Diff: cmsis_dsp/FilteringFunctions/arm_fir_q31.c

Revision:

1:fdd22bb7aa52

Child:

2:da51fb522205

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cmsis_dsp/FilteringFunctions/arm_fir_q31.c	Wed Nov 28 12:30:09 2012 +0000
@@ -0,0 +1,363 @@
+/* ----------------------------------------------------------------------    
+* Copyright (C) 2010 ARM Limited. All rights reserved.    
+*    
+* $Date:        15. February 2012  
+* $Revision:     V1.1.0  
+*    
+* Project:         CMSIS DSP Library    
+* Title:        arm_fir_q31.c    
+*    
+* Description:    Q31 FIR 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 0.0.5  2010/04/26     
+*      incorporated review comments and updated with latest CMSIS layer    
+*    
+* Version 0.0.3  2010/03/10     
+*    Initial version    
+* -------------------------------------------------------------------- */
+
+#include "arm_math.h"
+
+/**    
+ * @ingroup groupFilters    
+ */
+
+/**    
+ * @addtogroup FIR    
+ * @{    
+ */
+
+/**    
+ * @param[in] *S points to an instance of the Q31 FIR filter 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 per call.    
+ * @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 log2(numTaps) bits.    
+ * After all multiply-accumulates are performed, the 2.62 accumulator is right shifted by 31 bits and saturated to 1.31 format to yield the final result.  
+ *    
+ * \par    
+ * Refer to the function <code>arm_fir_fast_q31()</code> for a faster but less precise implementation of this filter for Cortex-M3 and Cortex-M4.    
+ */
+
+void arm_fir_q31(
+  const arm_fir_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 */
+
+
+#ifndef ARM_MATH_CM0
+
+  /* Run the below code for Cortex-M4 and Cortex-M3 */
+
+  q31_t x0, x1, x2;                              /* Temporary variables to hold state */
+  q31_t c0;                                      /* Temporary variable to hold coefficient value */
+  q31_t *px;                                     /* Temporary pointer for state */
+  q31_t *pb;                                     /* Temporary pointer for coefficient buffer */
+  q63_t acc0, acc1, acc2;                        /* Accumulators */
+  uint32_t numTaps = S->numTaps;                 /* Number of filter coefficients in the filter */
+  uint32_t i, tapCnt, blkCnt, tapCntN3;          /* Loop counters */
+
+  /* S->pState points to state array which contains previous frame (numTaps - 1) samples */
+  /* pStateCurnt points to the location where the new input data should be written */
+  pStateCurnt = &(S->pState[(numTaps - 1u)]);
+
+  /* Apply loop unrolling and compute 4 output values simultaneously.    
+   * The variables acc0 ... acc3 hold output values that are being computed:    
+   *    
+   *    acc0 =  b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0]    
+   *    acc1 =  b[numTaps-1] * x[n-numTaps] +   b[numTaps-2] * x[n-numTaps-1] + b[numTaps-3] * x[n-numTaps-2] +...+ b[0] * x[1]    
+   *    acc2 =  b[numTaps-1] * x[n-numTaps+1] + b[numTaps-2] * x[n-numTaps] +   b[numTaps-3] * x[n-numTaps-1] +...+ b[0] * x[2]    
+   *    acc3 =  b[numTaps-1] * x[n-numTaps+2] + b[numTaps-2] * x[n-numTaps+1] + b[numTaps-3] * x[n-numTaps]   +...+ b[0] * x[3]    
+   */
+  blkCnt = blockSize / 3;
+  blockSize = blockSize - (3 * blkCnt);
+
+  tapCnt = numTaps / 3;
+  tapCntN3 = numTaps - (3 * tapCnt);
+
+  /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.    
+   ** a second loop below computes the remaining 1 to 3 samples. */
+  while(blkCnt > 0u)
+  {
+    /* Copy three new input samples into the state buffer */
+    *pStateCurnt++ = *pSrc++;
+    *pStateCurnt++ = *pSrc++;
+    *pStateCurnt++ = *pSrc++;
+
+    /* Set all accumulators to zero */
+    acc0 = 0;
+    acc1 = 0;
+    acc2 = 0;
+
+    /* Initialize state pointer */
+    px = pState;
+
+    /* Initialize coefficient pointer */
+    pb = pCoeffs;
+
+    /* Read the first two samples from the state buffer:    
+     *  x[n-numTaps], x[n-numTaps-1] */
+    x0 = *(px++);
+    x1 = *(px++);
+
+    /* Loop unrolling.  Process 3 taps at a time. */
+    i = tapCnt;
+
+    while(i > 0u)
+    {
+      /* Read the b[numTaps] coefficient */
+      c0 = *pb;
+
+      /* Read x[n-numTaps-2] sample */
+      x2 = *(px++);
+
+      /* Perform the multiply-accumulates */
+      acc0 += ((q63_t) x0 * c0);
+      acc1 += ((q63_t) x1 * c0);
+      acc2 += ((q63_t) x2 * c0);
+
+      /* Read the coefficient and state */
+      c0 = *(pb + 1u);
+      x0 = *(px++);
+
+      /* Perform the multiply-accumulates */
+      acc0 += ((q63_t) x1 * c0);
+      acc1 += ((q63_t) x2 * c0);
+      acc2 += ((q63_t) x0 * c0);
+
+      /* Read the coefficient and state */
+      c0 = *(pb + 2u);
+      x1 = *(px++);
+
+      /* update coefficient pointer */
+      pb += 3u;
+
+      /* Perform the multiply-accumulates */
+      acc0 += ((q63_t) x2 * c0);
+      acc1 += ((q63_t) x0 * c0);
+      acc2 += ((q63_t) x1 * c0);
+
+      /* Decrement the loop counter */
+      i--;
+    }
+
+    /* If the filter length is not a multiple of 3, compute the remaining filter taps */
+
+    i = tapCntN3;
+
+    while(i > 0u)
+    {
+      /* Read coefficients */
+      c0 = *(pb++);
+
+      /* Fetch 1 state variable */
+      x2 = *(px++);
+
+      /* Perform the multiply-accumulates */
+      acc0 += ((q63_t) x0 * c0);
+      acc1 += ((q63_t) x1 * c0);
+      acc2 += ((q63_t) x2 * c0);
+
+      /* Reuse the present sample states for next sample */
+      x0 = x1;
+      x1 = x2;
+
+      /* Decrement the loop counter */
+      i--;
+    }
+
+    /* Advance the state pointer by 3 to process the next group of 3 samples */
+    pState = pState + 3;
+
+    /* The results in the 3 accumulators are in 2.30 format.  Convert to 1.31    
+     ** Then store the 3 outputs in the destination buffer. */
+    *pDst++ = (q31_t) (acc0 >> 31u);
+    *pDst++ = (q31_t) (acc1 >> 31u);
+    *pDst++ = (q31_t) (acc2 >> 31u);
+
+    /* Decrement the samples loop counter */
+    blkCnt--;
+  }
+
+  /* If the blockSize is not a multiple of 3, compute any remaining output samples here.    
+   ** No loop unrolling is used. */
+
+  while(blockSize > 0u)
+  {
+    /* Copy one sample at a time into state buffer */
+    *pStateCurnt++ = *pSrc++;
+
+    /* Set the accumulator to zero */
+    acc0 = 0;
+
+    /* Initialize state pointer */
+    px = pState;
+
+    /* Initialize Coefficient pointer */
+    pb = (pCoeffs);
+
+    i = numTaps;
+
+    /* Perform the multiply-accumulates */
+    do
+    {
+      acc0 += (q63_t) * (px++) * (*(pb++));
+      i--;
+    } while(i > 0u);
+
+    /* The result is in 2.62 format.  Convert to 1.31    
+     ** Then store the output in the destination buffer. */
+    *pDst++ = (q31_t) (acc0 >> 31u);
+
+    /* Advance state pointer by 1 for the next sample */
+    pState = pState + 1;
+
+    /* Decrement the samples loop counter */
+    blockSize--;
+  }
+
+  /* Processing is complete.    
+   ** Now copy the last numTaps - 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 = (numTaps - 1u) >> 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 = (numTaps - 1u) % 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 */
+
+  q31_t *px;                                     /* Temporary pointer for state */
+  q31_t *pb;                                     /* Temporary pointer for coefficient buffer */
+  q63_t acc;                                     /* Accumulator */
+  uint32_t numTaps = S->numTaps;                 /* Length of the filter */
+  uint32_t i, tapCnt, blkCnt;                    /* Loop counters */
+
+  /* S->pState buffer contains previous frame (numTaps - 1) samples */
+  /* pStateCurnt points to the location where the new input data should be written */
+  pStateCurnt = &(S->pState[(numTaps - 1u)]);
+
+  /* Initialize blkCnt with blockSize */
+  blkCnt = blockSize;
+
+  while(blkCnt > 0u)
+  {
+    /* Copy one sample at a time into state buffer */
+    *pStateCurnt++ = *pSrc++;
+
+    /* Set the accumulator to zero */
+    acc = 0;
+
+    /* Initialize state pointer */
+    px = pState;
+
+    /* Initialize Coefficient pointer */
+    pb = pCoeffs;
+
+    i = numTaps;
+
+    /* Perform the multiply-accumulates */
+    do
+    {
+      /* acc =  b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0] */
+      acc += (q63_t) * px++ * *pb++;
+      i--;
+    } while(i > 0u);
+
+    /* The result is in 2.62 format.  Convert to 1.31         
+     ** Then store the output in the destination buffer. */
+    *pDst++ = (q31_t) (acc >> 31u);
+
+    /* Advance state pointer by 1 for the next sample */
+    pState = pState + 1;
+
+    /* Decrement the samples loop counter */
+    blkCnt--;
+  }
+
+  /* Processing is complete.         
+   ** Now copy the last numTaps - 1 samples to the starting 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;
+
+  /* Copy numTaps number of values */
+  tapCnt = numTaps - 1u;
+
+  /* Copy the data */
+  while(tapCnt > 0u)
+  {
+    *pStateCurnt++ = *pState++;
+
+    /* Decrement the loop counter */
+    tapCnt--;
+  }
+
+
+#endif /*  #ifndef ARM_MATH_CM0 */
+
+}
+
+/**    
+ * @} end of FIR group    
+ */