diff options
Diffstat (limited to 'Drivers/CMSIS/DSP/Source/FilteringFunctions/arm_fir_q31.c')
| -rw-r--r-- | Drivers/CMSIS/DSP/Source/FilteringFunctions/arm_fir_q31.c | 288 |
1 files changed, 288 insertions, 0 deletions
diff --git a/Drivers/CMSIS/DSP/Source/FilteringFunctions/arm_fir_q31.c b/Drivers/CMSIS/DSP/Source/FilteringFunctions/arm_fir_q31.c new file mode 100644 index 0000000..518f87a --- /dev/null +++ b/Drivers/CMSIS/DSP/Source/FilteringFunctions/arm_fir_q31.c @@ -0,0 +1,288 @@ +/* ----------------------------------------------------------------------
+ * Project: CMSIS DSP Library
+ * Title: arm_fir_q31.c
+ * Description: Q31 FIR filter processing function
+ *
+ * $Date: 18. March 2019
+ * $Revision: V1.6.0
+ *
+ * Target Processor: Cortex-M cores
+ * -------------------------------------------------------------------- */
+/*
+ * Copyright (C) 2010-2019 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 groupFilters
+ */
+
+/**
+ @addtogroup FIR
+ @{
+ */
+
+/**
+ @brief Processing function for Q31 FIR filter.
+ @param[in] S points to an instance of the Q31 FIR filter structure
+ @param[in] pSrc points to the block of input data
+ @param[out] pDst points to the block of output data
+ @param[in] blockSize number of samples to process
+ @return none
+
+ @par Scaling and Overflow Behavior
+ The function is implemented using an internal 64-bit accumulator.
+ The accumulator has a 2.62 format and maintains full precision of the intermediate multiplication results but provides only a single guard bit.
+ Thus, if the accumulator result overflows it wraps around rather than clip.
+ In order to avoid overflows completely the input signal must be scaled down by log2(numTaps) bits.
+ After all multiply-accumulates are performed, the 2.62 accumulator is right shifted by 31 bits and saturated to 1.31 format to yield the final result.
+
+ @remark
+ Refer to \ref arm_fir_fast_q31() for a faster but less precise implementation of this filter.
+ */
+
+void arm_fir_q31(
+ const arm_fir_instance_q31 * S,
+ const q31_t * pSrc,
+ q31_t * pDst,
+ uint32_t blockSize)
+{
+ q31_t *pState = S->pState; /* State pointer */
+ const q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
+ q31_t *pStateCurnt; /* Points to the current sample of the state */
+ q31_t *px; /* Temporary pointer for state buffer */
+ const q31_t *pb; /* Temporary pointer for coefficient buffer */
+ q63_t acc0; /* Accumulator */
+ uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */
+ uint32_t i, tapCnt, blkCnt; /* Loop counters */
+
+#if defined (ARM_MATH_LOOPUNROLL)
+ q63_t acc1, acc2; /* Accumulators */
+ q31_t x0, x1, x2; /* Temporary variables to hold state values */
+ q31_t c0; /* Temporary variable to hold coefficient value */
+#endif
+
+ /* S->pState points to state array which contains previous frame (numTaps - 1) samples */
+ /* pStateCurnt points to the location where the new input data should be written */
+ pStateCurnt = &(S->pState[(numTaps - 1U)]);
+
+#if defined (ARM_MATH_LOOPUNROLL)
+
+ /* Loop unrolling: Compute 4 output values simultaneously.
+ * The variables acc0 ... acc3 hold output values that are being computed:
+ *
+ * acc0 = b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0]
+ * acc1 = b[numTaps-1] * x[n-numTaps] + b[numTaps-2] * x[n-numTaps-1] + b[numTaps-3] * x[n-numTaps-2] +...+ b[0] * x[1]
+ * acc2 = b[numTaps-1] * x[n-numTaps+1] + b[numTaps-2] * x[n-numTaps] + b[numTaps-3] * x[n-numTaps-1] +...+ b[0] * x[2]
+ * acc3 = b[numTaps-1] * x[n-numTaps+2] + b[numTaps-2] * x[n-numTaps+1] + b[numTaps-3] * x[n-numTaps] +...+ b[0] * x[3]
+ */
+
+ blkCnt = blockSize / 3;
+
+ while (blkCnt > 0U)
+ {
+ /* Copy 3 new input samples into the state buffer. */
+ *pStateCurnt++ = *pSrc++;
+ *pStateCurnt++ = *pSrc++;
+ *pStateCurnt++ = *pSrc++;
+
+ /* Set all accumulators to zero */
+ acc0 = 0;
+ acc1 = 0;
+ acc2 = 0;
+
+ /* Initialize state pointer */
+ px = pState;
+
+ /* Initialize coefficient pointer */
+ pb = pCoeffs;
+
+ /* Read the first 2 samples from the state buffer: x[n-numTaps], x[n-numTaps-1] */
+ x0 = *px++;
+ x1 = *px++;
+
+ /* Loop unrolling: process 3 taps at a time. */
+ tapCnt = numTaps / 3;
+
+ while (tapCnt > 0U)
+ {
+ /* Read the b[numTaps] coefficient */
+ c0 = *pb;
+
+ /* Read x[n-numTaps-2] sample */
+ x2 = *(px++);
+
+ /* Perform the multiply-accumulates */
+ acc0 += ((q63_t) x0 * c0);
+ acc1 += ((q63_t) x1 * c0);
+ acc2 += ((q63_t) x2 * c0);
+
+ /* Read the coefficient and state */
+ c0 = *(pb + 1U);
+ x0 = *(px++);
+
+ /* Perform the multiply-accumulates */
+ acc0 += ((q63_t) x1 * c0);
+ acc1 += ((q63_t) x2 * c0);
+ acc2 += ((q63_t) x0 * c0);
+
+ /* Read the coefficient and state */
+ c0 = *(pb + 2U);
+ x1 = *(px++);
+
+ /* update coefficient pointer */
+ pb += 3U;
+
+ /* Perform the multiply-accumulates */
+ acc0 += ((q63_t) x2 * c0);
+ acc1 += ((q63_t) x0 * c0);
+ acc2 += ((q63_t) x1 * c0);
+
+ /* Decrement loop counter */
+ tapCnt--;
+ }
+
+ /* Loop unrolling: Compute remaining outputs */
+ tapCnt = numTaps % 0x3U;
+
+ while (tapCnt > 0U)
+ {
+ /* Read coefficients */
+ c0 = *(pb++);
+
+ /* Fetch 1 state variable */
+ x2 = *(px++);
+
+ /* Perform the multiply-accumulates */
+ acc0 += ((q63_t) x0 * c0);
+ acc1 += ((q63_t) x1 * c0);
+ acc2 += ((q63_t) x2 * c0);
+
+ /* Reuse the present sample states for next sample */
+ x0 = x1;
+ x1 = x2;
+
+ /* Decrement loop counter */
+ tapCnt--;
+ }
+
+ /* Advance the state pointer by 3 to process the next group of 3 samples */
+ pState = pState + 3;
+
+ /* The result is in 2.30 format. Convert to 1.31 and store in destination buffer. */
+ *pDst++ = (q31_t) (acc0 >> 31U);
+ *pDst++ = (q31_t) (acc1 >> 31U);
+ *pDst++ = (q31_t) (acc2 >> 31U);
+
+ /* Decrement loop counter */
+ blkCnt--;
+ }
+
+ /* Loop unrolling: Compute remaining output samples */
+ blkCnt = blockSize % 0x3U;
+
+#else
+
+ /* Initialize blkCnt with number of taps */
+ blkCnt = blockSize;
+
+#endif /* #if defined (ARM_MATH_LOOPUNROLL) */
+
+ while (blkCnt > 0U)
+ {
+ /* Copy one sample at a time into state buffer */
+ *pStateCurnt++ = *pSrc++;
+
+ /* Set the accumulator to zero */
+ acc0 = 0;
+
+ /* Initialize state pointer */
+ px = pState;
+
+ /* Initialize Coefficient pointer */
+ pb = pCoeffs;
+
+ i = numTaps;
+
+ /* Perform the multiply-accumulates */
+ do
+ {
+ /* acc = b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0] */
+ acc0 += (q63_t) *px++ * *pb++;
+
+ i--;
+ } while (i > 0U);
+
+ /* Result is in 2.62 format. Convert to 1.31 and store in destination buffer. */
+ *pDst++ = (q31_t) (acc0 >> 31U);
+
+ /* Advance state pointer by 1 for the next sample */
+ pState = pState + 1U;
+
+ /* Decrement loop counter */
+ blkCnt--;
+ }
+
+ /* Processing is complete.
+ Now copy the last numTaps - 1 samples to the start of the state buffer.
+ This prepares the state buffer for the next function call. */
+
+ /* Points to the start of the state buffer */
+ pStateCurnt = S->pState;
+
+#if defined (ARM_MATH_LOOPUNROLL)
+
+ /* Loop unrolling: Compute 4 taps at a time */
+ tapCnt = (numTaps - 1U) >> 2U;
+
+ /* Copy data */
+ while (tapCnt > 0U)
+ {
+ *pStateCurnt++ = *pState++;
+ *pStateCurnt++ = *pState++;
+ *pStateCurnt++ = *pState++;
+ *pStateCurnt++ = *pState++;
+
+ /* Decrement loop counter */
+ tapCnt--;
+ }
+
+ /* Calculate remaining number of copies */
+ tapCnt = (numTaps - 1U) % 0x4U;
+
+#else
+
+ /* Initialize tapCnt with number of taps */
+ tapCnt = (numTaps - 1U);
+
+#endif /* #if defined (ARM_MATH_LOOPUNROLL) */
+
+ /* Copy remaining data */
+ while (tapCnt > 0U)
+ {
+ *pStateCurnt++ = *pState++;
+
+ /* Decrement loop counter */
+ tapCnt--;
+ }
+
+}
+
+/**
+ @} end of FIR group
+ */
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