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/*-----------------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date: 15. July 2011
* $Revision: V1.0.10
*
* Project: CMSIS DSP Library
* Title: arm_fir_interpolate_q15.c
*
* Description: Q15 FIR interpolation.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* 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
*
* Version 0.0.7 2010/06/10
* Misra-C changes done
* ---------------------------------------------------------------------------*/
#include "arm_math.h"
/**
* @ingroup groupFilters
*/
/**
* @addtogroup FIR_Interpolate
* @{
*/
/**
* @brief Processing function for the Q15 FIR interpolator.
* @param[in] *S points to an instance of the Q15 FIR interpolator 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
* 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.
*/
void arm_fir_interpolate_q15(
const arm_fir_interpolate_instance_q15 * S,
q15_t * pSrc,
q15_t * pDst,
uint32_t blockSize)
{
q15_t *pState = S->pState; /* State pointer */
q15_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
q15_t *pStateCurnt; /* Points to the current sample of the state */
q15_t *ptr1, *ptr2; /* Temporary pointers for state and coefficient buffers */
#ifndef ARM_MATH_CM0
/* Run the below code for Cortex-M4 and Cortex-M3 */
q63_t sum0; /* Accumulators */
q15_t x0, c0, c1; /* Temporary variables to hold state and coefficient values */
q31_t c, x;
uint32_t i, blkCnt, j, tapCnt; /* Loop counters */
uint16_t phaseLen = S->phaseLength; /* Length of each polyphase filter component */
/* S->pState buffer contains previous frame (phaseLen - 1) samples */
/* pStateCurnt points to the location where the new input data should be written */
pStateCurnt = S->pState + (phaseLen - 1u);
/* Total number of intput samples */
blkCnt = blockSize;
/* Loop over the blockSize. */
while(blkCnt > 0u)
{
/* Copy new input sample into the state buffer */
*pStateCurnt++ = *pSrc++;
/* Address modifier index of coefficient buffer */
j = 1u;
/* Loop over the Interpolation factor. */
i = S->L;
while(i > 0u)
{
/* Set accumulator to zero */
sum0 = 0;
/* Initialize state pointer */
ptr1 = pState;
/* Initialize coefficient pointer */
ptr2 = pCoeffs + (S->L - j);
/* Loop over the polyPhase length. Unroll by a factor of 4.
** Repeat until we've computed numTaps-(4*S->L) coefficients. */
tapCnt = (uint32_t) phaseLen >> 2u;
while(tapCnt > 0u)
{
/* Read the coefficient */
c0 = *(ptr2);
/* Upsampling is done by stuffing L-1 zeros between each sample.
* So instead of multiplying zeros with coefficients,
* Increment the coefficient pointer by interpolation factor times. */
ptr2 += S->L;
/* Read the coefficient */
c1 = *(ptr2);
/* Increment the coefficient pointer by interpolation factor times. */
ptr2 += S->L;
/* Pack the coefficients */
#ifndef ARM_MATH_BIG_ENDIAN
c = __PKHBT(c0, c1, 16);
#else
c = __PKHBT(c1, c0, 16);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* Read twp consecutive input samples */
x = *__SIMD32(ptr1)++;
/* Perform the multiply-accumulate */
sum0 = __SMLALD(x, c, sum0);
/* Read the coefficient */
c0 = *(ptr2);
/* Upsampling is done by stuffing L-1 zeros between each sample.
* So insted of multiplying zeros with coefficients,
* Increment the coefficient pointer by interpolation factor times. */
ptr2 += S->L;
/* Read the coefficient */
c1 = *(ptr2);
/* Increment the coefficient pointer by interpolation factor times. */
ptr2 += S->L;
/* Pack the coefficients */
#ifndef ARM_MATH_BIG_ENDIAN
c = __PKHBT(c0, c1, 16);
#else
c = __PKHBT(c1, c0, 16);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* Read twp consecutive input samples */
x = *__SIMD32(ptr1)++;
/* Perform the multiply-accumulate */
sum0 = __SMLALD(x, c, sum0);
/* Decrement the loop counter */
tapCnt--;
}
/* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */
tapCnt = (uint32_t) phaseLen & 0x3u;
while(tapCnt > 0u)
{
/* Read the coefficient */
c0 = *(ptr2);
/* Increment the coefficient pointer by interpolation factor times. */
ptr2 += S->L;
/* Read the input sample */
x0 = *(ptr1++);
/* Perform the multiply-accumulate */
sum0 = __SMLALD(x0, c0, sum0);
/* Decrement the loop counter */
tapCnt--;
}
/* The result is in the accumulator, store in the destination buffer. */
*pDst++ = (q15_t) (__SSAT((sum0 >> 15), 16));
/* Increment the address modifier index of coefficient buffer */
j++;
/* Decrement the loop counter */
i--;
}
/* Advance the state pointer by 1
* to process the next group of interpolation factor number samples */
pState = pState + 1;
/* Decrement the loop counter */
blkCnt--;
}
/* Processing is complete.
** Now copy the last phaseLen - 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 = ((uint32_t) phaseLen - 1u) >> 2u;
/* copy data */
while(i > 0u)
{
*__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;
*__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;
/* Decrement the loop counter */
i--;
}
i = ((uint32_t) phaseLen - 1u) % 0x04u;
while(i > 0u)
{
*pStateCurnt++ = *pState++;
/* Decrement the loop counter */
i--;
}
#else
/* Run the below code for Cortex-M0 */
q63_t sum; /* Accumulator */
q15_t x0, c0; /* Temporary variables to hold state and coefficient values */
uint32_t i, blkCnt, tapCnt; /* Loop counters */
uint16_t phaseLen = S->phaseLength; /* Length of each polyphase filter component */
/* S->pState buffer contains previous frame (phaseLen - 1) samples */
/* pStateCurnt points to the location where the new input data should be written */
pStateCurnt = S->pState + (phaseLen - 1u);
/* Total number of intput samples */
blkCnt = blockSize;
/* Loop over the blockSize. */
while(blkCnt > 0u)
{
/* Copy new input sample into the state buffer */
*pStateCurnt++ = *pSrc++;
/* Loop over the Interpolation factor. */
i = S->L;
while(i > 0u)
{
/* Set accumulator to zero */
sum = 0;
/* Initialize state pointer */
ptr1 = pState;
/* Initialize coefficient pointer */
ptr2 = pCoeffs + (i - 1u);
/* Loop over the polyPhase length */
tapCnt = (uint32_t) phaseLen;
while(tapCnt > 0u)
{
/* Read the coefficient */
c0 = *ptr2;
/* Increment the coefficient pointer by interpolation factor times. */
ptr2 += S->L;
/* Read the input sample */
x0 = *ptr1++;
/* Perform the multiply-accumulate */
sum += ((q31_t) x0 * c0);
/* Decrement the loop counter */
tapCnt--;
}
/* Store the result after converting to 1.15 format in the destination buffer */
*pDst++ = (q15_t) (__SSAT((sum >> 15), 16));
/* Decrement the loop counter */
i--;
}
/* Advance the state pointer by 1
* to process the next group of interpolation factor number samples */
pState = pState + 1;
/* Decrement the loop counter */
blkCnt--;
}
/* Processing is complete.
** Now copy the last phaseLen - 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;
i = (uint32_t) phaseLen - 1u;
while(i > 0u)
{
*pStateCurnt++ = *pState++;
/* Decrement the loop counter */
i--;
}
#endif /* #ifndef ARM_MATH_CM0 */
}
/**
* @} end of FIR_Interpolate group
*/
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