diff options
Diffstat (limited to 'Drivers/CMSIS/DSP/Source/FilteringFunctions/arm_fir_q15.c')
| -rw-r--r-- | Drivers/CMSIS/DSP/Source/FilteringFunctions/arm_fir_q15.c | 332 |
1 files changed, 332 insertions, 0 deletions
diff --git a/Drivers/CMSIS/DSP/Source/FilteringFunctions/arm_fir_q15.c b/Drivers/CMSIS/DSP/Source/FilteringFunctions/arm_fir_q15.c new file mode 100644 index 0000000..48506a8 --- /dev/null +++ b/Drivers/CMSIS/DSP/Source/FilteringFunctions/arm_fir_q15.c @@ -0,0 +1,332 @@ +/* ----------------------------------------------------------------------
+ * Project: CMSIS DSP Library
+ * Title: arm_fir_q15.c
+ * Description: Q15 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 the Q15 FIR filter.
+ @param[in] S points to an instance of the Q15 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 a 64-bit internal accumulator.
+ Both coefficients and state variables are represented in 1.15 format and multiplications yield a 2.30 result.
+ The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format.
+ There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved.
+ After all additions have been performed, the accumulator is truncated to 34.15 format by discarding low 15 bits.
+ Lastly, the accumulator is saturated to yield a result in 1.15 format.
+
+ @remark
+ Refer to \ref arm_fir_fast_q15() for a faster but less precise implementation of this function.
+ */
+
+void arm_fir_q15(
+ const arm_fir_instance_q15 * S,
+ const q15_t * pSrc,
+ q15_t * pDst,
+ uint32_t blockSize)
+{
+ q15_t *pState = S->pState; /* State pointer */
+ const q15_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
+ q15_t *pStateCurnt; /* Points to the current sample of the state */
+ q15_t *px; /* Temporary pointer for state buffer */
+ const q15_t *pb; /* Temporary pointer for coefficient buffer */
+ q63_t acc0; /* Accumulators */
+ uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */
+ uint32_t tapCnt, blkCnt; /* Loop counters */
+
+#if defined (ARM_MATH_LOOPUNROLL)
+ q63_t acc1, acc2, acc3; /* Accumulators */
+ q31_t x0, x1, x2, c0; /* Temporary variables to hold state and coefficient values */
+#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 >> 2U;
+
+ while (blkCnt > 0U)
+ {
+ /* Copy 4 new input samples into the state buffer. */
+ *pStateCurnt++ = *pSrc++;
+ *pStateCurnt++ = *pSrc++;
+ *pStateCurnt++ = *pSrc++;
+ *pStateCurnt++ = *pSrc++;
+
+ /* Set all accumulators to zero */
+ acc0 = 0;
+ acc1 = 0;
+ acc2 = 0;
+ acc3 = 0;
+
+ /* Typecast q15_t pointer to q31_t pointer for state reading in q31_t */
+ px = pState;
+
+ /* Typecast q15_t pointer to q31_t pointer for coefficient reading in q31_t */
+ pb = pCoeffs;
+
+ /* Read the first two samples from the state buffer: x[n-N], x[n-N-1] */
+ x0 = read_q15x2_ia (&px);
+
+ /* Read the third and forth samples from the state buffer: x[n-N-2], x[n-N-3] */
+ x2 = read_q15x2_ia (&px);
+
+ /* Loop over the number of taps. Unroll by a factor of 4.
+ Repeat until we've computed numTaps-(numTaps%4) coefficients. */
+ tapCnt = numTaps >> 2U;
+
+ while (tapCnt > 0U)
+ {
+ /* Read the first two coefficients using SIMD: b[N] and b[N-1] coefficients */
+ c0 = read_q15x2_ia ((q15_t **) &pb);
+
+ /* acc0 += b[N] * x[n-N] + b[N-1] * x[n-N-1] */
+ acc0 = __SMLALD(x0, c0, acc0);
+
+ /* acc2 += b[N] * x[n-N-2] + b[N-1] * x[n-N-3] */
+ acc2 = __SMLALD(x2, c0, acc2);
+
+ /* pack x[n-N-1] and x[n-N-2] */
+#ifndef ARM_MATH_BIG_ENDIAN
+ x1 = __PKHBT(x2, x0, 0);
+#else
+ x1 = __PKHBT(x0, x2, 0);
+#endif
+
+ /* Read state x[n-N-4], x[n-N-5] */
+ x0 = read_q15x2_ia (&px);
+
+ /* acc1 += b[N] * x[n-N-1] + b[N-1] * x[n-N-2] */
+ acc1 = __SMLALDX(x1, c0, acc1);
+
+ /* pack x[n-N-3] and x[n-N-4] */
+#ifndef ARM_MATH_BIG_ENDIAN
+ x1 = __PKHBT(x0, x2, 0);
+#else
+ x1 = __PKHBT(x2, x0, 0);
+#endif
+
+ /* acc3 += b[N] * x[n-N-3] + b[N-1] * x[n-N-4] */
+ acc3 = __SMLALDX(x1, c0, acc3);
+
+ /* Read coefficients b[N-2], b[N-3] */
+ c0 = read_q15x2_ia ((q15_t **) &pb);
+
+ /* acc0 += b[N-2] * x[n-N-2] + b[N-3] * x[n-N-3] */
+ acc0 = __SMLALD(x2, c0, acc0);
+
+ /* Read state x[n-N-6], x[n-N-7] with offset */
+ x2 = read_q15x2_ia (&px);
+
+ /* acc2 += b[N-2] * x[n-N-4] + b[N-3] * x[n-N-5] */
+ acc2 = __SMLALD(x0, c0, acc2);
+
+ /* acc1 += b[N-2] * x[n-N-3] + b[N-3] * x[n-N-4] */
+ acc1 = __SMLALDX(x1, c0, acc1);
+
+ /* pack x[n-N-5] and x[n-N-6] */
+#ifndef ARM_MATH_BIG_ENDIAN
+ x1 = __PKHBT(x2, x0, 0);
+#else
+ x1 = __PKHBT(x0, x2, 0);
+#endif
+
+ /* acc3 += b[N-2] * x[n-N-5] + b[N-3] * x[n-N-6] */
+ acc3 = __SMLALDX(x1, c0, acc3);
+
+ /* Decrement tap count */
+ tapCnt--;
+ }
+
+ /* If the filter length is not a multiple of 4, compute the remaining filter taps.
+ This is always be 2 taps since the filter length is even. */
+ if ((numTaps & 0x3U) != 0U)
+ {
+ /* Read last two coefficients */
+ c0 = read_q15x2_ia ((q15_t **) &pb);
+
+ /* Perform the multiply-accumulates */
+ acc0 = __SMLALD(x0, c0, acc0);
+ acc2 = __SMLALD(x2, c0, acc2);
+
+ /* pack state variables */
+#ifndef ARM_MATH_BIG_ENDIAN
+ x1 = __PKHBT(x2, x0, 0);
+#else
+ x1 = __PKHBT(x0, x2, 0);
+#endif
+
+ /* Read last state variables */
+ x0 = read_q15x2 (px);
+
+ /* Perform the multiply-accumulates */
+ acc1 = __SMLALDX(x1, c0, acc1);
+
+ /* pack state variables */
+#ifndef ARM_MATH_BIG_ENDIAN
+ x1 = __PKHBT(x0, x2, 0);
+#else
+ x1 = __PKHBT(x2, x0, 0);
+#endif
+
+ /* Perform the multiply-accumulates */
+ acc3 = __SMLALDX(x1, c0, acc3);
+ }
+
+ /* The results in the 4 accumulators are in 2.30 format. Convert to 1.15 with saturation.
+ Then store the 4 outputs in the destination buffer. */
+#ifndef ARM_MATH_BIG_ENDIAN
+ write_q15x2_ia (&pDst, __PKHBT(__SSAT((acc0 >> 15), 16), __SSAT((acc1 >> 15), 16), 16));
+ write_q15x2_ia (&pDst, __PKHBT(__SSAT((acc2 >> 15), 16), __SSAT((acc3 >> 15), 16), 16));
+#else
+ write_q15x2_ia (&pDst, __PKHBT(__SSAT((acc1 >> 15), 16), __SSAT((acc0 >> 15), 16), 16));
+ write_q15x2_ia (&pDst, __PKHBT(__SSAT((acc3 >> 15), 16), __SSAT((acc2 >> 15), 16), 16));
+#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
+
+ /* Advance the state pointer by 4 to process the next group of 4 samples */
+ pState = pState + 4U;
+
+ /* Decrement loop counter */
+ blkCnt--;
+ }
+
+ /* Loop unrolling: Compute remaining output samples */
+ blkCnt = blockSize % 0x4U;
+
+#else
+
+ /* Initialize blkCnt with number of taps */
+ blkCnt = blockSize;
+
+#endif /* #if defined (ARM_MATH_LOOPUNROLL) */
+
+ while (blkCnt > 0U)
+ {
+ /* Copy two samples into state buffer */
+ *pStateCurnt++ = *pSrc++;
+
+ /* Set the accumulator to zero */
+ acc0 = 0;
+
+ /* Use SIMD to hold states and coefficients */
+ px = pState;
+ pb = pCoeffs;
+
+ tapCnt = numTaps >> 1U;
+
+ do
+ {
+ acc0 += (q31_t) *px++ * *pb++;
+ acc0 += (q31_t) *px++ * *pb++;
+
+ tapCnt--;
+ }
+ while (tapCnt > 0U);
+
+ /* The result is in 2.30 format. Convert to 1.15 with saturation.
+ Then store the output in the destination buffer. */
+ *pDst++ = (q15_t) (__SSAT((acc0 >> 15), 16));
+
+ /* 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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