/*----------------------------------------------------------------------------- * 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. * * Scaling and Overflow Behavior: * \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 */