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# arm_fir_interpolate_f32.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_f32.c
    00009 *
    00010 * Description:  FIR interpolation for floating-point sequences.
    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
    00132 void arm_fir_interpolate_f32(
    00133   const arm_fir_interpolate_instance_f32 * S,
    00134   float32_t * pSrc,
    00135   float32_t * pDst,
    00136   uint32_t blockSize)
    00137 {
    00138   float32_t *pState = S->pState;                 /* State pointer */
    00139   float32_t *pCoeffs = S->pCoeffs;               /* Coefficient pointer */
    00140   float32_t *pStateCurnt;                        /* Points to the current sample of the state */
    00141   float32_t *ptr1, *ptr2;                        /* Temporary pointers for state and coefficient buffers */
    00142   float32_t sum0;                                /* Accumulators */
    00143   float32_t x0, c0;                              /* Temporary variables to hold state and coefficient values */
    00144   uint32_t i, blkCnt, j;                         /* Loop counters */
    00145   uint16_t phaseLen = S->phaseLength, tapCnt;    /* Length of each polyphase filter component */
    00146
    00147
    00148   /* S->pState buffer contains previous frame (phaseLen - 1) samples */
    00149   /* pStateCurnt points to the location where the new input data should be written */
    00150   pStateCurnt = S->pState + (phaseLen - 1u);
    00151
    00152   /* Total number of intput samples */
    00153   blkCnt = blockSize;
    00154
    00155   /* Loop over the blockSize. */
    00156   while(blkCnt > 0u)
    00157   {
    00158     /* Copy new input sample into the state buffer */
    00159     *pStateCurnt++ = *pSrc++;
    00160
    00161     /* Address modifier index of coefficient buffer */
    00162     j = 1u;
    00163
    00164     /* Loop over the Interpolation factor. */
    00165     i = S->L;
    00166     while(i > 0u)
    00167     {
    00168       /* Set accumulator to zero */
    00169       sum0 = 0.0f;
    00170
    00171       /* Initialize state pointer */
    00172       ptr1 = pState;
    00173
    00174       /* Initialize coefficient pointer */
    00175       ptr2 = pCoeffs + (S->L - j);
    00176
    00177       /* Loop over the polyPhase length. Unroll by a factor of 4.
    00178        ** Repeat until we've computed numTaps-(4*S->L) coefficients. */
    00179       tapCnt = phaseLen >> 2u;
    00180       while(tapCnt > 0u)
    00181       {
    00182
    00183         /* Read the coefficient */
    00184         c0 = *(ptr2);
    00185
    00186         /* Upsampling is done by stuffing L-1 zeros between each sample.
    00187          * So instead of multiplying zeros with coefficients,
    00188          * Increment the coefficient pointer by interpolation factor times. */
    00189         ptr2 += S->L;
    00190
    00191         /* Read the input sample */
    00192         x0 = *(ptr1++);
    00193
    00194         /* Perform the multiply-accumulate */
    00195         sum0 += x0 * c0;
    00196
    00197         /* Read the coefficient */
    00198         c0 = *(ptr2);
    00199
    00200         /* Increment the coefficient pointer by interpolation factor times. */
    00201         ptr2 += S->L;
    00202
    00203         /* Read the input sample */
    00204         x0 = *(ptr1++);
    00205
    00206         /* Perform the multiply-accumulate */
    00207         sum0 += x0 * c0;
    00208
    00209         /* Read the coefficient */
    00210         c0 = *(ptr2);
    00211
    00212         /* Increment the coefficient pointer by interpolation factor times. */
    00213         ptr2 += S->L;
    00214
    00215         /* Read the input sample */
    00216         x0 = *(ptr1++);
    00217
    00218         /* Perform the multiply-accumulate */
    00219         sum0 += x0 * c0;
    00220
    00221         /* Read the coefficient */
    00222         c0 = *(ptr2);
    00223
    00224         /* Increment the coefficient pointer by interpolation factor times. */
    00225         ptr2 += S->L;
    00226
    00227         /* Read the input sample */
    00228         x0 = *(ptr1++);
    00229
    00230         /* Perform the multiply-accumulate */
    00231         sum0 += x0 * c0;
    00232
    00233         /* Decrement the loop counter */
    00234         tapCnt--;
    00235       }
    00236
    00237       /* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */
    00238       tapCnt = phaseLen % 0x4u;
    00239
    00240       while(tapCnt > 0u)
    00241       {
    00242         /* Perform the multiply-accumulate */
    00243         sum0 += *(ptr1++) * (*ptr2);
    00244
    00245         /* Increment the coefficient pointer by interpolation factor times. */
    00246         ptr2 += S->L;
    00247
    00248         /* Decrement the loop counter */
    00249         tapCnt--;
    00250       }
    00251
    00252       /* The result is in the accumulator, store in the destination buffer. */
    00253       *pDst++ = sum0;
    00254
    00255       /* Increment the address modifier index of coefficient buffer */
    00256       j++;
    00257
    00258       /* Decrement the loop counter */
    00259       i--;
    00260     }
    00261
    00262     /* Advance the state pointer by 1
    00263      * to process the next group of interpolation factor number samples */
    00264     pState = pState + 1;
    00265
    00266     /* Decrement the loop counter */
    00267     blkCnt--;
    00268   }
    00269
    00270   /* Processing is complete.
    00271    ** Now copy the last phaseLen - 1 samples to the satrt of the state buffer.
    00272    ** This prepares the state buffer for the next function call. */
    00273
    00274   /* Points to the start of the state buffer */
    00275   pStateCurnt = S->pState;
    00276
    00277   tapCnt = (phaseLen - 1u) >> 2u;
    00278
    00279   /* copy data */
    00280   while(tapCnt > 0u)
    00281   {
    00282     *pStateCurnt++ = *pState++;
    00283     *pStateCurnt++ = *pState++;
    00284     *pStateCurnt++ = *pState++;
    00285     *pStateCurnt++ = *pState++;
    00286
    00287     /* Decrement the loop counter */
    00288     tapCnt--;
    00289   }
    00290
    00291   tapCnt = (phaseLen - 1u) % 0x04u;
    00292
    00293   while(tapCnt > 0u)
    00294   {
    00295     *pStateCurnt++ = *pState++;
    00296
    00297     /* Decrement the loop counter */
    00298     tapCnt--;
    00299   }
    00300 }
    00301

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