arm_cos_q15.c
Go to the documentation of this file.
00001 /* ---------------------------------------------------------------------- 00002 * Copyright (C) 2011 ARM Limited. All rights reserved. 00003 * 00004 * $Date: 15. December 2011 00005 * $Revision: V2.0.0 00006 * 00007 * Project: Cortex-R DSP Library 00008 * Title: arm_cos_q15.c 00009 * 00010 * Description: Fast cosine calculation for Q15 values. 00011 * 00012 * Target Processor: Cortex-R4/R5 00013 * 00014 * Version 1.0.0 2011/03/08 00015 * Alpha release. 00016 * 00017 * Version 1.0.1 2011/09/30 00018 * Beta release. 00019 * 00020 * Version 2.0.0 2011/12/15 00021 * Final release. 00022 * 00023 * -------------------------------------------------------------------- */ 00024 #include "arm_math.h" 00025 00054 static const q15_t cosTableQ15[259] = { 00055 0x7ff6, 0x7fff, 0x7ff6, 0x7fd9, 0x7fa7, 0x7f62, 0x7f0a, 0x7e9d, 00056 0x7e1e, 0x7d8a, 0x7ce4, 0x7c2a, 0x7b5d, 0x7a7d, 0x798a, 0x7885, 00057 0x776c, 0x7642, 0x7505, 0x73b6, 0x7255, 0x70e3, 0x6f5f, 0x6dca, 00058 0x6c24, 0x6a6e, 0x68a7, 0x66d0, 0x64e9, 0x62f2, 0x60ec, 0x5ed7, 00059 0x5cb4, 0x5a82, 0x5843, 0x55f6, 0x539b, 0x5134, 0x4ec0, 0x4c40, 00060 0x49b4, 0x471d, 0x447b, 0x41ce, 0x3f17, 0x3c57, 0x398d, 0x36ba, 00061 0x33df, 0x30fc, 0x2e11, 0x2b1f, 0x2827, 0x2528, 0x2224, 0x1f1a, 00062 0x1c0c, 0x18f9, 0x15e2, 0x12c8, 0xfab, 0xc8c, 0x96b, 0x648, 00063 0x324, 0x0, 0xfcdc, 0xf9b8, 0xf695, 0xf374, 0xf055, 0xed38, 00064 0xea1e, 0xe707, 0xe3f4, 0xe0e6, 0xdddc, 0xdad8, 0xd7d9, 0xd4e1, 00065 0xd1ef, 0xcf04, 0xcc21, 0xc946, 0xc673, 0xc3a9, 0xc0e9, 0xbe32, 00066 0xbb85, 0xb8e3, 0xb64c, 0xb3c0, 0xb140, 0xaecc, 0xac65, 0xaa0a, 00067 0xa7bd, 0xa57e, 0xa34c, 0xa129, 0x9f14, 0x9d0e, 0x9b17, 0x9930, 00068 0x9759, 0x9592, 0x93dc, 0x9236, 0x90a1, 0x8f1d, 0x8dab, 0x8c4a, 00069 0x8afb, 0x89be, 0x8894, 0x877b, 0x8676, 0x8583, 0x84a3, 0x83d6, 00070 0x831c, 0x8276, 0x81e2, 0x8163, 0x80f6, 0x809e, 0x8059, 0x8027, 00071 0x800a, 0x8000, 0x800a, 0x8027, 0x8059, 0x809e, 0x80f6, 0x8163, 00072 0x81e2, 0x8276, 0x831c, 0x83d6, 0x84a3, 0x8583, 0x8676, 0x877b, 00073 0x8894, 0x89be, 0x8afb, 0x8c4a, 0x8dab, 0x8f1d, 0x90a1, 0x9236, 00074 0x93dc, 0x9592, 0x9759, 0x9930, 0x9b17, 0x9d0e, 0x9f14, 0xa129, 00075 0xa34c, 0xa57e, 0xa7bd, 0xaa0a, 0xac65, 0xaecc, 0xb140, 0xb3c0, 00076 0xb64c, 0xb8e3, 0xbb85, 0xbe32, 0xc0e9, 0xc3a9, 0xc673, 0xc946, 00077 0xcc21, 0xcf04, 0xd1ef, 0xd4e1, 0xd7d9, 0xdad8, 0xdddc, 0xe0e6, 00078 0xe3f4, 0xe707, 0xea1e, 0xed38, 0xf055, 0xf374, 0xf695, 0xf9b8, 00079 0xfcdc, 0x0, 0x324, 0x648, 0x96b, 0xc8c, 0xfab, 0x12c8, 00080 0x15e2, 0x18f9, 0x1c0c, 0x1f1a, 0x2224, 0x2528, 0x2827, 0x2b1f, 00081 0x2e11, 0x30fc, 0x33df, 0x36ba, 0x398d, 0x3c57, 0x3f17, 0x41ce, 00082 0x447b, 0x471d, 0x49b4, 0x4c40, 0x4ec0, 0x5134, 0x539b, 0x55f6, 00083 0x5843, 0x5a82, 0x5cb4, 0x5ed7, 0x60ec, 0x62f2, 0x64e9, 0x66d0, 00084 0x68a7, 0x6a6e, 0x6c24, 0x6dca, 0x6f5f, 0x70e3, 0x7255, 0x73b6, 00085 0x7505, 0x7642, 0x776c, 0x7885, 0x798a, 0x7a7d, 0x7b5d, 0x7c2a, 00086 0x7ce4, 0x7d8a, 0x7e1e, 0x7e9d, 0x7f0a, 0x7f62, 0x7fa7, 0x7fd9, 00087 0x7ff6, 0x7fff, 0x7ff6 00088 }; 00089 00090 00099 q15_t arm_cos_q15( 00100 q15_t x) 00101 { 00102 q31_t cosVal; /* Temporary variable for output */ 00103 q15_t *tablePtr; /* Pointer to table */ 00104 q15_t in, in2; /* Temporary variables for input */ 00105 q31_t wa, wb, wc, wd; /* Cubic interpolation coefficients */ 00106 q15_t a, b, c, d; /* Four nearest output values */ 00107 q15_t fract, fractCube, fractSquare; /* Variables for fractional value */ 00108 q15_t oneBy6 = 0x1555; /* Fixed point value of 1/6 */ 00109 q15_t tableSpacing = TABLE_SPACING_Q15; /* Table spacing */ 00110 int32_t index; /* Index variable */ 00111 00112 in = x; 00113 00114 /* Calculate the nearest index */ 00115 index = (uint32_t) in / (uint32_t) tableSpacing; 00116 00117 /* Calculate the nearest value of input */ 00118 in2 = (q15_t) index *tableSpacing; 00119 00120 /* Calculation of fractional value */ 00121 fract = (in - in2) << 8; 00122 00123 /* fractSquare = fract * fract */ 00124 fractSquare = (q15_t) ((fract * fract) >> 15); 00125 00126 /* fractCube = fract * fract * fract */ 00127 fractCube = (q15_t) ((fractSquare * fract) >> 15); 00128 00129 /* Initialise table pointer */ 00130 tablePtr = (q15_t *) & cosTableQ15[index]; 00131 00132 /* Cubic interpolation process */ 00133 /* Calculation of wa */ 00134 /* wa = -(oneBy6)*fractCube + (fractSquare >> 1u) - (0x2AAA)*fract; */ 00135 wa = (q31_t) oneBy6 *fractCube; 00136 wa += (q31_t) 0x2AAA * fract; 00137 00138 /* Calculation of wb */ 00139 wb = (((fractCube >> 1u) - fractSquare) - (fract >> 1u)) + 0x7FFF; 00140 00141 wa = -(wa >> 15); 00142 wa += (fractSquare >> 1u); 00143 00144 /* Read first nearest value of output from the cos table */ 00145 a = tablePtr[0]; 00146 00147 /* cosVal = a * wa */ 00148 cosVal = a * wa; 00149 00150 /* Read second nearest value of output from the cos table */ 00151 b = tablePtr[1]; 00152 00153 /* cosVal += b*wb */ 00154 cosVal += b * wb; 00155 00156 /* Calculation of wc */ 00157 wc = -(q31_t) fractCube + fractSquare; 00158 wc = (wc >> 1u) + fract; 00159 00160 /* Read third nearest value of output from the cos table */ 00161 c = tablePtr[2]; 00162 00163 /* cosVal += c*wc */ 00164 cosVal += c * wc; 00165 00166 /* Calculation of wd */ 00167 /* wd = (oneBy6)*fractCube - (oneBy6)*fract; */ 00168 fractCube = fractCube - fract; 00169 wd = ((q15_t) (((q31_t) oneBy6 * fractCube) >> 15)); 00170 00171 /* Read fourth nearest value of output from the cos table */ 00172 d = tablePtr[3]; 00173 00174 /* cosVal += d*wd; */ 00175 cosVal += d * wd; 00176 00177 /* Return the output value in 1.15(q15) format */ 00178 return ((q15_t) (cosVal >> 15u)); 00179 00180 } 00181
