Code for making an automatic flip for Flix drone (draft) https://github.com/okalachev/flix. See the video at https://t.me/opensourcequadcopter/21

flip.ino

// Copyright (c) 2024 Oleg Kalachev <okalachev@gmail.com>

// Flip controller for the Flix drone https://github.com/okalachev/flix
// Video and details: https://t.me/opensourcequadcopter/21

#define BOUNCE_TIME 0.6
#define ACCELERATE_TIME 0.07
#define BRAKE_TIME ACCELERATE_TIME

enum {
	WAIT,
	BOUNCE,
	ACCELERATE,
	ROTATE,
	BRAKE,
	POST_BRAKE,
	RECOVERY
} flipStage = ACCELERATE;

void controlFlip() {
	if (!armed) {
		memset(motors, 0, sizeof(motors));
		return;
	}

	static float stageTime = 0;
	static float lastTime = -999;
	static float maxRate = 0;
	static float accelerationAngleZ;
	static float brakeTime;
	static float accelerationWhenRotatingTime;

	if (t - lastTime > 0.1) {
		// flip reset
		flipStage = WAIT;
		stageTime = t;
		maxRate = 0;
	}
	lastTime = t;

	if (flipStage == WAIT) {
		// wait for ideal conditions
		controls[RC_CHANNEL_MODE] = 0; // stab mode
		interpretRC();
		if (abs(rates.x) < 0.05 && (abs(attitude.toEulerZYX().x) < 0.02)) {
			flipStage = BOUNCE;
			stageTime = t;
		}

	} else if (flipStage == BOUNCE) {
		thrustTarget = 0.8;
		attitudeTarget = Quaternion::fromEulerZYX(Vector(0, 0, attitude.getYaw()));
		yawMode = YAW;
		controlAttitude();
		controlRate();
		controlTorque();

		if (t - stageTime > BOUNCE_TIME) {
			flipStage = ACCELERATE;
			stageTime = t;
		}

	} else if (flipStage == ACCELERATE) {
		thrustTarget = 0.1; // mark for log analysis

		motors[MOTOR_REAR_LEFT] = 1;
		motors[MOTOR_REAR_RIGHT] = 0;
		motors[MOTOR_FRONT_LEFT] = 1;
		motors[MOTOR_FRONT_RIGHT] = 0;

		if (t - stageTime > ACCELERATE_TIME) {
			flipStage = ROTATE;
			stageTime = t;
		}

	} else if (flipStage == ROTATE) {
		thrustTarget = 0.2; // mark for log analysis

		// free rotation
		memset(motors, 0, sizeof(motors));

		Vector up = attitude.rotate(Vector(0, 0, -1));

		if (abs(rates.x) > abs(maxRate)) {
			maxRate = rates.x;
			accelerationAngleZ = up.z;
			accelerationWhenRotatingTime = t - stageTime;
		}

		if (up.z < accelerationAngleZ) {
			flipStage = BRAKE;
			stageTime = t;
		}

	} else if (flipStage == BRAKE) {
		thrustTarget = 0.3; // mark for log analysis

		motors[MOTOR_REAR_LEFT] = 0;
		motors[MOTOR_REAR_RIGHT] = 1;
		motors[MOTOR_FRONT_LEFT] = 0;
		motors[MOTOR_FRONT_RIGHT] = 1;

		if (t - stageTime > BRAKE_TIME) {
			flipStage = POST_BRAKE;
			stageTime = t;
		}

	} else if (flipStage == POST_BRAKE) {
		thrustTarget = 0.4; // mark for log analysis

		motors[MOTOR_REAR_LEFT] = 0.3;
		motors[MOTOR_REAR_RIGHT] = 0.3;
		motors[MOTOR_FRONT_LEFT] = 0.3;
		motors[MOTOR_FRONT_RIGHT] = 0.3;

		if (t - stageTime > accelerationWhenRotatingTime) {
			flipStage = RECOVERY;
			stageTime = t;
			rollRatePID.reset();
			pitchRatePID.reset();
			yawRatePID.reset();
		}

	} else if (flipStage == RECOVERY) {
		controls[RC_CHANNEL_MODE] = 0; // stab mode
		interpretRC();
		if (t - stageTime < 0.4) {
			// gain thrust on first 0.4 seconds
			thrustTarget = 0.8;
		}
	}
}

flix.patch

diff --git a/flix/control.ino b/flix/control.ino
index ce0f0d6..b1c5ac8 100644
--- a/flix/control.ino
+++ b/flix/control.ino
@@ -74,7 +74,9 @@ void interpretRC() {
 	if (controls[RC_CHANNEL_MODE] < 0.25) {
 		mode = STAB;
 	} else if (controls[RC_CHANNEL_MODE] < 0.75) {
-		mode = STAB;
+		mode = USER;
+		controlFlip();
+		return;
 	} else {
 		mode = STAB;
 	}
diff --git a/flix/imu.ino b/flix/imu.ino
index acbade5..026a1c6 100644
--- a/flix/imu.ino
+++ b/flix/imu.ino
@@ -25,6 +25,7 @@ void setupIMU() {
 	if (LOAD_GYRO_CAL) loadGyroCal();
 	loadAccelCal();
 
+	IMU.setGyroRange(MPU9250::GYRO_RANGE_2000DPS); // this somehow lowers IMU rate to 500 Hz despite the SRD setting
 	IMU.setSrd(0); // set sample rate to 1000 Hz
 	// NOTE: very important, without the above the rate would be terrible 50 Hz
 }
diff --git a/gazebo/flix.h b/gazebo/flix.h
index a8ce214..cb9d062 100644
--- a/gazebo/flix.h
+++ b/gazebo/flix.h
@@ -48,6 +48,7 @@ void sendMavlink();
 void sendMessage(const void *msg);
 void receiveMavlink();
 void handleMavlink(const void *_msg);
+void controlFlip();
 
 // mocks
 void setLED(bool on) {};
diff --git a/gazebo/simulator.cpp b/gazebo/simulator.cpp
index f681513..5b2a556 100644
--- a/gazebo/simulator.cpp
+++ b/gazebo/simulator.cpp
@@ -26,6 +26,7 @@
 #include "log.ino"
 #include "cli.ino"
 #include "mavlink.ino"
+#include "flip.ino"
 #include "lpf.h"
 
 using ignition::math::Vector3d;