Diff: cmsis_dsp/FilteringFunctions/arm_biquad_cascade_df1_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_q31.c	Wed Nov 28 12:30:09 2012 +0000
@@ -0,0 +1,400 @@
+/* ----------------------------------------------------------------------    
+* 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_q31.c    
+*    
+* Description:    Processing function for the    
+*                Q31 Biquad cascade filter    
+*    
+* 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 BiquadCascadeDF1    
+ * @{    
+ */
+
+/**    
+ * @brief Processing function for the Q31 Biquad cascade filter.    
+ * @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    
+ * 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 bits and lie in the range [-0.25 +0.25).    
+ * After all 5 multiply-accumulates are performed, the 2.62 accumulator is shifted by <code>postShift</code> bits and the result truncated to    
+ * 1.31 format by discarding the low 32 bits.    
+ *    
+ * \par    
+ * Refer to the function <code>arm_biquad_cascade_df1_fast_q31()</code> for a faster but less precise implementation of this filter for Cortex-M3 and Cortex-M4.    
+ */
+
+void arm_biquad_cascade_df1_q31(
+  const arm_biquad_casd_df1_inst_q31 * S,
+  q31_t * pSrc,
+  q31_t * pDst,
+  uint32_t blockSize)
+{
+  q63_t acc;                                     /*  accumulator                   */
+  uint32_t uShift = ((uint32_t) S->postShift + 1u);
+  uint32_t lShift = 32u - uShift;                /*  Shift to be applied to the output */
+  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 Xn1, Xn2, Yn1, Yn2;                      /*  Filter state variables        */
+  q31_t b0, b1, b2, a1, a2;                      /*  Filter coefficients           */
+  q31_t Xn;                                      /*  temporary input               */
+  uint32_t sample, stage = S->numStages;         /*  loop counters                     */
+
+
+#ifndef ARM_MATH_CM0
+
+  q31_t acc_l, acc_h;                            /*  temporary output variables    */
+
+  /* Run the below code for Cortex-M4 and Cortex-M3 */
+
+  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 variable acc 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 = (q63_t) b0 *Xn;
+      /* acc +=  b1 * x[n-1] */
+      acc += (q63_t) b1 *Xn1;
+      /* acc +=  b[2] * x[n-2] */
+      acc += (q63_t) b2 *Xn2;
+      /* acc +=  a1 * y[n-1] */
+      acc += (q63_t) a1 *Yn1;
+      /* acc +=  a2 * y[n-2] */
+      acc += (q63_t) a2 *Yn2;
+
+      /* The result is converted to 1.31 , Yn2 variable is reused */
+
+      /* Calc lower part of acc */
+      acc_l = acc & 0xffffffff;
+
+      /* Calc upper part of acc */
+      acc_h = (acc >> 32) & 0xffffffff;
+
+      /* Apply shift for lower part of acc and upper part of acc */
+      Yn2 = (uint32_t) acc_l >> lShift | acc_h << uShift;
+
+      /* Store the output in the destination buffer. */
+      *pOut++ = Yn2;
+
+      /* Read the second input */
+      Xn2 = *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 = (q63_t) b0 *Xn2;
+      /* acc +=  b1 * x[n-1] */
+      acc += (q63_t) b1 *Xn;
+      /* acc +=  b[2] * x[n-2] */
+      acc += (q63_t) b2 *Xn1;
+      /* acc +=  a1 * y[n-1] */
+      acc += (q63_t) a1 *Yn2;
+      /* acc +=  a2 * y[n-2] */
+      acc += (q63_t) a2 *Yn1;
+
+
+      /* The result is converted to 1.31, Yn1 variable is reused  */
+
+      /* Calc lower part of acc */
+      acc_l = acc & 0xffffffff;
+
+      /* Calc upper part of acc */
+      acc_h = (acc >> 32) & 0xffffffff;
+
+
+      /* Apply shift for lower part of acc and upper part of acc */
+      Yn1 = (uint32_t) acc_l >> lShift | acc_h << uShift;
+
+      /* Store the output in the destination buffer. */
+      *pOut++ = Yn1;
+
+      /* Read the third input  */
+      Xn1 = *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 = (q63_t) b0 *Xn1;
+      /* acc +=  b1 * x[n-1] */
+      acc += (q63_t) b1 *Xn2;
+      /* acc +=  b[2] * x[n-2] */
+      acc += (q63_t) b2 *Xn;
+      /* acc +=  a1 * y[n-1] */
+      acc += (q63_t) a1 *Yn1;
+      /* acc +=  a2 * y[n-2] */
+      acc += (q63_t) a2 *Yn2;
+
+      /* The result is converted to 1.31, Yn2 variable is reused  */
+      /* Calc lower part of acc */
+      acc_l = acc & 0xffffffff;
+
+      /* Calc upper part of acc */
+      acc_h = (acc >> 32) & 0xffffffff;
+
+
+      /* Apply shift for lower part of acc and upper part of acc */
+      Yn2 = (uint32_t) acc_l >> lShift | acc_h << uShift;
+
+      /* Store the output in the destination buffer. */
+      *pOut++ = Yn2;
+
+      /* Read the forth 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 = (q63_t) b0 *Xn;
+      /* acc +=  b1 * x[n-1] */
+      acc += (q63_t) b1 *Xn1;
+      /* acc +=  b[2] * x[n-2] */
+      acc += (q63_t) b2 *Xn2;
+      /* acc +=  a1 * y[n-1] */
+      acc += (q63_t) a1 *Yn2;
+      /* acc +=  a2 * y[n-2] */
+      acc += (q63_t) a2 *Yn1;
+
+      /* The result is converted to 1.31, Yn1 variable is reused  */
+      /* Calc lower part of acc */
+      acc_l = acc & 0xffffffff;
+
+      /* Calc upper part of acc */
+      acc_h = (acc >> 32) & 0xffffffff;
+
+      /* Apply shift for lower part of acc and upper part of acc */
+      Yn1 = (uint32_t) acc_l >> lShift | acc_h << uShift;
+
+      /* 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;
+
+      /* Store the output in the destination buffer. */
+      *pOut++ = Yn1;
+
+      /* 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 = (q63_t) b0 *Xn;
+      /* acc +=  b1 * x[n-1] */
+      acc += (q63_t) b1 *Xn1;
+      /* acc +=  b[2] * x[n-2] */
+      acc += (q63_t) b2 *Xn2;
+      /* acc +=  a1 * y[n-1] */
+      acc += (q63_t) a1 *Yn1;
+      /* acc +=  a2 * y[n-2] */
+      acc += (q63_t) a2 *Yn2;
+
+      /* The result is converted to 1.31  */
+      acc = acc >> lShift;
+
+      /* 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 = (q31_t) acc;
+
+      /* Store the output in the destination buffer. */
+      *pOut++ = (q31_t) 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);
+
+#else
+
+  /* Run the below code for Cortex-M0 */
+
+  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];
+
+    /*      The variables acc holds the output value that is computed:         
+     *    acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]         
+     */
+
+    sample = blockSize;
+
+    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 = (q63_t) b0 *Xn;
+
+      /* acc +=  b1 * x[n-1] */
+      acc += (q63_t) b1 *Xn1;
+      /* acc +=  b[2] * x[n-2] */
+      acc += (q63_t) b2 *Xn2;
+      /* acc +=  a1 * y[n-1] */
+      acc += (q63_t) a1 *Yn1;
+      /* acc +=  a2 * y[n-2] */
+      acc += (q63_t) a2 *Yn2;
+
+      /* The result is converted to 1.31  */
+      acc = acc >> lShift;
+
+      /* 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 = (q31_t) acc;
+
+      /* Store the output in the destination buffer. */
+      *pOut++ = (q31_t) 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);
+
+#endif /*  #ifndef ARM_MATH_CM0 */
+}
+
+/**    
+  * @} end of BiquadCascadeDF1 group    
+  */