jaewon lee / Mbed 2 deprecated 4180finalproject

4180 final project

Dependencies:   LSM9DS0 USBDevice mbed

Quaternion/Quaternion.cpp@0:ebbc3cd3a61e, 2015-12-05 (annotated)

Committer:
jlee887
Date:
Sat Dec 05 18:39:33 2015 +0000
Revision:
0:ebbc3cd3a61e
d

Who changed what in which revision?

UserRevisionLine numberNew contents of line
jlee887 0:ebbc3cd3a61e 1
jlee887 0:ebbc3cd3a61e 2 #include "Quaternion.h"
jlee887 0:ebbc3cd3a61e 3 #include "mbed.h"
jlee887 0:ebbc3cd3a61e 4 #define M_PI 3.14159265
jlee887 0:ebbc3cd3a61e 5
jlee887 0:ebbc3cd3a61e 6 Timer t;
jlee887 0:ebbc3cd3a61e 7 /**
jlee887 0:ebbc3cd3a61e 8 * Default constructor.
jlee887 0:ebbc3cd3a61e 9 **/
jlee887 0:ebbc3cd3a61e 10 Quaternion::Quaternion() {
jlee887 0:ebbc3cd3a61e 11 q0 = 1.0f;
jlee887 0:ebbc3cd3a61e 12 q1 = 0.0f;
jlee887 0:ebbc3cd3a61e 13 q2 = 0.0f;
jlee887 0:ebbc3cd3a61e 14 q3 = 0.0f;
jlee887 0:ebbc3cd3a61e 15 twoKp = twoKpDef;
jlee887 0:ebbc3cd3a61e 16 twoKi = twoKiDef;
jlee887 0:ebbc3cd3a61e 17 sampleFreq = 0.0f;
jlee887 0:ebbc3cd3a61e 18 lastUpdate = 0L;
jlee887 0:ebbc3cd3a61e 19 now = 0L;
jlee887 0:ebbc3cd3a61e 20 integralFBx = 0.0f;
jlee887 0:ebbc3cd3a61e 21 integralFBy = 0.0f;
jlee887 0:ebbc3cd3a61e 22 integralFBz = 0.0f;
jlee887 0:ebbc3cd3a61e 23 t.start();
jlee887 0:ebbc3cd3a61e 24 }
jlee887 0:ebbc3cd3a61e 25
jlee887 0:ebbc3cd3a61e 26 /**
jlee887 0:ebbc3cd3a61e 27 * Updates the sample frequency based on the elapsed time.
jlee887 0:ebbc3cd3a61e 28 **/
jlee887 0:ebbc3cd3a61e 29 void Quaternion::updateSampleFrequency() {
jlee887 0:ebbc3cd3a61e 30 now = t.read();
jlee887 0:ebbc3cd3a61e 31 sampleFreq = 1.0 / ((now - lastUpdate));
jlee887 0:ebbc3cd3a61e 32 lastUpdate = now;
jlee887 0:ebbc3cd3a61e 33 }
jlee887 0:ebbc3cd3a61e 34 /**
jlee887 0:ebbc3cd3a61e 35 * Returns the quaternion representation of the orientation.
jlee887 0:ebbc3cd3a61e 36 **/
jlee887 0:ebbc3cd3a61e 37 void Quaternion::getQ(float * q) {
jlee887 0:ebbc3cd3a61e 38 q[0] = q0;
jlee887 0:ebbc3cd3a61e 39 q[1] = q1;
jlee887 0:ebbc3cd3a61e 40 q[2] = q2;
jlee887 0:ebbc3cd3a61e 41 q[3] = q3;
jlee887 0:ebbc3cd3a61e 42 }
jlee887 0:ebbc3cd3a61e 43
jlee887 0:ebbc3cd3a61e 44 /**
jlee887 0:ebbc3cd3a61e 45 * Gets the linear acceleration by estimating gravity and then subtracting it. All accelerations
jlee887 0:ebbc3cd3a61e 46 * need to be scaled to 1 g. So if at 1 g your accelerometer reads 245, divide it by 245 before passing it
jlee887 0:ebbc3cd3a61e 47 * to this function.
jlee887 0:ebbc3cd3a61e 48 * @param *linearAccel, pointer to float array for linear accelerations,
jlee887 0:ebbc3cd3a61e 49 * @param ax, the scaled acceleration in the x direction.
jlee887 0:ebbc3cd3a61e 50 * @param ay, the scaled acceleration in the y direction.
jlee887 0:ebbc3cd3a61e 51 * @param az, the scaled acceleration in the z direction.
jlee887 0:ebbc3cd3a61e 52 **/
jlee887 0:ebbc3cd3a61e 53 void Quaternion::getLinearAcceleration(float * linearAccel, float ax, float ay, float az) {
jlee887 0:ebbc3cd3a61e 54
jlee887 0:ebbc3cd3a61e 55 float gravity[3];
jlee887 0:ebbc3cd3a61e 56 getGravity(gravity);
jlee887 0:ebbc3cd3a61e 57
jlee887 0:ebbc3cd3a61e 58
jlee887 0:ebbc3cd3a61e 59
jlee887 0:ebbc3cd3a61e 60 float xwog = ax - gravity[0];
jlee887 0:ebbc3cd3a61e 61 float ywog = ay - gravity[1];
jlee887 0:ebbc3cd3a61e 62 float zwog = az - gravity[2];
jlee887 0:ebbc3cd3a61e 63
jlee887 0:ebbc3cd3a61e 64 linearAccel[0] = xwog * 9.8;
jlee887 0:ebbc3cd3a61e 65 linearAccel[1] = ywog * 9.8;
jlee887 0:ebbc3cd3a61e 66 linearAccel[2] = zwog * 9.8;
jlee887 0:ebbc3cd3a61e 67 }
jlee887 0:ebbc3cd3a61e 68
jlee887 0:ebbc3cd3a61e 69 /**
jlee887 0:ebbc3cd3a61e 70 * Returns the euler angles psi, theta and phi.
jlee887 0:ebbc3cd3a61e 71 **/
jlee887 0:ebbc3cd3a61e 72 void Quaternion::getEulerAngles(float * angles) {
jlee887 0:ebbc3cd3a61e 73 angles[0] = atan2(2 * q1 * q2- 2 * q0 * q3, 2 * q0*q0 + 2 * q1 * q1 - 1) * 180/M_PI; // psi
jlee887 0:ebbc3cd3a61e 74 angles[1] = -asin(2 * q1 * q3 + 2 * q0 * q2) * 180/M_PI; // theta
jlee887 0:ebbc3cd3a61e 75 angles[2] = atan2(2 * q2 * q3 - 2 * q0 * q1, 2 * q0 * q0 + 2 * q3 * q3 - 1) * 180/M_PI; // phi
jlee887 0:ebbc3cd3a61e 76 }
jlee887 0:ebbc3cd3a61e 77
jlee887 0:ebbc3cd3a61e 78 /**
jlee887 0:ebbc3cd3a61e 79 * Returns the yaw pitch and roll of the device.
jlee887 0:ebbc3cd3a61e 80 **/
jlee887 0:ebbc3cd3a61e 81 void Quaternion::getYawPitchRoll(double * ypr) {
jlee887 0:ebbc3cd3a61e 82
jlee887 0:ebbc3cd3a61e 83 ypr[0] = atan2(double(2*q1*q2 + 2*q0*q3), double(q0*q0 + q1*q1 - q2*q2 - q3*q3)) * 180/M_PI; //yaw
jlee887 0:ebbc3cd3a61e 84 ypr[1] = -asin(2*q0*q2 - 2*q1*q3) * 180/M_PI; // pitch
jlee887 0:ebbc3cd3a61e 85 ypr[2] = -atan2(2*q2*q3 + 2*q0*q1, -q0*q0 + q1*q1 + q2*q2 - q3*q3) * 180/M_PI; //roll
jlee887 0:ebbc3cd3a61e 86
jlee887 0:ebbc3cd3a61e 87 }
jlee887 0:ebbc3cd3a61e 88 /**
jlee887 0:ebbc3cd3a61e 89 * Gets an estimation of gravity based on quaternion orientation representation.
jlee887 0:ebbc3cd3a61e 90 **/
jlee887 0:ebbc3cd3a61e 91 void Quaternion::getGravity(float * gravity) {
jlee887 0:ebbc3cd3a61e 92 float q[4];
jlee887 0:ebbc3cd3a61e 93 getQ(q);
jlee887 0:ebbc3cd3a61e 94 gravity[0] = 2 * (q[1] * q[3] - q[0] *q[2]);
jlee887 0:ebbc3cd3a61e 95 gravity[1] = 2 * (q[0] * q[1] + q[2] * q[3]);
jlee887 0:ebbc3cd3a61e 96 gravity[2] = q[0] * q[0] - q[1] * q[1] - q[2] * q[2] + q[3] * q[3];
jlee887 0:ebbc3cd3a61e 97 }
jlee887 0:ebbc3cd3a61e 98
jlee887 0:ebbc3cd3a61e 99 /**
jlee887 0:ebbc3cd3a61e 100 * Calculates the quaternion representation based on a 6DOF sensor.
jlee887 0:ebbc3cd3a61e 101 * @param gx, the rotation about the x axis in rad/sec
jlee887 0:ebbc3cd3a61e 102 * @param gy, the rotation about the y axis in rad/sec
jlee887 0:ebbc3cd3a61e 103 * @param gz, the rotation about the z axis in rad/sec
jlee887 0:ebbc3cd3a61e 104 * @param ax, the raw acceleration in the x direction.
jlee887 0:ebbc3cd3a61e 105 * @param ay, the raw acceleration in the y direction.
jlee887 0:ebbc3cd3a61e 106 * @param az, the raw acceleration in the z direction.
jlee887 0:ebbc3cd3a61e 107 **/
jlee887 0:ebbc3cd3a61e 108 void Quaternion::update6DOF(float gx, float gy, float gz, float ax, float ay, float az) {
jlee887 0:ebbc3cd3a61e 109 updateSampleFrequency();
jlee887 0:ebbc3cd3a61e 110 float recipNorm;
jlee887 0:ebbc3cd3a61e 111 float halfvx, halfvy, halfvz;
jlee887 0:ebbc3cd3a61e 112 float halfex, halfey, halfez;
jlee887 0:ebbc3cd3a61e 113 float qa, qb, qc;
jlee887 0:ebbc3cd3a61e 114
jlee887 0:ebbc3cd3a61e 115 // Compute feedback only if accelerometer measurement valid (avoids NaN in accelerometer normalisation)
jlee887 0:ebbc3cd3a61e 116 if(!((ax == 0.0f) && (ay == 0.0f) && (az == 0.0f))) {
jlee887 0:ebbc3cd3a61e 117
jlee887 0:ebbc3cd3a61e 118 // Normalise accelerometer measurement
jlee887 0:ebbc3cd3a61e 119 recipNorm = invSqrt(ax * ax + ay * ay + az * az);
jlee887 0:ebbc3cd3a61e 120 ax *= recipNorm;
jlee887 0:ebbc3cd3a61e 121 ay *= recipNorm;
jlee887 0:ebbc3cd3a61e 122 az *= recipNorm;
jlee887 0:ebbc3cd3a61e 123
jlee887 0:ebbc3cd3a61e 124 // Estimated direction of gravity and vector perpendicular to magnetic flux
jlee887 0:ebbc3cd3a61e 125 halfvx = q1 * q3 - q0 * q2;
jlee887 0:ebbc3cd3a61e 126 halfvy = q0 * q1 + q2 * q3;
jlee887 0:ebbc3cd3a61e 127 halfvz = q0 * q0 - 0.5f + q3 * q3;
jlee887 0:ebbc3cd3a61e 128
jlee887 0:ebbc3cd3a61e 129 // Error is sum of cross product between estimated and measured direction of gravity
jlee887 0:ebbc3cd3a61e 130 halfex = (ay * halfvz - az * halfvy);
jlee887 0:ebbc3cd3a61e 131 halfey = (az * halfvx - ax * halfvz);
jlee887 0:ebbc3cd3a61e 132 halfez = (ax * halfvy - ay * halfvx);
jlee887 0:ebbc3cd3a61e 133
jlee887 0:ebbc3cd3a61e 134 // Compute and apply integral feedback if enabled
jlee887 0:ebbc3cd3a61e 135 if(twoKi > 0.0f) {
jlee887 0:ebbc3cd3a61e 136 integralFBx += twoKi * halfex * (1.0f / sampleFreq); // integral error scaled by Ki
jlee887 0:ebbc3cd3a61e 137 integralFBy += twoKi * halfey * (1.0f / sampleFreq);
jlee887 0:ebbc3cd3a61e 138 integralFBz += twoKi * halfez * (1.0f / sampleFreq);
jlee887 0:ebbc3cd3a61e 139 gx += integralFBx; // apply integral feedback
jlee887 0:ebbc3cd3a61e 140 gy += integralFBy;
jlee887 0:ebbc3cd3a61e 141 gz += integralFBz;
jlee887 0:ebbc3cd3a61e 142 }
jlee887 0:ebbc3cd3a61e 143 else {
jlee887 0:ebbc3cd3a61e 144 integralFBx = 0.0f; // prevent integral windup
jlee887 0:ebbc3cd3a61e 145 integralFBy = 0.0f;
jlee887 0:ebbc3cd3a61e 146 integralFBz = 0.0f;
jlee887 0:ebbc3cd3a61e 147 }
jlee887 0:ebbc3cd3a61e 148
jlee887 0:ebbc3cd3a61e 149 // Apply proportional feedback
jlee887 0:ebbc3cd3a61e 150 gx += twoKp * halfex;
jlee887 0:ebbc3cd3a61e 151 gy += twoKp * halfey;
jlee887 0:ebbc3cd3a61e 152 gz += twoKp * halfez;
jlee887 0:ebbc3cd3a61e 153 }
jlee887 0:ebbc3cd3a61e 154
jlee887 0:ebbc3cd3a61e 155 // Integrate rate of change of quaternion
jlee887 0:ebbc3cd3a61e 156 gx *= (0.5f * (1.0f / sampleFreq)); // pre-multiply common factors
jlee887 0:ebbc3cd3a61e 157 gy *= (0.5f * (1.0f / sampleFreq));
jlee887 0:ebbc3cd3a61e 158 gz *= (0.5f * (1.0f / sampleFreq));
jlee887 0:ebbc3cd3a61e 159 qa = q0;
jlee887 0:ebbc3cd3a61e 160 qb = q1;
jlee887 0:ebbc3cd3a61e 161 qc = q2;
jlee887 0:ebbc3cd3a61e 162 q0 += (-qb * gx - qc * gy - q3 * gz);
jlee887 0:ebbc3cd3a61e 163 q1 += (qa * gx + qc * gz - q3 * gy);
jlee887 0:ebbc3cd3a61e 164 q2 += (qa * gy - qb * gz + q3 * gx);
jlee887 0:ebbc3cd3a61e 165 q3 += (qa * gz + qb * gy - qc * gx);
jlee887 0:ebbc3cd3a61e 166
jlee887 0:ebbc3cd3a61e 167 // Normalise quaternion
jlee887 0:ebbc3cd3a61e 168 recipNorm = invSqrt(q0 * q0 + q1 * q1 + q2 * q2 + q3 * q3);
jlee887 0:ebbc3cd3a61e 169 q0 *= recipNorm;
jlee887 0:ebbc3cd3a61e 170 q1 *= recipNorm;
jlee887 0:ebbc3cd3a61e 171 q2 *= recipNorm;
jlee887 0:ebbc3cd3a61e 172 q3 *= recipNorm;
jlee887 0:ebbc3cd3a61e 173
jlee887 0:ebbc3cd3a61e 174 }
jlee887 0:ebbc3cd3a61e 175
jlee887 0:ebbc3cd3a61e 176 /**
jlee887 0:ebbc3cd3a61e 177 * Calculates the quaternion representation based on a 9DOF sensor.
jlee887 0:ebbc3cd3a61e 178 * @param gx, the rotation about the x axis in rad/sec
jlee887 0:ebbc3cd3a61e 179 * @param gy, the rotation about the y axis in rad/sec
jlee887 0:ebbc3cd3a61e 180 * @param gz, the rotation about the z axis in rad/sec
jlee887 0:ebbc3cd3a61e 181 * @param ax, the raw acceleration in the x direction.
jlee887 0:ebbc3cd3a61e 182 * @param ay, the raw acceleration in the y direction.
jlee887 0:ebbc3cd3a61e 183 * @param az, the raw acceleration in the z direction.
jlee887 0:ebbc3cd3a61e 184 * @param mx, the raw magnometer heading in the x direction.
jlee887 0:ebbc3cd3a61e 185 * @param my, the raw magnometer heading in the y direction.
jlee887 0:ebbc3cd3a61e 186 * @param mz, the raw magnometer heading in the z direction.
jlee887 0:ebbc3cd3a61e 187 **/
jlee887 0:ebbc3cd3a61e 188 void Quaternion::update9DOF(float gx, float gy, float gz, float ax, float ay, float az, float mx, float my, float mz) {
jlee887 0:ebbc3cd3a61e 189 //update the frequency first.
jlee887 0:ebbc3cd3a61e 190 updateSampleFrequency();
jlee887 0:ebbc3cd3a61e 191 float recipNorm;
jlee887 0:ebbc3cd3a61e 192 float q0q0, q0q1, q0q2, q0q3, q1q1, q1q2, q1q3, q2q2, q2q3, q3q3;
jlee887 0:ebbc3cd3a61e 193 float hx, hy, bx, bz;
jlee887 0:ebbc3cd3a61e 194 float halfvx, halfvy, halfvz, halfwx, halfwy, halfwz;
jlee887 0:ebbc3cd3a61e 195 float halfex, halfey, halfez;
jlee887 0:ebbc3cd3a61e 196 float qa, qb, qc;
jlee887 0:ebbc3cd3a61e 197
jlee887 0:ebbc3cd3a61e 198 // Use IMU algorithm if magnetometer measurement invalid (avoids NaN in magnetometer normalisation)
jlee887 0:ebbc3cd3a61e 199 if((mx == 0.0f) && (my == 0.0f) && (mz == 0.0f)) {
jlee887 0:ebbc3cd3a61e 200 update6DOF(gx, gy, gz, ax, ay, az);
jlee887 0:ebbc3cd3a61e 201 return;
jlee887 0:ebbc3cd3a61e 202 }
jlee887 0:ebbc3cd3a61e 203
jlee887 0:ebbc3cd3a61e 204 // Compute feedback only if accelerometer measurement valid (avoids NaN in accelerometer normalisation)
jlee887 0:ebbc3cd3a61e 205 if(!((ax == 0.0f) && (ay == 0.0f) && (az == 0.0f))) {
jlee887 0:ebbc3cd3a61e 206
jlee887 0:ebbc3cd3a61e 207 // Normalise accelerometer measurement
jlee887 0:ebbc3cd3a61e 208 recipNorm = invSqrt(ax * ax + ay * ay + az * az);
jlee887 0:ebbc3cd3a61e 209 ax *= recipNorm;
jlee887 0:ebbc3cd3a61e 210 ay *= recipNorm;
jlee887 0:ebbc3cd3a61e 211 az *= recipNorm;
jlee887 0:ebbc3cd3a61e 212
jlee887 0:ebbc3cd3a61e 213 // Normalise magnetometer measurement
jlee887 0:ebbc3cd3a61e 214 recipNorm = invSqrt(mx * mx + my * my + mz * mz);
jlee887 0:ebbc3cd3a61e 215 mx *= recipNorm;
jlee887 0:ebbc3cd3a61e 216 my *= recipNorm;
jlee887 0:ebbc3cd3a61e 217 mz *= recipNorm;
jlee887 0:ebbc3cd3a61e 218
jlee887 0:ebbc3cd3a61e 219 // Auxiliary variables to avoid repeated arithmetic
jlee887 0:ebbc3cd3a61e 220 q0q0 = q0 * q0;
jlee887 0:ebbc3cd3a61e 221 q0q1 = q0 * q1;
jlee887 0:ebbc3cd3a61e 222 q0q2 = q0 * q2;
jlee887 0:ebbc3cd3a61e 223 q0q3 = q0 * q3;
jlee887 0:ebbc3cd3a61e 224 q1q1 = q1 * q1;
jlee887 0:ebbc3cd3a61e 225 q1q2 = q1 * q2;
jlee887 0:ebbc3cd3a61e 226 q1q3 = q1 * q3;
jlee887 0:ebbc3cd3a61e 227 q2q2 = q2 * q2;
jlee887 0:ebbc3cd3a61e 228 q2q3 = q2 * q3;
jlee887 0:ebbc3cd3a61e 229 q3q3 = q3 * q3;
jlee887 0:ebbc3cd3a61e 230
jlee887 0:ebbc3cd3a61e 231 // Reference direction of Earth's magnetic field
jlee887 0:ebbc3cd3a61e 232 hx = 2.0f * (mx * (0.5f - q2q2 - q3q3) + my * (q1q2 - q0q3) + mz * (q1q3 + q0q2));
jlee887 0:ebbc3cd3a61e 233 hy = 2.0f * (mx * (q1q2 + q0q3) + my * (0.5f - q1q1 - q3q3) + mz * (q2q3 - q0q1));
jlee887 0:ebbc3cd3a61e 234 bx = sqrt(hx * hx + hy * hy);
jlee887 0:ebbc3cd3a61e 235 bz = 2.0f * (mx * (q1q3 - q0q2) + my * (q2q3 + q0q1) + mz * (0.5f - q1q1 - q2q2));
jlee887 0:ebbc3cd3a61e 236
jlee887 0:ebbc3cd3a61e 237 // Estimated direction of gravity and magnetic field
jlee887 0:ebbc3cd3a61e 238 halfvx = q1q3 - q0q2;
jlee887 0:ebbc3cd3a61e 239 halfvy = q0q1 + q2q3;
jlee887 0:ebbc3cd3a61e 240 halfvz = q0q0 - 0.5f + q3q3;
jlee887 0:ebbc3cd3a61e 241 halfwx = bx * (0.5f - q2q2 - q3q3) + bz * (q1q3 - q0q2);
jlee887 0:ebbc3cd3a61e 242 halfwy = bx * (q1q2 - q0q3) + bz * (q0q1 + q2q3);
jlee887 0:ebbc3cd3a61e 243 halfwz = bx * (q0q2 + q1q3) + bz * (0.5f - q1q1 - q2q2);
jlee887 0:ebbc3cd3a61e 244
jlee887 0:ebbc3cd3a61e 245 // Error is sum of cross product between estimated direction and measured direction of field vectors
jlee887 0:ebbc3cd3a61e 246 halfex = (ay * halfvz - az * halfvy) + (my * halfwz - mz * halfwy);
jlee887 0:ebbc3cd3a61e 247 halfey = (az * halfvx - ax * halfvz) + (mz * halfwx - mx * halfwz);
jlee887 0:ebbc3cd3a61e 248 halfez = (ax * halfvy - ay * halfvx) + (mx * halfwy - my * halfwx);
jlee887 0:ebbc3cd3a61e 249
jlee887 0:ebbc3cd3a61e 250 // Compute and apply integral feedback if enabled
jlee887 0:ebbc3cd3a61e 251 if(twoKi > 0.0f) {
jlee887 0:ebbc3cd3a61e 252 integralFBx += twoKi * halfex * (1.0f / sampleFreq); // integral error scaled by Ki
jlee887 0:ebbc3cd3a61e 253 integralFBy += twoKi * halfey * (1.0f / sampleFreq);
jlee887 0:ebbc3cd3a61e 254 integralFBz += twoKi * halfez * (1.0f / sampleFreq);
jlee887 0:ebbc3cd3a61e 255 gx += integralFBx; // apply integral feedback
jlee887 0:ebbc3cd3a61e 256 gy += integralFBy;
jlee887 0:ebbc3cd3a61e 257 gz += integralFBz;
jlee887 0:ebbc3cd3a61e 258 }
jlee887 0:ebbc3cd3a61e 259 else {
jlee887 0:ebbc3cd3a61e 260 integralFBx = 0.0f; // prevent integral windup
jlee887 0:ebbc3cd3a61e 261 integralFBy = 0.0f;
jlee887 0:ebbc3cd3a61e 262 integralFBz = 0.0f;
jlee887 0:ebbc3cd3a61e 263 }
jlee887 0:ebbc3cd3a61e 264
jlee887 0:ebbc3cd3a61e 265 // Apply proportional feedback
jlee887 0:ebbc3cd3a61e 266 gx += twoKp * halfex;
jlee887 0:ebbc3cd3a61e 267 gy += twoKp * halfey;
jlee887 0:ebbc3cd3a61e 268 gz += twoKp * halfez;
jlee887 0:ebbc3cd3a61e 269 }
jlee887 0:ebbc3cd3a61e 270
jlee887 0:ebbc3cd3a61e 271 // Integrate rate of change of quaternion
jlee887 0:ebbc3cd3a61e 272 gx *= (0.5f * (1.0f / sampleFreq)); // pre-multiply common factors
jlee887 0:ebbc3cd3a61e 273 gy *= (0.5f * (1.0f / sampleFreq));
jlee887 0:ebbc3cd3a61e 274 gz *= (0.5f * (1.0f / sampleFreq));
jlee887 0:ebbc3cd3a61e 275 qa = q0;
jlee887 0:ebbc3cd3a61e 276 qb = q1;
jlee887 0:ebbc3cd3a61e 277 qc = q2;
jlee887 0:ebbc3cd3a61e 278 q0 += (-qb * gx - qc * gy - q3 * gz);
jlee887 0:ebbc3cd3a61e 279 q1 += (qa * gx + qc * gz - q3 * gy);
jlee887 0:ebbc3cd3a61e 280 q2 += (qa * gy - qb * gz + q3 * gx);
jlee887 0:ebbc3cd3a61e 281 q3 += (qa * gz + qb * gy - qc * gx);
jlee887 0:ebbc3cd3a61e 282
jlee887 0:ebbc3cd3a61e 283 // Normalise quaternion
jlee887 0:ebbc3cd3a61e 284 recipNorm = invSqrt(q0 * q0 + q1 * q1 + q2 * q2 + q3 * q3);
jlee887 0:ebbc3cd3a61e 285 q0 *= recipNorm;
jlee887 0:ebbc3cd3a61e 286 q1 *= recipNorm;
jlee887 0:ebbc3cd3a61e 287 q2 *= recipNorm;
jlee887 0:ebbc3cd3a61e 288 q3 *= recipNorm;
jlee887 0:ebbc3cd3a61e 289 }
jlee887 0:ebbc3cd3a61e 290
jlee887 0:ebbc3cd3a61e 291 /**
jlee887 0:ebbc3cd3a61e 292 * Super fast inverted square root.
jlee887 0:ebbc3cd3a61e 293 **/
jlee887 0:ebbc3cd3a61e 294 float Quaternion::invSqrt(float x) {
jlee887 0:ebbc3cd3a61e 295 float halfx = 0.5f * x;
jlee887 0:ebbc3cd3a61e 296 float y = x;
jlee887 0:ebbc3cd3a61e 297 long i = *(long*)&y;
jlee887 0:ebbc3cd3a61e 298 i = 0x5f3759df - (i>>1);
jlee887 0:ebbc3cd3a61e 299 y = *(float*)&i;
jlee887 0:ebbc3cd3a61e 300 y = y * (1.5f - (halfx * y * y));
jlee887 0:ebbc3cd3a61e 301 return y;
jlee887 0:ebbc3cd3a61e 302 }