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Diffstat (limited to 'src/modules/mathlib/CMSIS/DSP_Lib/Source/FilteringFunctions/arm_fir_decimate_fast_q31.c')
| -rw-r--r-- | src/modules/mathlib/CMSIS/DSP_Lib/Source/FilteringFunctions/arm_fir_decimate_fast_q31.c | 343 |
1 files changed, 343 insertions, 0 deletions
diff --git a/src/modules/mathlib/CMSIS/DSP_Lib/Source/FilteringFunctions/arm_fir_decimate_fast_q31.c b/src/modules/mathlib/CMSIS/DSP_Lib/Source/FilteringFunctions/arm_fir_decimate_fast_q31.c new file mode 100644 index 000000000..a43fd0b4c --- /dev/null +++ b/src/modules/mathlib/CMSIS/DSP_Lib/Source/FilteringFunctions/arm_fir_decimate_fast_q31.c @@ -0,0 +1,343 @@ +/* ----------------------------------------------------------------------
+* Copyright (C) 2010 ARM Limited. All rights reserved.
+*
+* $Date: 15. February 2012
+* $Revision: V1.1.0
+*
+* Project: CMSIS DSP Library
+* Title: arm_fir_decimate_fast_q31.c
+*
+* Description: Fast Q31 FIR Decimator.
+*
+* Target Processor: Cortex-M4/Cortex-M3
+*
+* Version 1.1.0 2012/02/15
+* Updated with more optimizations, bug fixes and minor API changes.
+*
+* Version 1.0.10 2011/7/15
+* Big Endian support added and Merged M0 and M3/M4 Source code.
+*
+* Version 1.0.3 2010/11/29
+* Re-organized the CMSIS folders and updated documentation.
+*
+* Version 1.0.2 2010/11/11
+* Documentation updated.
+*
+* Version 1.0.1 2010/10/05
+* Production release and review comments incorporated.
+*
+* Version 1.0.0 2010/09/20
+* Production release and review comments incorporated.
+* -------------------------------------------------------------------- */
+
+#include "arm_math.h"
+
+/**
+ * @ingroup groupFilters
+ */
+
+/**
+ * @addtogroup FIR_decimate
+ * @{
+ */
+
+/**
+ * @brief Processing function for the Q31 FIR decimator (fast variant) for Cortex-M3 and Cortex-M4.
+ * @param[in] *S points to an instance of the Q31 FIR decimator 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 input samples to process per call.
+ * @return none
+ *
+ * <b>Scaling and Overflow Behavior:</b>
+ *
+ * \par
+ * This function is optimized for speed at the expense of fixed-point precision and overflow protection.
+ * The result of each 1.31 x 1.31 multiplication is truncated to 2.30 format.
+ * These intermediate results are added to a 2.30 accumulator.
+ * Finally, the accumulator is saturated and converted to a 1.31 result.
+ * The fast version has the same overflow behavior as the standard version and provides less precision since it discards the low 32 bits of each multiplication result.
+ * In order to avoid overflows completely the input signal must be scaled down by log2(numTaps) bits (where log2 is read as log to the base 2).
+ *
+ * \par
+ * Refer to the function <code>arm_fir_decimate_q31()</code> for a slower implementation of this function which uses a 64-bit accumulator to provide higher precision.
+ * Both the slow and the fast versions use the same instance structure.
+ * Use the function <code>arm_fir_decimate_init_q31()</code> to initialize the filter structure.
+ */
+
+void arm_fir_decimate_fast_q31(
+ arm_fir_decimate_instance_q31 * S,
+ q31_t * pSrc,
+ q31_t * pDst,
+ uint32_t blockSize)
+{
+ q31_t *pState = S->pState; /* State pointer */
+ q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
+ q31_t *pStateCurnt; /* Points to the current sample of the state */
+ q31_t x0, c0; /* Temporary variables to hold state and coefficient values */
+ q31_t *px; /* Temporary pointers for state buffer */
+ q31_t *pb; /* Temporary pointers for coefficient buffer */
+ q31_t sum0; /* Accumulator */
+ uint32_t numTaps = S->numTaps; /* Number of taps */
+ uint32_t i, tapCnt, blkCnt, outBlockSize = blockSize / S->M; /* Loop counters */
+ uint32_t blkCntN2;
+ q31_t x1;
+ q31_t acc0, acc1;
+ q31_t *px0, *px1;
+
+ /* S->pState buffer contains previous frame (numTaps - 1) samples */
+ /* pStateCurnt points to the location where the new input data should be written */
+ pStateCurnt = S->pState + (numTaps - 1u);
+
+ /* Total number of output samples to be computed */
+
+ blkCnt = outBlockSize / 2;
+ blkCntN2 = outBlockSize - (2 * blkCnt);
+
+ while(blkCnt > 0u)
+ {
+ /* Copy decimation factor number of new input samples into the state buffer */
+ i = 2 * S->M;
+
+ do
+ {
+ *pStateCurnt++ = *pSrc++;
+
+ } while(--i);
+
+ /* Set accumulator to zero */
+ acc0 = 0;
+ acc1 = 0;
+
+ /* Initialize state pointer */
+ px0 = pState;
+ px1 = pState + S->M;
+
+ /* Initialize coeff pointer */
+ pb = pCoeffs;
+
+ /* Loop unrolling. Process 4 taps at a time. */
+ tapCnt = numTaps >> 2;
+
+ /* Loop over the number of taps. Unroll by a factor of 4.
+ ** Repeat until we've computed numTaps-4 coefficients. */
+ while(tapCnt > 0u)
+ {
+ /* Read the b[numTaps-1] coefficient */
+ c0 = *(pb);
+
+ /* Read x[n-numTaps-1] for sample 0 sample 1 */
+ x0 = *(px0);
+ x1 = *(px1);
+
+ /* Perform the multiply-accumulate */
+ acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
+ acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
+
+ /* Read the b[numTaps-2] coefficient */
+ c0 = *(pb + 1u);
+
+ /* Read x[n-numTaps-2] for sample 0 sample 1 */
+ x0 = *(px0 + 1u);
+ x1 = *(px1 + 1u);
+
+ /* Perform the multiply-accumulate */
+ acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
+ acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
+
+ /* Read the b[numTaps-3] coefficient */
+ c0 = *(pb + 2u);
+
+ /* Read x[n-numTaps-3] for sample 0 sample 1 */
+ x0 = *(px0 + 2u);
+ x1 = *(px1 + 2u);
+ pb += 4u;
+
+ /* Perform the multiply-accumulate */
+ acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
+ acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
+
+ /* Read the b[numTaps-4] coefficient */
+ c0 = *(pb - 1u);
+
+ /* Read x[n-numTaps-4] for sample 0 sample 1 */
+ x0 = *(px0 + 3u);
+ x1 = *(px1 + 3u);
+
+
+ /* Perform the multiply-accumulate */
+ acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
+ acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
+
+ /* update state pointers */
+ px0 += 4u;
+ px1 += 4u;
+
+ /* Decrement the loop counter */
+ tapCnt--;
+ }
+
+ /* If the filter length is not a multiple of 4, compute the remaining filter taps */
+ tapCnt = numTaps % 0x4u;
+
+ while(tapCnt > 0u)
+ {
+ /* Read coefficients */
+ c0 = *(pb++);
+
+ /* Fetch 1 state variable */
+ x0 = *(px0++);
+ x1 = *(px1++);
+
+ /* Perform the multiply-accumulate */
+ acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
+ acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
+
+ /* Decrement the loop counter */
+ tapCnt--;
+ }
+
+ /* Advance the state pointer by the decimation factor
+ * to process the next group of decimation factor number samples */
+ pState = pState + S->M * 2;
+
+ /* The result is in the accumulator, store in the destination buffer. */
+ *pDst++ = (q31_t) (acc0 << 1);
+ *pDst++ = (q31_t) (acc1 << 1);
+
+ /* Decrement the loop counter */
+ blkCnt--;
+ }
+
+ while(blkCntN2 > 0u)
+ {
+ /* Copy decimation factor number of new input samples into the state buffer */
+ i = S->M;
+
+ do
+ {
+ *pStateCurnt++ = *pSrc++;
+
+ } while(--i);
+
+ /* Set accumulator to zero */
+ sum0 = 0;
+
+ /* Initialize state pointer */
+ px = pState;
+
+ /* Initialize coeff pointer */
+ pb = pCoeffs;
+
+ /* Loop unrolling. Process 4 taps at a time. */
+ tapCnt = numTaps >> 2;
+
+ /* Loop over the number of taps. Unroll by a factor of 4.
+ ** Repeat until we've computed numTaps-4 coefficients. */
+ while(tapCnt > 0u)
+ {
+ /* Read the b[numTaps-1] coefficient */
+ c0 = *(pb++);
+
+ /* Read x[n-numTaps-1] sample */
+ x0 = *(px++);
+
+ /* Perform the multiply-accumulate */
+ sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32);
+
+ /* Read the b[numTaps-2] coefficient */
+ c0 = *(pb++);
+
+ /* Read x[n-numTaps-2] sample */
+ x0 = *(px++);
+
+ /* Perform the multiply-accumulate */
+ sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32);
+
+ /* Read the b[numTaps-3] coefficient */
+ c0 = *(pb++);
+
+ /* Read x[n-numTaps-3] sample */
+ x0 = *(px++);
+
+ /* Perform the multiply-accumulate */
+ sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32);
+
+ /* Read the b[numTaps-4] coefficient */
+ c0 = *(pb++);
+
+ /* Read x[n-numTaps-4] sample */
+ x0 = *(px++);
+
+ /* Perform the multiply-accumulate */
+ sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32);
+
+ /* Decrement the loop counter */
+ tapCnt--;
+ }
+
+ /* If the filter length is not a multiple of 4, compute the remaining filter taps */
+ tapCnt = numTaps % 0x4u;
+
+ while(tapCnt > 0u)
+ {
+ /* Read coefficients */
+ c0 = *(pb++);
+
+ /* Fetch 1 state variable */
+ x0 = *(px++);
+
+ /* Perform the multiply-accumulate */
+ sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32);
+
+ /* Decrement the loop counter */
+ tapCnt--;
+ }
+
+ /* Advance the state pointer by the decimation factor
+ * to process the next group of decimation factor number samples */
+ pState = pState + S->M;
+
+ /* The result is in the accumulator, store in the destination buffer. */
+ *pDst++ = (q31_t) (sum0 << 1);
+
+ /* Decrement the loop counter */
+ blkCntN2--;
+ }
+
+ /* Processing is complete.
+ ** Now copy the last numTaps - 1 samples to the satrt 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;
+
+ i = (numTaps - 1u) >> 2u;
+
+ /* copy data */
+ while(i > 0u)
+ {
+ *pStateCurnt++ = *pState++;
+ *pStateCurnt++ = *pState++;
+ *pStateCurnt++ = *pState++;
+ *pStateCurnt++ = *pState++;
+
+ /* Decrement the loop counter */
+ i--;
+ }
+
+ i = (numTaps - 1u) % 0x04u;
+
+ /* copy data */
+ while(i > 0u)
+ {
+ *pStateCurnt++ = *pState++;
+
+ /* Decrement the loop counter */
+ i--;
+ }
+}
+
+/**
+ * @} end of FIR_decimate group
+ */
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