altos: Add gyro-based orientation tracking

This tracks the angle-from-vertical as an additional input to the pyro
channels.

Signed-off-by: Keith Packard <keithp@keithp.com>

9 files changed, 222 insertions, 15 deletions

diff --git a/src/core/ao_data.h b/src/core/ao_data.h
index 339afe69..5a232885 100644
--- a/src/core/ao_data.h
+++ b/src/core/ao_data.h
@@ -18,6 +18,8 @@
 #ifndef _AO_DATA_H_
 #define _AO_DATA_H_
 
+#define GRAVITY 9.80665
+
 #if HAS_ADC
 #define AO_DATA_ADC	(1 << 0)
 #else
@@ -300,8 +302,8 @@ typedef int16_t accel_t;
 
 #define HAS_GYRO	1
 
-typedef int16_t	gyro_t;
-typedef int32_t angle_t;
+typedef int16_t	gyro_t;		/* in raw sample units */
+typedef int16_t angle_t;	/* in degrees */
 
 /* Y axis is aligned with the direction of motion (along) */
 /* X axis is aligned in the other board axis (across) */
diff --git a/src/core/ao_flight.c b/src/core/ao_flight.c
index 2495a44b..240b348a 100644
--- a/src/core/ao_flight.c
+++ b/src/core/ao_flight.c
@@ -20,6 +20,10 @@
 #include <ao_log.h>
 #endif
 
+#if HAS_MPU6000
+#include <ao_quaternion.h>
+#endif
+
 #ifndef HAS_ACCEL
 #error Please define HAS_ACCEL
 #endif
diff --git a/src/core/ao_kalman.c b/src/core/ao_kalman.c
index 762b2c0a..7fd4f889 100644
--- a/src/core/ao_kalman.c
+++ b/src/core/ao_kalman.c
@@ -292,7 +292,4 @@ ao_kalman(void)
 	else 
 #endif
 		ao_avg_height = (ao_avg_height_scaled + 63) >> 7;
-#ifdef AO_FLIGHT_TEST
-	ao_sample_prev_tick = ao_sample_tick;
-#endif
 }
diff --git a/src/core/ao_pyro.c b/src/core/ao_pyro.c
index 531e1f50..24c9fe99 100644
--- a/src/core/ao_pyro.c
+++ b/src/core/ao_pyro.c
@@ -113,7 +113,7 @@ ao_pyro_ready(struct ao_pyro *pyro)
 				continue;
 			break;
 
-#if HAS_ORIENT
+#if HAS_GYRO
 		case ao_pyro_orient_less:
 			if (ao_orient <= pyro->orient_less)
 				continue;
@@ -310,7 +310,7 @@ const struct {
 	{ "h<",	ao_pyro_height_less,	offsetof(struct ao_pyro, height_less), HELP("height less (m)") },
 	{ "h>",	ao_pyro_height_greater,	offsetof(struct ao_pyro, height_greater), HELP("height greater (m)") },
 
-#if HAS_ORIENT
+#if HAS_GYRO
 	{ "o<",	ao_pyro_orient_less,	offsetof(struct ao_pyro, orient_less), HELP("orient less (deg)") },
 	{ "o>",	ao_pyro_orient_greater,	offsetof(struct ao_pyro, orient_greater), HELP("orient greater (deg)")  },
 #endif
diff --git a/src/core/ao_quaternion.h b/src/core/ao_quaternion.h
new file mode 100644
index 00000000..f4b8aaa4
--- /dev/null
+++ b/src/core/ao_quaternion.h
@@ -0,0 +1,116 @@
+/*
+ * Copyright © 2013 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#ifndef _AO_QUATERNION_H_
+#define _AO_QUATERNION_H_
+
+#include <math.h>
+
+struct ao_quaternion {
+	float	r;		/* real bit */
+	float	x, y, z;	/* imaginary bits */
+};
+
+static inline void ao_quaternion_multiply(struct ao_quaternion *r,
+					  struct ao_quaternion *a,
+					  struct ao_quaternion *b)
+{
+	struct ao_quaternion	t;
+#define T(_a,_b)	(((a)->_a) * ((b)->_b))
+	t.r = T(r,r) - T(x,x) - T(y,y) - T(z,z);
+	t.x = T(r,x) + T(x,r) + T(y,z) - T(z,y);
+	t.y = T(r,y) - T(x,z) + T(y,r) + T(z,x);
+	t.z = T(r,z) + T(x,y) - T(y,x) + T(z,r);
+#undef T
+	*r = t;
+}
+
+static inline void ao_quaternion_conjugate(struct ao_quaternion *r,
+					   struct ao_quaternion *a)
+{
+	r->r = a->r;
+	r->x = -a->x;
+	r->y = -a->y;
+	r->z = -a->z;
+}
+
+static inline float ao_quaternion_normal(struct ao_quaternion *a)
+{
+#define S(_a)	(((a)->_a) * ((a)->_a))
+	return S(r) + S(x) + S(y) + S(z);
+#undef S
+}
+
+static inline void ao_quaternion_scale(struct ao_quaternion *r,
+				       struct ao_quaternion *a,
+				       float b)
+{
+	r->r = a->r * b;
+	r->x = a->x * b;
+	r->y = a->y * b;
+	r->z = a->z * b;
+}
+
+static inline void ao_quaternion_normalize(struct ao_quaternion *r,
+					   struct ao_quaternion *a)
+{
+	float	n = ao_quaternion_normal(a);
+
+	if (n > 0)
+		ao_quaternion_scale(r, a, 1/sqrtf(n));
+	else
+		*r = *a;
+}
+
+static inline void ao_quaternion_rotate(struct ao_quaternion *r,
+					struct ao_quaternion *a,
+					struct ao_quaternion *b)
+{
+	struct ao_quaternion	c;
+	struct ao_quaternion	t;
+
+	ao_quaternion_conjugate(&c, b);
+	ao_quaternion_multiply(&t, b, a);
+	ao_quaternion_multiply(r, &t, &c);
+}
+
+static inline void ao_quaternion_init_vector(struct ao_quaternion *r,
+					     float x, float y, float z)
+{
+	r->r = 0;
+	r->x = x;
+	r->y = y;
+	r->z = z;
+}
+
+static inline void ao_quaternion_init_rotation(struct ao_quaternion *r,
+					       float x, float y, float z,
+					       float s, float c)
+{
+	r->r = c;
+	r->x = s * x;
+	r->y = s * y;
+	r->z = s * z;
+}
+
+static inline void ao_quaternion_init_zero_rotation(struct ao_quaternion *r)
+{
+	r->r = 1;
+	r->x = r->y = r->z = 0;
+}
+
+#endif /* _AO_QUATERNION_H_ */
diff --git a/src/core/ao_sample.c b/src/core/ao_sample.c
index dec44f9f..676e0ffd 100644
--- a/src/core/ao_sample.c
+++ b/src/core/ao_sample.c
@@ -20,6 +20,10 @@
 #include <ao_data.h>
 #endif
 
+#if HAS_GYRO
+#include <ao_quaternion.h>
+#endif
+
 /*
  * Current sensor values
  */
@@ -44,8 +48,7 @@ __pdata accel_t		ao_sample_accel_through;
 __pdata gyro_t		ao_sample_roll;
 __pdata gyro_t		ao_sample_pitch;
 __pdata gyro_t		ao_sample_yaw;
-__pdata angle_t		ao_sample_angle;
-__pdata angle_t		ao_sample_roll_angle;
+__pdata angle_t		ao_orient;
 #endif
 
 __data uint8_t		ao_sample_data;
@@ -86,6 +89,8 @@ __pdata int32_t	ao_sample_accel_through_sum;
 __pdata int32_t ao_sample_pitch_sum;
 __pdata int32_t ao_sample_yaw_sum;
 __pdata int32_t	ao_sample_roll_sum;
+static struct ao_quaternion ao_rotation;
+static struct ao_quaternion ao_pad_orientation;
 #endif
 
 static void
@@ -129,11 +134,91 @@ ao_sample_preflight_set(void)
 	ao_sample_pitch_sum = 0;
 	ao_sample_yaw_sum = 0;
 	ao_sample_roll_sum = 0;
-	ao_sample_angle = 0;
+	ao_orient = 0;
+
+	/* No rotation yet */
+	ao_quaternion_init_zero_rotation(&ao_rotation);
+
+	/* XXX Assume we're pointing straight up for now */
+	ao_quaternion_init_vector(&ao_pad_orientation,
+				  ao_ground_accel_across,
+				  ao_ground_accel_through,
+				  -ao_ground_accel_along);
+	ao_quaternion_normalize(&ao_pad_orientation,
+				&ao_pad_orientation);
+				  
+	printf ("pad r%8.5f x%8.5f y%8.5f z%8.5f\n",
+		ao_pad_orientation.r,
+		ao_pad_orientation.x,
+		ao_pad_orientation.y,
+		ao_pad_orientation.z);
 #endif	
 	nsamples = 0;
 }
 
+#if HAS_GYRO
+static void
+ao_sample_rotate(void)
+{
+#ifdef AO_FLIGHT_TEST
+	float	dt = (ao_sample_tick - ao_sample_prev_tick) / 100.0;
+#else
+	static const float dt = 1/100.0;
+#endif
+	float	x = ao_mpu6000_gyro(ao_sample_pitch - ao_ground_pitch) * dt;
+	float	y = ao_mpu6000_gyro(ao_sample_yaw - ao_ground_yaw) * dt;
+	float	z = ao_mpu6000_gyro(ao_sample_roll - ao_ground_roll) * dt;
+
+	float			n_2, n;
+	float			s, c;
+	
+	struct ao_quaternion	rot;
+	struct ao_quaternion	point;
+
+	/* The amount of rotation is just the length of the vector. Now,
+	 * here's the trick -- assume that the rotation amount is small. In this case,
+	 * sin(x) ≃ x, so we can just make this the sin.
+	 */
+
+	n_2 = x*x + y*y + z*z;
+	n = sqrtf(n_2);
+	s = n / 2;
+	if (s > 1)
+		s = 1;
+	c = sqrtf(1 - s*s);
+
+	/* Make unit vector */
+	if (n > 0) {
+		x /= n;
+		y /= n;
+		z /= n;
+	}
+
+	/* Now compute the unified rotation quaternion */
+
+	ao_quaternion_init_rotation(&rot,
+				    x, y, z,
+				    s, c);
+
+	/* Integrate with the previous rotation amount */
+	ao_quaternion_multiply(&ao_rotation, &ao_rotation, &rot);
+
+	/* And normalize to make sure it remains a unit vector */
+	ao_quaternion_normalize(&ao_rotation, &ao_rotation);
+
+	/* Compute pitch angle from vertical by taking the pad
+	 * orientation vector and rotating it by the current total
+	 * rotation value. That will be a unit vector pointing along
+	 * the airframe axis. The Z value will be the cosine of the
+	 * change in the angle from vertical since boost
+	 */
+
+	ao_quaternion_rotate(&point, &ao_pad_orientation, &ao_rotation);
+
+	ao_orient = acosf(point.z) * (float) (180.0/M_PI);
+}
+#endif
+
 static void
 ao_sample_preflight(void)
 {
@@ -232,9 +317,12 @@ ao_sample(void)
 				ao_sample_preflight_update();
 			ao_kalman();
 #if HAS_GYRO
-			/* do quaternion stuff here... */
+			ao_sample_rotate();
 #endif
 		}
+#ifdef AO_FLIGHT_TEST
+		ao_sample_prev_tick = ao_sample_tick;
+#endif
 		ao_sample_data = ao_data_ring_next(ao_sample_data);
 	}
 	return !ao_preflight;
@@ -264,7 +352,7 @@ ao_sample_init(void)
 	ao_sample_pitch = 0;
 	ao_sample_yaw = 0;
 	ao_sample_roll = 0;
-	ao_sample_angle = 0;
+	ao_orient = 0;
 #endif
 	ao_sample_data = ao_data_head;
 	ao_preflight = TRUE;
diff --git a/src/core/ao_sample.h b/src/core/ao_sample.h
index 5bd29536..1d1bcc7c 100644
--- a/src/core/ao_sample.h
+++ b/src/core/ao_sample.h
@@ -64,8 +64,6 @@
  * for all further flight computations
  */
 
-#define GRAVITY 9.80665
-
 /*
  * Above this height, the baro sensor doesn't work
  */
@@ -118,6 +116,7 @@ extern __pdata accel_t	ao_ground_accel_through;
 extern __pdata gyro_t	ao_ground_pitch;
 extern __pdata gyro_t	ao_ground_yaw;
 extern __pdata gyro_t	ao_ground_roll;
+extern __pdata angle_t	ao_orient;
 #endif
 
 void ao_sample_init(void);
diff --git a/src/core/ao_telemetry.c b/src/core/ao_telemetry.c
index 6b47a06a..a2726016 100644
--- a/src/core/ao_telemetry.c
+++ b/src/core/ao_telemetry.c
@@ -115,6 +115,7 @@ ao_send_mega_sensor(void)
 	telemetry.generic.tick = packet->tick;
 	telemetry.generic.type = AO_TELEMETRY_MEGA_SENSOR;
 
+	telemetry.mega_sensor.orient = ao_orient;
 	telemetry.mega_sensor.accel = ao_data_accel(packet);
 	telemetry.mega_sensor.pres = ao_data_pres(packet);
 	telemetry.mega_sensor.temp = ao_data_temp(packet);
diff --git a/src/core/ao_telemetry.h b/src/core/ao_telemetry.h
index fd6b76b3..237a35ab 100644
--- a/src/core/ao_telemetry.h
+++ b/src/core/ao_telemetry.h
@@ -162,7 +162,7 @@ struct ao_telemetry_mega_sensor {
 	uint16_t	tick;		/*  2 */
 	uint8_t		type;		/*  4 */
 
-	uint8_t		pad5;		/*  5 */
+	uint8_t		orient;		/*  5 angle from vertical */
 	int16_t		accel;		/*  6 Z axis */
 
 	int32_t		pres;		/*  8 Pa * 10 */