MadgwickAHRS
MadgwickAHRS.cpp@0:0f88b99a97ce, 2019-04-25 (annotated)
- Committer:
- 771_8bit
- Date:
- Thu Apr 25 04:03:54 2019 +0000
- Revision:
- 0:0f88b99a97ce
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Who changed what in which revision?
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771_8bit | 0:0f88b99a97ce | 1 | //============================================================================================= |
771_8bit | 0:0f88b99a97ce | 2 | // MadgwickAHRS.c |
771_8bit | 0:0f88b99a97ce | 3 | //============================================================================================= |
771_8bit | 0:0f88b99a97ce | 4 | // |
771_8bit | 0:0f88b99a97ce | 5 | // Implementation of Madgwick's IMU and AHRS algorithms. |
771_8bit | 0:0f88b99a97ce | 6 | // See: http://www.x-io.co.uk/open-source-imu-and-ahrs-algorithms/ |
771_8bit | 0:0f88b99a97ce | 7 | // |
771_8bit | 0:0f88b99a97ce | 8 | // From the x-io website "Open-source resources available on this website are |
771_8bit | 0:0f88b99a97ce | 9 | // provided under the GNU General Public Licence unless an alternative licence |
771_8bit | 0:0f88b99a97ce | 10 | // is provided in source." |
771_8bit | 0:0f88b99a97ce | 11 | // |
771_8bit | 0:0f88b99a97ce | 12 | // Date Author Notes |
771_8bit | 0:0f88b99a97ce | 13 | // 29/09/2011 SOH Madgwick Initial release |
771_8bit | 0:0f88b99a97ce | 14 | // 02/10/2011 SOH Madgwick Optimised for reduced CPU load |
771_8bit | 0:0f88b99a97ce | 15 | // 19/02/2012 SOH Madgwick Magnetometer measurement is normalised |
771_8bit | 0:0f88b99a97ce | 16 | // 18/12/2016 Added better fast inverse square root |
771_8bit | 0:0f88b99a97ce | 17 | // |
771_8bit | 0:0f88b99a97ce | 18 | //============================================================================================= |
771_8bit | 0:0f88b99a97ce | 19 | |
771_8bit | 0:0f88b99a97ce | 20 | //------------------------------------------------------------------------------------------- |
771_8bit | 0:0f88b99a97ce | 21 | // Header files |
771_8bit | 0:0f88b99a97ce | 22 | |
771_8bit | 0:0f88b99a97ce | 23 | #include "MadgwickAHRS.h" |
771_8bit | 0:0f88b99a97ce | 24 | #include <math.h> |
771_8bit | 0:0f88b99a97ce | 25 | |
771_8bit | 0:0f88b99a97ce | 26 | //------------------------------------------------------------------------------------------- |
771_8bit | 0:0f88b99a97ce | 27 | // Definitions |
771_8bit | 0:0f88b99a97ce | 28 | |
771_8bit | 0:0f88b99a97ce | 29 | #define sampleFreqDef 500.0f // sample frequency in Hz |
771_8bit | 0:0f88b99a97ce | 30 | #define betaDef 0.1f // 2 * proportional gain 0.1 - 0.5 - 5 |
771_8bit | 0:0f88b99a97ce | 31 | |
771_8bit | 0:0f88b99a97ce | 32 | |
771_8bit | 0:0f88b99a97ce | 33 | //============================================================================================ |
771_8bit | 0:0f88b99a97ce | 34 | // Functions |
771_8bit | 0:0f88b99a97ce | 35 | |
771_8bit | 0:0f88b99a97ce | 36 | //------------------------------------------------------------------------------------------- |
771_8bit | 0:0f88b99a97ce | 37 | // AHRS algorithm update |
771_8bit | 0:0f88b99a97ce | 38 | |
771_8bit | 0:0f88b99a97ce | 39 | Madgwick::Madgwick() { |
771_8bit | 0:0f88b99a97ce | 40 | beta = betaDef; |
771_8bit | 0:0f88b99a97ce | 41 | q0 = 1.0f; |
771_8bit | 0:0f88b99a97ce | 42 | q1 = 0.0f; |
771_8bit | 0:0f88b99a97ce | 43 | q2 = 0.0f; |
771_8bit | 0:0f88b99a97ce | 44 | q3 = 0.0f; |
771_8bit | 0:0f88b99a97ce | 45 | invSampleFreq = 1.0f / sampleFreqDef; |
771_8bit | 0:0f88b99a97ce | 46 | anglesComputed = 0; |
771_8bit | 0:0f88b99a97ce | 47 | } |
771_8bit | 0:0f88b99a97ce | 48 | |
771_8bit | 0:0f88b99a97ce | 49 | void Madgwick::update(float gx, float gy, float gz, float ax, float ay, float az, float mx, float my, float mz) { |
771_8bit | 0:0f88b99a97ce | 50 | float recipNorm; |
771_8bit | 0:0f88b99a97ce | 51 | float s0, s1, s2, s3; |
771_8bit | 0:0f88b99a97ce | 52 | float qDot1, qDot2, qDot3, qDot4; |
771_8bit | 0:0f88b99a97ce | 53 | float hx, hy; |
771_8bit | 0:0f88b99a97ce | 54 | float _2q0mx, _2q0my, _2q0mz, _2q1mx, _2bx, _2bz, _4bx, _4bz, _2q0, _2q1, _2q2, _2q3, _2q0q2, _2q2q3, q0q0, q0q1, q0q2, q0q3, q1q1, q1q2, q1q3, q2q2, q2q3, q3q3; |
771_8bit | 0:0f88b99a97ce | 55 | |
771_8bit | 0:0f88b99a97ce | 56 | // Use IMU algorithm if magnetometer measurement invalid (avoids NaN in magnetometer normalisation) |
771_8bit | 0:0f88b99a97ce | 57 | if((mx == 0.0f) && (my == 0.0f) && (mz == 0.0f)) { |
771_8bit | 0:0f88b99a97ce | 58 | updateIMU(gx, gy, gz, ax, ay, az); |
771_8bit | 0:0f88b99a97ce | 59 | return; |
771_8bit | 0:0f88b99a97ce | 60 | } |
771_8bit | 0:0f88b99a97ce | 61 | |
771_8bit | 0:0f88b99a97ce | 62 | // Convert gyroscope degrees/sec to radians/sec |
771_8bit | 0:0f88b99a97ce | 63 | gx *= 0.0174533f; |
771_8bit | 0:0f88b99a97ce | 64 | gy *= 0.0174533f; |
771_8bit | 0:0f88b99a97ce | 65 | gz *= 0.0174533f; |
771_8bit | 0:0f88b99a97ce | 66 | |
771_8bit | 0:0f88b99a97ce | 67 | // Rate of change of quaternion from gyroscope |
771_8bit | 0:0f88b99a97ce | 68 | qDot1 = 0.5f * (-q1 * gx - q2 * gy - q3 * gz); |
771_8bit | 0:0f88b99a97ce | 69 | qDot2 = 0.5f * (q0 * gx + q2 * gz - q3 * gy); |
771_8bit | 0:0f88b99a97ce | 70 | qDot3 = 0.5f * (q0 * gy - q1 * gz + q3 * gx); |
771_8bit | 0:0f88b99a97ce | 71 | qDot4 = 0.5f * (q0 * gz + q1 * gy - q2 * gx); |
771_8bit | 0:0f88b99a97ce | 72 | |
771_8bit | 0:0f88b99a97ce | 73 | // Compute feedback only if accelerometer measurement valid (avoids NaN in accelerometer normalisation) |
771_8bit | 0:0f88b99a97ce | 74 | if(!((ax == 0.0f) && (ay == 0.0f) && (az == 0.0f))) { |
771_8bit | 0:0f88b99a97ce | 75 | |
771_8bit | 0:0f88b99a97ce | 76 | // Normalise accelerometer measurement |
771_8bit | 0:0f88b99a97ce | 77 | recipNorm = invSqrt(ax * ax + ay * ay + az * az); |
771_8bit | 0:0f88b99a97ce | 78 | ax *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 79 | ay *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 80 | az *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 81 | |
771_8bit | 0:0f88b99a97ce | 82 | // Normalise magnetometer measurement |
771_8bit | 0:0f88b99a97ce | 83 | recipNorm = invSqrt(mx * mx + my * my + mz * mz); |
771_8bit | 0:0f88b99a97ce | 84 | mx *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 85 | my *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 86 | mz *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 87 | |
771_8bit | 0:0f88b99a97ce | 88 | // Auxiliary variables to avoid repeated arithmetic |
771_8bit | 0:0f88b99a97ce | 89 | _2q0mx = 2.0f * q0 * mx; |
771_8bit | 0:0f88b99a97ce | 90 | _2q0my = 2.0f * q0 * my; |
771_8bit | 0:0f88b99a97ce | 91 | _2q0mz = 2.0f * q0 * mz; |
771_8bit | 0:0f88b99a97ce | 92 | _2q1mx = 2.0f * q1 * mx; |
771_8bit | 0:0f88b99a97ce | 93 | _2q0 = 2.0f * q0; |
771_8bit | 0:0f88b99a97ce | 94 | _2q1 = 2.0f * q1; |
771_8bit | 0:0f88b99a97ce | 95 | _2q2 = 2.0f * q2; |
771_8bit | 0:0f88b99a97ce | 96 | _2q3 = 2.0f * q3; |
771_8bit | 0:0f88b99a97ce | 97 | _2q0q2 = 2.0f * q0 * q2; |
771_8bit | 0:0f88b99a97ce | 98 | _2q2q3 = 2.0f * q2 * q3; |
771_8bit | 0:0f88b99a97ce | 99 | q0q0 = q0 * q0; |
771_8bit | 0:0f88b99a97ce | 100 | q0q1 = q0 * q1; |
771_8bit | 0:0f88b99a97ce | 101 | q0q2 = q0 * q2; |
771_8bit | 0:0f88b99a97ce | 102 | q0q3 = q0 * q3; |
771_8bit | 0:0f88b99a97ce | 103 | q1q1 = q1 * q1; |
771_8bit | 0:0f88b99a97ce | 104 | q1q2 = q1 * q2; |
771_8bit | 0:0f88b99a97ce | 105 | q1q3 = q1 * q3; |
771_8bit | 0:0f88b99a97ce | 106 | q2q2 = q2 * q2; |
771_8bit | 0:0f88b99a97ce | 107 | q2q3 = q2 * q3; |
771_8bit | 0:0f88b99a97ce | 108 | q3q3 = q3 * q3; |
771_8bit | 0:0f88b99a97ce | 109 | |
771_8bit | 0:0f88b99a97ce | 110 | // Reference direction of Earth's magnetic field |
771_8bit | 0:0f88b99a97ce | 111 | hx = mx * q0q0 - _2q0my * q3 + _2q0mz * q2 + mx * q1q1 + _2q1 * my * q2 + _2q1 * mz * q3 - mx * q2q2 - mx * q3q3; |
771_8bit | 0:0f88b99a97ce | 112 | hy = _2q0mx * q3 + my * q0q0 - _2q0mz * q1 + _2q1mx * q2 - my * q1q1 + my * q2q2 + _2q2 * mz * q3 - my * q3q3; |
771_8bit | 0:0f88b99a97ce | 113 | _2bx = sqrtf(hx * hx + hy * hy); |
771_8bit | 0:0f88b99a97ce | 114 | _2bz = -_2q0mx * q2 + _2q0my * q1 + mz * q0q0 + _2q1mx * q3 - mz * q1q1 + _2q2 * my * q3 - mz * q2q2 + mz * q3q3; |
771_8bit | 0:0f88b99a97ce | 115 | _4bx = 2.0f * _2bx; |
771_8bit | 0:0f88b99a97ce | 116 | _4bz = 2.0f * _2bz; |
771_8bit | 0:0f88b99a97ce | 117 | |
771_8bit | 0:0f88b99a97ce | 118 | // Gradient decent algorithm corrective step |
771_8bit | 0:0f88b99a97ce | 119 | s0 = -_2q2 * (2.0f * q1q3 - _2q0q2 - ax) + _2q1 * (2.0f * q0q1 + _2q2q3 - ay) - _2bz * q2 * (_2bx * (0.5f - q2q2 - q3q3) + _2bz * (q1q3 - q0q2) - mx) + (-_2bx * q3 + _2bz * q1) * (_2bx * (q1q2 - q0q3) + _2bz * (q0q1 + q2q3) - my) + _2bx * q2 * (_2bx * (q0q2 + q1q3) + _2bz * (0.5f - q1q1 - q2q2) - mz); |
771_8bit | 0:0f88b99a97ce | 120 | s1 = _2q3 * (2.0f * q1q3 - _2q0q2 - ax) + _2q0 * (2.0f * q0q1 + _2q2q3 - ay) - 4.0f * q1 * (1 - 2.0f * q1q1 - 2.0f * q2q2 - az) + _2bz * q3 * (_2bx * (0.5f - q2q2 - q3q3) + _2bz * (q1q3 - q0q2) - mx) + (_2bx * q2 + _2bz * q0) * (_2bx * (q1q2 - q0q3) + _2bz * (q0q1 + q2q3) - my) + (_2bx * q3 - _4bz * q1) * (_2bx * (q0q2 + q1q3) + _2bz * (0.5f - q1q1 - q2q2) - mz); |
771_8bit | 0:0f88b99a97ce | 121 | s2 = -_2q0 * (2.0f * q1q3 - _2q0q2 - ax) + _2q3 * (2.0f * q0q1 + _2q2q3 - ay) - 4.0f * q2 * (1 - 2.0f * q1q1 - 2.0f * q2q2 - az) + (-_4bx * q2 - _2bz * q0) * (_2bx * (0.5f - q2q2 - q3q3) + _2bz * (q1q3 - q0q2) - mx) + (_2bx * q1 + _2bz * q3) * (_2bx * (q1q2 - q0q3) + _2bz * (q0q1 + q2q3) - my) + (_2bx * q0 - _4bz * q2) * (_2bx * (q0q2 + q1q3) + _2bz * (0.5f - q1q1 - q2q2) - mz); |
771_8bit | 0:0f88b99a97ce | 122 | s3 = _2q1 * (2.0f * q1q3 - _2q0q2 - ax) + _2q2 * (2.0f * q0q1 + _2q2q3 - ay) + (-_4bx * q3 + _2bz * q1) * (_2bx * (0.5f - q2q2 - q3q3) + _2bz * (q1q3 - q0q2) - mx) + (-_2bx * q0 + _2bz * q2) * (_2bx * (q1q2 - q0q3) + _2bz * (q0q1 + q2q3) - my) + _2bx * q1 * (_2bx * (q0q2 + q1q3) + _2bz * (0.5f - q1q1 - q2q2) - mz); |
771_8bit | 0:0f88b99a97ce | 123 | recipNorm = invSqrt(s0 * s0 + s1 * s1 + s2 * s2 + s3 * s3); // normalise step magnitude |
771_8bit | 0:0f88b99a97ce | 124 | s0 *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 125 | s1 *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 126 | s2 *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 127 | s3 *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 128 | |
771_8bit | 0:0f88b99a97ce | 129 | // Apply feedback step |
771_8bit | 0:0f88b99a97ce | 130 | qDot1 -= beta * s0; |
771_8bit | 0:0f88b99a97ce | 131 | qDot2 -= beta * s1; |
771_8bit | 0:0f88b99a97ce | 132 | qDot3 -= beta * s2; |
771_8bit | 0:0f88b99a97ce | 133 | qDot4 -= beta * s3; |
771_8bit | 0:0f88b99a97ce | 134 | } |
771_8bit | 0:0f88b99a97ce | 135 | |
771_8bit | 0:0f88b99a97ce | 136 | // Integrate rate of change of quaternion to yield quaternion |
771_8bit | 0:0f88b99a97ce | 137 | q0 += qDot1 * invSampleFreq; |
771_8bit | 0:0f88b99a97ce | 138 | q1 += qDot2 * invSampleFreq; |
771_8bit | 0:0f88b99a97ce | 139 | q2 += qDot3 * invSampleFreq; |
771_8bit | 0:0f88b99a97ce | 140 | q3 += qDot4 * invSampleFreq; |
771_8bit | 0:0f88b99a97ce | 141 | |
771_8bit | 0:0f88b99a97ce | 142 | // Normalise quaternion |
771_8bit | 0:0f88b99a97ce | 143 | recipNorm = invSqrt(q0 * q0 + q1 * q1 + q2 * q2 + q3 * q3); |
771_8bit | 0:0f88b99a97ce | 144 | q0 *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 145 | q1 *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 146 | q2 *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 147 | q3 *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 148 | anglesComputed = 0; |
771_8bit | 0:0f88b99a97ce | 149 | } |
771_8bit | 0:0f88b99a97ce | 150 | |
771_8bit | 0:0f88b99a97ce | 151 | //------------------------------------------------------------------------------------------- |
771_8bit | 0:0f88b99a97ce | 152 | // IMU algorithm update |
771_8bit | 0:0f88b99a97ce | 153 | |
771_8bit | 0:0f88b99a97ce | 154 | void Madgwick::updateIMU(float gx, float gy, float gz, float ax, float ay, float az) { |
771_8bit | 0:0f88b99a97ce | 155 | float recipNorm; |
771_8bit | 0:0f88b99a97ce | 156 | float s0, s1, s2, s3; |
771_8bit | 0:0f88b99a97ce | 157 | float qDot1, qDot2, qDot3, qDot4; |
771_8bit | 0:0f88b99a97ce | 158 | float _2q0, _2q1, _2q2, _2q3, _4q0, _4q1, _4q2 ,_8q1, _8q2, q0q0, q1q1, q2q2, q3q3; |
771_8bit | 0:0f88b99a97ce | 159 | |
771_8bit | 0:0f88b99a97ce | 160 | // Convert gyroscope degrees/sec to radians/sec |
771_8bit | 0:0f88b99a97ce | 161 | gx *= 0.0174533f; |
771_8bit | 0:0f88b99a97ce | 162 | gy *= 0.0174533f; |
771_8bit | 0:0f88b99a97ce | 163 | gz *= 0.0174533f; |
771_8bit | 0:0f88b99a97ce | 164 | |
771_8bit | 0:0f88b99a97ce | 165 | // Rate of change of quaternion from gyroscope |
771_8bit | 0:0f88b99a97ce | 166 | qDot1 = 0.5f * (-q1 * gx - q2 * gy - q3 * gz); |
771_8bit | 0:0f88b99a97ce | 167 | qDot2 = 0.5f * (q0 * gx + q2 * gz - q3 * gy); |
771_8bit | 0:0f88b99a97ce | 168 | qDot3 = 0.5f * (q0 * gy - q1 * gz + q3 * gx); |
771_8bit | 0:0f88b99a97ce | 169 | qDot4 = 0.5f * (q0 * gz + q1 * gy - q2 * gx); |
771_8bit | 0:0f88b99a97ce | 170 | |
771_8bit | 0:0f88b99a97ce | 171 | // Compute feedback only if accelerometer measurement valid (avoids NaN in accelerometer normalisation) |
771_8bit | 0:0f88b99a97ce | 172 | if(!((ax == 0.0f) && (ay == 0.0f) && (az == 0.0f))) { |
771_8bit | 0:0f88b99a97ce | 173 | |
771_8bit | 0:0f88b99a97ce | 174 | // Normalise accelerometer measurement |
771_8bit | 0:0f88b99a97ce | 175 | recipNorm = invSqrt(ax * ax + ay * ay + az * az); |
771_8bit | 0:0f88b99a97ce | 176 | ax *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 177 | ay *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 178 | az *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 179 | |
771_8bit | 0:0f88b99a97ce | 180 | // Auxiliary variables to avoid repeated arithmetic |
771_8bit | 0:0f88b99a97ce | 181 | _2q0 = 2.0f * q0; |
771_8bit | 0:0f88b99a97ce | 182 | _2q1 = 2.0f * q1; |
771_8bit | 0:0f88b99a97ce | 183 | _2q2 = 2.0f * q2; |
771_8bit | 0:0f88b99a97ce | 184 | _2q3 = 2.0f * q3; |
771_8bit | 0:0f88b99a97ce | 185 | _4q0 = 4.0f * q0; |
771_8bit | 0:0f88b99a97ce | 186 | _4q1 = 4.0f * q1; |
771_8bit | 0:0f88b99a97ce | 187 | _4q2 = 4.0f * q2; |
771_8bit | 0:0f88b99a97ce | 188 | _8q1 = 8.0f * q1; |
771_8bit | 0:0f88b99a97ce | 189 | _8q2 = 8.0f * q2; |
771_8bit | 0:0f88b99a97ce | 190 | q0q0 = q0 * q0; |
771_8bit | 0:0f88b99a97ce | 191 | q1q1 = q1 * q1; |
771_8bit | 0:0f88b99a97ce | 192 | q2q2 = q2 * q2; |
771_8bit | 0:0f88b99a97ce | 193 | q3q3 = q3 * q3; |
771_8bit | 0:0f88b99a97ce | 194 | |
771_8bit | 0:0f88b99a97ce | 195 | // Gradient decent algorithm corrective step |
771_8bit | 0:0f88b99a97ce | 196 | s0 = _4q0 * q2q2 + _2q2 * ax + _4q0 * q1q1 - _2q1 * ay; |
771_8bit | 0:0f88b99a97ce | 197 | s1 = _4q1 * q3q3 - _2q3 * ax + 4.0f * q0q0 * q1 - _2q0 * ay - _4q1 + _8q1 * q1q1 + _8q1 * q2q2 + _4q1 * az; |
771_8bit | 0:0f88b99a97ce | 198 | s2 = 4.0f * q0q0 * q2 + _2q0 * ax + _4q2 * q3q3 - _2q3 * ay - _4q2 + _8q2 * q1q1 + _8q2 * q2q2 + _4q2 * az; |
771_8bit | 0:0f88b99a97ce | 199 | s3 = 4.0f * q1q1 * q3 - _2q1 * ax + 4.0f * q2q2 * q3 - _2q2 * ay; |
771_8bit | 0:0f88b99a97ce | 200 | recipNorm = invSqrt(s0 * s0 + s1 * s1 + s2 * s2 + s3 * s3); // normalise step magnitude |
771_8bit | 0:0f88b99a97ce | 201 | s0 *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 202 | s1 *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 203 | s2 *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 204 | s3 *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 205 | |
771_8bit | 0:0f88b99a97ce | 206 | // Apply feedback step |
771_8bit | 0:0f88b99a97ce | 207 | qDot1 -= beta * s0; |
771_8bit | 0:0f88b99a97ce | 208 | qDot2 -= beta * s1; |
771_8bit | 0:0f88b99a97ce | 209 | qDot3 -= beta * s2; |
771_8bit | 0:0f88b99a97ce | 210 | qDot4 -= beta * s3; |
771_8bit | 0:0f88b99a97ce | 211 | } |
771_8bit | 0:0f88b99a97ce | 212 | |
771_8bit | 0:0f88b99a97ce | 213 | // Integrate rate of change of quaternion to yield quaternion |
771_8bit | 0:0f88b99a97ce | 214 | q0 += qDot1 * invSampleFreq; |
771_8bit | 0:0f88b99a97ce | 215 | q1 += qDot2 * invSampleFreq; |
771_8bit | 0:0f88b99a97ce | 216 | q2 += qDot3 * invSampleFreq; |
771_8bit | 0:0f88b99a97ce | 217 | q3 += qDot4 * invSampleFreq; |
771_8bit | 0:0f88b99a97ce | 218 | |
771_8bit | 0:0f88b99a97ce | 219 | // Normalise quaternion |
771_8bit | 0:0f88b99a97ce | 220 | recipNorm = invSqrt(q0 * q0 + q1 * q1 + q2 * q2 + q3 * q3); |
771_8bit | 0:0f88b99a97ce | 221 | q0 *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 222 | q1 *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 223 | q2 *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 224 | q3 *= recipNorm; |
771_8bit | 0:0f88b99a97ce | 225 | anglesComputed = 0; |
771_8bit | 0:0f88b99a97ce | 226 | } |
771_8bit | 0:0f88b99a97ce | 227 | |
771_8bit | 0:0f88b99a97ce | 228 | //------------------------------------------------------------------------------------------- |
771_8bit | 0:0f88b99a97ce | 229 | // Fast inverse square-root |
771_8bit | 0:0f88b99a97ce | 230 | // See: http://en.wikipedia.org/wiki/Fast_inverse_square_root |
771_8bit | 0:0f88b99a97ce | 231 | |
771_8bit | 0:0f88b99a97ce | 232 | /*float Madgwick::invSqrt(float x) { |
771_8bit | 0:0f88b99a97ce | 233 | float halfx = 0.5f * x; |
771_8bit | 0:0f88b99a97ce | 234 | float y = x; |
771_8bit | 0:0f88b99a97ce | 235 | long i = *(long*)&y; |
771_8bit | 0:0f88b99a97ce | 236 | i = 0x5f3759df - (i>>1); |
771_8bit | 0:0f88b99a97ce | 237 | y = *(float*)&i; |
771_8bit | 0:0f88b99a97ce | 238 | y = y * (1.5f - (halfx * y * y)); |
771_8bit | 0:0f88b99a97ce | 239 | y = y * (1.5f - (halfx * y * y)); |
771_8bit | 0:0f88b99a97ce | 240 | return y; |
771_8bit | 0:0f88b99a97ce | 241 | } */ |
771_8bit | 0:0f88b99a97ce | 242 | |
771_8bit | 0:0f88b99a97ce | 243 | float Madgwick::invSqrt(float x){ |
771_8bit | 0:0f88b99a97ce | 244 | unsigned int i = 0x5F1F1412 - (*(unsigned int*)&x >> 1); |
771_8bit | 0:0f88b99a97ce | 245 | float tmp = *(float*)&i; |
771_8bit | 0:0f88b99a97ce | 246 | return tmp * (1.69000231f - 0.714158168f * x * tmp * tmp); |
771_8bit | 0:0f88b99a97ce | 247 | } |
771_8bit | 0:0f88b99a97ce | 248 | |
771_8bit | 0:0f88b99a97ce | 249 | //------------------------------------------------------------------------------------------- |
771_8bit | 0:0f88b99a97ce | 250 | |
771_8bit | 0:0f88b99a97ce | 251 | void Madgwick::computeAngles() |
771_8bit | 0:0f88b99a97ce | 252 | { |
771_8bit | 0:0f88b99a97ce | 253 | roll = atan2f(q0*q1 + q2*q3, 0.5f - q1*q1 - q2*q2); |
771_8bit | 0:0f88b99a97ce | 254 | pitch = asinf(-2.0f * (q1*q3 - q0*q2)); |
771_8bit | 0:0f88b99a97ce | 255 | yaw = atan2f(q1*q2 + q0*q3, 0.5f - q2*q2 - q3*q3); |
771_8bit | 0:0f88b99a97ce | 256 | anglesComputed = 1; |
771_8bit | 0:0f88b99a97ce | 257 | } |