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# arm_fir_interpolate_q15.c

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    00001 /*-----------------------------------------------------------------------------
    00002 * Copyright (C) 2010 ARM Limited. All rights reserved.
    00003 *
    00004 * $Date:        29. November 2010
    00005 * $Revision:    V1.0.3
    00006 *
    00007 * Project:      CMSIS DSP Library
    00008 * Title:        arm_fir_interpolate_q15.c
    00009 *
    00010 * Description:  Q15 FIR interpolation.
    00011 *
    00012 * Target Processor: Cortex-M4/Cortex-M3
    00013 *
    00014 * Version 1.0.3 2010/11/29
    00015 *    Re-organized the CMSIS folders and updated documentation.
    00016 *
    00017 * Version 1.0.2 2010/11/11
    00018 *    Documentation updated.
    00019 *
    00020 * Version 1.0.1 2010/10/05
    00021 *    Production release and review comments incorporated.
    00022 *
    00023 * Version 1.0.0 2010/09/20
    00024 *    Production release and review comments incorporated
    00025 *
    00026 * Version 0.0.7  2010/06/10
    00027 *    Misra-C changes done
    00028 * ---------------------------------------------------------------------------*/
    00029
    00030 #include "arm_math.h"
    00031
    00059 void arm_fir_interpolate_q15(
    00060   const arm_fir_interpolate_instance_q15 * S,
    00061   q15_t * pSrc,
    00062   q15_t * pDst,
    00063   uint32_t blockSize)
    00064 {
    00065   q15_t *pState = S->pState;                     /* State pointer                                            */
    00066   q15_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer                                      */
    00067   q15_t *pStateCurnt;                            /* Points to the current sample of the state                */
    00068   q15_t *ptr1, *ptr2;                            /* Temporary pointers for state and coefficient buffers     */
    00069   q63_t sum0;                                    /* Accumulators                                             */
    00070   q15_t x0, c0, c1;                              /* Temporary variables to hold state and coefficient values */
    00071   q31_t c, x;
    00072   uint32_t i, blkCnt, j, tapCnt;                 /* Loop counters                                            */
    00073   uint16_t phaseLen = S->phaseLength;            /* Length of each polyphase filter component */
    00074
    00075
    00076   /* S->pState buffer contains previous frame (phaseLen - 1) samples */
    00077   /* pStateCurnt points to the location where the new input data should be written */
    00078   pStateCurnt = S->pState + (phaseLen - 1u);
    00079
    00080   /* Total number of intput samples */
    00081   blkCnt = blockSize;
    00082
    00083   /* Loop over the blockSize. */
    00084   while(blkCnt > 0u)
    00085   {
    00086     /* Copy new input sample into the state buffer */
    00087     *pStateCurnt++ = *pSrc++;
    00088
    00089     /* Address modifier index of coefficient buffer */
    00090     j = 1u;
    00091
    00092     /* Loop over the Interpolation factor. */
    00093     i = S->L;
    00094     while(i > 0u)
    00095     {
    00096       /* Set accumulator to zero */
    00097       sum0 = 0;
    00098
    00099       /* Initialize state pointer */
    00100       ptr1 = pState;
    00101
    00102       /* Initialize coefficient pointer */
    00103       ptr2 = pCoeffs + (S->L - j);
    00104
    00105       /* Loop over the polyPhase length. Unroll by a factor of 4.
    00106        ** Repeat until we've computed numTaps-(4*S->L) coefficients. */
    00107       tapCnt = (uint32_t) phaseLen >> 2u;
    00108       while(tapCnt > 0u)
    00109       {
    00110         /* Read the coefficient */
    00111         c0 = *(ptr2);
    00112
    00113         /* Upsampling is done by stuffing L-1 zeros between each sample.
    00114          * So instead of multiplying zeros with coefficients,
    00115          * Increment the coefficient pointer by interpolation factor times. */
    00116         ptr2 += S->L;
    00117
    00118         /* Read the coefficient */
    00119         c1 = *(ptr2);
    00120
    00121         /* Increment the coefficient pointer by interpolation factor times. */
    00122         ptr2 += S->L;
    00123
    00124         /* Pack the coefficients */
    00125         c = __PKHBT(c0, c1, 16);
    00126
    00127         /* Read twp consecutive input samples */
    00128         x = *__SIMD32(ptr1)++;
    00129
    00130         /* Perform the multiply-accumulate */
    00131         sum0 = __SMLALD(x, c, sum0);
    00132
    00133         /* Read the coefficient */
    00134         c0 = *(ptr2);
    00135
    00136         /* Upsampling is done by stuffing L-1 zeros between each sample.
    00137          * So insted of multiplying zeros with coefficients,
    00138          * Increment the coefficient pointer by interpolation factor times. */
    00139         ptr2 += S->L;
    00140
    00141         /* Read the coefficient */
    00142         c1 = *(ptr2);
    00143
    00144         /* Increment the coefficient pointer by interpolation factor times. */
    00145         ptr2 += S->L;
    00146
    00147         /* Pack the coefficients */
    00148         c = __PKHBT(c0, c1, 16);
    00149
    00150         /* Read twp consecutive input samples */
    00151         x = *__SIMD32(ptr1)++;
    00152
    00153         /* Perform the multiply-accumulate */
    00154         sum0 = __SMLALD(x, c, sum0);
    00155
    00156         /* Decrement the loop counter */
    00157         tapCnt--;
    00158       }
    00159
    00160       /* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */
    00161       tapCnt = (uint32_t) phaseLen & 0x3u;
    00162
    00163       while(tapCnt > 0u)
    00164       {
    00165         /* Read the coefficient */
    00166         c0 = *(ptr2);
    00167
    00168         /* Increment the coefficient pointer by interpolation factor times. */
    00169         ptr2 += S->L;
    00170
    00171         /* Read the input sample */
    00172         x0 = *(ptr1++);
    00173
    00174         /* Perform the multiply-accumulate */
    00175         sum0 = __SMLALD(x0, c0, sum0);
    00176
    00177         /* Decrement the loop counter */
    00178         tapCnt--;
    00179       }
    00180
    00181       /* The result is in the accumulator, store in the destination buffer. */
    00182       *pDst++ = (q15_t) (__SSAT((sum0 >> 15), 16));
    00183
    00184       /* Increment the address modifier index of coefficient buffer */
    00185       j++;
    00186
    00187       /* Decrement the loop counter */
    00188       i--;
    00189     }
    00190
    00191     /* Advance the state pointer by 1
    00192      * to process the next group of interpolation factor number samples */
    00193     pState = pState + 1;
    00194
    00195     /* Decrement the loop counter */
    00196     blkCnt--;
    00197   }
    00198
    00199   /* Processing is complete.
    00200    ** Now copy the last phaseLen - 1 samples to the satrt of the state buffer.
    00201    ** This prepares the state buffer for the next function call. */
    00202
    00203   /* Points to the start of the state buffer */
    00204   pStateCurnt = S->pState;
    00205
    00206   i = ((uint32_t) phaseLen - 1u) >> 2u;
    00207
    00208   /* copy data */
    00209   while(i > 0u)
    00210   {
    00211     *__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;
    00212     *__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;
    00213
    00214     /* Decrement the loop counter */
    00215     i--;
    00216   }
    00217
    00218   i = ((uint32_t) phaseLen - 1u) % 0x04u;
    00219
    00220   while(i > 0u)
    00221   {
    00222     *pStateCurnt++ = *pState++;
    00223
    00224     /* Decrement the loop counter */
    00225     i--;
    00226   }
    00227
    00228 }
    00229

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