RTT works

Drivers/CMSIS/DSP/Source/BasicMathFunctions/arm_abs_q7.c

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+/* ----------------------------------------------------------------------
+ * Project:      CMSIS DSP Library
+ * Title:        arm_abs_q7.c
+ * Description:  Q7 vector absolute value
+ *
+ * $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"
+
+/**
+ * @ingroup groupMath
+ */
+
+/**
+ * @addtogroup BasicAbs
+ * @{
+ */
+
+/**
+ * @brief Q7 vector absolute value.
+ * @param[in]       *pSrc points to the input buffer
+ * @param[out]      *pDst points to the output buffer
+ * @param[in]       blockSize number of samples in each vector
+ * @return none.
+ *
+ * \par Conditions for optimum performance
+ *  Input and output buffers should be aligned by 32-bit
+ *
+ *
+ * <b>Scaling and Overflow Behavior:</b>
+ * \par
+ * The function uses saturating arithmetic.
+ * The Q7 value -1 (0x80) will be saturated to the maximum allowable positive value 0x7F.
+ */
+
+void arm_abs_q7(
+  q7_t * pSrc,
+  q7_t * pDst,
+  uint32_t blockSize)
+{
+  uint32_t blkCnt;                               /* loop counter */
+  q7_t in;                                       /* Input value1 */
+
+#if defined (ARM_MATH_DSP)
+
+  /* Run the below code for Cortex-M4 and Cortex-M3 */
+  q31_t in1, in2, in3, in4;                      /* temporary input variables */
+  q31_t out1, out2, out3, out4;                  /* temporary output variables */
+
+  /*loop Unrolling */
+  blkCnt = blockSize >> 2U;
+
+  /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
+   ** a second loop below computes the remaining 1 to 3 samples. */
+  while (blkCnt > 0U)
+  {
+    /* C = |A| */
+    /* Read inputs */
+    in1 = (q31_t) * pSrc;
+    in2 = (q31_t) * (pSrc + 1);
+    in3 = (q31_t) * (pSrc + 2);
+
+    /* find absolute value */
+    out1 = (in1 > 0) ? in1 : (q31_t)__QSUB8(0, in1);
+
+    /* read input */
+    in4 = (q31_t) * (pSrc + 3);
+
+    /* find absolute value */
+    out2 = (in2 > 0) ? in2 : (q31_t)__QSUB8(0, in2);
+
+    /* store result to destination */
+    *pDst = (q7_t) out1;
+
+    /* find absolute value */
+    out3 = (in3 > 0) ? in3 : (q31_t)__QSUB8(0, in3);
+
+    /* find absolute value */
+    out4 = (in4 > 0) ? in4 : (q31_t)__QSUB8(0, in4);
+
+    /* store result to destination */
+    *(pDst + 1) = (q7_t) out2;
+
+    /* store result to destination */
+    *(pDst + 2) = (q7_t) out3;
+
+    /* store result to destination */
+    *(pDst + 3) = (q7_t) out4;
+
+    /* update pointers to process next samples */
+    pSrc += 4U;
+    pDst += 4U;
+
+    /* Decrement the loop counter */
+    blkCnt--;
+  }
+
+  /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
+   ** No loop unrolling is used. */
+  blkCnt = blockSize % 0x4U;
+#else
+
+  /* Run the below code for Cortex-M0 */
+  blkCnt = blockSize;
+
+#endif /* #define ARM_MATH_CM0_FAMILY */
+
+  while (blkCnt > 0U)
+  {
+    /* C = |A| */
+    /* Read the input */
+    in = *pSrc++;
+
+    /* Store the Absolute result in the destination buffer */
+    *pDst++ = (in > 0) ? in : ((in == (q7_t) 0x80) ? 0x7f : -in);
+
+    /* Decrement the loop counter */
+    blkCnt--;
+  }
+}
+
+/**
+ * @} end of BasicAbs group
+ */