Diff: cmsis_dsp/FilteringFunctions/arm_biquad_cascade_df1_fast_q15.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_q15.c	Wed Nov 28 12:30:09 2012 +0000
@@ -0,0 +1,283 @@
+/* ----------------------------------------------------------------------    
+* 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_q15.c    
+*    
+* Description:    Fast processing function for the    
+*                Q15 Biquad cascade 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  2010/08/16     
+*    Initial version    
+*    
+*    
+* -------------------------------------------------------------------- */
+
+#include "arm_math.h"
+
+/**    
+ * @ingroup groupFilters    
+ */
+
+/**    
+ * @addtogroup BiquadCascadeDF1    
+ * @{    
+ */
+
+/**    
+ * @details    
+ * @param[in]  *S points to an instance of the Q15 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 fast version uses a 32-bit accumulator with 2.30 format.    
+ * The accumulator maintains full precision of the intermediate multiplication results but provides only a single guard bit.    
+ * Thus, if the accumulator result overflows it wraps around and distorts the 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).    
+ * The 2.30 accumulator is then shifted by <code>postShift</code> bits and the result truncated to 1.15 format by discarding the low 16 bits.    
+ *    
+ * \par    
+ * Refer to the function <code>arm_biquad_cascade_df1_q15()</code> for a slower implementation of this function which uses 64-bit accumulation to avoid wrap around distortion.  Both the slow and the fast versions use the same instance structure.    
+ * Use the function <code>arm_biquad_cascade_df1_init_q15()</code> to initialize the filter structure.    
+ *    
+ */
+
+void arm_biquad_cascade_df1_fast_q15(
+  const arm_biquad_casd_df1_inst_q15 * S,
+  q15_t * pSrc,
+  q15_t * pDst,
+  uint32_t blockSize)
+{
+  q15_t *pIn = pSrc;                             /*  Source pointer                               */
+  q15_t *pOut = pDst;                            /*  Destination pointer                          */
+  q31_t in;                                      /*  Temporary variable to hold input value       */
+  q31_t out;                                     /*  Temporary variable to hold output value      */
+  q31_t b0;                                      /*  Temporary variable to hold bo value          */
+  q31_t b1, a1;                                  /*  Filter coefficients                          */
+  q31_t state_in, state_out;                     /*  Filter state variables                       */
+  q31_t acc;                                     /*  Accumulator                                  */
+  int32_t shift = (int32_t) (15 - S->postShift); /*  Post shift                                   */
+  q15_t *pState = S->pState;                     /*  State pointer                                */
+  q15_t *pCoeffs = S->pCoeffs;                   /*  Coefficient pointer                          */
+  uint32_t sample, stage = S->numStages;         /*  Stage loop counter                           */
+
+
+
+  do
+  {
+
+    /* Read the b0 and 0 coefficients using SIMD  */
+    b0 = *__SIMD32(pCoeffs)++;
+
+    /* Read the b1 and b2 coefficients using SIMD */
+    b1 = *__SIMD32(pCoeffs)++;
+
+    /* Read the a1 and a2 coefficients using SIMD */
+    a1 = *__SIMD32(pCoeffs)++;
+
+    /* Read the input state values from the state buffer:  x[n-1], x[n-2] */
+    state_in = *__SIMD32(pState)++;
+
+    /* Read the output state values from the state buffer:  y[n-1], y[n-2] */
+    state_out = *__SIMD32(pState)--;
+
+    /* Apply loop unrolling and compute 2 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]       
+     *    acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]       
+     */
+    sample = blockSize >> 1u;
+
+    /* First part of the processing with loop unrolling.  Compute 2 outputs at a time.    
+     ** a second loop below computes the remaining 1 sample. */
+    while(sample > 0u)
+    {
+
+      /* Read the input */
+      in = *__SIMD32(pIn)++;
+
+      /* out =  b0 * x[n] + 0 * 0 */
+      out = __SMUAD(b0, in);
+      /* acc =  b1 * x[n-1] + acc +=  b2 * x[n-2] + out */
+      acc = __SMLAD(b1, state_in, out);
+      /* acc +=  a1 * y[n-1] + acc +=  a2 * y[n-2] */
+      acc = __SMLAD(a1, state_out, acc);
+
+      /* The result is converted from 3.29 to 1.31 and then saturation is applied */
+      out = __SSAT((acc >> shift), 16);
+
+      /* 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   */
+      /* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */
+      /* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */
+
+#ifndef  ARM_MATH_BIG_ENDIAN
+
+      state_in = __PKHBT(in, state_in, 16);
+      state_out = __PKHBT(out, state_out, 16);
+
+#else
+
+      state_in = __PKHBT(state_in >> 16, (in >> 16), 16);
+      state_out = __PKHBT(state_out >> 16, (out), 16);
+
+#endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */
+
+      /* out =  b0 * x[n] + 0 * 0 */
+      out = __SMUADX(b0, in);
+      /* acc0 =  b1 * x[n-1] , acc0 +=  b2 * x[n-2] + out */
+      acc = __SMLAD(b1, state_in, out);
+      /* acc +=  a1 * y[n-1] + acc +=  a2 * y[n-2] */
+      acc = __SMLAD(a1, state_out, acc);
+
+      /* The result is converted from 3.29 to 1.31 and then saturation is applied */
+      out = __SSAT((acc >> shift), 16);
+
+
+      /* Store the output in the destination buffer. */
+
+#ifndef  ARM_MATH_BIG_ENDIAN
+
+      *__SIMD32(pOut)++ = __PKHBT(state_out, out, 16);
+
+#else
+
+      *__SIMD32(pOut)++ = __PKHBT(out, state_out >> 16, 16);
+
+#endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */
+
+      /* 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   */
+      /* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */
+      /* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */
+
+#ifndef  ARM_MATH_BIG_ENDIAN
+
+      state_in = __PKHBT(in >> 16, state_in, 16);
+      state_out = __PKHBT(out, state_out, 16);
+
+#else
+
+      state_in = __PKHBT(state_in >> 16, in, 16);
+      state_out = __PKHBT(state_out >> 16, out, 16);
+
+#endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */
+
+
+      /* Decrement the loop counter */
+      sample--;
+
+    }
+
+    /* If the blockSize is not a multiple of 2, compute any remaining output samples here.    
+     ** No loop unrolling is used. */
+
+    if((blockSize & 0x1u) != 0u)
+    {
+      /* Read the input */
+      in = *pIn++;
+
+      /* out =  b0 * x[n] + 0 * 0 */
+
+#ifndef  ARM_MATH_BIG_ENDIAN
+
+      out = __SMUAD(b0, in);
+
+#else
+
+      out = __SMUADX(b0, in);
+
+#endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */
+
+      /* acc =  b1 * x[n-1], acc +=  b2 * x[n-2] + out */
+      acc = __SMLAD(b1, state_in, out);
+      /* acc +=  a1 * y[n-1] + acc +=  a2 * y[n-2] */
+      acc = __SMLAD(a1, state_out, acc);
+
+      /* The result is converted from 3.29 to 1.31 and then saturation is applied */
+      out = __SSAT((acc >> shift), 16);
+
+      /* Store the output in the destination buffer. */
+      *pOut++ = (q15_t) out;
+
+      /* 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   */
+      /* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */
+      /* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */
+
+#ifndef  ARM_MATH_BIG_ENDIAN
+
+      state_in = __PKHBT(in, state_in, 16);
+      state_out = __PKHBT(out, state_out, 16);
+
+#else
+
+      state_in = __PKHBT(state_in >> 16, in, 16);
+      state_out = __PKHBT(state_out >> 16, out, 16);
+
+#endif /*   #ifndef  ARM_MATH_BIG_ENDIAN    */
+
+    }
+
+    /*  The first stage goes from the input buffer to the output buffer.  */
+    /*  Subsequent (numStages - 1) occur in-place in the output buffer  */
+    pIn = pDst;
+
+    /* Reset the output pointer */
+    pOut = pDst;
+
+    /*  Store the updated state variables back into the state array */
+    *__SIMD32(pState)++ = state_in;
+    *__SIMD32(pState)++ = state_out;
+
+
+    /* Decrement the loop counter */
+    stage--;
+
+  } while(stage > 0u);
+}
+
+
+/**    
+ * @} end of BiquadCascadeDF1 group    
+ */