Eli Hughes / CMSIS_DSP_401

V4.0.1 of the ARM CMSIS DSP libraries. Note that arm_bitreversal2.s, arm_cfft_f32.c and arm_rfft_fast_f32.c had to be removed. arm_bitreversal2.s will not assemble with the online tools. So, the fast f32 FFT functions are not yet available. All the other FFT functions are available.

Dependents:   MPU9150_Example fir_f32 fir_f32 MPU9150_nucleo_noni2cdev ... more

FilteringFunctions/arm_biquad_cascade_df1_fast_q31.c@0:3d9c67d97d6f, 2014-07-28 (annotated)

Committer:
emh203
Date:
Mon Jul 28 15:03:15 2014 +0000
Revision:
0:3d9c67d97d6f
1st working commit.   Had to remove arm_bitreversal2.s     arm_cfft_f32.c and arm_rfft_fast_f32.c.    The .s will not assemble.      For now I removed these functions so we could at least have a library for the other functions.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
emh203 0:3d9c67d97d6f 1 /* ----------------------------------------------------------------------
emh203 0:3d9c67d97d6f 2 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.
emh203 0:3d9c67d97d6f 3 *
emh203 0:3d9c67d97d6f 4 * $Date: 12. March 2014
emh203 0:3d9c67d97d6f 5 * $Revision: V1.4.3
emh203 0:3d9c67d97d6f 6 *
emh203 0:3d9c67d97d6f 7 * Project: CMSIS DSP Library
emh203 0:3d9c67d97d6f 8 * Title: arm_biquad_cascade_df1_fast_q31.c
emh203 0:3d9c67d97d6f 9 *
emh203 0:3d9c67d97d6f 10 * Description: Processing function for the
emh203 0:3d9c67d97d6f 11 * Q31 Fast Biquad cascade DirectFormI(DF1) filter.
emh203 0:3d9c67d97d6f 12 *
emh203 0:3d9c67d97d6f 13 * Target Processor: Cortex-M4/Cortex-M3
emh203 0:3d9c67d97d6f 14 *
emh203 0:3d9c67d97d6f 15 * Redistribution and use in source and binary forms, with or without
emh203 0:3d9c67d97d6f 16 * modification, are permitted provided that the following conditions
emh203 0:3d9c67d97d6f 17 * are met:
emh203 0:3d9c67d97d6f 18 * - Redistributions of source code must retain the above copyright
emh203 0:3d9c67d97d6f 19 * notice, this list of conditions and the following disclaimer.
emh203 0:3d9c67d97d6f 20 * - Redistributions in binary form must reproduce the above copyright
emh203 0:3d9c67d97d6f 21 * notice, this list of conditions and the following disclaimer in
emh203 0:3d9c67d97d6f 22 * the documentation and/or other materials provided with the
emh203 0:3d9c67d97d6f 23 * distribution.
emh203 0:3d9c67d97d6f 24 * - Neither the name of ARM LIMITED nor the names of its contributors
emh203 0:3d9c67d97d6f 25 * may be used to endorse or promote products derived from this
emh203 0:3d9c67d97d6f 26 * software without specific prior written permission.
emh203 0:3d9c67d97d6f 27 *
emh203 0:3d9c67d97d6f 28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
emh203 0:3d9c67d97d6f 29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
emh203 0:3d9c67d97d6f 30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
emh203 0:3d9c67d97d6f 31 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
emh203 0:3d9c67d97d6f 32 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
emh203 0:3d9c67d97d6f 33 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
emh203 0:3d9c67d97d6f 34 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
emh203 0:3d9c67d97d6f 35 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
emh203 0:3d9c67d97d6f 36 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
emh203 0:3d9c67d97d6f 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
emh203 0:3d9c67d97d6f 38 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
emh203 0:3d9c67d97d6f 39 * POSSIBILITY OF SUCH DAMAGE.
emh203 0:3d9c67d97d6f 40 * -------------------------------------------------------------------- */
emh203 0:3d9c67d97d6f 41
emh203 0:3d9c67d97d6f 42 #include "arm_math.h"
emh203 0:3d9c67d97d6f 43
emh203 0:3d9c67d97d6f 44 /**
emh203 0:3d9c67d97d6f 45 * @ingroup groupFilters
emh203 0:3d9c67d97d6f 46 */
emh203 0:3d9c67d97d6f 47
emh203 0:3d9c67d97d6f 48 /**
emh203 0:3d9c67d97d6f 49 * @addtogroup BiquadCascadeDF1
emh203 0:3d9c67d97d6f 50 * @{
emh203 0:3d9c67d97d6f 51 */
emh203 0:3d9c67d97d6f 52
emh203 0:3d9c67d97d6f 53 /**
emh203 0:3d9c67d97d6f 54 * @details
emh203 0:3d9c67d97d6f 55 *
emh203 0:3d9c67d97d6f 56 * @param[in] *S points to an instance of the Q31 Biquad cascade structure.
emh203 0:3d9c67d97d6f 57 * @param[in] *pSrc points to the block of input data.
emh203 0:3d9c67d97d6f 58 * @param[out] *pDst points to the block of output data.
emh203 0:3d9c67d97d6f 59 * @param[in] blockSize number of samples to process per call.
emh203 0:3d9c67d97d6f 60 * @return none.
emh203 0:3d9c67d97d6f 61 *
emh203 0:3d9c67d97d6f 62 * <b>Scaling and Overflow Behavior:</b>
emh203 0:3d9c67d97d6f 63 * \par
emh203 0:3d9c67d97d6f 64 * This function is optimized for speed at the expense of fixed-point precision and overflow protection.
emh203 0:3d9c67d97d6f 65 * The result of each 1.31 x 1.31 multiplication is truncated to 2.30 format.
emh203 0:3d9c67d97d6f 66 * These intermediate results are added to a 2.30 accumulator.
emh203 0:3d9c67d97d6f 67 * Finally, the accumulator is saturated and converted to a 1.31 result.
emh203 0:3d9c67d97d6f 68 * 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.
emh203 0:3d9c67d97d6f 69 * 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
emh203 0:3d9c67d97d6f 70 * arm_biquad_cascade_df1_init_q31() to initialize filter structure.
emh203 0:3d9c67d97d6f 71 *
emh203 0:3d9c67d97d6f 72 * \par
emh203 0:3d9c67d97d6f 73 * 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.
emh203 0:3d9c67d97d6f 74 * Use the function <code>arm_biquad_cascade_df1_init_q31()</code> to initialize the filter structure.
emh203 0:3d9c67d97d6f 75 */
emh203 0:3d9c67d97d6f 76
emh203 0:3d9c67d97d6f 77 void arm_biquad_cascade_df1_fast_q31(
emh203 0:3d9c67d97d6f 78 const arm_biquad_casd_df1_inst_q31 * S,
emh203 0:3d9c67d97d6f 79 q31_t * pSrc,
emh203 0:3d9c67d97d6f 80 q31_t * pDst,
emh203 0:3d9c67d97d6f 81 uint32_t blockSize)
emh203 0:3d9c67d97d6f 82 {
emh203 0:3d9c67d97d6f 83 q31_t acc = 0; /* accumulator */
emh203 0:3d9c67d97d6f 84 q31_t Xn1, Xn2, Yn1, Yn2; /* Filter state variables */
emh203 0:3d9c67d97d6f 85 q31_t b0, b1, b2, a1, a2; /* Filter coefficients */
emh203 0:3d9c67d97d6f 86 q31_t *pIn = pSrc; /* input pointer initialization */
emh203 0:3d9c67d97d6f 87 q31_t *pOut = pDst; /* output pointer initialization */
emh203 0:3d9c67d97d6f 88 q31_t *pState = S->pState; /* pState pointer initialization */
emh203 0:3d9c67d97d6f 89 q31_t *pCoeffs = S->pCoeffs; /* coeff pointer initialization */
emh203 0:3d9c67d97d6f 90 q31_t Xn; /* temporary input */
emh203 0:3d9c67d97d6f 91 int32_t shift = (int32_t) S->postShift + 1; /* Shift to be applied to the output */
emh203 0:3d9c67d97d6f 92 uint32_t sample, stage = S->numStages; /* loop counters */
emh203 0:3d9c67d97d6f 93
emh203 0:3d9c67d97d6f 94
emh203 0:3d9c67d97d6f 95 do
emh203 0:3d9c67d97d6f 96 {
emh203 0:3d9c67d97d6f 97 /* Reading the coefficients */
emh203 0:3d9c67d97d6f 98 b0 = *pCoeffs++;
emh203 0:3d9c67d97d6f 99 b1 = *pCoeffs++;
emh203 0:3d9c67d97d6f 100 b2 = *pCoeffs++;
emh203 0:3d9c67d97d6f 101 a1 = *pCoeffs++;
emh203 0:3d9c67d97d6f 102 a2 = *pCoeffs++;
emh203 0:3d9c67d97d6f 103
emh203 0:3d9c67d97d6f 104 /* Reading the state values */
emh203 0:3d9c67d97d6f 105 Xn1 = pState[0];
emh203 0:3d9c67d97d6f 106 Xn2 = pState[1];
emh203 0:3d9c67d97d6f 107 Yn1 = pState[2];
emh203 0:3d9c67d97d6f 108 Yn2 = pState[3];
emh203 0:3d9c67d97d6f 109
emh203 0:3d9c67d97d6f 110 /* Apply loop unrolling and compute 4 output values simultaneously. */
emh203 0:3d9c67d97d6f 111 /* The variables acc ... acc3 hold output values that are being computed:
emh203 0:3d9c67d97d6f 112 *
emh203 0:3d9c67d97d6f 113 * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
emh203 0:3d9c67d97d6f 114 */
emh203 0:3d9c67d97d6f 115
emh203 0:3d9c67d97d6f 116 sample = blockSize >> 2u;
emh203 0:3d9c67d97d6f 117
emh203 0:3d9c67d97d6f 118 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
emh203 0:3d9c67d97d6f 119 ** a second loop below computes the remaining 1 to 3 samples. */
emh203 0:3d9c67d97d6f 120 while(sample > 0u)
emh203 0:3d9c67d97d6f 121 {
emh203 0:3d9c67d97d6f 122 /* Read the input */
emh203 0:3d9c67d97d6f 123 Xn = *pIn;
emh203 0:3d9c67d97d6f 124
emh203 0:3d9c67d97d6f 125 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emh203 0:3d9c67d97d6f 126 /* acc = b0 * x[n] */
emh203 0:3d9c67d97d6f 127 //acc = (q31_t) (((q63_t) b1 * Xn1) >> 32);
emh203 0:3d9c67d97d6f 128 mult_32x32_keep32_R(acc, b1, Xn1);
emh203 0:3d9c67d97d6f 129 /* acc += b1 * x[n-1] */
emh203 0:3d9c67d97d6f 130 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b0 * (Xn))) >> 32);
emh203 0:3d9c67d97d6f 131 multAcc_32x32_keep32_R(acc, b0, Xn);
emh203 0:3d9c67d97d6f 132 /* acc += b[2] * x[n-2] */
emh203 0:3d9c67d97d6f 133 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32);
emh203 0:3d9c67d97d6f 134 multAcc_32x32_keep32_R(acc, b2, Xn2);
emh203 0:3d9c67d97d6f 135 /* acc += a1 * y[n-1] */
emh203 0:3d9c67d97d6f 136 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32);
emh203 0:3d9c67d97d6f 137 multAcc_32x32_keep32_R(acc, a1, Yn1);
emh203 0:3d9c67d97d6f 138 /* acc += a2 * y[n-2] */
emh203 0:3d9c67d97d6f 139 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32);
emh203 0:3d9c67d97d6f 140 multAcc_32x32_keep32_R(acc, a2, Yn2);
emh203 0:3d9c67d97d6f 141
emh203 0:3d9c67d97d6f 142 /* The result is converted to 1.31 , Yn2 variable is reused */
emh203 0:3d9c67d97d6f 143 Yn2 = acc << shift;
emh203 0:3d9c67d97d6f 144
emh203 0:3d9c67d97d6f 145 /* Read the second input */
emh203 0:3d9c67d97d6f 146 Xn2 = *(pIn + 1u);
emh203 0:3d9c67d97d6f 147
emh203 0:3d9c67d97d6f 148 /* Store the output in the destination buffer. */
emh203 0:3d9c67d97d6f 149 *pOut = Yn2;
emh203 0:3d9c67d97d6f 150
emh203 0:3d9c67d97d6f 151 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emh203 0:3d9c67d97d6f 152 /* acc = b0 * x[n] */
emh203 0:3d9c67d97d6f 153 //acc = (q31_t) (((q63_t) b0 * (Xn2)) >> 32);
emh203 0:3d9c67d97d6f 154 mult_32x32_keep32_R(acc, b0, Xn2);
emh203 0:3d9c67d97d6f 155 /* acc += b1 * x[n-1] */
emh203 0:3d9c67d97d6f 156 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn))) >> 32);
emh203 0:3d9c67d97d6f 157 multAcc_32x32_keep32_R(acc, b1, Xn);
emh203 0:3d9c67d97d6f 158 /* acc += b[2] * x[n-2] */
emh203 0:3d9c67d97d6f 159 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn1))) >> 32);
emh203 0:3d9c67d97d6f 160 multAcc_32x32_keep32_R(acc, b2, Xn1);
emh203 0:3d9c67d97d6f 161 /* acc += a1 * y[n-1] */
emh203 0:3d9c67d97d6f 162 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn2))) >> 32);
emh203 0:3d9c67d97d6f 163 multAcc_32x32_keep32_R(acc, a1, Yn2);
emh203 0:3d9c67d97d6f 164 /* acc += a2 * y[n-2] */
emh203 0:3d9c67d97d6f 165 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn1))) >> 32);
emh203 0:3d9c67d97d6f 166 multAcc_32x32_keep32_R(acc, a2, Yn1);
emh203 0:3d9c67d97d6f 167
emh203 0:3d9c67d97d6f 168 /* The result is converted to 1.31, Yn1 variable is reused */
emh203 0:3d9c67d97d6f 169 Yn1 = acc << shift;
emh203 0:3d9c67d97d6f 170
emh203 0:3d9c67d97d6f 171 /* Read the third input */
emh203 0:3d9c67d97d6f 172 Xn1 = *(pIn + 2u);
emh203 0:3d9c67d97d6f 173
emh203 0:3d9c67d97d6f 174 /* Store the output in the destination buffer. */
emh203 0:3d9c67d97d6f 175 *(pOut + 1u) = Yn1;
emh203 0:3d9c67d97d6f 176
emh203 0:3d9c67d97d6f 177 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emh203 0:3d9c67d97d6f 178 /* acc = b0 * x[n] */
emh203 0:3d9c67d97d6f 179 //acc = (q31_t) (((q63_t) b0 * (Xn1)) >> 32);
emh203 0:3d9c67d97d6f 180 mult_32x32_keep32_R(acc, b0, Xn1);
emh203 0:3d9c67d97d6f 181 /* acc += b1 * x[n-1] */
emh203 0:3d9c67d97d6f 182 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn2))) >> 32);
emh203 0:3d9c67d97d6f 183 multAcc_32x32_keep32_R(acc, b1, Xn2);
emh203 0:3d9c67d97d6f 184 /* acc += b[2] * x[n-2] */
emh203 0:3d9c67d97d6f 185 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn))) >> 32);
emh203 0:3d9c67d97d6f 186 multAcc_32x32_keep32_R(acc, b2, Xn);
emh203 0:3d9c67d97d6f 187 /* acc += a1 * y[n-1] */
emh203 0:3d9c67d97d6f 188 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32);
emh203 0:3d9c67d97d6f 189 multAcc_32x32_keep32_R(acc, a1, Yn1);
emh203 0:3d9c67d97d6f 190 /* acc += a2 * y[n-2] */
emh203 0:3d9c67d97d6f 191 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32);
emh203 0:3d9c67d97d6f 192 multAcc_32x32_keep32_R(acc, a2, Yn2);
emh203 0:3d9c67d97d6f 193
emh203 0:3d9c67d97d6f 194 /* The result is converted to 1.31, Yn2 variable is reused */
emh203 0:3d9c67d97d6f 195 Yn2 = acc << shift;
emh203 0:3d9c67d97d6f 196
emh203 0:3d9c67d97d6f 197 /* Read the forth input */
emh203 0:3d9c67d97d6f 198 Xn = *(pIn + 3u);
emh203 0:3d9c67d97d6f 199
emh203 0:3d9c67d97d6f 200 /* Store the output in the destination buffer. */
emh203 0:3d9c67d97d6f 201 *(pOut + 2u) = Yn2;
emh203 0:3d9c67d97d6f 202 pIn += 4u;
emh203 0:3d9c67d97d6f 203
emh203 0:3d9c67d97d6f 204 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emh203 0:3d9c67d97d6f 205 /* acc = b0 * x[n] */
emh203 0:3d9c67d97d6f 206 //acc = (q31_t) (((q63_t) b0 * (Xn)) >> 32);
emh203 0:3d9c67d97d6f 207 mult_32x32_keep32_R(acc, b0, Xn);
emh203 0:3d9c67d97d6f 208 /* acc += b1 * x[n-1] */
emh203 0:3d9c67d97d6f 209 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn1))) >> 32);
emh203 0:3d9c67d97d6f 210 multAcc_32x32_keep32_R(acc, b1, Xn1);
emh203 0:3d9c67d97d6f 211 /* acc += b[2] * x[n-2] */
emh203 0:3d9c67d97d6f 212 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32);
emh203 0:3d9c67d97d6f 213 multAcc_32x32_keep32_R(acc, b2, Xn2);
emh203 0:3d9c67d97d6f 214 /* acc += a1 * y[n-1] */
emh203 0:3d9c67d97d6f 215 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn2))) >> 32);
emh203 0:3d9c67d97d6f 216 multAcc_32x32_keep32_R(acc, a1, Yn2);
emh203 0:3d9c67d97d6f 217 /* acc += a2 * y[n-2] */
emh203 0:3d9c67d97d6f 218 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn1))) >> 32);
emh203 0:3d9c67d97d6f 219 multAcc_32x32_keep32_R(acc, a2, Yn1);
emh203 0:3d9c67d97d6f 220
emh203 0:3d9c67d97d6f 221 /* Every time after the output is computed state should be updated. */
emh203 0:3d9c67d97d6f 222 /* The states should be updated as: */
emh203 0:3d9c67d97d6f 223 /* Xn2 = Xn1 */
emh203 0:3d9c67d97d6f 224 Xn2 = Xn1;
emh203 0:3d9c67d97d6f 225
emh203 0:3d9c67d97d6f 226 /* The result is converted to 1.31, Yn1 variable is reused */
emh203 0:3d9c67d97d6f 227 Yn1 = acc << shift;
emh203 0:3d9c67d97d6f 228
emh203 0:3d9c67d97d6f 229 /* Xn1 = Xn */
emh203 0:3d9c67d97d6f 230 Xn1 = Xn;
emh203 0:3d9c67d97d6f 231
emh203 0:3d9c67d97d6f 232 /* Store the output in the destination buffer. */
emh203 0:3d9c67d97d6f 233 *(pOut + 3u) = Yn1;
emh203 0:3d9c67d97d6f 234 pOut += 4u;
emh203 0:3d9c67d97d6f 235
emh203 0:3d9c67d97d6f 236 /* decrement the loop counter */
emh203 0:3d9c67d97d6f 237 sample--;
emh203 0:3d9c67d97d6f 238 }
emh203 0:3d9c67d97d6f 239
emh203 0:3d9c67d97d6f 240 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
emh203 0:3d9c67d97d6f 241 ** No loop unrolling is used. */
emh203 0:3d9c67d97d6f 242 sample = (blockSize & 0x3u);
emh203 0:3d9c67d97d6f 243
emh203 0:3d9c67d97d6f 244 while(sample > 0u)
emh203 0:3d9c67d97d6f 245 {
emh203 0:3d9c67d97d6f 246 /* Read the input */
emh203 0:3d9c67d97d6f 247 Xn = *pIn++;
emh203 0:3d9c67d97d6f 248
emh203 0:3d9c67d97d6f 249 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emh203 0:3d9c67d97d6f 250 /* acc = b0 * x[n] */
emh203 0:3d9c67d97d6f 251 //acc = (q31_t) (((q63_t) b0 * (Xn)) >> 32);
emh203 0:3d9c67d97d6f 252 mult_32x32_keep32_R(acc, b0, Xn);
emh203 0:3d9c67d97d6f 253 /* acc += b1 * x[n-1] */
emh203 0:3d9c67d97d6f 254 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn1))) >> 32);
emh203 0:3d9c67d97d6f 255 multAcc_32x32_keep32_R(acc, b1, Xn1);
emh203 0:3d9c67d97d6f 256 /* acc += b[2] * x[n-2] */
emh203 0:3d9c67d97d6f 257 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32);
emh203 0:3d9c67d97d6f 258 multAcc_32x32_keep32_R(acc, b2, Xn2);
emh203 0:3d9c67d97d6f 259 /* acc += a1 * y[n-1] */
emh203 0:3d9c67d97d6f 260 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32);
emh203 0:3d9c67d97d6f 261 multAcc_32x32_keep32_R(acc, a1, Yn1);
emh203 0:3d9c67d97d6f 262 /* acc += a2 * y[n-2] */
emh203 0:3d9c67d97d6f 263 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32);
emh203 0:3d9c67d97d6f 264 multAcc_32x32_keep32_R(acc, a2, Yn2);
emh203 0:3d9c67d97d6f 265
emh203 0:3d9c67d97d6f 266 /* The result is converted to 1.31 */
emh203 0:3d9c67d97d6f 267 acc = acc << shift;
emh203 0:3d9c67d97d6f 268
emh203 0:3d9c67d97d6f 269 /* Every time after the output is computed state should be updated. */
emh203 0:3d9c67d97d6f 270 /* The states should be updated as: */
emh203 0:3d9c67d97d6f 271 /* Xn2 = Xn1 */
emh203 0:3d9c67d97d6f 272 /* Xn1 = Xn */
emh203 0:3d9c67d97d6f 273 /* Yn2 = Yn1 */
emh203 0:3d9c67d97d6f 274 /* Yn1 = acc */
emh203 0:3d9c67d97d6f 275 Xn2 = Xn1;
emh203 0:3d9c67d97d6f 276 Xn1 = Xn;
emh203 0:3d9c67d97d6f 277 Yn2 = Yn1;
emh203 0:3d9c67d97d6f 278 Yn1 = acc;
emh203 0:3d9c67d97d6f 279
emh203 0:3d9c67d97d6f 280 /* Store the output in the destination buffer. */
emh203 0:3d9c67d97d6f 281 *pOut++ = acc;
emh203 0:3d9c67d97d6f 282
emh203 0:3d9c67d97d6f 283 /* decrement the loop counter */
emh203 0:3d9c67d97d6f 284 sample--;
emh203 0:3d9c67d97d6f 285 }
emh203 0:3d9c67d97d6f 286
emh203 0:3d9c67d97d6f 287 /* The first stage goes from the input buffer to the output buffer. */
emh203 0:3d9c67d97d6f 288 /* Subsequent stages occur in-place in the output buffer */
emh203 0:3d9c67d97d6f 289 pIn = pDst;
emh203 0:3d9c67d97d6f 290
emh203 0:3d9c67d97d6f 291 /* Reset to destination pointer */
emh203 0:3d9c67d97d6f 292 pOut = pDst;
emh203 0:3d9c67d97d6f 293
emh203 0:3d9c67d97d6f 294 /* Store the updated state variables back into the pState array */
emh203 0:3d9c67d97d6f 295 *pState++ = Xn1;
emh203 0:3d9c67d97d6f 296 *pState++ = Xn2;
emh203 0:3d9c67d97d6f 297 *pState++ = Yn1;
emh203 0:3d9c67d97d6f 298 *pState++ = Yn2;
emh203 0:3d9c67d97d6f 299
emh203 0:3d9c67d97d6f 300 } while(--stage);
emh203 0:3d9c67d97d6f 301 }
emh203 0:3d9c67d97d6f 302
emh203 0:3d9c67d97d6f 303 /**
emh203 0:3d9c67d97d6f 304 * @} end of BiquadCascadeDF1 group
emh203 0:3d9c67d97d6f 305 */