Diff: cmsis_dsp/FilteringFunctions/arm_biquad_cascade_df1_fast_q31.c

Revision:

1:fdd22bb7aa52

Child:

2:da51fb522205

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cmsis_dsp/FilteringFunctions/arm_biquad_cascade_df1_fast_q31.c	Wed Nov 28 12:30:09 2012 +0000
@@ -0,0 +1,275 @@
+/* ----------------------------------------------------------------------    
+* Copyright (C) 2010 ARM Limited. All rights reserved.    
+*    
+* $Date:        15. February 2012  
+* $Revision:     V1.1.0  
+*    
+* Project:         CMSIS DSP Library    
+* Title:        arm_biquad_cascade_df1_fast_q31.c    
+*    
+* Description:    Processing function for the    
+*                Q31 Fast Biquad cascade DirectFormI(DF1) filter.    
+*    
+* Target Processor: Cortex-M4/Cortex-M3
+*  
+* 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 0.0.9  2010/08/27     
+*    Initial version    
+*    
+* -------------------------------------------------------------------- */
+
+#include "arm_math.h"
+
+/**    
+ * @ingroup groupFilters    
+ */
+
+/**    
+ * @addtogroup BiquadCascadeDF1    
+ * @{    
+ */
+
+/**    
+ * @details    
+ *    
+ * @param[in]  *S        points to an instance of the Q31 Biquad cascade 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.    
+ *    
+ * <b>Scaling and Overflow Behavior:</b>    
+ * \par    
+ * This function is optimized for speed at the expense of fixed-point precision and overflow protection.    
+ * The result of each 1.31 x 1.31 multiplication is truncated to 2.30 format.    
+ * These intermediate results are added to a 2.30 accumulator.    
+ * Finally, the accumulator is saturated and converted to a 1.31 result.    
+ * The fast version has the same overflow behavior as the standard version and provides less precision since it discards the low 32 bits of each multiplication result.    
+ * In order to avoid overflows completely the input signal must be scaled down by two bits and lie in the range [-0.25 +0.25). Use the intialization function    
+ * arm_biquad_cascade_df1_init_q31() to initialize filter structure.    
+ *    
+ * \par    
+ * Refer to the function <code>arm_biquad_cascade_df1_q31()</code> for a slower implementation of this function which uses 64-bit accumulation to provide higher precision.  Both the slow and the fast versions use the same instance structure.    
+ * Use the function <code>arm_biquad_cascade_df1_init_q31()</code> to initialize the filter structure.    
+ */
+
+void arm_biquad_cascade_df1_fast_q31(
+  const arm_biquad_casd_df1_inst_q31 * S,
+  q31_t * pSrc,
+  q31_t * pDst,
+  uint32_t blockSize)
+{
+  q31_t acc;                                     /*  accumulator                   */
+  q31_t Xn1, Xn2, Yn1, Yn2;                      /*  Filter state variables        */
+  q31_t b0, b1, b2, a1, a2;                      /*  Filter coefficients           */
+  q31_t *pIn = pSrc;                             /*  input pointer initialization  */
+  q31_t *pOut = pDst;                            /*  output pointer initialization */
+  q31_t *pState = S->pState;                     /*  pState pointer initialization */
+  q31_t *pCoeffs = S->pCoeffs;                   /*  coeff pointer initialization  */
+  q31_t Xn;                                      /*  temporary input               */
+  int32_t shift = (int32_t) S->postShift + 1;    /*  Shift to be applied to the output */
+  uint32_t sample, stage = S->numStages;         /*  loop counters                     */
+
+
+  do
+  {
+    /* Reading the coefficients */
+    b0 = *pCoeffs++;
+    b1 = *pCoeffs++;
+    b2 = *pCoeffs++;
+    a1 = *pCoeffs++;
+    a2 = *pCoeffs++;
+
+    /* Reading the state values */
+    Xn1 = pState[0];
+    Xn2 = pState[1];
+    Yn1 = pState[2];
+    Yn2 = pState[3];
+
+    /* Apply loop unrolling and compute 4 output values simultaneously. */
+    /*      The variables acc ... acc3 hold output values that are being computed:       
+     *       
+     *    acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]       
+     */
+
+    sample = blockSize >> 2u;
+
+    /* 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(sample > 0u)
+    {
+      /* Read the input */
+      Xn = *pIn;
+
+      /* acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
+      /* acc =  b0 * x[n] */
+      acc = (q31_t) (((q63_t) b1 * Xn1) >> 32);
+      /* acc +=  b1 * x[n-1] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b0 * (Xn))) >> 32);
+      /* acc +=  b[2] * x[n-2] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32);
+      /* acc +=  a1 * y[n-1] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32);
+      /* acc +=  a2 * y[n-2] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32);
+
+      /* The result is converted to 1.31 , Yn2 variable is reused */
+      Yn2 = acc << shift;
+
+      /* Read the second input */
+      Xn2 = *(pIn + 1u);
+
+      /* Store the output in the destination buffer. */
+      *pOut = Yn2;
+
+      /* acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
+      /* acc =  b0 * x[n] */
+      acc = (q31_t) (((q63_t) b0 * (Xn2)) >> 32);
+      /* acc +=  b1 * x[n-1] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn))) >> 32);
+      /* acc +=  b[2] * x[n-2] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn1))) >> 32);
+      /* acc +=  a1 * y[n-1] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn2))) >> 32);
+      /* acc +=  a2 * y[n-2] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn1))) >> 32);
+
+      /* The result is converted to 1.31, Yn1 variable is reused  */
+      Yn1 = acc << shift;
+
+      /* Read the third input  */
+      Xn1 = *(pIn + 2u);
+
+      /* Store the output in the destination buffer. */
+      *(pOut + 1u) = Yn1;
+
+      /* acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
+      /* acc =  b0 * x[n] */
+      acc = (q31_t) (((q63_t) b0 * (Xn1)) >> 32);
+      /* acc +=  b1 * x[n-1] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn2))) >> 32);
+      /* acc +=  b[2] * x[n-2] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn))) >> 32);
+      /* acc +=  a1 * y[n-1] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32);
+      /* acc +=  a2 * y[n-2] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32);
+
+      /* The result is converted to 1.31, Yn2 variable is reused  */
+      Yn2 = acc << shift;
+
+      /* Read the forth input */
+      Xn = *(pIn + 3u);
+
+      /* Store the output in the destination buffer. */
+      *(pOut + 2u) = Yn2;
+      pIn += 4u;
+
+      /* acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
+      /* acc =  b0 * x[n] */
+      acc = (q31_t) (((q63_t) b0 * (Xn)) >> 32);
+      /* acc +=  b1 * x[n-1] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn1))) >> 32);
+      /* acc +=  b[2] * x[n-2] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32);
+      /* acc +=  a1 * y[n-1] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn2))) >> 32);
+      /* acc +=  a2 * y[n-2] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn1))) >> 32);
+
+      /* Every time after the output is computed state should be updated. */
+      /* The states should be updated as:  */
+      /* Xn2 = Xn1    */
+      Xn2 = Xn1;
+
+      /* The result is converted to 1.31, Yn1 variable is reused  */
+      Yn1 = acc << shift;
+
+      /* Xn1 = Xn     */
+      Xn1 = Xn;
+
+      /* Store the output in the destination buffer. */
+      *(pOut + 3u) = Yn1;
+      pOut += 4u;
+
+      /* decrement the loop counter */
+      sample--;
+    }
+
+    /* If the blockSize is not a multiple of 4, compute any remaining output samples here.       
+     ** No loop unrolling is used. */
+    sample = (blockSize & 0x3u);
+
+    while(sample > 0u)
+    {
+      /* Read the input */
+      Xn = *pIn++;
+
+      /* acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
+      /* acc =  b0 * x[n] */
+      acc = (q31_t) (((q63_t) b0 * (Xn)) >> 32);
+      /* acc +=  b1 * x[n-1] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn1))) >> 32);
+      /* acc +=  b[2] * x[n-2] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32);
+      /* acc +=  a1 * y[n-1] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32);
+      /* acc +=  a2 * y[n-2] */
+      acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32);
+      /* The result is converted to 1.31  */
+      acc = acc << shift;
+
+      /* Every time after the output is computed state should be updated. */
+      /* The states should be updated as:  */
+      /* Xn2 = Xn1    */
+      /* Xn1 = Xn     */
+      /* Yn2 = Yn1    */
+      /* Yn1 = acc    */
+      Xn2 = Xn1;
+      Xn1 = Xn;
+      Yn2 = Yn1;
+      Yn1 = acc;
+
+      /* Store the output in the destination buffer. */
+      *pOut++ = acc;
+
+      /* decrement the loop counter */
+      sample--;
+    }
+
+    /*  The first stage goes from the input buffer to the output buffer. */
+    /*  Subsequent stages occur in-place in the output buffer */
+    pIn = pDst;
+
+    /* Reset to destination pointer */
+    pOut = pDst;
+
+    /*  Store the updated state variables back into the pState array */
+    *pState++ = Xn1;
+    *pState++ = Xn2;
+    *pState++ = Yn1;
+    *pState++ = Yn2;
+
+  } while(--stage);
+}
+
+/**    
+  * @} end of BiquadCascadeDF1 group    
+  */