🚁 FPV Drone Flight Controller

Dive deep into aerodynamics. Build a flight controller from scratch to stabilize a quadcopter.

📋 Overview

Flight controllers process thousands of calculations per second to keep a drone in the air. You will read receiver inputs, compute the drone's 3D orientation, and drive four Electronic Speed Controllers (ESCs).

What you'll learn: Reading PWM receiver signals via interrupts, mixing thrust for roll/pitch/yaw, and implementing cascaded PID controllers.

Estimated time: 10+ hours. Difficulty: ⭐⭐⭐⭐⭐ Expert.

🧩 Components Needed

Component	Specification	Qty	Notes
STM32 Blue Pill	ARM Cortex-M3	1	Fast enough for flight loops
MPU6050	6-DOF IMU	1
Brushless Motors	High KV	4
ESCs	30A	4	Electronic Speed Controllers
RC Receiver	PWM/PPM/SBUS	1

📖 Step-by-Step Tutorial

Read the Receiver

Use hardware interrupts (or input capture) to read the PWM width of the Throttle, Roll, Pitch, and Yaw channels from your RC receiver.

Calibrate ESCs

ESCs need to know the min and max throttle ranges. Write a utility script to send max PWM, wait for the beep, then min PWM.

Cascaded PID

Drones use two PID loops per axis: an "Angle" loop (outer) that asks for a specific rotation rate, and a "Rate" loop (inner) that uses the gyro to hit that rate.

Motor Mixing

Combine the PID outputs to determine individual motor speeds. E.g. Motor1 = Throttle + PitchPID - RollPID - YawPID.

💡

ALWAYS remove the propellers when testing flight controller code on the bench. Brushless motors can cause serious injury if they spin up unexpectedly.

💻 Code / Configuration

flight_controller.ino

INO

// Flight Controller Motor Mixing (Snippet) - Volt X
int throttle, roll_pid, pitch_pid, yaw_pid;
int motor1, motor2, motor3, motor4;

void calculateMotorPulses() {
  // Motor 1: Front Right (CCW)
  motor1 = throttle - pitch_pid - roll_pid - yaw_pid;
  
  // Motor 2: Rear Right (CW)
  motor2 = throttle + pitch_pid - roll_pid + yaw_pid;
  
  // Motor 3: Rear Left (CCW)
  motor3 = throttle + pitch_pid + roll_pid - yaw_pid;
  
  // Motor 4: Front Left (CW)
  motor4 = throttle - pitch_pid + roll_pid + yaw_pid;
  
  // Constrain outputs to valid ESC PWM range (usually 1000-2000us)
  motor1 = constrain(motor1, 1000, 2000);
  motor2 = constrain(motor2, 1000, 2000);
  motor3 = constrain(motor3, 1000, 2000);
  motor4 = constrain(motor4, 1000, 2000);
  
  // Send pulses to ESCs...
}

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