Mercurial > public > hwos_code
annotate src/compass.c @ 625:5c2ca77ce2df
doc update (Byte 59)
| author | heinrichsweikamp |
|---|---|
| date | Sun, 23 Jun 2019 13:29:17 +0200 |
| parents | 1ad0531e9078 |
| children | c40025d8e750 |
| rev | line source |
|---|---|
|
282
7d9edd3b8c86
Make a more compact COMPASS calibration code (<7KB), and add more tests.
jDG
parents:
214
diff
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:
214
diff
changeset
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2 /// compass.c |
| 604 | 3 /// Compute north direction from magnetic/acceleration measures |
| 4 /// | |
|
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Make a more compact COMPASS calibration code (<7KB), and add more tests.
jDG
parents:
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5 /// Copyright (c) 2012-2015, JD Gascuel, HeinrichsWeikamp, all right reserved. |
| 0 | 6 ////////////////////////////////////////////////////////////////////////////// |
| 7 // HISTORY | |
| 8 // 2012-12-01 [jDG] Creation | |
| 9 // 2012-12-23 [jDG] Added filtering. | |
| 10 // 2012-12-30 [jDG] Added calibration (spherical best fit). | |
|
282
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Make a more compact COMPASS calibration code (<7KB), and add more tests.
jDG
parents:
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changeset
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11 // 2015-05-22 [jDG] Minor cleanups. Smaller calibration code. |
| 0 | 12 |
| 13 #include "compass.h" | |
| 14 | |
| 15 ////////////////////////////////////////////////////////////////////////////// | |
| 604 | 16 // mH: crude work-around, needs to be fixed up |
| 0 | 17 #ifndef UNIX |
| 604 | 18 # pragma udata overlay bank8=0x800 |
| 19 static char C_STACK[256]; // overlay C-code data stack here | |
| 20 # define RESET_C_STACK \ | |
| 21 _asm \ | |
| 22 LFSR 1, 0x800 \ | |
| 23 LFSR 2, 0x800 \ | |
| 24 _endasm | |
| 25 # pragma udata overlay bank9_compass | |
| 26 # pragma code compass_run | |
| 0 | 27 #else |
| 604 | 28 # define RESET_C_STACK |
| 0 | 29 #endif |
| 30 | |
| 31 ////////////////////////////////////////////////////////////////////////////// | |
| 32 // fifth order of polynomial approximation of atan(), giving 0.05 deg max error | |
| 33 // | |
| 604 | 34 #define K1 (5701) // needs K1/2**16 |
| 35 #define K2 (1645) // needs K2/2**48 WAS NEGATIV | |
| 36 #define K3 ( 446) // needs K3/2**80 | |
| 37 | |
| 0 | 38 |
| 39 ////////////////////////////////////////////////////////////////////////////// | |
| 604 | 40 // Interface to assembler multiplies |
| 41 | |
| 0 | 42 Int16 umul(PARAMETER Int16 a, PARAMETER Int16 b) |
| 43 { | |
| 604 | 44 extern Int16 compass_umul(void); |
| 45 extern Int16 compass_a, compass_b; | |
| 46 compass_a = a; | |
| 47 compass_b = b; | |
| 48 return compass_umul(); | |
| 0 | 49 } |
| 50 | |
| 51 Int16 imul(PARAMETER Int16 a, PARAMETER Int16 b) | |
| 52 { | |
| 604 | 53 extern Int16 compass_imul(void); |
| 54 extern Int16 compass_a, compass_b; | |
| 55 compass_a = a; | |
| 56 compass_b = b; | |
| 57 return compass_imul(); | |
| 0 | 58 } |
| 59 | |
| 60 ////////////////////////////////////////////////////////////////////////////// | |
| 61 /// Returns a / b * 2**16 | |
| 62 /// | |
| 604 | 63 /// A 16/16 -> 16 bits divide, returning a scaled result. |
| 0 | 64 /// Used to multiply fractional numbers in the range 0..1, |
| 65 /// represented as 0..32767. | |
| 604 | 66 |
| 0 | 67 Int16 udiv(PARAMETER Int16 a, PARAMETER Int16 b) |
| 68 { | |
| 604 | 69 OVERLAY Int16 d, r; |
| 620 | 70 OVERLAY char failsafe=250; |
| 71 | |
| 604 | 72 //---- Pre-scale both numerator and denominator -------------------------- |
| 73 while( (((a>>8) | (b>>8)) & 0xC0) == 0 ) | |
| 74 { | |
| 620 | 75 failsafe--; |
| 621 | 76 if (failsafe==0) break; |
| 604 | 77 a <<= 1; |
| 78 b <<= 1; | |
| 79 } | |
| 0 | 80 |
| 604 | 81 //---- Make division trials ---------------------------------------------- |
| 82 d = 0x4000; // start with 0.5, because 1.0 is sign bit | |
| 83 b >>= 1; // hence pre-shift b | |
| 84 r = 0; | |
| 85 do { | |
| 86 if( a >= b ) // a is big enough ? | |
| 87 { | |
| 88 a -= b; // then count d times b out of it | |
| 89 r |= d; // and accumulate that bit | |
| 90 } | |
| 91 b >>= 1; // then loop trying twice smaller | |
| 92 d >>= 1; | |
| 93 } while( b ); | |
| 94 return r; | |
| 0 | 95 } |
| 96 | |
| 97 ////////////////////////////////////////////////////////////////////////////// | |
| 98 /// Computes atan(y/x) in Angle, for x, y in range 0..32767 | |
| 99 /// | |
| 100 /// Results a single quadrant Angle, in the range 0 .. Q_PI/2 | |
| 604 | 101 |
| 0 | 102 Angle utan(PARAMETER Int16 y, PARAMETER Int16 x) |
| 103 { | |
| 604 | 104 OVERLAY Int16 ratio, angle, x2, x3; |
| 0 | 105 |
| 604 | 106 //---- Handle zero divisor ----------------------------------------------- |
| 107 if( x == 0 ) | |
| 108 return (y == 0) ? 0 : Q_PIO2; | |
| 0 | 109 |
| 604 | 110 //---- Make it half-quadrant : 0 .. 45 deg ------------------------------- |
| 111 ratio = (x > y) ? udiv(y, x) : udiv(x, y); | |
| 0 | 112 |
| 604 | 113 //---- Then apply the polynomial approximation --------------------------- |
| 114 angle = umul(K1, ratio); // r*K1 / 2**16 | |
| 115 x2 = umul(ratio, ratio); // r**2 / 2**16 | |
| 116 x3 = umul(x2, ratio); // r**3 / 2**32 | |
| 117 angle -= umul(x3, K2); // K2*r**3 / 2**48: NEGATIV. | |
| 0 | 118 |
| 604 | 119 x3 = umul(x3, x2); // r**5 / 2**64 |
| 120 angle += umul(x3, K3); // K3*r**5 / 2**80 | |
| 0 | 121 |
| 604 | 122 //---- Recover the full quadrant ----------------------------------------- |
| 123 return (x < y) ? (Angle)(Q_PIO2 - angle) | |
| 124 : (Angle)(angle); | |
| 0 | 125 } |
| 126 | |
| 127 ////////////////////////////////////////////////////////////////////////////// | |
| 128 /// Computes atan2(y/x) in Angle, for x, y in range -32768 to 32767 | |
| 129 /// | |
| 130 /// Results a four quadrant Angle, in the range -Q_PI .. +Q_PI | |
| 604 | 131 |
| 0 | 132 Angle itan(PARAMETER Int16 y, PARAMETER Int16 x) |
| 133 { | |
| 604 | 134 // Beware: -32768 is not properly handled (sign error) |
| 135 if( x == -32768 ) x = -32767; | |
| 136 if( y == -32768 ) y = -32767; | |
| 0 | 137 |
| 604 | 138 if( x >= 0 ) |
| 139 if( y >= 0 ) // first quadrant: 0..90 deg. | |
| 140 return utan(y,x); | |
| 141 else // fourth quadrant: 0..-90 deg | |
| 142 return -utan(-y,x); | |
| 143 else | |
| 144 if( y >= 0 ) // second quadrant: 90..180 deg | |
| 145 return Q_PI - utan(y, -x); | |
| 146 else // third quadrant: -90..-180 deg; | |
| 147 return -Q_PI + utan(-y, -x); | |
| 0 | 148 } |
| 149 | |
| 150 ////////////////////////////////////////////////////////////////////////////// | |
| 151 /// Computes cos(theta) = sqrtf(x2/h2), | |
| 152 /// when theta = atan(y/x) and h2=x*x+y*y | |
| 153 /// | |
| 604 | 154 |
| 0 | 155 Int16 cosxh(PARAMETER Int16 x2, PARAMETER Int16 h2) |
| 156 { | |
| 604 | 157 OVERLAY Int16 r = 0; |
| 158 OVERLAY Int16 d = 0x4000; | |
| 0 | 159 |
| 604 | 160 do { |
| 161 OVERLAY Int16 a = r + d; | |
| 162 a = umul(a, a); | |
| 163 a = umul(a, h2); | |
| 164 if( a <= x2 ) r += d; | |
| 165 d >>= 1; | |
| 166 } while( d ); | |
| 0 | 167 |
| 604 | 168 return r; |
| 0 | 169 } |
| 170 | |
| 171 ////////////////////////////////////////////////////////////////////////////// | |
| 172 /// Computes both sin and cos of angle y/x, | |
| 173 /// with h = sqrt(x**2+y**2). | |
| 174 /// | |
| 604 | 175 |
| 0 | 176 void sincos(PARAMETER Int16 x, PARAMETER Int16 y, Int16* sin, Int16* cos) |
| 177 { | |
| 604 | 178 OVERLAY Int16 x2, y2, h2; |
| 621 | 179 OVERLAY char failsafe=250; |
| 180 | |
| 604 | 181 //---- Fold into one quadant --------------------------------------------- |
| 182 OVERLAY char neg = 0; | |
| 183 if( x < 0 ) | |
| 184 { | |
| 185 neg |= 1; | |
| 186 x = -x; | |
| 187 } | |
| 188 if( y < 0 ) | |
| 189 { | |
| 190 neg |= 2; | |
| 191 y = -y; | |
| 192 } | |
| 621 | 193 |
| 194 //---- Pre-scale both numerator and denominator ---------------------- | |
| 604 | 195 while( (((x>>8) | (y>>8)) & 0xE0) == 0 ) |
| 196 { | |
| 620 | 197 failsafe--; |
| 621 | 198 if (failsafe==0) break; |
| 604 | 199 x <<= 1; |
| 200 y <<= 1; | |
| 201 } | |
| 0 | 202 |
| 604 | 203 //---- Uses trig() to do the stuff one on quadrant ------------------- |
| 204 x2 = umul(x,x); | |
| 205 y2 = umul(y,y); | |
| 206 h2 = x2 + y2; | |
| 207 x2 = cosxh(x2, h2); | |
| 0 | 208 |
| 604 | 209 //---- Results back in four quadrants -------------------------------- |
| 210 *cos = (neg & 1) ? -x2 : x2; | |
| 211 y2 = cosxh(y2, h2); | |
| 212 *sin = (neg & 2) ? -y2 : y2; | |
| 0 | 213 } |
| 214 | |
| 215 ////////////////////////////////////////////////////////////////////////////// | |
| 216 // | |
| 217 | |
| 218 void compass(void) | |
| 219 { | |
| 604 | 220 OVERLAY Int16 sin, cos; |
| 221 OVERLAY Int16 iBfx, iBfy, Gz; | |
| 222 OVERLAY Int16 iBpx, iBpy, iBpz; | |
| 223 | |
| 224 RESET_C_STACK; | |
| 0 | 225 |
| 604 | 226 //---- Make hard iron correction ----------------------------------------- |
| 227 // Measured magnetometer orientation, measured ok | |
| 228 // From matthias drawing: (X,Y,Z) --> (X,Y,Z) : no rotation | |
| 229 iBpx = compass_DX_f - compass_CX_f; // X | |
| 230 iBpy = compass_DY_f - compass_CY_f; // Y | |
| 231 iBpz = compass_DZ_f - compass_CZ_f; // Z | |
| 0 | 232 |
| 604 | 233 //---- Calculate sine and cosine of roll angle Phi ----------------------- |
| 234 sincos(accel_DZ_f, accel_DY_f, &sin, &cos); | |
| 0 | 235 |
| 604 | 236 //---- rotate by roll angle (-Phi) --------------------------------------- |
| 237 iBfy = imul(iBpy, cos) - imul(iBpz, sin); | |
| 238 iBpz = imul(iBpy, sin) + imul(iBpz, cos); | |
| 239 Gz = imul(accel_DY_f, sin) + imul(accel_DZ_f, cos); | |
| 0 | 240 |
| 604 | 241 //---- calculate sin and cosine of pitch angle Theta --------------------- |
| 242 sincos(Gz, -accel_DX_f, &sin, &cos); // NOTE: changed sin sign | |
| 0 | 243 |
| 604 | 244 /* correct cosine if pitch not in range -90 to 90 degrees */ |
| 245 if( cos < 0 ) cos = -cos; | |
| 0 | 246 |
| 604 | 247 ///---- de-rotate by pitch angle Theta ----------------------------------- |
| 248 iBfx = imul(iBpx, cos) + imul(iBpz, sin); | |
| 0 | 249 |
| 604 | 250 //---- Detect uncalibrated compass --------------------------------------- |
| 251 if( !compass_CX_f && !compass_CY_f && !compass_CZ_f ) | |
| 252 { | |
| 253 compass_heading = -1; | |
| 254 return; | |
| 255 } | |
| 0 | 256 |
| 604 | 257 //---- calculate current yaw = e-compass angle Psi ----------------------- |
| 258 // Result in degree (no need of 0.01 deg precision... | |
| 259 compass_heading = itan(-iBfy, iBfx) / 100; | |
| 0 | 260 |
| 604 | 261 // Result in 0..360 range: |
| 262 if( compass_heading < 0 ) | |
| 263 compass_heading += 360; | |
| 0 | 264 } |