| /*----------------------------------------------------------------------------- |
| * Copyright (C) 2010 ARM Limited. All rights reserved. |
| * |
| * $Date: 15. July 2011 |
| * $Revision: V1.0.10 |
| * |
| * Project: CMSIS DSP Library |
| * Title: arm_fir_interpolate_q31.c |
| * |
| * Description: Q31 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 Q31 FIR interpolator. |
| * @param[in] *S points to an instance of the Q31 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 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 <code>1/(numTaps/L)</code>. |
| * since <code>numTaps/L</code> additions occur per output sample. |
| * After all multiply-accumulates are performed, the 2.62 accumulator is truncated to 1.32 format and then saturated to 1.31 format. |
| */ |
| |
| |
| void arm_fir_interpolate_q31( |
| const arm_fir_interpolate_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 *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 */ |
| q31_t x0, c0; /* Temporary variables to hold state and coefficient values */ |
| uint32_t i, blkCnt, j; /* Loop counters */ |
| uint16_t phaseLen = S->phaseLength, tapCnt; /* 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 + ((q31_t) phaseLen - 1); |
| |
| /* 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 = phaseLen >> 2; |
| 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 input sample */ |
| x0 = *(ptr1++); |
| |
| /* Perform the multiply-accumulate */ |
| sum0 += (q63_t) x0 *c0; |
| |
| /* 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 += (q63_t) x0 *c0; |
| |
| /* 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 += (q63_t) x0 *c0; |
| |
| /* 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 += (q63_t) x0 *c0; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| /* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */ |
| tapCnt = 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 += (q63_t) x0 *c0; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| /* The result is in the accumulator, store in the destination buffer. */ |
| *pDst++ = (q31_t) (sum0 >> 31); |
| |
| /* 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; |
| |
| tapCnt = (phaseLen - 1u) >> 2u; |
| |
| /* copy data */ |
| while(tapCnt > 0u) |
| { |
| *pStateCurnt++ = *pState++; |
| *pStateCurnt++ = *pState++; |
| *pStateCurnt++ = *pState++; |
| *pStateCurnt++ = *pState++; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| tapCnt = (phaseLen - 1u) % 0x04u; |
| |
| /* copy data */ |
| while(tapCnt > 0u) |
| { |
| *pStateCurnt++ = *pState++; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| #else |
| |
| /* Run the below code for Cortex-M0 */ |
| |
| q63_t sum; /* Accumulator */ |
| q31_t x0, c0; /* Temporary variables to hold state and coefficient values */ |
| uint32_t i, blkCnt; /* Loop counters */ |
| uint16_t phaseLen = S->phaseLength, tapCnt; /* 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 + ((q31_t) phaseLen - 1); |
| |
| /* 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); |
| |
| tapCnt = 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 += (q63_t) x0 *c0; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| /* The result is in the accumulator, store in the destination buffer. */ |
| *pDst++ = (q31_t) (sum >> 31); |
| |
| /* 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; |
| |
| tapCnt = phaseLen - 1u; |
| |
| /* copy data */ |
| while(tapCnt > 0u) |
| { |
| *pStateCurnt++ = *pState++; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| #endif /* #ifndef ARM_MATH_CM0 */ |
| |
| } |
| |
| /** |
| * @} end of FIR_Interpolate group |
| */ |
