| Arend van Spriel | 10f8113 | 2011-05-31 11:22:16 +0200 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2011 Broadcom Corporation |
| 3 | * |
| 4 | * Permission to use, copy, modify, and/or distribute this software for any |
| 5 | * purpose with or without fee is hereby granted, provided that the above |
| 6 | * copyright notice and this permission notice appear in all copies. |
| 7 | * |
| 8 | * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES |
| 9 | * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
| 10 | * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY |
| 11 | * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
| 12 | * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION |
| 13 | * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN |
| 14 | * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
| 15 | */ |
| 16 | #include <linux/module.h> |
| 17 | #include <linux/cordic.h> |
| 18 | |
| 19 | #define CORDIC_ANGLE_GEN 39797 |
| 20 | #define CORDIC_PRECISION_SHIFT 16 |
| 21 | #define CORDIC_NUM_ITER (CORDIC_PRECISION_SHIFT + 2) |
| 22 | |
| 23 | #define FIXED(X) ((s32)((X) << CORDIC_PRECISION_SHIFT)) |
| 24 | #define FLOAT(X) (((X) >= 0) \ |
| 25 | ? ((((X) >> (CORDIC_PRECISION_SHIFT - 1)) + 1) >> 1) \ |
| 26 | : -((((-(X)) >> (CORDIC_PRECISION_SHIFT - 1)) + 1) >> 1)) |
| 27 | |
| 28 | static const s32 arctan_table[] = { |
| 29 | 2949120, |
| 30 | 1740967, |
| 31 | 919879, |
| 32 | 466945, |
| 33 | 234379, |
| 34 | 117304, |
| 35 | 58666, |
| 36 | 29335, |
| 37 | 14668, |
| 38 | 7334, |
| 39 | 3667, |
| 40 | 1833, |
| 41 | 917, |
| 42 | 458, |
| 43 | 229, |
| 44 | 115, |
| 45 | 57, |
| 46 | 29 |
| 47 | }; |
| 48 | |
| 49 | /* |
| 50 | * cordic_calc_iq() - calculates the i/q coordinate for given angle |
| 51 | * |
| 52 | * theta: angle in degrees for which i/q coordinate is to be calculated |
| 53 | * coord: function output parameter holding the i/q coordinate |
| 54 | */ |
| 55 | struct cordic_iq cordic_calc_iq(s32 theta) |
| 56 | { |
| 57 | struct cordic_iq coord; |
| 58 | s32 angle, valtmp; |
| 59 | unsigned iter; |
| 60 | int signx = 1; |
| 61 | int signtheta; |
| 62 | |
| 63 | coord.i = CORDIC_ANGLE_GEN; |
| 64 | coord.q = 0; |
| 65 | angle = 0; |
| 66 | |
| 67 | theta = FIXED(theta); |
| 68 | signtheta = (theta < 0) ? -1 : 1; |
| 69 | theta = ((theta + FIXED(180) * signtheta) % FIXED(360)) - |
| 70 | FIXED(180) * signtheta; |
| 71 | |
| 72 | if (FLOAT(theta) > 90) { |
| 73 | theta -= FIXED(180); |
| 74 | signx = -1; |
| 75 | } else if (FLOAT(theta) < -90) { |
| 76 | theta += FIXED(180); |
| 77 | signx = -1; |
| 78 | } |
| 79 | |
| 80 | for (iter = 0; iter < CORDIC_NUM_ITER; iter++) { |
| 81 | if (theta > angle) { |
| 82 | valtmp = coord.i - (coord.q >> iter); |
| 83 | coord.q += (coord.i >> iter); |
| 84 | angle += arctan_table[iter]; |
| 85 | } else { |
| 86 | valtmp = coord.i + (coord.q >> iter); |
| 87 | coord.q -= (coord.i >> iter); |
| 88 | angle -= arctan_table[iter]; |
| 89 | } |
| 90 | coord.i = valtmp; |
| 91 | } |
| 92 | |
| 93 | coord.i *= signx; |
| 94 | coord.q *= signx; |
| 95 | return coord; |
| 96 | } |
| 97 | EXPORT_SYMBOL(cordic_calc_iq); |
| 98 | |
| 99 | MODULE_DESCRIPTION("Cordic functions"); |
| 100 | MODULE_AUTHOR("Broadcom Corporation"); |
| 101 | MODULE_LICENSE("Dual BSD/GPL"); |