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Diffstat (limited to 'DSP_Lib/Source/FastMathFunctions/arm_cos_q31.c')
-rw-r--r-- | DSP_Lib/Source/FastMathFunctions/arm_cos_q31.c | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/DSP_Lib/Source/FastMathFunctions/arm_cos_q31.c b/DSP_Lib/Source/FastMathFunctions/arm_cos_q31.c new file mode 100644 index 0000000..72c51e6 --- /dev/null +++ b/DSP_Lib/Source/FastMathFunctions/arm_cos_q31.c @@ -0,0 +1,96 @@ +/* ---------------------------------------------------------------------- +* Copyright (C) 2010-2014 ARM Limited. All rights reserved. +* +* $Date: 07. September 2015 +* $Revision: V.1.4.5 a +* +* Project: CMSIS DSP Library +* Title: arm_cos_q31.c +* +* Description: Fast cosine calculation for Q31 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 + */ + + /** + * @addtogroup cos + * @{ + */ + +/** + * @brief Fast approximation to the trigonometric cosine function for Q31 data. + * @param[in] x Scaled input value in radians. + * @return cos(x). + * + * The Q31 input value is in the range [0 +0.9999] and is mapped to a radian + * value in the range [0 2*pi). + */ + +q31_t arm_cos_q31( + q31_t x) +{ + q31_t cosVal; /* Temporary variables for input, output */ + int32_t index; /* Index variables */ + q31_t a, b; /* Four nearest output values */ + q31_t fract; /* Temporary values for fractional values */ + + /* add 0.25 (pi/2) to read sine table */ + x = (uint32_t)x + 0x20000000; + if(x < 0) + { /* convert negative numbers to corresponding positive ones */ + x = (uint32_t)x + 0x80000000; + } + + /* Calculate the nearest index */ + index = (uint32_t)x >> FAST_MATH_Q31_SHIFT; + + /* Calculation of fractional value */ + fract = (x - (index << FAST_MATH_Q31_SHIFT)) << 9; + + /* Read two nearest values of input value from the sin table */ + a = sinTable_q31[index]; + b = sinTable_q31[index+1]; + + /* Linear interpolation process */ + cosVal = (q63_t)(0x80000000-fract)*a >> 32; + cosVal = (q31_t)((((q63_t)cosVal << 32) + ((q63_t)fract*b)) >> 32); + + return cosVal << 1; +} + +/** + * @} end of cos group + */ |