MultiWii flight controller firmware with ultrasonic sonar sensor for altitude hold (2014)

Part of Daniel Dieser's drone research period (2012-2014) in Puerto Madryn, Patagonia.

A modified version of MultiWii firmware that integrates an ultrasonic sonar sensor for precise altitude hold capabilities. This was essential for indoor drone flight experiments where GPS and barometer-based altitude hold are unreliable.

Standard altitude hold options in 2014:

• Barometer -- Works outdoors but drifts significantly indoors
• GPS -- Doesn't work indoors at all
• Sonar -- Precise to centimeters, perfect for indoor experiments

Adding sonar to MultiWii meant the drone could hold altitude indoors with centimeter-level precision -- critical for the laboratory flight experiments conducted alongside the DronePilot companion computer software.

• MultiWii 2.4 base with sonar altitude integration
• QUADX configuration -- X-frame quadcopter
• MPU6050 -- 6-axis IMU for attitude stabilization
• Sonar sensor -- Ultrasonic distance measurement (HC-SR04 compatible)

1. Sonar sensor measures distance to ground (0-400cm range)
2. Reading is filtered to remove noise spikes
3. Altitude PID controller uses sonar data instead of barometer
4. Motor throttle is adjusted to maintain target altitude

• MultiWii/MultiWii.ino -- Main firmware
• MultiWii/config.h -- Sensor and board configuration
• MultiWii/Sensors.cpp -- Sonar reading implementation
• MultiWii/Serial.ino -- Serial protocol (MSP) communication

• multiwii-sonar-v2 -- Improved sonar implementation
• multiwii-humidity-sensor -- DHT environmental sensor variant
• drone-pilot -- Companion computer pilot that uses MultiWii
• fly-drone-controller -- Python tools for MultiWii drones

GPL v3

Daniel Dieser -- Puerto Madryn, Patagonia, Argentina Telegram: @mrmoz33