dRehmFlight F-35 VTOL - PlatformIO Port

PlatformIO port of the dRehmFlight F-35 Lightning II inspired VTOL tricopter flight controller.

Project Overview

This is a specialized flight controller for an F-35 tricopter VTOL (Vertical Take-Off and Landing) vehicle based on the Teensy 4.0 microcontroller. The project has been converted from Arduino IDE to PlatformIO for better development workflow and dependency management.

Original Project: dRehmFlight F-35
Author: Nicholas Rehm, University of Maryland

Hardware Configuration

F-35 VTOL Specific Hardware (Current Configuration)

• Flight Controller: Teensy 4.0 microcontroller
• IMU: GY-521 MPU6050 6DOF IMU
• Radio: Matek ELRS R24-P6V PWM receiver (ExpressLRS 2.4GHz)
• Motors: 3x 2306 brushless motors (~2450 KV)
• ESC: iFlight BLITZ E55S 4-in-1 ESC (OneShot125 protocol)
• Servos: 5x SG90 micro servos for control surfaces
• Power: 4S LiPo battery with WANGCL 5V/3A UBEC

Pin Assignments

Radio (PWM):
- CH1 (Throttle) → Pin 15
- CH2 (Aileron)  → Pin 16  
- CH3 (Elevator) → Pin 17
- CH4 (Rudder)   → Pin 20
- CH5 (Gear)     → Pin 21
- CH6 (Aux1)     → Pin 22

IMU (I2C):
- MPU6050 SDA → Pin 18
- MPU6050 SCL → Pin 19

Motors (OneShot125):
- M1 (Nose)  → Pin 0
- M2 (Right) → Pin 1  
- M3 (Left)  → Pin 2

Servos:
- S1-S7 → Various pins for control surfaces

Development Setup

Prerequisites

• PlatformIO Core or PlatformIO IDE
• Visual Studio Code (recommended)

Building the Project

# Build the project
pio run

# Upload to Teensy 4.0
pio run --target upload

# Monitor serial output
pio device monitor --baud 115200

Hardware Configuration Options

The flight controller supports multiple hardware configurations through platformio.ini build flags:

Current F-35 Configuration

build_flags = 
    -DUSE_PWM_RX          # PWM receiver
    -DUSE_MPU6050_I2C     # MPU6050 IMU
    -DGYRO_500DPS         # 500°/s gyro range
    -DACCEL_2G            # 2G accelerometer

Alternative Configurations

To use different hardware, modify the build flags in platformio.ini:

Receiver Options:

• -DUSE_PWM_RX - PWM receiver (current)
• -DUSE_PPM_RX - PPM receiver
• -DUSE_SBUS_RX - SBUS receiver

IMU Options:

• -DUSE_MPU6050_I2C - MPU6050 via I2C (current)
• -DUSE_MPU9250_SPI - MPU9250 via SPI

Gyro Range:

• -DGYRO_250DPS - 250°/s
• -DGYRO_500DPS - 500°/s (current)
• -DGYRO_1000DPS - 1000°/s
• -DGYRO_2000DPS - 2000°/s

Accelerometer Range:

• -DACCEL_2G - 2G (current)
• -DACCEL_4G - 4G
• -DACCEL_8G - 8G
• -DACCEL_16G - 16G

Flight Modes

The F-35 VTOL controller features three distinct flight modes:

1. Hover Mode (CH6 > 1700): Standard multicopter hover control
2. Transition Mode (1300 < CH6 < 1700): Gradual transition between hover and forward flight
3. Forward Flight (CH6 < 1300): Airplane-like forward flight with elevon control

Control Features

• Thrust Vectoring: Rear tilt servo for yaw control
• Elevon Control: Wing control surfaces for pitch/roll in forward flight
• Flight Mode Switching: Dynamic PID gains and control limits per mode
• Smooth Transitions: Gradual motor mixing during mode changes

Debugging

Enable debug output by uncommenting print functions in the main loop:

• printRadioData() - Radio PWM values
• printGyroData() - IMU gyro data
• printServoCommands() - Servo positions
• printMotorCommands() - Motor commands
• printLoopRate() - Control loop timing

Safety

⚠️ IMPORTANT SAFETY NOTES

• This is experimental flight controller software
• Always test thoroughly on the bench before flight
• Use appropriate safety measures and failsafes
• Follow all local regulations for RC aircraft operation
• Never fly over people or property

License

This code is entirely free to use. See COPYING.txt for license details.

Credits

• Original Author: Nicholas Rehm (nrehm@umd.edu)
• Institution: University of Maryland, Department of Aerospace Engineering
• PlatformIO Port: Community contribution

Support

• Original dRehmFlight Repository
• RC Groups Support Thread
• F-35 Tutorial Video