- Main Page
- Modules
- Data Structures
- Files
- Examples

- File List
- Globals

# arm_iir_lattice_f32.c

Go to the documentation of this file.

    00001 /* ----------------------------------------------------------------------
    00002 * Copyright (C) 2010 ARM Limited. All rights reserved.
    00003 *
    00004 * $Date:        15. July 2011
    00005 * $Revision:    V1.0.10
    00006 *
    00007 * Project:      CMSIS DSP Library
    00008 * Title:        arm_iir_lattice_f32.c
    00009 *
    00010 * Description:  Floating-point IIR Lattice filter processing function.
    00011 *
    00012 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
    00013 *
    00014 * Version 1.0.10 2011/7/15
    00015 *    Big Endian support added and Merged M0 and M3/M4 Source code.
    00016 *
    00017 * Version 1.0.3 2010/11/29
    00018 *    Re-organized the CMSIS folders and updated documentation.
    00019 *
    00020 * Version 1.0.2 2010/11/11
    00021 *    Documentation updated.
    00022 *
    00023 * Version 1.0.1 2010/10/05
    00024 *    Production release and review comments incorporated.
    00025 *
    00026 * Version 1.0.0 2010/09/20
    00027 *    Production release and review comments incorporated
    00028 *
    00029 * Version 0.0.7  2010/06/10
    00030 *    Misra-C changes done
    00031 * -------------------------------------------------------------------- */
    00032
    00033 #include "arm_math.h"
    00034
    00120 void arm_iir_lattice_f32(
    00121   const arm_iir_lattice_instance_f32 * S,
    00122   float32_t * pSrc,
    00123   float32_t * pDst,
    00124   uint32_t blockSize)
    00125 {
    00126   float32_t fcurr, fnext = 0, gcurr, gnext;      /* Temporary variables for lattice stages */
    00127   float32_t acc;                                 /* Accumlator */
    00128   uint32_t blkCnt, tapCnt;                       /* temporary variables for counts */
    00129   float32_t *px1, *px2, *pk, *pv;                /* temporary pointers for state and coef */
    00130   uint32_t numStages = S->numStages;             /* number of stages */
    00131   float32_t *pState;                             /* State pointer */
    00132   float32_t *pStateCurnt;                        /* State current pointer */
    00133
    00134
    00135 #ifndef ARM_MATH_CM0
    00136
    00137   /* Run the below code for Cortex-M4 and Cortex-M3 */
    00138
    00139   gcurr = 0.0f;
    00140   blkCnt = blockSize;
    00141
    00142   pState = &S->pState[0];
    00143
    00144   /* Sample processing */
    00145   while(blkCnt > 0u)
    00146   {
    00147     /* Read Sample from input buffer */
    00148     /* fN(n) = x(n) */
    00149     fcurr = *pSrc++;
    00150
    00151     /* Initialize state read pointer */
    00152     px1 = pState;
    00153     /* Initialize state write pointer */
    00154     px2 = pState;
    00155     /* Set accumulator to zero */
    00156     acc = 0.0f;
    00157     /* Initialize Ladder coeff pointer */
    00158     pv = &S->pvCoeffs[0];
    00159     /* Initialize Reflection coeff pointer */
    00160     pk = &S->pkCoeffs[0];
    00161
    00162
    00163     /* Process sample for first tap */
    00164     gcurr = *px1++;
    00165     /* fN-1(n) = fN(n) - kN * gN-1(n-1) */
    00166     fnext = fcurr - ((*pk) * gcurr);
    00167     /* gN(n) = kN * fN-1(n) + gN-1(n-1) */
    00168     gnext = (fnext * (*pk++)) + gcurr;
    00169     /* write gN(n) into state for next sample processing */
    00170     *px2++ = gnext;
    00171     /* y(n) += gN(n) * vN  */
    00172     acc += (gnext * (*pv++));
    00173
    00174     /* Update f values for next coefficient processing */
    00175     fcurr = fnext;
    00176
    00177     /* Loop unrolling.  Process 4 taps at a time. */
    00178     tapCnt = (numStages - 1u) >> 2;
    00179
    00180     while(tapCnt > 0u)
    00181     {
    00182       /* Process sample for 2nd, 6th ...taps */
    00183       /* Read gN-2(n-1) from state buffer */
    00184       gcurr = *px1++;
    00185       /* Process sample for 2nd, 6th .. taps */
    00186       /* fN-2(n) = fN-1(n) - kN-1 * gN-2(n-1) */
    00187       fnext = fcurr - ((*pk) * gcurr);
    00188       /* gN-1(n) = kN-1 * fN-2(n) + gN-2(n-1) */
    00189       gnext = (fnext * (*pk++)) + gcurr;
    00190       /* y(n) += gN-1(n) * vN-1  */
    00191       /* process for gN-5(n) * vN-5, gN-9(n) * vN-9 ... */
    00192       acc += (gnext * (*pv++));
    00193       /* write gN-1(n) into state for next sample processing */
    00194       *px2++ = gnext;
    00195
    00196
    00197       /* Process sample for 3nd, 7th ...taps */
    00198       /* Read gN-3(n-1) from state buffer */
    00199       gcurr = *px1++;
    00200       /* Process sample for 3rd, 7th .. taps */
    00201       /* fN-3(n) = fN-2(n) - kN-2 * gN-3(n-1) */
    00202       fcurr = fnext - ((*pk) * gcurr);
    00203       /* gN-2(n) = kN-2 * fN-3(n) + gN-3(n-1) */
    00204       gnext = (fcurr * (*pk++)) + gcurr;
    00205       /* y(n) += gN-2(n) * vN-2  */
    00206       /* process for gN-6(n) * vN-6, gN-10(n) * vN-10 ... */
    00207       acc += (gnext * (*pv++));
    00208       /* write gN-2(n) into state for next sample processing */
    00209       *px2++ = gnext;
    00210
    00211
    00212       /* Process sample for 4th, 8th ...taps */
    00213       /* Read gN-4(n-1) from state buffer */
    00214       gcurr = *px1++;
    00215       /* Process sample for 4th, 8th .. taps */
    00216       /* fN-4(n) = fN-3(n) - kN-3 * gN-4(n-1) */
    00217       fnext = fcurr - ((*pk) * gcurr);
    00218       /* gN-3(n) = kN-3 * fN-4(n) + gN-4(n-1) */
    00219       gnext = (fnext * (*pk++)) + gcurr;
    00220       /* y(n) += gN-3(n) * vN-3  */
    00221       /* process for gN-7(n) * vN-7, gN-11(n) * vN-11 ... */
    00222       acc += (gnext * (*pv++));
    00223       /* write gN-3(n) into state for next sample processing */
    00224       *px2++ = gnext;
    00225
    00226
    00227       /* Process sample for 5th, 9th ...taps */
    00228       /* Read gN-5(n-1) from state buffer */
    00229       gcurr = *px1++;
    00230       /* Process sample for 5th, 9th .. taps */
    00231       /* fN-5(n) = fN-4(n) - kN-4 * gN-1(n-1) */
    00232       fcurr = fnext - ((*pk) * gcurr);
    00233       /* gN-4(n) = kN-4 * fN-5(n) + gN-5(n-1) */
    00234       gnext = (fcurr * (*pk++)) + gcurr;
    00235       /* y(n) += gN-4(n) * vN-4  */
    00236       /* process for gN-8(n) * vN-8, gN-12(n) * vN-12 ... */
    00237       acc += (gnext * (*pv++));
    00238       /* write gN-4(n) into state for next sample processing */
    00239       *px2++ = gnext;
    00240
    00241       tapCnt--;
    00242
    00243     }
    00244
    00245     fnext = fcurr;
    00246
    00247     /* If the filter length is not a multiple of 4, compute the remaining filter taps */
    00248     tapCnt = (numStages - 1u) % 0x4u;
    00249
    00250     while(tapCnt > 0u)
    00251     {
    00252       gcurr = *px1++;
    00253       /* Process sample for last taps */
    00254       fnext = fcurr - ((*pk) * gcurr);
    00255       gnext = (fnext * (*pk++)) + gcurr;
    00256       /* Output samples for last taps */
    00257       acc += (gnext * (*pv++));
    00258       *px2++ = gnext;
    00259       fcurr = fnext;
    00260
    00261       tapCnt--;
    00262
    00263     }
    00264
    00265
    00266     /* y(n) += g0(n) * v0 */
    00267     acc += (fnext * (*pv));
    00268
    00269     *px2++ = fnext;
    00270
    00271     /* write out into pDst */
    00272     *pDst++ = acc;
    00273
    00274     /* Advance the state pointer by 4 to process the next group of 4 samples */
    00275     pState = pState + 1u;
    00276     blkCnt--;
    00277
    00278   }
    00279
    00280   /* Processing is complete. Now copy last S->numStages samples to start of the buffer
    00281      for the preperation of next frame process */
    00282
    00283   /* Points to the start of the state buffer */
    00284   pStateCurnt = &S->pState[0];
    00285   pState = &S->pState[blockSize];
    00286
    00287   tapCnt = numStages >> 2u;
    00288
    00289   /* copy data */
    00290   while(tapCnt > 0u)
    00291   {
    00292     *pStateCurnt++ = *pState++;
    00293     *pStateCurnt++ = *pState++;
    00294     *pStateCurnt++ = *pState++;
    00295     *pStateCurnt++ = *pState++;
    00296
    00297     /* Decrement the loop counter */
    00298     tapCnt--;
    00299
    00300   }
    00301
    00302   /* Calculate remaining number of copies */
    00303   tapCnt = (numStages) % 0x4u;
    00304
    00305   /* Copy the remaining q31_t data */
    00306   while(tapCnt > 0u)
    00307   {
    00308     *pStateCurnt++ = *pState++;
    00309
    00310     /* Decrement the loop counter */
    00311     tapCnt--;
    00312   }
    00313
    00314 #else
    00315
    00316   /* Run the below code for Cortex-M0 */
    00317
    00318   blkCnt = blockSize;
    00319
    00320   pState = &S->pState[0];
    00321
    00322   /* Sample processing */
    00323   while(blkCnt > 0u)
    00324   {
    00325     /* Read Sample from input buffer */
    00326     /* fN(n) = x(n) */
    00327     fcurr = *pSrc++;
    00328
    00329     /* Initialize state read pointer */
    00330     px1 = pState;
    00331     /* Initialize state write pointer */
    00332     px2 = pState;
    00333     /* Set accumulator to zero */
    00334     acc = 0.0f;
    00335     /* Initialize Ladder coeff pointer */
    00336     pv = &S->pvCoeffs[0];
    00337     /* Initialize Reflection coeff pointer */
    00338     pk = &S->pkCoeffs[0];
    00339
    00340
    00341     /* Process sample for numStages */
    00342     tapCnt = numStages;
    00343
    00344     while(tapCnt > 0u)
    00345     {
    00346       gcurr = *px1++;
    00347       /* Process sample for last taps */
    00348       fnext = fcurr - ((*pk) * gcurr);
    00349       gnext = (fnext * (*pk++)) + gcurr;
    00350
    00351       /* Output samples for last taps */
    00352       acc += (gnext * (*pv++));
    00353       *px2++ = gnext;
    00354       fcurr = fnext;
    00355
    00356       /* Decrementing loop counter */
    00357       tapCnt--;
    00358
    00359     }
    00360
    00361     /* y(n) += g0(n) * v0 */
    00362     acc += (fnext * (*pv));
    00363
    00364     *px2++ = fnext;
    00365
    00366     /* write out into pDst */
    00367     *pDst++ = acc;
    00368
    00369     /* Advance the state pointer by 1 to process the next group of samples */
    00370     pState = pState + 1u;
    00371     blkCnt--;
    00372
    00373   }
    00374
    00375   /* Processing is complete. Now copy last S->numStages samples to start of the buffer
    00376      for the preperation of next frame process */
    00377
    00378   /* Points to the start of the state buffer */
    00379   pStateCurnt = &S->pState[0];
    00380   pState = &S->pState[blockSize];
    00381
    00382   tapCnt = numStages;
    00383
    00384   /* Copy the data */
    00385   while(tapCnt > 0u)
    00386   {
    00387     *pStateCurnt++ = *pState++;
    00388
    00389     /* Decrement the loop counter */
    00390     tapCnt--;
    00391   }
    00392
    00393 #endif /*   #ifndef ARM_MATH_CM0 */
    00394
    00395 }
    00396
    00397
    00398
    00399

All Data Structures Files Functions Variables Typedefs Enumerations Enumerator Defines