Flix

Flix (flight + X) — making an open source ESP32-based quadcopter from scratch.

Version 1 (3D-printed frame)	Version 0

Features

• Simple and clean Arduino based source code.
• Acro and Stabilized flight using remote control.
• Precise simulation using Gazebo.
• In-RAM logging.
• Command line interface through USB port.
• Wi-Fi support.
• MAVLink support.
• Control using mobile phone (with QGroundControl app).
• Completely 3D-printed frame.
• Textbook and videos for students on writing a flight controller¹.
• Position control and autonomous flights using external camera¹.
• Building and running instructions.

¹ — planned.

It actually flies

See detailed demo video (for version 0): https://youtu.be/8GzzIQ3C6DQ.

Version 1 test flight: https://t.me/opensourcequadcopter/42.

Simulation

The simulator is implemented using Gazebo and runs the original Arduino code:

See instructions on running the simulation.

Components (version 1)

Type	Part	Image	Quantity
Microcontroller board	ESP32 Mini		1
IMU and barometer² board	GY-91 (or other MPU-9250/MPU-6500 board)		1
Motor	8520 3.7V brushed motor (shaft 0.8mm!)		4
Propeller	Hubsan 55 mm		4
MOSFET (transistor)	100N03A or analog		4
Pull-down resistor	10 kΩ		4
3.7V Li-Po battery	LW 952540 (or any compatible by the size)		1
Li-Po Battery charger	Any		1
Screws for IMU board mounting	M3x5		2
Screws for frame assembly	M1.4x5		4
Frame bottom part	3D printed: flix-frame.stl flix-frame.step		1
Frame top part	3D printed: esp32-holder.stl esp32-holder.step		1
Washer for IMU board mounting	3D printed: washer-m3.stl washer-m3.step		1
RC transmitter (optional)	KINGKONG TINY X8 or other³		1
RC receiver (optional)	DF500 or other³		1
Wires	28 AWG recommended
Tape, double-sided tape

² — barometer is not used for now.
³ — you may use any transmitter-receiver pair with SBUS interface.

Tools required for assembly:

• 3D printer.
• Soldering iron.
• Solder wire (with flux).
• Screwdrivers.
• Multimeter.

Feel free to modify the design and or code, and create your own improved versions of Flix! Send your results to the official Telegram chat, or directly to the author (E-mail, Telegram).

Schematics (version 1)

Simplified connection diagram

Motor connection scheme:

Complete diagram is Work-in-Progress.

Notes

• Power ESP32 Mini with Li-Po battery using VCC (+) and GND (-) pins.

• Connect the GY-91 board to the ESP32 Mini using VSPI, power it using 3.3V and GND pins:

  GY-91 pin	ESP32 pin
  GND	GND
  3.3V	3.3V
  SCL (SCK)	SVP (GPIO18)
  SDA (MOSI)	GPIO23
  SAO (MISO)	GPIO19
  NCS	GPIO5

• Solder pull-down resistors to the MOSFETs.

• Connect the motors to the ESP32 Mini using MOSFETs, by following scheme:

  Motor	Position	Direction	Wires	GPIO
  Motor 0	Rear left	Counter-clockwise	Black & White	GPIO12
  Motor 1	Rear right	Clockwise	Blue & Red	GPIO13
  Motor 2	Front right	Counter-clockwise	Black & White	GPIO14
  Motor 3	Front left	Clockwise	Blue & Red	GPIO15

  Counter-clockwise motors have black and white wires and clockwise motors have blue and red wires.

• Optionally connect the RC receiver to the ESP32's UART2:

  Receiver pin	ESP32 pin
  GND	GND
  VIN	VC (or 3.3V depending on the receiver)
  Signal	GPIO4⁴

⁴ — UART2 RX pin was changed to GPIO4 in Arduino ESP32 core 3.0.

Version 0

See the information on the obsolete version 0 in the corresponding article.

Materials

Subscribe to the Telegram channel on developing the drone and the flight controller (in Russian): https://t.me/opensourcequadcopter.

Join the official Telegram chat: https://t.me/opensourcequadcopterchat.

Detailed article on Habr.com about the development of the drone (in Russian): https://habr.com/ru/articles/814127/.