Diff: cmsis_dsp/FilteringFunctions/arm_iir_lattice_q31.c

Revision:

1:fdd22bb7aa52

Child:

2:da51fb522205

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cmsis_dsp/FilteringFunctions/arm_iir_lattice_q31.c	Wed Nov 28 12:30:09 2012 +0000
@@ -0,0 +1,345 @@
+/* ----------------------------------------------------------------------    
+* Copyright (C) 2010 ARM Limited. All rights reserved.    
+*    
+* $Date:        15. February 2012  
+* $Revision:     V1.1.0  
+*    
+* Project:         CMSIS DSP Library    
+* Title:        arm_iir_lattice_q31.c    
+*    
+* Description:    Q31 IIR lattice filter processing function.    
+*    
+* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
+*  
+* Version 1.1.0 2012/02/15 
+*    Updated with more optimizations, bug fixes and minor API changes.  
+*   
+* 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 IIR_Lattice    
+ * @{    
+ */
+
+/**    
+ * @brief Processing function for the Q31 IIR lattice filter.    
+ * @param[in] *S points to an instance of the Q31 IIR lattice 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 samples to process.    
+ * @return none.    
+ *    
+ * @details    
+ * <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 2*log2(numStages) bits.    
+ * After all multiply-accumulates are performed, the 2.62 accumulator is saturated to 1.32 format and then truncated to 1.31 format.    
+ */
+
+void arm_iir_lattice_q31(
+  const arm_iir_lattice_instance_q31 * S,
+  q31_t * pSrc,
+  q31_t * pDst,
+  uint32_t blockSize)
+{
+  q31_t fcurr, fnext = 0, gcurr = 0, gnext;      /* Temporary variables for lattice stages */
+  q63_t acc;                                     /* Accumlator */
+  uint32_t blkCnt, tapCnt;                       /* Temporary variables for counts */
+  q31_t *px1, *px2, *pk, *pv;                    /* Temporary pointers for state and coef */
+  uint32_t numStages = S->numStages;             /* number of stages */
+  q31_t *pState;                                 /* State pointer */
+  q31_t *pStateCurnt;                            /* State current pointer */
+
+  blkCnt = blockSize;
+
+  pState = &S->pState[0];
+
+
+#ifndef ARM_MATH_CM0
+
+  /* Run the below code for Cortex-M4 and Cortex-M3 */
+
+  /* Sample processing */
+  while(blkCnt > 0u)
+  {
+    /* Read Sample from input buffer */
+    /* fN(n) = x(n) */
+    fcurr = *pSrc++;
+
+    /* Initialize state read pointer */
+    px1 = pState;
+    /* Initialize state write pointer */
+    px2 = pState;
+    /* Set accumulator to zero */
+    acc = 0;
+    /* Initialize Ladder coeff pointer */
+    pv = &S->pvCoeffs[0];
+    /* Initialize Reflection coeff pointer */
+    pk = &S->pkCoeffs[0];
+
+
+    /* Process sample for first tap */
+    gcurr = *px1++;
+    /* fN-1(n) = fN(n) - kN * gN-1(n-1) */
+    fnext = __QSUB(fcurr, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
+    /* gN(n) = kN * fN-1(n) + gN-1(n-1) */
+    gnext = __QADD(gcurr, (q31_t) (((q63_t) fnext * (*pk++)) >> 31));
+    /* write gN-1(n-1) into state for next sample processing */
+    *px2++ = gnext;
+    /* y(n) += gN(n) * vN  */
+    acc += ((q63_t) gnext * *pv++);
+
+    /* Update f values for next coefficient processing */
+    fcurr = fnext;
+
+    /* Loop unrolling.  Process 4 taps at a time. */
+    tapCnt = (numStages - 1u) >> 2;
+
+    while(tapCnt > 0u)
+    {
+
+      /* Process sample for 2nd, 6th .. taps */
+      /* Read gN-2(n-1) from state buffer */
+      gcurr = *px1++;
+      /* fN-2(n) = fN-1(n) - kN-1 * gN-2(n-1) */
+      fnext = __QSUB(fcurr, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
+      /* gN-1(n) = kN-1 * fN-2(n) + gN-2(n-1) */
+      gnext = __QADD(gcurr, (q31_t) (((q63_t) fnext * (*pk++)) >> 31));
+      /* y(n) += gN-1(n) * vN-1  */
+      /* process for gN-5(n) * vN-5, gN-9(n) * vN-9 ... */
+      acc += ((q63_t) gnext * *pv++);
+      /* write gN-1(n) into state for next sample processing */
+      *px2++ = gnext;
+
+      /* Process sample for 3nd, 7th ...taps */
+      /* Read gN-3(n-1) from state buffer */
+      gcurr = *px1++;
+      /* Process sample for 3rd, 7th .. taps */
+      /* fN-3(n) = fN-2(n) - kN-2 * gN-3(n-1) */
+      fcurr = __QSUB(fnext, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
+      /* gN-2(n) = kN-2 * fN-3(n) + gN-3(n-1) */
+      gnext = __QADD(gcurr, (q31_t) (((q63_t) fcurr * (*pk++)) >> 31));
+      /* y(n) += gN-2(n) * vN-2  */
+      /* process for gN-6(n) * vN-6, gN-10(n) * vN-10 ... */
+      acc += ((q63_t) gnext * *pv++);
+      /* write gN-2(n) into state for next sample processing */
+      *px2++ = gnext;
+
+
+      /* Process sample for 4th, 8th ...taps */
+      /* Read gN-4(n-1) from state buffer */
+      gcurr = *px1++;
+      /* Process sample for 4th, 8th .. taps */
+      /* fN-4(n) = fN-3(n) - kN-3 * gN-4(n-1) */
+      fnext = __QSUB(fcurr, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
+      /* gN-3(n) = kN-3 * fN-4(n) + gN-4(n-1) */
+      gnext = __QADD(gcurr, (q31_t) (((q63_t) fnext * (*pk++)) >> 31));
+      /* y(n) += gN-3(n) * vN-3  */
+      /* process for gN-7(n) * vN-7, gN-11(n) * vN-11 ... */
+      acc += ((q63_t) gnext * *pv++);
+      /* write gN-3(n) into state for next sample processing */
+      *px2++ = gnext;
+
+
+      /* Process sample for 5th, 9th ...taps */
+      /* Read gN-5(n-1) from state buffer */
+      gcurr = *px1++;
+      /* Process sample for 5th, 9th .. taps */
+      /* fN-5(n) = fN-4(n) - kN-4 * gN-1(n-1) */
+      fcurr = __QSUB(fnext, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
+      /* gN-4(n) = kN-4 * fN-5(n) + gN-5(n-1) */
+      gnext = __QADD(gcurr, (q31_t) (((q63_t) fcurr * (*pk++)) >> 31));
+      /* y(n) += gN-4(n) * vN-4  */
+      /* process for gN-8(n) * vN-8, gN-12(n) * vN-12 ... */
+      acc += ((q63_t) gnext * *pv++);
+      /* write gN-4(n) into state for next sample processing */
+      *px2++ = gnext;
+
+      tapCnt--;
+
+    }
+
+    fnext = fcurr;
+
+    /* If the filter length is not a multiple of 4, compute the remaining filter taps */
+    tapCnt = (numStages - 1u) % 0x4u;
+
+    while(tapCnt > 0u)
+    {
+      gcurr = *px1++;
+      /* Process sample for last taps */
+      fnext = __QSUB(fcurr, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
+      gnext = __QADD(gcurr, (q31_t) (((q63_t) fnext * (*pk++)) >> 31));
+      /* Output samples for last taps */
+      acc += ((q63_t) gnext * *pv++);
+      *px2++ = gnext;
+      fcurr = fnext;
+
+      tapCnt--;
+
+    }
+
+    /* y(n) += g0(n) * v0 */
+    acc += (q63_t) fnext *(
+  *pv++);
+
+    *px2++ = fnext;
+
+    /* write out into pDst */
+    *pDst++ = (q31_t) (acc >> 31u);
+
+    /* Advance the state pointer by 4 to process the next group of 4 samples */
+    pState = pState + 1u;
+    blkCnt--;
+
+  }
+
+  /* Processing is complete. Now copy last S->numStages samples to start of the buffer    
+     for the preperation of next frame process */
+
+  /* Points to the start of the state buffer */
+  pStateCurnt = &S->pState[0];
+  pState = &S->pState[blockSize];
+
+  tapCnt = numStages >> 2u;
+
+  /* copy data */
+  while(tapCnt > 0u)
+  {
+    *pStateCurnt++ = *pState++;
+    *pStateCurnt++ = *pState++;
+    *pStateCurnt++ = *pState++;
+    *pStateCurnt++ = *pState++;
+
+    /* Decrement the loop counter */
+    tapCnt--;
+
+  }
+
+  /* Calculate remaining number of copies */
+  tapCnt = (numStages) % 0x4u;
+
+  /* Copy the remaining q31_t data */
+  while(tapCnt > 0u)
+  {
+    *pStateCurnt++ = *pState++;
+
+    /* Decrement the loop counter */
+    tapCnt--;
+  };
+
+#else
+
+  /* Run the below code for Cortex-M0 */
+  /* Sample processing */
+  while(blkCnt > 0u)
+  {
+    /* Read Sample from input buffer */
+    /* fN(n) = x(n) */
+    fcurr = *pSrc++;
+
+    /* Initialize state read pointer */
+    px1 = pState;
+    /* Initialize state write pointer */
+    px2 = pState;
+    /* Set accumulator to zero */
+    acc = 0;
+    /* Initialize Ladder coeff pointer */
+    pv = &S->pvCoeffs[0];
+    /* Initialize Reflection coeff pointer */
+    pk = &S->pkCoeffs[0];
+
+    tapCnt = numStages;
+
+    while(tapCnt > 0u)
+    {
+      gcurr = *px1++;
+      /* Process sample */
+      /* fN-1(n) = fN(n) - kN * gN-1(n-1) */
+      fnext =
+        clip_q63_to_q31(((q63_t) fcurr -
+                         ((q31_t) (((q63_t) gcurr * (*pk)) >> 31))));
+      /* gN(n) = kN * fN-1(n) + gN-1(n-1) */
+      gnext =
+        clip_q63_to_q31(((q63_t) gcurr +
+                         ((q31_t) (((q63_t) fnext * (*pk++)) >> 31))));
+      /* Output samples */
+      /* y(n) += gN(n) * vN  */
+      acc += ((q63_t) gnext * *pv++);
+      /* write gN-1(n-1) into state for next sample processing */
+      *px2++ = gnext;
+      /* Update f values for next coefficient processing */
+      fcurr = fnext;
+
+      tapCnt--;
+    }
+
+    /* y(n) += g0(n) * v0 */
+    acc += (q63_t) fnext *(
+  *pv++);
+
+    *px2++ = fnext;
+
+    /* write out into pDst */
+    *pDst++ = (q31_t) (acc >> 31u);
+
+    /* Advance the state pointer by 1 to process the next group of samples */
+    pState = pState + 1u;
+    blkCnt--;
+
+  }
+
+  /* Processing is complete. Now copy last S->numStages samples to start of the buffer           
+     for the preperation of next frame process */
+
+  /* Points to the start of the state buffer */
+  pStateCurnt = &S->pState[0];
+  pState = &S->pState[blockSize];
+
+  tapCnt = numStages;
+
+  /* Copy the remaining q31_t data */
+  while(tapCnt > 0u)
+  {
+    *pStateCurnt++ = *pState++;
+
+    /* Decrement the loop counter */
+    tapCnt--;
+  }
+
+#endif /*   #ifndef ARM_MATH_CM0 */
+
+}
+
+
+
+
+/**    
+ * @} end of IIR_Lattice group    
+ */