102 lines
2.5 KiB
C
102 lines
2.5 KiB
C
/*
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* Copyright (c) 2011 Broadcom Corporation
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
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* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <linux/module.h>
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#include <linux/cordic.h>
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#define CORDIC_ANGLE_GEN 39797
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#define CORDIC_PRECISION_SHIFT 16
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#define CORDIC_NUM_ITER (CORDIC_PRECISION_SHIFT + 2)
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#define FIXED(X) ((s32)((X) << CORDIC_PRECISION_SHIFT))
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#define FLOAT(X) (((X) >= 0) \
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? ((((X) >> (CORDIC_PRECISION_SHIFT - 1)) + 1) >> 1) \
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: -((((-(X)) >> (CORDIC_PRECISION_SHIFT - 1)) + 1) >> 1))
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static const s32 arctan_table[] = {
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2949120,
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1740967,
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919879,
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466945,
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234379,
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117304,
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58666,
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29335,
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14668,
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7334,
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3667,
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1833,
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917,
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458,
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229,
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115,
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57,
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29
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};
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/*
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* cordic_calc_iq() - calculates the i/q coordinate for given angle
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*
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* theta: angle in degrees for which i/q coordinate is to be calculated
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* coord: function output parameter holding the i/q coordinate
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*/
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struct cordic_iq cordic_calc_iq(s32 theta)
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{
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struct cordic_iq coord;
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s32 angle, valtmp;
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unsigned iter;
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int signx = 1;
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int signtheta;
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coord.i = CORDIC_ANGLE_GEN;
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coord.q = 0;
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angle = 0;
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theta = FIXED(theta);
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signtheta = (theta < 0) ? -1 : 1;
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theta = ((theta + FIXED(180) * signtheta) % FIXED(360)) -
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FIXED(180) * signtheta;
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if (FLOAT(theta) > 90) {
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theta -= FIXED(180);
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signx = -1;
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} else if (FLOAT(theta) < -90) {
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theta += FIXED(180);
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signx = -1;
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}
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for (iter = 0; iter < CORDIC_NUM_ITER; iter++) {
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if (theta > angle) {
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valtmp = coord.i - (coord.q >> iter);
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coord.q += (coord.i >> iter);
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angle += arctan_table[iter];
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} else {
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valtmp = coord.i + (coord.q >> iter);
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coord.q -= (coord.i >> iter);
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angle -= arctan_table[iter];
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}
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coord.i = valtmp;
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}
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coord.i *= signx;
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coord.q *= signx;
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return coord;
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}
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EXPORT_SYMBOL(cordic_calc_iq);
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MODULE_DESCRIPTION("CORDIC algorithm");
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MODULE_AUTHOR("Broadcom Corporation");
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MODULE_LICENSE("Dual BSD/GPL");
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