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annotate src/compass.c @ 389:9175429bdeba
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| author | heinrichsweikamp |
|---|---|
| date | Tue, 27 Oct 2015 13:45:10 +0100 |
| parents | 7d9edd3b8c86 |
| children | ca4556fb60b9 |
| rev | line source |
|---|---|
|
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7d9edd3b8c86
Make a more compact COMPASS calibration code (<7KB), and add more tests.
jDG
parents:
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changeset
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1 ////////////////////////////////////////////////////////////////////////////// |
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7d9edd3b8c86
Make a more compact COMPASS calibration code (<7KB), and add more tests.
jDG
parents:
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2 /// compass.c |
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7d9edd3b8c86
Make a more compact COMPASS calibration code (<7KB), and add more tests.
jDG
parents:
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3 /// Compute north direction from magnetic/acceleration measures. |
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7d9edd3b8c86
Make a more compact COMPASS calibration code (<7KB), and add more tests.
jDG
parents:
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4 /// Copyright (c) 2012-2015, JD Gascuel, HeinrichsWeikamp, all right reserved. |
| 0 | 5 ////////////////////////////////////////////////////////////////////////////// |
| 6 // HISTORY | |
| 7 // 2012-12-01 [jDG] Creation | |
| 8 // 2012-12-23 [jDG] Added filtering. | |
| 9 // 2012-12-30 [jDG] Added calibration (spherical best fit). | |
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Make a more compact COMPASS calibration code (<7KB), and add more tests.
jDG
parents:
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10 // 2015-05-22 [jDG] Minor cleanups. Smaller calibration code. |
| 0 | 11 |
| 12 #include "compass.h" | |
| 13 | |
| 14 ////////////////////////////////////////////////////////////////////////////// | |
| 15 // mH: Crude work-around, needs to be made right | |
| 16 #ifndef UNIX | |
| 17 # pragma udata overlay bank8=0x800 | |
| 18 static char C_STACK[256]; // Overlay C-code data stack here. | |
| 19 # define RESET_C_STACK \ | |
| 20 _asm \ | |
| 21 LFSR 1, 0x800 \ | |
| 22 LFSR 2, 0x800 \ | |
| 23 _endasm | |
| 24 # pragma udata overlay bank9_compass | |
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Make a more compact COMPASS calibration code (<7KB), and add more tests.
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parents:
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25 # pragma code compass_run |
| 0 | 26 #else |
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282
7d9edd3b8c86
Make a more compact COMPASS calibration code (<7KB), and add more tests.
jDG
parents:
214
diff
changeset
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27 # define RESET_C_STACK |
| 0 | 28 #endif |
| 29 | |
| 30 ////////////////////////////////////////////////////////////////////////////// | |
| 31 // fifth order of polynomial approximation of atan(), giving 0.05 deg max error | |
| 32 // | |
| 33 #define K1 (5701) // Needs K1/2**16 | |
| 34 #define K2 (1645) // Needs K2/2**48 WAS NEGATIV | |
| 35 #define K3 ( 446) // Needs K3/2**80 | |
| 36 | |
| 37 ////////////////////////////////////////////////////////////////////////////// | |
| 38 // Interface to assembleur multiplies | |
| 39 Int16 umul(PARAMETER Int16 a, PARAMETER Int16 b) | |
| 40 { | |
| 41 extern Int16 compass_umul(void); | |
| 42 extern Int16 compass_a, compass_b; | |
| 43 compass_a = a; | |
| 44 compass_b = b; | |
| 45 return compass_umul(); | |
| 46 } | |
| 47 | |
| 48 Int16 imul(PARAMETER Int16 a, PARAMETER Int16 b) | |
| 49 { | |
| 50 extern Int16 compass_imul(void); | |
| 51 extern Int16 compass_a, compass_b; | |
| 52 compass_a = a; | |
| 53 compass_b = b; | |
| 54 return compass_imul(); | |
| 55 } | |
| 56 | |
| 57 ////////////////////////////////////////////////////////////////////////////// | |
| 58 /// Returns a / b * 2**16 | |
| 59 /// | |
| 60 /// A 16/16 -> 16 bits divide, returning a scalled result. | |
| 61 /// Used to multiply fractional numbers in the range 0..1, | |
| 62 /// represented as 0..32767. | |
| 63 Int16 udiv(PARAMETER Int16 a, PARAMETER Int16 b) | |
| 64 { | |
| 65 OVERLAY Int16 d, r; | |
| 66 | |
| 67 //---- Pre-scale both numerator and denominator -------------------------- | |
| 68 while( (((a>>8) | (b>>8)) & 0xC0) == 0 ) | |
| 69 { | |
| 70 a <<= 1; | |
| 71 b <<= 1; | |
| 72 } | |
| 73 | |
| 74 //---- Make division trials ---------------------------------------------- | |
| 75 d = 0x4000; // Starts with 0.5, because 1.0 is sign bit. | |
| 76 b >>= 1; // Hence pre-shift b. | |
| 77 r = 0; | |
| 78 do { | |
| 79 if( a >= b ) { // a is big enough ? | |
| 80 a -= b; // then count d times b out of it. | |
| 81 r |= d; // and accumulate that bit. | |
| 82 } | |
| 83 b >>= 1; // then loop trying twice smaller. | |
| 84 d >>= 1; | |
| 85 } while( b ); | |
| 86 return r; | |
| 87 } | |
| 88 | |
| 89 ////////////////////////////////////////////////////////////////////////////// | |
| 90 /// Computes atan(y/x) in Angle, for x, y in range 0..32767 | |
| 91 /// | |
| 92 /// Results a single quadrant Angle, in the range 0 .. Q_PI/2 | |
| 93 Angle utan(PARAMETER Int16 y, PARAMETER Int16 x) | |
| 94 { | |
| 95 OVERLAY Int16 ratio, angle, x2, x3; | |
| 96 | |
| 97 //---- Handle zero divisor ----------------------------------------------- | |
| 98 if( x == 0 ) | |
| 99 return (y == 0) ? 0 : Q_PIO2; | |
| 100 | |
| 101 //---- Make it half-quadrant : 0 .. 45 deg ------------------------------- | |
| 102 ratio = (x > y) ? udiv(y, x) : udiv(x, y); | |
| 103 | |
| 104 //---- Then apply the polynomial approximation --------------------------- | |
| 105 angle = umul(K1, ratio); // r*K1 / 2**16 | |
| 106 x2 = umul(ratio, ratio); // r**2 / 2**16 | |
| 107 x3 = umul(x2, ratio); // r**3 / 2**32 | |
| 108 angle -= umul(x3, K2); // K2*r**3 / 2**48: NEGATIV. | |
| 109 | |
| 110 x3 = umul(x3, x2); // r**5 / 2**64 | |
| 111 angle += umul(x3, K3); // K3*r**5 / 2**80 | |
| 112 | |
| 113 //---- Recover the full quadrant ----------------------------------------- | |
| 114 return (x < y) ? (Angle)(Q_PIO2 - angle) | |
| 115 : (Angle)(angle); | |
| 116 } | |
| 117 | |
| 118 ////////////////////////////////////////////////////////////////////////////// | |
| 119 /// Computes atan2(y/x) in Angle, for x, y in range -32768 to 32767 | |
| 120 /// | |
| 121 /// Results a four quadrant Angle, in the range -Q_PI .. +Q_PI | |
| 122 Angle itan(PARAMETER Int16 y, PARAMETER Int16 x) | |
| 123 { | |
| 124 // Beware: -32768 is not properly handled (sgn error). | |
| 125 if( x == -32768 ) x = -32767; | |
| 126 if( y == -32768 ) y = -32767; | |
| 127 | |
| 128 if( x >= 0 ) | |
| 129 if( y >= 0 ) // First quadrant: 0..90 deg. | |
| 130 return utan(y,x); | |
| 131 else // Fourth quadrant: 0..-90 deg | |
| 132 return -utan(-y,x); | |
| 133 else | |
| 134 if( y >= 0 ) // Second quadrant: 90..180 deg | |
| 135 return Q_PI - utan(y, -x); | |
| 136 else // Third quadrant: -90..-180 deg; | |
| 137 return -Q_PI + utan(-y, -x); | |
| 138 } | |
| 139 | |
| 140 ////////////////////////////////////////////////////////////////////////////// | |
| 141 /// Computes cos(theta) = sqrtf(x2/h2), | |
| 142 /// when theta = atan(y/x) and h2=x*x+y*y | |
| 143 /// | |
| 144 Int16 cosxh(PARAMETER Int16 x2, PARAMETER Int16 h2) | |
| 145 { | |
| 146 OVERLAY Int16 r = 0; | |
| 147 OVERLAY Int16 d = 0x4000; | |
| 148 | |
| 149 do { | |
| 150 OVERLAY Int16 a = r + d; | |
| 151 a = umul(a, a); | |
| 152 a = umul(a, h2); | |
| 153 if( a <= x2 ) r += d; | |
| 154 d >>= 1; | |
| 155 } while( d ); | |
| 156 | |
| 157 return r; | |
| 158 } | |
| 159 | |
| 160 ////////////////////////////////////////////////////////////////////////////// | |
| 161 /// Computes both sin and cos of angle y/x, | |
| 162 /// with h = sqrt(x**2+y**2). | |
| 163 /// | |
| 164 void sincos(PARAMETER Int16 x, PARAMETER Int16 y, Int16* sin, Int16* cos) | |
| 165 { | |
| 166 OVERLAY Int16 x2, y2, h2; | |
| 167 | |
| 168 //---- Fold into one quadant --------------------------------------------- | |
| 169 OVERLAY char neg = 0; | |
| 170 if( x < 0 ) | |
| 171 { | |
| 172 neg |= 1; | |
| 173 x = -x; | |
| 174 } | |
| 175 if( y < 0 ) | |
| 176 { | |
| 177 neg |= 2; | |
| 178 y = -y; | |
| 179 } | |
| 180 | |
| 181 //---- Pre-scale both numerator and denominator ---------------------- | |
| 182 while( (((x>>8) | (y>>8)) & 0xE0) == 0 ) | |
| 183 { | |
| 184 x <<= 1; | |
| 185 y <<= 1; | |
| 186 } | |
| 187 | |
| 188 //---- Uses trig() to do the stuff one on quadrant ------------------- | |
| 189 x2 = umul(x,x); | |
| 190 y2 = umul(y,y); | |
| 191 h2 = x2 + y2; | |
| 192 x2 = cosxh(x2, h2); | |
| 193 | |
| 194 //---- Results back in four quadrants -------------------------------- | |
| 195 *cos = (neg & 1) ? -x2 : x2; | |
| 196 y2 = cosxh(y2, h2); | |
| 197 *sin = (neg & 2) ? -y2 : y2; | |
| 198 } | |
| 199 | |
| 200 ////////////////////////////////////////////////////////////////////////////// | |
| 201 // | |
| 202 | |
| 203 void compass(void) | |
| 204 { | |
| 205 OVERLAY Int16 sin, cos; | |
| 206 OVERLAY Int16 iBfx, iBfy, Gz; | |
| 207 OVERLAY Int16 iBpx, iBpy, iBpz; | |
| 208 RESET_C_STACK; | |
| 209 | |
| 210 //---- Make hard iron correction ----------------------------------------- | |
| 211 // Measured magnetometer orientation, measured ok. | |
| 212 // From matthias drawing: (X,Y,Z) --> (X,Y,Z) : no rotation. | |
| 213 iBpx = compass_DX_f - compass_CX_f; // X | |
| 214 iBpy = compass_DY_f - compass_CY_f; // Y | |
| 215 iBpz = compass_DZ_f - compass_CZ_f; // Z | |
| 216 | |
| 217 //---- Calculate sine and cosine of roll angle Phi ----------------------- | |
| 218 sincos(accel_DZ_f, accel_DY_f, &sin, &cos); | |
| 219 | |
| 220 //---- rotate by roll angle (-Phi) --------------------------------------- | |
| 221 iBfy = imul(iBpy, cos) - imul(iBpz, sin); | |
| 222 iBpz = imul(iBpy, sin) + imul(iBpz, cos); | |
| 223 Gz = imul(accel_DY_f, sin) + imul(accel_DZ_f, cos); | |
| 224 | |
| 225 //---- calculate sin and cosine of pitch angle Theta --------------------- | |
| 226 sincos(Gz, -accel_DX_f, &sin, &cos); // NOTE: changed sin sign. | |
| 227 | |
| 228 /* correct cosine if pitch not in range -90 to 90 degrees */ | |
| 229 if( cos < 0 ) cos = -cos; | |
| 230 | |
| 231 ///---- de-rotate by pitch angle Theta ----------------------------------- | |
| 232 iBfx = imul(iBpx, cos) + imul(iBpz, sin); | |
| 233 | |
| 234 //---- Detect uncalibrated compass --------------------------------------- | |
| 235 if( !compass_CX_f && !compass_CY_f && !compass_CZ_f ) | |
| 236 { | |
| 237 compass_heading = -1; | |
| 238 return; | |
| 239 } | |
| 240 | |
| 241 //---- calculate current yaw = e-compass angle Psi ----------------------- | |
| 242 // Result in degree (no need of 0.01 deg precision... | |
| 243 compass_heading = itan(-iBfy, iBfx) / 100; | |
| 244 | |
| 245 // Result in 0..360 range: | |
| 246 if( compass_heading < 0 ) | |
| 247 compass_heading += 360; | |
| 248 } |