# Flix

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

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

## Features

* Simple and clean Arduino based source code.
* Acro and Stabilized flight using remote control.
* Precise simulation using Gazebo.
* [In-RAM logging](docs/log.md).
* 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](https://quadcopter.dev)).
* *Position control and autonomous flights using external camera¹*.
* [Building and running instructions](docs/build.md).

*¹ — planned.*

## It actually flies

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

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

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

<a href="https://t.me/opensourcequadcopter/42"><img width=500 src="docs/img/flight-video.jpg"></a>

## Simulation

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

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

See [instructions on running the simulation](docs/build.md).

## Components (version 1)

|Type|Part|Image|Quantity|
|-|-|:-:|:-:|
|Microcontroller board|ESP32 Mini|<img src="docs/img/esp32.jpg" width=100>|1|
|IMU (and barometer²) board|GY‑91 (or other MPU‑9250/MPU‑6500 board), ICM‑20948³|<img src="docs/img/gy-91.jpg" width=90 align=center><img src="docs/img/icm-20948.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 bottom part|3D printed⁴:<br>[`flix-frame.stl`](docs/assets/flix-frame.stl) [`flix-frame.step`](docs/assets/flix-frame.step)|<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>|1|
|*RC transmitter (optional)*|*KINGKONG TINY X8 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>
*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 (version 1)

### 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">

Complete diagram is Work-in-Progress.

### 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|
  |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|VCC (or 3.3V depending on the receiver)|
  |Signal|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.

## Version 0

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

## 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/.