# Flix

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

<table>
  <tr>
    <td align=center><strong>Version 1.1</strong> (3D-printed frame)</td>
    <td align=center><strong>Version 0</strong></td>
  </tr>
  <tr>
    <td><img src="docs/img/flix1.1.jpg" width=500 alt="Flix quadcopter"></td>
    <td><img src="docs/img/flix.jpg" width=500 alt="Flix quadcopter"></td>
  </tr>
</table>

## Features

* Dedicated for education and research.
* Made from general-purpose components.
* Simple and clean source code in Arduino.
* Control using remote control or smartphone.
* Precise simulation with Gazebo.
* Wi-Fi and MAVLink support.
* Wireless command line interface and analyzing.
* Textbook on flight control theory and practice ([in development](https://quadcopter.dev)).
* *Position control (using external camera) and autonomous flights¹*.

*¹ — planned.*

## It actually flies

See detailed demo video: https://youtu.be/hT46CZ1CgC4.

<a href="https://youtu.be/hT46CZ1CgC4"><img width=500 src="https://i3.ytimg.com/vi/hT46CZ1CgC4/maxresdefault.jpg"></a>

Version 0 demo video: https://youtu.be/8GzzIQ3C6DQ.

<a href="https://youtu.be/8GzzIQ3C6DQ"><img width=500 src="https://i3.ytimg.com/vi/8GzzIQ3C6DQ/maxresdefault.jpg"></a>

See the [user builds gallery](docs/user.md).

<a href="docs/user.md"><img src="docs/img/user/user.jpg" width=500></a>

## Simulation

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

<img src="docs/img/simulator1.png" width=500 alt="Flix simulator">

## Articles

* [Assembly instructions](docs/assembly.md).
* [Building and running the code](docs/build.md).
* [Troubleshooting](docs/troubleshooting.md).
* [Firmware architecture overview](docs/firmware.md).
* [Log analysis](docs/log.md).
* [User builds gallery](docs/user.md).

## Components

|Type|Part|Image|Quantity|
|-|-|:-:|:-:|
|Microcontroller board|ESP32 Mini|<img src="docs/img/esp32.jpg" width=100>|1|
|IMU (and barometer²) board|GY‑91, MPU-9265 (or other MPU‑9250/MPU‑6500 board)<br>ICM‑20948³<br>GY-521 (MPU-6050)³⁻¹|<img src="docs/img/gy-91.jpg" width=90 align=center><br><img src="docs/img/icm-20948.jpg" width=100><br><img src="docs/img/gy-521.jpg" width=100>|1|
|<span style="background:yellow">(Recommended) Buck-boost converter</span>|To be determined, output 5V or 3.3V, see [user-contributed schematics](https://miro.com/app/board/uXjVN-dTjoo=/?moveToWidget=3458764612179508274&cot=14)|<img src="docs/img/buck-boost.jpg" width=100>|1|
|Motor|8520 3.7V brushed motor (shaft 0.8mm).<br>Motor with exact 3.7V voltage is needed, not ranged working voltage (3.7V — 6V).|<img src="docs/img/motor.jpeg" width=100>|4|
|Propeller|Hubsan 55 mm|<img src="docs/img/prop.jpg" width=100>|4|
|MOSFET (transistor)|100N03A or [analog](https://t.me/opensourcequadcopter/33)|<img src="docs/img/100n03a.jpg" width=100>|4|
|Pull-down resistor|10 kΩ|<img src="docs/img/resistor10k.jpg" width=100>|4|
|3.7V Li-Po battery|LW 952540 (or any compatible by the size)|<img src="docs/img/battery.jpg" width=100>|1|
|Battery connector cable|MX2.0 2P female|<img src="docs/img/mx.png" width=100>|1|
|Li-Po Battery charger|Any|<img src="docs/img/charger.jpg" width=100>|1|
|Screws for IMU board mounting|M3x5|<img src="docs/img/screw-m3.jpg" width=100>|2|
|Screws for frame assembly|M1.4x5|<img src="docs/img/screw-m1.4.jpg" height=30 align=center>|4|
|Frame main part|3D printed⁴:<br>[`flix-frame-1.1.stl`](docs/assets/flix-frame-1.1.stl) [`flix-frame-1.1.step`](docs/assets/flix-frame-1.1.step)<br>Recommended settings: layer 0.2 mm, line 0.4 mm, infill 100%.|<img src="docs/img/frame1.jpg" width=100>|1|
|Frame top part|3D printed:<br>[`esp32-holder.stl`](docs/assets/esp32-holder.stl) [`esp32-holder.step`](docs/assets/esp32-holder.step)|<img src="docs/img/esp32-holder.jpg" width=100>|1|
|Washer for IMU board mounting|3D printed:<br>[`washer-m3.stl`](docs/assets/washer-m3.stl) [`washer-m3.step`](docs/assets/washer-m3.step)|<img src="docs/img/washer-m3.jpg" width=100>|2|
|*RC transmitter (optional)*|*KINGKONG TINY X8 (warning: lacks USB support) or other⁵*|<img src="docs/img/tx.jpg" width=100>|1|
|*RC receiver (optional)*|*DF500 or other⁵*|<img src="docs/img/rx.jpg" width=100>|1|
|Wires|28 AWG recommended|<img src="docs/img/wire-28awg.jpg" width=100>||
|Tape, double-sided tape||||

*² — barometer is not used for now.*<br>
*³ — change `MPU9250` to `ICM20948` in `imu.ino` file if using ICM-20948 board.*<br>
*³⁻¹ — MPU-6050 supports I²C interface only (not recommended). To use it change IMU declaration to `MPU6050 IMU(Wire)`.*<br>
*⁴ — this frame is optimized for GY-91 board, if using other, the board mount holes positions should be modified.*<br>
*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 the [official Telegram chat](https://t.me/opensourcequadcopterchat), or directly to the author ([E-mail](mailto:okalachev@gmail.com), [Telegram](https://t.me/okalachev)).

## Schematics

### Simplified connection diagram

<img src="docs/img/schematics1.svg" width=800 alt="Flix version 1 schematics">

Motor connection scheme:

<img src="docs/img/mosfet-connection.png" height=400 alt="MOSFET connection scheme">

You can see a user-contributed [variant of complete circuit diagram](https://miro.com/app/board/uXjVN-dTjoo=/?moveToWidget=3458764612338222067&cot=14) of the drone.

See [assembly guide](docs/assembly.md) for instructions on assembling the drone.

### Notes

* 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 was [changed](https://docs.espressif.com/projects/arduino-esp32/en/latest/migration_guides/2.x_to_3.0.html#id14) to GPIO4 in Arduino ESP32 core 3.0.*

### IMU placement

Default IMU orientation in the code is **LFD** (Left-Forward-Down):

<img src="docs/img/gy91-lfd.svg" width=400 alt="GY-91 axes">

In case of using other IMU orientation, modify the `rotateIMU` function in the `imu.ino` file.

See [FlixPeriph documentation](https://github.com/okalachev/flixperiph?tab=readme-ov-file#imu-axes-orientation) to learn axis orientation of other IMU boards.

## 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/.

See the information on the obsolete version 0 in the [corresponding article](docs/version0.md).

## Disclaimer

This is a fun DIY project, and I hope you find it interesting and useful. However, it's not easy to assemble and set up, and it's provided "as is" without any warranties. There’s no guarantee that it will work perfectly — or even work at all.

⚠️ The author is not responsible for any damage, injury, or loss resulting from the use of this project. Use at your own risk!