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Diffstat (limited to 'platform/CMSIS/DSP_Lib/Source/FastMathFunctions/arm_cos_f32.c')
| -rw-r--r-- | platform/CMSIS/DSP_Lib/Source/FastMathFunctions/arm_cos_f32.c | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/platform/CMSIS/DSP_Lib/Source/FastMathFunctions/arm_cos_f32.c b/platform/CMSIS/DSP_Lib/Source/FastMathFunctions/arm_cos_f32.c new file mode 100644 index 0000000..f483e09 --- /dev/null +++ b/platform/CMSIS/DSP_Lib/Source/FastMathFunctions/arm_cos_f32.c @@ -0,0 +1,138 @@ +/* ---------------------------------------------------------------------- +* Copyright (C) 2010-2014 ARM Limited. All rights reserved. +* +* $Date: 12. March 2014 +* $Revision: V1.4.4 +* +* Project: CMSIS DSP Library +* Title: arm_cos_f32.c +* +* Description: Fast cosine calculation for floating-point values. +* +* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 +* +* Redistribution and use in source and binary forms, with or without +* modification, are permitted provided that the following conditions +* are met: +* - Redistributions of source code must retain the above copyright +* notice, this list of conditions and the following disclaimer. +* - Redistributions in binary form must reproduce the above copyright +* notice, this list of conditions and the following disclaimer in +* the documentation and/or other materials provided with the +* distribution. +* - Neither the name of ARM LIMITED nor the names of its contributors +* may be used to endorse or promote products derived from this +* software without specific prior written permission. +* +* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS +* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE +* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, +* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, +* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; +* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER +* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN +* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE +* POSSIBILITY OF SUCH DAMAGE. +* -------------------------------------------------------------------- */ + +#include "arm_math.h" +#include "arm_common_tables.h" +/** + * @ingroup groupFastMath + */ + +/** + * @defgroup cos Cosine + * + * Computes the trigonometric cosine function using a combination of table lookup + * and cubic interpolation. There are separate functions for + * Q15, Q31, and floating-point data types. + * The input to the floating-point version is in radians while the + * fixed-point Q15 and Q31 have a scaled input with the range + * [0 +0.9999] mapping to [0 2*pi). The fixed-point range is chosen so that a + * value of 2*pi wraps around to 0. + * + * The implementation is based on table lookup using 256 values together with cubic interpolation. + * The steps used are: + * -# Calculation of the nearest integer table index + * -# Fetch the four table values a, b, c, and d + * -# Compute the fractional portion (fract) of the table index. + * -# Calculation of wa, wb, wc, wd + * -# The final result equals <code>a*wa + b*wb + c*wc + d*wd</code> + * + * where + * <pre> + * a=Table[index-1]; + * b=Table[index+0]; + * c=Table[index+1]; + * d=Table[index+2]; + * </pre> + * and + * <pre> + * wa=-(1/6)*fract.^3 + (1/2)*fract.^2 - (1/3)*fract; + * wb=(1/2)*fract.^3 - fract.^2 - (1/2)*fract + 1; + * wc=-(1/2)*fract.^3+(1/2)*fract.^2+fract; + * wd=(1/6)*fract.^3 - (1/6)*fract; + * </pre> + */ + + /** + * @addtogroup cos + * @{ + */ + +/** + * @brief Fast approximation to the trigonometric cosine function for floating-point data. + * @param[in] x input value in radians. + * @return cos(x). + */ + +float32_t arm_cos_f32( + float32_t x) +{ + float32_t cosVal, fract, in; /* Temporary variables for input, output */ + uint16_t index; /* Index variable */ + float32_t a, b; /* Two nearest output values */ + int32_t n; + float32_t findex; + + /* input x is in radians */ + /* Scale the input to [0 1] range from [0 2*PI] , divide input by 2*pi, add 0.25 (pi/2) to read sine table */ + in = x * 0.159154943092f + 0.25f; + + /* Calculation of floor value of input */ + n = (int32_t) in; + + /* Make negative values towards -infinity */ + if(in < 0.0f) + { + n--; + } + + /* Map input value to [0 1] */ + in = in - (float32_t) n; + + /* Calculation of index of the table */ + findex = (float32_t) FAST_MATH_TABLE_SIZE * in; + index = ((uint16_t)findex) & 0x1ff; + + /* fractional value calculation */ + fract = findex - (float32_t) index; + + /* Read two nearest values of input value from the cos table */ + a = sinTable_f32[index]; + b = sinTable_f32[index+1]; + + /* Linear interpolation process */ + cosVal = (1.0f-fract)*a + fract*b; + + /* Return the output value */ + return (cosVal); +} + +/** + * @} end of cos group + */ |