RTT works

Drivers/CMSIS/DSP/Source/FastMathFunctions/arm_cos_q31.c

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+/* ----------------------------------------------------------------------
+ * Project:      CMSIS DSP Library
+ * Title:        arm_cos_q31.c
+ * Description:  Fast cosine calculation for Q31 values
+ *
+ * $Date:        27. January 2017
+ * $Revision:    V.1.5.1
+ *
+ * Target Processor: Cortex-M cores
+ * -------------------------------------------------------------------- */
+/*
+ * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the License); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an AS IS BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#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
+ */