altos: Correct incremental rotation computation

[fw/altos] / src / core / ao_sample.c

diff --git a/src/core/ao_sample.c b/src/core/ao_sample.c
index fc8f8680df2acb0826520f01c3f12789ed0b8dca..adf8399dd702535d960804791669cde9f204a812 100644 (file)
--- a/src/core/ao_sample.c
+++ b/src/core/ao_sample.c
@@ -164,47 +164,24 @@ ao_sample_preflight_set(void)
 }
 
 #if HAS_GYRO
+
+#define TIME_DIV       200.0f
+
 static void
 ao_sample_rotate(void)
 {
 #ifdef AO_FLIGHT_TEST
-       float   dt = (ao_sample_tick - ao_sample_prev_tick) / 100.0;
+       float   dt = (ao_sample_tick - ao_sample_prev_tick) / TIME_DIV;
 #else
-       static const float dt = 1/100.0;
+       static const float dt = 1/TIME_DIV;
 #endif
        float   x = ao_mpu6000_gyro((float) ((ao_sample_pitch << 9) - ao_ground_pitch) / 512.0f) * dt;
        float   y = ao_mpu6000_gyro((float) ((ao_sample_yaw << 9) - ao_ground_yaw) / 512.0f) * dt;
        float   z = ao_mpu6000_gyro((float) ((ao_sample_roll << 9) - ao_ground_roll) / 512.0f) * dt;
        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);
+       ao_quaternion_init_half_euler(&rot, x, y, z);
+       ao_quaternion_multiply(&ao_rotation, &rot, &ao_rotation);
 
        /* And normalize to make sure it remains a unit vector */
        ao_quaternion_normalize(&ao_rotation, &ao_rotation);