Flightcontroller

Flight Controller

A custom STM32F411-based flight controller PCB designed for multirotor, UAV, robotics, and embedded flight-control applications.

The board integrates an IMU, magnetometer, barometric sensor, EEPROM, MicroSD storage, USB-C, SWD debugging, UART interfaces, and dedicated motor/auxiliary outputs on a compact 2-layer PCB designed in KiCad.

3D Render

✈️ Overview

This project is a custom flight-controller hardware design centered around the STM32F411RET6 ARM Cortex-M4 microcontroller.

The STM32 handles sensor acquisition, flight-control processing, peripheral communication, data logging, and motor/auxiliary output generation.

The board combines:

• Inertial sensing
• Magnetic heading measurement
• Barometric altitude measurement
• Non-volatile configuration storage
• Flight-data logging
• USB communication
• SWD programming/debugging
• Motor and auxiliary outputs
• UART communication

The PCB was designed in KiCad, with emphasis on compact routing, sensor decoupling, accessible debugging, and organized external interfaces.

🔧 Hardware Features

The complete hardware feature set is documented in the original design specification.

🧠 System Architecture

                         USB Type-C
                             │
                             ▼
                       USB Protection
                             │
                             ▼
                       Power / 3.3 V
                             │
                             ▼
                    ┌─────────────────┐
                    │   STM32F411     │
                    │   Flight MCU    │
                    └────────┬────────┘
                             │
          ┌──────────────────┼──────────────────┐
          │                  │                  │
          ▼                  ▼                  ▼
        I²C                 SPI               UART
          │                  │                  │
    ┌─────┼─────┐       ┌────┴────┐       ┌────┴────┐
    ▼     ▼     ▼       ▼         ▼       ▼         ▼
  LSM6DS3 LIS3MDL EEPROM BMP280   MicroSD  UART1    UART2
    │     │
    └─────┴────── Sensor Data

📡 Sensors & Peripherals

LSM6DS3 IMU

The LSM6DS3 provides:

• 3-axis accelerometer
• 3-axis gyroscope

It serves as the primary inertial sensor for attitude estimation, angular-rate measurement, motion detection, and flight-control feedback.

The IMU communicates with the STM32 through I²C.

LIS3MDL Magnetometer

The LIS3MDL provides 3-axis magnetic-field measurements and can be used as a magnetic heading reference for navigation and orientation estimation.

It communicates through I²C and includes an interrupt connection to the MCU.

BMP280 Barometer

The BMP280 provides pressure measurements for:

• Relative altitude estimation
• Altitude-hold applications
• Vertical-motion estimation
• Flight-data logging

The sensor is connected through SPI.

AT24C256A EEPROM

The onboard EEPROM provides non-volatile storage for:

• Configuration parameters
• Calibration data
• Controller settings
• Persistent system information

MicroSD

A dedicated MicroSD interface provides onboard flight-data storage using SPI:

SD_SPI_MOSI
SD_SPI_MISO
SD_SPI_SCK
SD_CHIPSEL

It can be used for sensor measurements, telemetry, debugging information, controller parameters, and flight logs.

🔌 Interfaces

Motor Outputs

Three dedicated motor interfaces are provided:

MOTOR1_OUT
MOTOR2_OUT
MOTOR3_OUT

Each connector provides:

+5V
GND
SIGNAL

The motor-control signals are generated using STM32 timer peripherals and can interface with external ESCs or motor-control hardware.

Auxiliary Outputs

AUX1_OUT
AUX2_OUT
AUX3_OUT

Each provides:

+5V
GND
SIGNAL

These can be used for additional actuators or flight-controller peripherals.

UART

Two serial interfaces are exposed:

UART1_TX
UART1_RX

UART2_TX
UART2_RX

Potential applications include GPS, telemetry, radio receivers, external sensors, and configuration interfaces.

SWD

A dedicated SWD interface is provided for programming and debugging:

SWDIO
SWCLK
3.3V
GND

The board also includes test points for convenient hardware debugging.

⚡ Power Architecture

The board uses an onboard 3.3 V regulation stage for the STM32 and peripheral electronics.

The power section includes:

• Schottky diode protection
• AMS1117-3.3 regulator
• Input/output filtering capacitors
• Power indicator LED
• Ferrite filtering for the MCU supply

The additional ferrite filtering is intended to reduce high-frequency supply noise around the MCU.

🖥️ USB & Debugging

The board includes a USB Type-C interface providing:

• USB D+
• USB D−
• VBUS
• GND

USB ESD protection is included on the data interface.

The USB connection can be used for firmware development, communication, configuration, debugging, and powering the board during development.

Dedicated BOOT and RESET buttons are also provided for firmware programming, recovery, and MCU reset.

🧩 PCB Design

Designed using KiCad, the PCB focuses on compact two-layer implementation and practical hardware debugging.

Design considerations

• Compact 2-layer PCB
• Dedicated ground routing/plane
• Local sensor decoupling
• Short high-speed peripheral connections
• Compact MCU placement
• Accessible SWD interface
• Dedicated motor and auxiliary connectors
• UART connectors
• USB Type-C
• Ferrite-filtered MCU supply
• Separated sensitive sensor circuitry
• Hardware test points
• Perimeter mounting holes

🔄 Flight-Control Data Flow

        ┌─────────────┐
        │    IMU      │
        │   LSM6DS3   │
        └──────┬──────┘
               │
        ┌──────▼──────┐
        │ Magnetometer│
        │   LIS3MDL   │
        └──────┬──────┘
               │
        ┌──────▼──────┐
        │  Barometer  │
        │    BMP280   │
        └──────┬──────┘
               │
               ▼
        ┌──────────────┐
        │  STM32F411   │
        │    MCU       │
        └──────┬───────┘
               │
        ┌──────┼──────────┐
        ▼      ▼          ▼
     Motors   AUX     Telemetry

The STM32 acquires sensor data, processes the measurements using flight-control firmware, and generates outputs for connected ESCs, motors, and auxiliary peripherals.

🛠️ Tools & Technologies

• KiCad – Schematic & PCB design
• STM32F411RET6 – ARM Cortex-M4 MCU
• STM32 development tools / STM32CubeIDE
• I²C
• SPI
• USART
• USB
• SWD

🚀 Potential Future Improvements

Possible future revisions include:

• Additional motor channels
• CAN / CAN-FD
• GPS connector
• Dedicated telemetry interface
• Battery voltage/current monitoring
• Buzzer interface
• Additional IMU / redundant sensors
• External compass connector
• Barometer isolation
• Improved power-input protection
• Dedicated receiver interface
• Additional test points
• Improved PCB signal integrity

🎯 Applications

This hardware platform can be explored for:

• Multirotor flight controllers
• UAV development
• Drone flight-control systems
• Autonomous aerial vehicles
• Embedded navigation
• Sensor-fusion experiments
• Flight-data logging
• Robotics
• Embedded control systems
• UAV hardware prototyping

📌 Project Status

Hardware: PCB design completed EDA: KiCad Architecture: STM32F411-based PCB: 2-layer

This project is intended for educational, research, and UAV hardware-development purposes.

📄 License

This project is open-source and intended for educational, research, and UAV hardware-development purposes.