if_bwn_cordic.h

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    1 /*-
    2  * Copyright (c) 2016 Adrian Chadd <adrian@FreeBSD.org>
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer,
   10  *    without modification.
   11  * 2. Redistributions in binary form must reproduce at minimum a disclaimer
   12  *    similar to the "NO WARRANTY" disclaimer below ("Disclaimer") and any
   13  *    redistribution must be conditioned upon including a substantially
   14  *    similar Disclaimer requirement for further binary redistribution.
   15  *
   16  * NO WARRANTY
   17  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   18  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   19  * LIMITED TO, THE IMPLIED WARRANTIES OF NONINFRINGEMENT, MERCHANTIBILITY
   20  * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
   21  * THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY,
   22  * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   23  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   24  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
   25  * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   26  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
   27  * THE POSSIBILITY OF SUCH DAMAGES.
   28  *
   29  * $FreeBSD$
   30  */
   31 #ifndef __IF_BWN_CORDIC_H__
   32 #define __IF_BWN_CORDIC_H__
   33 
   34 /*
   35  * These functions are used by the PHY code.
   36  */
   37 
   38 /* Complex number using 2 32-bit signed integers */
   39 struct bwn_c32 {
   40         int32_t i;
   41         int32_t q;
   42 };
   43 
   44 #define CORDIC_CONVERT(value)   (((value) >= 0) ?       \
   45             ((((value) >> 15) + 1) >> 1) :              \
   46             -((((-(value)) >> 15) + 1) >> 1))
   47 
   48 static const uint32_t bwn_arctg[] = {
   49     2949120, 1740967, 919879, 466945, 234379, 117304, 58666, 29335, 14668,
   50     7334, 3667, 1833, 917, 458, 229, 115, 57, 29,
   51 };
   52 
   53 /* http://bcm-v4.sipsolutions.net/802.11/PHY/Cordic */
   54 static inline struct bwn_c32
   55 bwn_cordic(int theta)
   56 {
   57         uint8_t i;
   58         int32_t tmp;
   59         int8_t signx = 1;
   60         uint32_t angle = 0;
   61         struct bwn_c32 ret = { .i = 39797, .q = 0, };
   62 
   63         while (theta > (180 << 16))
   64                 theta -= (360 << 16);
   65         while (theta < -(180 << 16))
   66                 theta += (360 << 16);
   67 
   68         if (theta > (90 << 16)) {
   69                 theta -= (180 << 16);
   70                 signx = -1;
   71         } else if (theta < -(90 << 16)) {
   72                 theta += (180 << 16);
   73                 signx = -1;
   74         }
   75 
   76         for (i = 0; i <= 17; i++) {
   77                 if (theta > angle) {
   78                         tmp = ret.i - (ret.q >> i);
   79                         ret.q += ret.i >> i;
   80                         ret.i = tmp;
   81                         angle += bwn_arctg[i];
   82                 } else {
   83                         tmp = ret.i + (ret.q >> i);
   84                         ret.q -= ret.i >> i;
   85                         ret.i = tmp;
   86                         angle -= bwn_arctg[i];
   87                 }
   88         }
   89 
   90         ret.i *= signx;
   91         ret.q *= signx;
   92 
   93         return ret;
   94 }
   95 
   96 #endif  /* __IF_BWN_CORDIC_H__ */

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FreeBSD/Linux Kernel Cross Reference sys/dev/bwn/if_bwn_cordic.h

FreeBSD/Linux Kernel Cross Reference
sys/dev/bwn/if_bwn_cordic.h