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| Rev | Author | Line No. | Line |
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| 1920 | - | 1 | /****************************************************************/ |
| 2 | /* */ |
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| 3 | /* NG-Video 5,8GHz */ |
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| 4 | /* */ |
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| 5 | /* Copyright (C) 2011 - gebad */ |
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| 6 | /* */ |
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| 7 | /* This code is distributed under the GNU Public License */ |
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| 8 | /* which can be found at http://www.gnu.org/licenses/gpl.txt */ |
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| 9 | /* */ |
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| 10 | /****************************************************************/ |
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| 11 | |||
| 12 | #include <stdio.h> |
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| 13 | #include <stdlib.h> |
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| 14 | #include <math.h> |
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| 15 | #include <avr/pgmspace.h> |
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| 16 | |||
| 17 | #include "mymath.h" |
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| 18 | |||
| 19 | // http://www.mikrocontroller.net/articles/AVR_Arithmetik#avr-gcc_Implementierung_.2832_Bit.29 |
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| 20 | unsigned int sqrt32(uint32_t q) |
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| 21 | { uint16_t r, mask; |
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| 22 | uint16_t i = 8*sizeof (r) -1; |
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| 23 | |||
| 24 | r = mask = 1 << i; |
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| 25 | for (; i > 0; i--) { |
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| 26 | mask >>= 1; |
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| 27 | |||
| 28 | if (q < (uint32_t) r*r) |
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| 29 | r -= mask; |
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| 30 | else |
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| 31 | r += mask; |
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| 32 | } |
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| 33 | |||
| 34 | if (q < (uint32_t) r*r) |
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| 35 | r -= 1; |
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| 36 | |||
| 37 | return r; |
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| 38 | } |
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| 39 | |||
| 40 | // aus Orginal MK source code |
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| 41 | // sinus with argument in degree at an angular resolution of 1 degree and a discretisation of 13 bit. |
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| 42 | const uint16_t sinlookup[91] = {0, 143, 286, 429, 571, 714, 856, 998, 1140, 1282, 1423, 1563, 1703, \ |
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| 43 | 1843, 1982, 2120, 2258, 2395, 2531, 2667, 2802, 2936, 3069, 3201, 3332, \ |
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| 44 | 3462, 3591, 3719, 3846, 3972, 4096, 4219, 4341, 4462, 4581, 4699, 4815, \ |
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| 45 | 4930, 5043, 5155, 5266, 5374, 5482, 5587, 5691, 5793, 5893, 5991, 6088, \ |
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| 46 | 6183, 6275, 6366, 6455, 6542, 6627, 6710, 6791, 6870, 6947, 7022, 7094, \ |
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| 47 | 7165, 7233, 7299, 7363, 7424, 7484, 7541, 7595, 7648, 7698, 7746, 7791, \ |
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| 48 | 7834, 7875, 7913, 7949, 7982, 8013, 8041, 8068, 8091, 8112, 8131, 8147, \ |
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| 49 | 8161, 8172, 8181, 8187, 8191, 8192}; |
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| 50 | |||
| 51 | //double c_cos_8192(int16_t angle) |
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| 52 | int16_t c_cos_8192(int16_t angle) |
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| 53 | { |
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| 54 | int8_t m,n; |
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| 55 | int16_t sinus; |
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| 56 | |||
| 57 | angle = 90 - angle; |
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| 58 | // avoid negative angles |
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| 59 | if (angle < 0) |
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| 60 | { |
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| 61 | m = -1; |
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| 62 | angle = -angle; |
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| 63 | } |
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| 64 | else m = +1; |
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| 65 | |||
| 66 | // fold angle to interval 0 to 359 |
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| 67 | angle %= 360; |
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| 68 | |||
| 69 | // check quadrant |
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| 70 | if (angle <= 90) n = 1; // first quadrant |
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| 71 | else if ((angle > 90) && (angle <= 180)) {angle = 180 - angle; n = 1;} // second quadrant |
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| 72 | else if ((angle > 180) && (angle <= 270)) {angle = angle - 180; n = -1;} // third quadrant |
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| 73 | else {angle = 360 - angle; n = -1;} //fourth quadrant |
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| 74 | // get lookup value |
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| 75 | sinus = sinlookup[angle]; |
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| 76 | // calculate sinus value |
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| 77 | return (sinus * m * n); |
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| 78 | } |
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| 79 | |||
| 80 | /* ---------------------------------------------------------------------------------------------- |
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| 81 | |||
| 82 | atan2.S |
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| 83 | |||
| 84 | Author: Reiner Patommel |
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| 85 | |||
| 86 | atan2.S uses CORDIC, an algorithm which was developed in 1956 by Jack Volder. |
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| 87 | CORDIC can be used to calculate trigonometric, hyperbolic and linear |
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| 88 | functions and is until today implemented in most pocket calculators. |
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| 89 | The algorithm makes only use of simple integer arithmetic. |
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| 90 | |||
| 91 | The CORDIC equations in vectoring mode for trigonometric functions are: |
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| 92 | Xi+1 = Xi - Si * (Yi * 1 / 2^i) |
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| 93 | Yi+1 = Yi + Si * (Xi * 1 / 2^i) |
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| 94 | Zi+1 = Zi - Si * atan(1 / 2^i) |
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| 95 | where Si = +1 if Yi < 0 else Si = -1 |
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| 96 | The rotation angles are limited to -PI/2 and PI/2 i.e. |
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| 97 | -90 degrees ... +90 degrees |
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| 98 | |||
| 99 | For the calculation of atan2(x,y) we need a small pre-calculated table of |
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| 100 | angles or radians with the values Tn = atan(1/2^i). |
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| 101 | We rotate the vector(Xo,Yo) in steps to the x-axis i.e. we drive Y to 0 and |
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| 102 | accumulate the rotated angles or radians in Z. The direction of the rotation |
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| 103 | will be positive or negative depending on the sign of Y after the previous |
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| 104 | rotation and the rotation angle will decrease from step to step. (The first |
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| 105 | step is 45 degrees, the last step is 0.002036 degrees for n = 15). |
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| 106 | |||
| 107 | After n rotations the variables will have the following values: |
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| 108 | Yn = ideally 0 |
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| 109 | Xn = c*sqrt(Xo^2+Yo^2) (magnitude of the vector) |
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| 110 | Zn = Zo+atan(Yo/Xo) (accumulated rotation angles or radians) |
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| 111 | |||
| 112 | c, the cordic gain, is the product Pn of sqrt(1+2^(-2i)) and amounts to |
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| 113 | approx. 1.64676 for n = 15. |
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| 114 | |||
| 115 | In order to represent X, Y and Z as integers we introduce a scaling factor Q |
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| 116 | which is chosen as follows: |
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| 117 | 1. We normalize Xo and Yo (starting values) to be less than or equal to 1*Q and |
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| 118 | set Zo = 0 i.e. Xomax = 1*Q, Yomax = 1*Q, Zo = 0. |
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| 119 | 2. With Xo = 1*Q and Yo = 1*Q, Xn will be Xnmax = Q*c*sqrt(2) = 2.329*Q |
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| 120 | 3. In order to boost accuracy we only cover the rotation angles between 0 and PI/2 |
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| 121 | i.e. X and Z are always > 0 and therefore can be unsigned. |
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| 122 | (We do the quadrant correction afterwards based on the initial signs of x and y) |
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| 123 | 4. If X is an unsigned int, Xnmax = 65536, and Q = 65536/2.329 = 28140. |
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| 124 | i.e. |
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| 125 | Xnmax = 65536 --> unsigned int |
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| 126 | Ynmax = +/- 28140 --> signed int |
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| 127 | Znmax = PI/2 * 28140 = 44202 --> unsigned int |
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| 128 | The systematic error is 90/44202 = 0.002036 degrees or 0.0000355 rad. |
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| 129 | |||
| 130 | Below is atan2 and atan in C: */ |
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| 131 | |||
| 132 | #define getAtanVal(x) (uint16_t)pgm_read_word(&atantab[x]) |
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| 133 | |||
| 134 | uint16_t atantab[T] PROGMEM = {22101,13047,6894,3499,1756,879,440,220,110,55,27,14,7,3,2,1}; |
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| 135 | |||
| 136 | int16_t my_atan2(int32_t y, int32_t x) |
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| 137 | { unsigned char i; |
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| 138 | uint32_t xQ; |
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| 139 | int32_t yQ; |
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| 140 | uint32_t angle = 0; |
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| 141 | uint32_t tmp; |
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| 142 | double x1, y1; |
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| 143 | |||
| 144 | x1 = abs(x); |
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| 145 | y1 = abs(y); |
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| 146 | |||
| 147 | if (y1 == 0) { |
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| 148 | if (x < 0) |
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| 149 | return (180); |
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| 150 | else |
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| 151 | return 0; |
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| 152 | } |
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| 153 | |||
| 154 | if (x1 < y1) { |
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| 155 | x1 /= y1; |
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| 156 | y1 = 1; |
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| 157 | } |
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| 158 | else { |
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| 159 | y1 /= x1; |
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| 160 | x1 = 1; |
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| 161 | } |
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| 162 | |||
| 163 | xQ = SCALED(x1); |
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| 164 | yQ = SCALED(y1); |
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| 165 | |||
| 166 | for (i = 0; i < T-1; i++) { |
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| 167 | tmp = xQ >> i; |
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| 168 | if (yQ < 0) { |
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| 169 | xQ -= yQ >> i; |
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| 170 | yQ += tmp; |
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| 171 | angle -= getAtanVal(i); |
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| 172 | } |
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| 173 | else { |
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| 174 | xQ += yQ >> i; |
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| 175 | yQ -= tmp; |
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| 176 | angle += getAtanVal(i); |
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| 177 | } |
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| 178 | } |
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| 179 | |||
| 180 | angle = RAD_TO_DEG * angle/Q; |
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| 181 | if (x <= 0) |
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| 182 | angle = 180 - angle; |
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| 183 | if (y <= 0) |
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| 184 | return(-angle); |
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| 185 | return(angle); |
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| 186 | } |
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| 187 |