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init-flight-stack

Status License Platform Language

A mini brushed DC quadcopter built entirely from scratch. No off-the-shelf flight controller software. Custom hardware, custom firmware, custom drivers.

Table of Contents

Overview

This project is a complete from-scratch implementation of a mini quadcopter and its RC controller. The goal is to understand and build every layer of the stack — from raw sensor data to stable flight — without relying on existing flight controller frameworks.

Key design decisions:

  • Bare metal C using the Raspberry Pi Pico C/C++ SDK
  • Dual-core RP2040: Core 0 handles flight control, Core 1 handles radio
  • Custom drivers written from scratch for nRF24L01 and MPU6050
  • No FreeRTOS, no MicroPython, no Betaflight

Hardware

Drone

Component Part Notes
Flight controller Raspberry Pi Pico RP2040 dual-core
IMU MPU6050 I2C1, GP14/GP15, addr 0x68
Radio nRF24L01 SMD SPI0, GP6-GP10, PCB antenna
Motor driver TA6586 x4 PWM on IN1 (GP0-GP3), IN2 to GND
Motors 8520 coreless brushed DC 3.7V, ~50g thrust each, 1mm shaft
Battery 1S LiPo 360mAh 30C JST-PH 1.25mm, direct to VSYS
Buzzer Piezo GP16
Frame Custom 3D printed 75-100mm diagonal

Power architecture:

  • 1S LiPo (3.7-4.2V) direct to Pico VSYS
  • Pico 3.3V rail powers nRF24L01 and MPU6050
  • LiPo direct to TA6586 VM pins
  • No external voltage regulators

AUW: ~67g estimated. Ceiling: 133g (1.5:1 thrust ratio).

RC Controller

Component Part Notes
MCU Raspberry Pi Pico RP2040
Radio nRF24L01 PA+LNA SPI0, GP6-GP10, external antenna
Analog mux CD4051 4 joystick axes via GP26 (ADC0)
Joysticks 2x analog with button Axes to CD4051, buttons to GP2-GP3
Switches 2x latching GP4 arm/disarm, GP5 flight mode
Display 0.96 inch OLED I2C1, GP14-GP15
Buzzer Piezo Pair and signal loss indicator
Battery 18650 cell Direct to VSYS, TP4056 charging

Controls mapping:

Input Function
Left stick Y Throttle
Left stick X Yaw
Right stick Y Pitch
Right stick X Roll
Switch 1 Arm / Disarm
Switch 2 Flight mode (reserved)
Left stick button Pairing
Right stick button OLED navigation

Firmware

Written in bare metal C using the Pico C/C++ SDK. Structured across three repositories:

Repository Description
pico-nrf24l01 Custom nRF24L01 driver for Pico C SDK
pico-mpu6050 Custom MPU6050 driver for Pico C SDK
init-flight-stack Main drone and controller firmware (this repo)

Radio protocol:

  • 12-byte packets at 100Hz default (configurable)
  • 6 channels: throttle, yaw, pitch, roll, arm, flight mode
  • Failsafe: motors cut immediately after 500ms signal loss
  • Drone buzzer activates continuously on signal loss for crash location

Dependencies:

Project Structure

init-flight-stack/
├── drone/
│   ├── src/
│   └── include/
├── controller/
│   ├── src/
│   └── include/
└── docs/

Structure will be populated starting Phase 2.

Build Status

Phase Status
Phase 1 - Requirements and Architecture Complete
Phase 2 - Hardware Design In progress
Phase 3 - Firmware Development Pending
Phase 4 - Mechanical Design Pending
Phase 5 - Integration and Bench Testing Pending
Phase 6 - Flight Testing and Tuning Pending

License

MIT License. See LICENSE for details.