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

Version 1.1 (3D-printed frame)	Version 0

• 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 for students on writing a flight controller (in development).
• Position control and autonomous flights using external camera¹.
• Building and running instructions.

¹ — planned.

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

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

See theuser builds gallery.

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

Seeinstructions on running the simulation.

Type	Part	Image	Quantity
Microcontroller board	ESP32 Mini		1
IMU (and barometer²) board	GY‑91, MPU-9265 (or other MPU‑9250/MPU‑6500 board), ICM‑20948³		1
Motor	8520 3.7V brushed motor (shaft 0.8mm). Motor with exact 3.7V voltage is needed, not ranged working voltage (3.7V — 6V).		4
Propeller	Hubsan 55 mm		4
MOSFET (transistor)	100N03A oranalog		4
Pull-down resistor	10 kΩ		4
3.7V Li-Po battery	LW 952540 (or any compatible by the size)		1
Battery connector cable	MX2.0 2P female		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 printed⁴: flix-frame-1.1.stlflix-frame-1.1.step		1
Frame top part	3D printed: esp32-holder.stlesp32-holder.step		1
Washer for IMU board mounting	3D printed: washer-m3.stlwasher-m3.step		2
RC transmitter (optional)	KINGKONG TINY X8 (warning: lacks USB support) or other⁵		1
RC receiver (optional)	DF500 or other⁵		1
Wires	28 AWG recommended
Tape, double-sided tape

² — barometer is not used for now.
³ — changeMPU9250 toICM20948 inimu.ino file if using ICM-20948 board.
⁴ — this frame is optimized for GY-91 board, if using other, the board mount holes positions should be modified.
⁵ — 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 theofficial Telegram chat, or directly to the author (E-mail,Telegram).

Motor connection scheme:

You can see a user-contributedvariant of complete circuit diagram of the drone.

Seeassembly guide for instructions on assembling the drone.

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

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

  IMU 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 (TDI)
  Motor 1	Rear right	Clockwise	Blue & Red	GPIO13 (TCK)
  Motor 2	Front right	Counter-clockwise	Black & White	GPIO14 (TMS)
  Motor 3	Front left	Clockwise	Blue & Red	GPIO15 (TD0)

  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	VCC (or 3.3V depending on the receiver)
  Signal (TX)	GPIO4⁶

⁶ — UART2 RX pin waschanged to GPIO4 in Arduino ESP32 core 3.0.

Default IMU orientation in the code isLFD (Left-Forward-Down):

In case of using other IMU orientation, modify therotateIMU function in theimu.ino file.

SeeFlixPeriph documentation to learn axis orientation of other IMU boards.

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

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/.