasses provide temperature compensation that adjusts the output according to ambient temperature.

Barometer: MS5611

Based on piezoelectric sensor technology, the MS5611 measures atmospheric pressure from 10 to 1100 hPa. Its digital output can be accurately calibrated and compensated across temperature changes, providing high reliability and stability. A UAV needs accurate altitude information for stable flight and mission execution. The MS5611 measures atmospheric pressure in real time and calculates the UAV's relative altitude from the difference between current and ground-level pressure. Used together with data from other sensors, such as gyroscopes and accelerometers, it enables accurate altitude control. The MS5611 can also support barometric altitude hold. To maintain a specific altitude, such as while hovering or performing an altitude-specific mission, the UAV periodically compares pressure measurements with the target altitude and adjusts throttle to maintain stable altitude.

Optical Flow Sensor

1. Introduction

Optical flow generally results from the movement of foreground objects in a scene, camera motion, or a combination of both. Optical flow processes changes between images to detect ground conditions and monitor aircraft movement. It is mainly used to maintain the aircraft's horizontal position and to support altitude and position hold indoors.

2. Principle

As shown above, when the optical flow sensor moves the same distance to the left at different altitudes, the apparent distance that the same object moves to the right within the sensor camera's field of view differs.

The optical flow sensor uses the instantaneous velocity of a moving object's pixels on the imaging plane to calculate motion and altitude information.

The sensor outputs velocity data along the x and y axes, not position data. Position feedback can be obtained by integrating velocity, which inevitably introduces drift. In practice, integrated navigation algorithms can still provide satisfactory performance.

3. Optical Flow Algorithm

A downward-facing camera captures image data. Frames from different times are analyzed to determine pixel velocity, which is then converted into aircraft velocity.

The optical flow constraint equation assumes that I(x,y,t) is the value (brightness) of pixel (x,y) at time t, and that this pixel moves by Δx, Δy, and Δt between two image frames. This leads to the brightness-constancy assumption. For small motion, (dx/dt, dy/dt) = (u, v), where (u, v) is the optical flow of the pixel to be determined.

The Lucas-Kanade optical flow algorithm uses optical-flow concepts and assumptions to calculate differences between adjacent frames and estimate the spatial and temporal motion vector of each pixel. Its core principle is to describe changes between adjacent frames using a Taylor-series expansion of the image signal, then estimate optical flow from the partial derivatives of those changes.

Function:

In environments without GPS, the optical flow module detects the UAV's horizontal movement in real time, enabling a stable hover over extended periods. The following functional diagram shows the downward-facing optical flow camera capturing the scene directly beneath the UAV and sending the images to the optical flow processing board. The board uses an intelligent optical-flow hover algorithm to calculate aircraft displacement and convert it into hover-control commands. These commands are sent to the flight controller over UART to control horizontal movement and maintain a hover.

4. How the Flight Controller Processes Optical Flow Output

First, optical flow performance depends on altitude. The data is generally effective at low altitude, for example below 5 m. Accuracy decreases above a certain height. Because the data has a linear relationship with altitude, the body-frame x- and y-axis velocities obtained from optical flow are scaled according to altitude.

Second, attitude compensation is applied.

If the aircraft rocks in place, for example from side to side, the optical flow sensor may output velocity even though the aircraft's position has not changed. This falsely detected velocity must be corrected.

Finally, yaw-rotation compensation is applied.

If the optical flow sensor is not located at the center of the aircraft, rotating in place about the yaw axis can produce asymmetrical and erroneous x- and y-axis output even though the aircraft has not translated. This unwanted output must be compensated.

Flight Controller Interfaces

DSM

DSM is a digital serial communication protocol commonly used to communicate with a remote controller. The interface can transmit remote-control channel data and other controller status information.

The DSM interface can be used for the following extended applications:

1. Remote-controller binding: The DSM interface can receive a binding signal from a remote controller to establish a communication link. This pairs the flight controller with a specific remote controller so that only the bound controller can operate the aircraft.

2. Remote-controller input: Through the DSM interface, the flight controller can receive channel data for throttle, roll, pitch, yaw, and other commands. This data can control aircraft attitude, altitude, speed, and other parameters. The flight controller processes and decodes the input signals to execute the corresponding control algorithms.

3. Remote-controller status: In addition to channel data, the DSM interface can carry status information such as control deflection, controller battery level, and signal strength. This information can be used to monitor the remote controller and issue alerts or take appropriate action when necessary.

The DSM interface provides communication between the aircraft and its remote controller. By receiving control inputs and status information, the flight controller can control the aircraft and exchange information with the controller.

USB

USB is a communication interface for connecting external devices to the flight controller. It is commonly located on the flight controller board and provides a standard USB Type-A or Micro-USB connector for data transfer and communication with a computer, remote controller, or other device.

Power1/Power2

Through the Power1 and Power2 interfaces, the flight controller can receive DC power from a battery or another power module and provide the power required by the flight controller and related devices. These interfaces normally have polarity markings to help ensure correct power connection.

GPS1 and GPS2

These ports connect Global Positioning System (GPS) modules for accurate positioning and navigation. Compared with GPS2, GPS1 includes an additional safety switch for enhanced location privacy and security. Activating the safety switch allows you to disable GPS on the device and prevent applications and services from obtaining location information. GPS2 can also connect an I2C device, whereas GPS1 cannot.

TELEM1/TELEM2/TELEM3

These ports provide serial communication with a remote controller or other device for transmitting commands and data. Port order does not affect their use. TELEM3 can connect one I2C device, whereas TELEM1 and TELEM2 cannot. TELEM1 has a 1.5 A current limit; TELEM2 and TELEM3 do not have this limit.

CAN1/CAN2

CAN interfaces are commonly used to connect external devices such as electronic speed controllers (ESCs), battery management systems (BMSs), optical flow sensors, and gyroscopes. The CAN bus supports bidirectional data exchange between these devices and the flight controller for multi-channel control and data transmission. The flight controller can send commands and instructions to external devices and receive their status and sensor data. This improves overall system performance and reliability while reducing the use of other interfaces. CAN1 and CAN2 have the same function and are interchangeable.

SBUS OUT

The SBUS OUT interface sends remote-controller signals from the flight controller to other devices, such as UAV electronic speed controllers or devices that support SBUS input. This enables communication and control between the flight controller and other equipment for precise attitude control and flight operation.

SBUS OUT normally uses a standard three-pin connector with signal, power, and ground conductors. Before connecting another device, verify the pinout and follow the relevant operating instructions.

SBUS OUT is generally configurable. Use the flight-controller configuration software or parameters to select the appropriate SBUS output channels and mapping for the connected equipment and control requirements.

I2C

The I2C interface can connect sensors such as barometers, temperature sensors, and compasses, as well as expansion modules such as GPS modules, optical flow sensors, and range sensors. These external devices exchange data with the flight controller over the I2C bus. Observe the following when connecting I2C devices:

Correct connection: Connect the I2C SDA (data) and SCL (clock) lines to the appropriate pins according to the specifications of the device and flight controller.

Address conflicts: When multiple devices share an I2C bus, each device must have a unique address. Configure the device's I2C address correctly and set the corresponding flight-controller parameters to avoid conflicts.

Power and logic levels: Verify the external device's power requirements and logic-level compatibility to ensure correct power delivery and signal transmission.

Configuration and calibration: Before using the external device, configure and calibrate the flight controller as required so that it can identify and communicate with the device correctly.

PPM/SBUS RC IN

This interface receives remote-controller signals and supports two common input protocols: PPM (pulse-position modulation) and SBUS (serial bus).

PPM: PPM combines the control signals of multiple channels into a single transmitted signal. Through the PPM input, the flight controller receives a PPM signal from the connected remote controller and decodes the control value of each channel, including throttle, yaw, and pitch.

SBUS: SBUS is a serial-bus protocol that transmits multiple control channels as a digital sequence. Through the SBUS input, the flight controller directly receives signals from a remote controller that supports SBUS output and decodes the control value of each channel.

FMU PWM OUT/IO OUT

These are two different output interfaces with different functions and uses.

FMU PWM OUT: Controlled by the flight management unit (FMU), this interface outputs PWM signals to servos or electronic speed controllers. The PWM channels are generally used to control aircraft functions such as throttle, pitch, roll, and yaw. Each channel can be configured independently and controls the position or speed of the corresponding servo or ESC through a PWM signal.

I/O OUT: This general-purpose input/output interface can connect various external devices or sensors. It normally carries digital high/low signals and can be used to trigger or control other equipment or to transfer data. By configuring the relevant parameters, the interface can be used for applications such as triggering a camera shutter, connecting an LED strip, or connecting a range sensor.

I/O Debug

Used to debug the I/O chip and read debugging information.

FMU Debug

Used to debug the FMU chip and read debugging information.