Dragonfly

Dragonfly

A custom all-in-one flight controller + ESC, built entirely from discrete ICs rather than premade modules, designed for me by me. Flight control and all 4 motor drivers live on a single 4-layer PCB, designed from scratch in KiCad.

Why I Built This

I wanted to go past just building a flight controller most DIY FC projects stop at a board that reads a gyro and outputs signals. I wanted the whole thing: FC and ESC combined on one board, IC-level design instead of stacking pre-built modules, a custom 3D-printed frame, and firmware configured to actually fly and hold up to real maneuvers, not just hover.

This became a fromscratch systems project schematic, PCB layout, mechanical frame design, and firmware, all built and understood end-to-end rather than assembled from a kit.

Features

• 4-layer PCB designed from scratch in KiCad, all-in-one FC + ESC on a single board
• STM32F405RGTx flight controller MCU running Betaflight, custom unified target
• 4x independent ESC channels, each with its own AT32F421G8U7 MCU running AM32 firmware real per-motor commutation, not a single shared driver
• FD6288Q 3-phase gate drivers + discrete MOSFETs per channel, sized for freestyle current draw, not just hover
• ICM-20602 IMU (SPI), isolated placement and routing to minimize motor-noise coupling into gyro data
• AT7456E OSD for FPV video overlay (battery voltage, timer)
• BMP280 barometer for altitude hold
• TPS5430 buck (5V) + AMS1117-3.3 LDO + dedicated L78L08 8V rail for gate drivers — separate, correctly isolated power domains
• Individual SWD test points per ESC channel for one-time AM32 flashing
• ELRS receiver support (Happymodel Nano RX) over UART
• Custom 3" toothpick-class frame, designed in Fusion 360, 3D printed
• Estimated build cost: ~$250–300 (board, motors, frame, battery, receiver, transmitter)

What's Inside

Firmware

Status: in progress configuration and pin-mapping stage, not reqady to flash

Two separate firmware bases run on this board:

• Betaflight (main STM32F405) custom unified target describing this board's exact pin map (motors, IMU SPI, receiver UART)
• AM32 (each of the 4 AT32F421 ESC MCUs) open-source ESC firmware, flashed individually per channel via dedicated SWD test points

firmware/
├── betaflight-unified-target/   # Unified target config for the main FC
├── am32/                        # AM32 firmware source, per-channel builds
└── notes.md                     # Pin mapping reference

How to Use

Hardware

1. PCB files are located in PCB/
2. Open the .kicad_pro file in KiCad 8+
3. Upload Gerbers from PCB/gerbers/ to JLCPCB (4-layer)
4. Order components using BOM/BOM.csv
5. Frame STEP file is available in CAD/

Firmware

1. Flash AM32 onto each of the 4 ESC MCUs individually, using the SWD test points per channel
2. Flash Betaflight onto the main STM32 via USB-C, using the custom unified target in firmware/betaflight-unified-target/
3. Configure IMU calibration, receiver binding, and OSD via Betaflight Configurator

Repository Structure

Dragonfly/
├── PCB/                         # KiCad project + Gerbers
├── CAD/                         # Fusion 360 frame design (.step)
├── firmware/                    # Betaflight unified target + AM32
├── BOM/                         # Bill of Materials
├── imgs/                        # Photos and renders
└── README.md

Built By

broccoli 🥦 — Solo hardware builder from Pakistan.

Chasing what I love. GE0

'geo geo geo