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CMSIS DSP library

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cmsis_dsp/FilteringFunctions/arm_biquad_cascade_df1_fast_q31.c@5:3762170b6d4d, 2015-11-20 (annotated)

Committer:
mbed_official
Date:
Fri Nov 20 08:45:18 2015 +0000
Revision:
5:3762170b6d4d
Parent:
3:7a284390b0ce 
Synchronized with git revision 2eb940b9a73af188d3004a2575fdfbb05febe62b



Full URL: https://github.com/mbedmicro/mbed/commit/2eb940b9a73af188d3004a2575fdfbb05febe62b/



Added option to build rpc library. closes #1426

Who changed what in which revision?

UserRevisionLine numberNew contents of line
emilmont 1:fdd22bb7aa52 1 /* ----------------------------------------------------------------------
mbed_official 5:3762170b6d4d 2 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.
emilmont 1:fdd22bb7aa52 3 *
mbed_official 5:3762170b6d4d 4 * $Date: 19. October 2015
mbed_official 5:3762170b6d4d 5 * $Revision: V.1.4.5 a
emilmont 1:fdd22bb7aa52 6 *
emilmont 2:da51fb522205 7 * Project: CMSIS DSP Library
emilmont 2:da51fb522205 8 * Title: arm_biquad_cascade_df1_fast_q31.c
emilmont 1:fdd22bb7aa52 9 *
emilmont 2:da51fb522205 10 * Description: Processing function for the
emilmont 2:da51fb522205 11 * Q31 Fast Biquad cascade DirectFormI(DF1) filter.
emilmont 1:fdd22bb7aa52 12 *
emilmont 1:fdd22bb7aa52 13 * Target Processor: Cortex-M4/Cortex-M3
emilmont 1:fdd22bb7aa52 14 *
mbed_official 3:7a284390b0ce 15 * Redistribution and use in source and binary forms, with or without
mbed_official 3:7a284390b0ce 16 * modification, are permitted provided that the following conditions
mbed_official 3:7a284390b0ce 17 * are met:
mbed_official 3:7a284390b0ce 18 * - Redistributions of source code must retain the above copyright
mbed_official 3:7a284390b0ce 19 * notice, this list of conditions and the following disclaimer.
mbed_official 3:7a284390b0ce 20 * - Redistributions in binary form must reproduce the above copyright
mbed_official 3:7a284390b0ce 21 * notice, this list of conditions and the following disclaimer in
mbed_official 3:7a284390b0ce 22 * the documentation and/or other materials provided with the
mbed_official 3:7a284390b0ce 23 * distribution.
mbed_official 3:7a284390b0ce 24 * - Neither the name of ARM LIMITED nor the names of its contributors
mbed_official 3:7a284390b0ce 25 * may be used to endorse or promote products derived from this
mbed_official 3:7a284390b0ce 26 * software without specific prior written permission.
mbed_official 3:7a284390b0ce 27 *
mbed_official 3:7a284390b0ce 28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
mbed_official 3:7a284390b0ce 29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
mbed_official 3:7a284390b0ce 30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
mbed_official 3:7a284390b0ce 31 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
mbed_official 3:7a284390b0ce 32 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
mbed_official 3:7a284390b0ce 33 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
mbed_official 3:7a284390b0ce 34 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
mbed_official 3:7a284390b0ce 35 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
mbed_official 3:7a284390b0ce 36 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
mbed_official 3:7a284390b0ce 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
mbed_official 3:7a284390b0ce 38 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
mbed_official 3:7a284390b0ce 39 * POSSIBILITY OF SUCH DAMAGE.
emilmont 1:fdd22bb7aa52 40 * -------------------------------------------------------------------- */
emilmont 1:fdd22bb7aa52 41
emilmont 1:fdd22bb7aa52 42 #include "arm_math.h"
emilmont 1:fdd22bb7aa52 43
emilmont 1:fdd22bb7aa52 44 /**
emilmont 1:fdd22bb7aa52 45 * @ingroup groupFilters
emilmont 1:fdd22bb7aa52 46 */
emilmont 1:fdd22bb7aa52 47
emilmont 1:fdd22bb7aa52 48 /**
emilmont 1:fdd22bb7aa52 49 * @addtogroup BiquadCascadeDF1
emilmont 1:fdd22bb7aa52 50 * @{
emilmont 1:fdd22bb7aa52 51 */
emilmont 1:fdd22bb7aa52 52
emilmont 1:fdd22bb7aa52 53 /**
emilmont 1:fdd22bb7aa52 54 * @details
emilmont 1:fdd22bb7aa52 55 *
emilmont 1:fdd22bb7aa52 56 * @param[in] *S points to an instance of the Q31 Biquad cascade structure.
emilmont 1:fdd22bb7aa52 57 * @param[in] *pSrc points to the block of input data.
emilmont 1:fdd22bb7aa52 58 * @param[out] *pDst points to the block of output data.
emilmont 1:fdd22bb7aa52 59 * @param[in] blockSize number of samples to process per call.
emilmont 2:da51fb522205 60 * @return none.
emilmont 1:fdd22bb7aa52 61 *
emilmont 1:fdd22bb7aa52 62 * <b>Scaling and Overflow Behavior:</b>
emilmont 1:fdd22bb7aa52 63 * \par
emilmont 1:fdd22bb7aa52 64 * This function is optimized for speed at the expense of fixed-point precision and overflow protection.
emilmont 1:fdd22bb7aa52 65 * The result of each 1.31 x 1.31 multiplication is truncated to 2.30 format.
emilmont 1:fdd22bb7aa52 66 * These intermediate results are added to a 2.30 accumulator.
emilmont 1:fdd22bb7aa52 67 * Finally, the accumulator is saturated and converted to a 1.31 result.
emilmont 1:fdd22bb7aa52 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.
emilmont 1:fdd22bb7aa52 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
emilmont 1:fdd22bb7aa52 70 * arm_biquad_cascade_df1_init_q31() to initialize filter structure.
emilmont 1:fdd22bb7aa52 71 *
emilmont 1:fdd22bb7aa52 72 * \par
emilmont 1:fdd22bb7aa52 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.
emilmont 1:fdd22bb7aa52 74 * Use the function <code>arm_biquad_cascade_df1_init_q31()</code> to initialize the filter structure.
emilmont 1:fdd22bb7aa52 75 */
emilmont 1:fdd22bb7aa52 76
emilmont 1:fdd22bb7aa52 77 void arm_biquad_cascade_df1_fast_q31(
emilmont 1:fdd22bb7aa52 78 const arm_biquad_casd_df1_inst_q31 * S,
emilmont 1:fdd22bb7aa52 79 q31_t * pSrc,
emilmont 1:fdd22bb7aa52 80 q31_t * pDst,
emilmont 1:fdd22bb7aa52 81 uint32_t blockSize)
emilmont 1:fdd22bb7aa52 82 {
mbed_official 3:7a284390b0ce 83 q31_t acc = 0; /* accumulator */
emilmont 1:fdd22bb7aa52 84 q31_t Xn1, Xn2, Yn1, Yn2; /* Filter state variables */
emilmont 1:fdd22bb7aa52 85 q31_t b0, b1, b2, a1, a2; /* Filter coefficients */
emilmont 1:fdd22bb7aa52 86 q31_t *pIn = pSrc; /* input pointer initialization */
emilmont 1:fdd22bb7aa52 87 q31_t *pOut = pDst; /* output pointer initialization */
emilmont 1:fdd22bb7aa52 88 q31_t *pState = S->pState; /* pState pointer initialization */
emilmont 1:fdd22bb7aa52 89 q31_t *pCoeffs = S->pCoeffs; /* coeff pointer initialization */
emilmont 1:fdd22bb7aa52 90 q31_t Xn; /* temporary input */
emilmont 1:fdd22bb7aa52 91 int32_t shift = (int32_t) S->postShift + 1; /* Shift to be applied to the output */
emilmont 1:fdd22bb7aa52 92 uint32_t sample, stage = S->numStages; /* loop counters */
emilmont 1:fdd22bb7aa52 93
emilmont 1:fdd22bb7aa52 94
emilmont 1:fdd22bb7aa52 95 do
emilmont 1:fdd22bb7aa52 96 {
emilmont 1:fdd22bb7aa52 97 /* Reading the coefficients */
emilmont 1:fdd22bb7aa52 98 b0 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 99 b1 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 100 b2 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 101 a1 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 102 a2 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 103
emilmont 1:fdd22bb7aa52 104 /* Reading the state values */
emilmont 1:fdd22bb7aa52 105 Xn1 = pState[0];
emilmont 1:fdd22bb7aa52 106 Xn2 = pState[1];
emilmont 1:fdd22bb7aa52 107 Yn1 = pState[2];
emilmont 1:fdd22bb7aa52 108 Yn2 = pState[3];
emilmont 1:fdd22bb7aa52 109
emilmont 1:fdd22bb7aa52 110 /* Apply loop unrolling and compute 4 output values simultaneously. */
emilmont 1:fdd22bb7aa52 111 /* The variables acc ... acc3 hold output values that are being computed:
emilmont 1:fdd22bb7aa52 112 *
emilmont 1:fdd22bb7aa52 113 * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
emilmont 1:fdd22bb7aa52 114 */
emilmont 1:fdd22bb7aa52 115
emilmont 1:fdd22bb7aa52 116 sample = blockSize >> 2u;
emilmont 1:fdd22bb7aa52 117
emilmont 1:fdd22bb7aa52 118 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
emilmont 1:fdd22bb7aa52 119 ** a second loop below computes the remaining 1 to 3 samples. */
emilmont 1:fdd22bb7aa52 120 while(sample > 0u)
emilmont 1:fdd22bb7aa52 121 {
emilmont 1:fdd22bb7aa52 122 /* Read the input */
emilmont 1:fdd22bb7aa52 123 Xn = *pIn;
emilmont 1:fdd22bb7aa52 124
emilmont 1:fdd22bb7aa52 125 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 126 /* acc = b0 * x[n] */
mbed_official 5:3762170b6d4d 127 /*acc = (q31_t) (((q63_t) b1 * Xn1) >> 32);*/
mbed_official 3:7a284390b0ce 128 mult_32x32_keep32_R(acc, b1, Xn1);
emilmont 1:fdd22bb7aa52 129 /* acc += b1 * x[n-1] */
mbed_official 5:3762170b6d4d 130 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b0 * (Xn))) >> 32);*/
mbed_official 3:7a284390b0ce 131 multAcc_32x32_keep32_R(acc, b0, Xn);
emilmont 1:fdd22bb7aa52 132 /* acc += b[2] * x[n-2] */
mbed_official 5:3762170b6d4d 133 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32);*/
mbed_official 3:7a284390b0ce 134 multAcc_32x32_keep32_R(acc, b2, Xn2);
emilmont 1:fdd22bb7aa52 135 /* acc += a1 * y[n-1] */
mbed_official 5:3762170b6d4d 136 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32);*/
mbed_official 3:7a284390b0ce 137 multAcc_32x32_keep32_R(acc, a1, Yn1);
emilmont 1:fdd22bb7aa52 138 /* acc += a2 * y[n-2] */
mbed_official 5:3762170b6d4d 139 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32);*/
mbed_official 3:7a284390b0ce 140 multAcc_32x32_keep32_R(acc, a2, Yn2);
emilmont 1:fdd22bb7aa52 141
emilmont 1:fdd22bb7aa52 142 /* The result is converted to 1.31 , Yn2 variable is reused */
emilmont 1:fdd22bb7aa52 143 Yn2 = acc << shift;
emilmont 1:fdd22bb7aa52 144
emilmont 1:fdd22bb7aa52 145 /* Read the second input */
emilmont 1:fdd22bb7aa52 146 Xn2 = *(pIn + 1u);
emilmont 1:fdd22bb7aa52 147
emilmont 1:fdd22bb7aa52 148 /* Store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 149 *pOut = Yn2;
emilmont 1:fdd22bb7aa52 150
emilmont 1:fdd22bb7aa52 151 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 152 /* acc = b0 * x[n] */
mbed_official 5:3762170b6d4d 153 /*acc = (q31_t) (((q63_t) b0 * (Xn2)) >> 32);*/
mbed_official 3:7a284390b0ce 154 mult_32x32_keep32_R(acc, b0, Xn2);
emilmont 1:fdd22bb7aa52 155 /* acc += b1 * x[n-1] */
mbed_official 5:3762170b6d4d 156 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn))) >> 32);*/
mbed_official 3:7a284390b0ce 157 multAcc_32x32_keep32_R(acc, b1, Xn);
emilmont 1:fdd22bb7aa52 158 /* acc += b[2] * x[n-2] */
mbed_official 5:3762170b6d4d 159 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn1))) >> 32);*/
mbed_official 3:7a284390b0ce 160 multAcc_32x32_keep32_R(acc, b2, Xn1);
emilmont 1:fdd22bb7aa52 161 /* acc += a1 * y[n-1] */
mbed_official 5:3762170b6d4d 162 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn2))) >> 32);*/
mbed_official 3:7a284390b0ce 163 multAcc_32x32_keep32_R(acc, a1, Yn2);
emilmont 1:fdd22bb7aa52 164 /* acc += a2 * y[n-2] */
mbed_official 5:3762170b6d4d 165 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn1))) >> 32);*/
mbed_official 3:7a284390b0ce 166 multAcc_32x32_keep32_R(acc, a2, Yn1);
emilmont 1:fdd22bb7aa52 167
emilmont 1:fdd22bb7aa52 168 /* The result is converted to 1.31, Yn1 variable is reused */
emilmont 1:fdd22bb7aa52 169 Yn1 = acc << shift;
emilmont 1:fdd22bb7aa52 170
emilmont 1:fdd22bb7aa52 171 /* Read the third input */
emilmont 1:fdd22bb7aa52 172 Xn1 = *(pIn + 2u);
emilmont 1:fdd22bb7aa52 173
emilmont 1:fdd22bb7aa52 174 /* Store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 175 *(pOut + 1u) = Yn1;
emilmont 1:fdd22bb7aa52 176
emilmont 1:fdd22bb7aa52 177 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 178 /* acc = b0 * x[n] */
mbed_official 5:3762170b6d4d 179 /*acc = (q31_t) (((q63_t) b0 * (Xn1)) >> 32);*/
mbed_official 3:7a284390b0ce 180 mult_32x32_keep32_R(acc, b0, Xn1);
emilmont 1:fdd22bb7aa52 181 /* acc += b1 * x[n-1] */
mbed_official 5:3762170b6d4d 182 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn2))) >> 32);*/
mbed_official 3:7a284390b0ce 183 multAcc_32x32_keep32_R(acc, b1, Xn2);
emilmont 1:fdd22bb7aa52 184 /* acc += b[2] * x[n-2] */
mbed_official 5:3762170b6d4d 185 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn))) >> 32);*/
mbed_official 3:7a284390b0ce 186 multAcc_32x32_keep32_R(acc, b2, Xn);
emilmont 1:fdd22bb7aa52 187 /* acc += a1 * y[n-1] */
mbed_official 5:3762170b6d4d 188 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32);*/
mbed_official 3:7a284390b0ce 189 multAcc_32x32_keep32_R(acc, a1, Yn1);
emilmont 1:fdd22bb7aa52 190 /* acc += a2 * y[n-2] */
mbed_official 5:3762170b6d4d 191 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32);*/
mbed_official 3:7a284390b0ce 192 multAcc_32x32_keep32_R(acc, a2, Yn2);
emilmont 1:fdd22bb7aa52 193
emilmont 1:fdd22bb7aa52 194 /* The result is converted to 1.31, Yn2 variable is reused */
emilmont 1:fdd22bb7aa52 195 Yn2 = acc << shift;
emilmont 1:fdd22bb7aa52 196
emilmont 1:fdd22bb7aa52 197 /* Read the forth input */
emilmont 1:fdd22bb7aa52 198 Xn = *(pIn + 3u);
emilmont 1:fdd22bb7aa52 199
emilmont 1:fdd22bb7aa52 200 /* Store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 201 *(pOut + 2u) = Yn2;
emilmont 1:fdd22bb7aa52 202 pIn += 4u;
emilmont 1:fdd22bb7aa52 203
emilmont 1:fdd22bb7aa52 204 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 205 /* acc = b0 * x[n] */
mbed_official 5:3762170b6d4d 206 /*acc = (q31_t) (((q63_t) b0 * (Xn)) >> 32);*/
mbed_official 3:7a284390b0ce 207 mult_32x32_keep32_R(acc, b0, Xn);
emilmont 1:fdd22bb7aa52 208 /* acc += b1 * x[n-1] */
mbed_official 5:3762170b6d4d 209 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn1))) >> 32);*/
mbed_official 3:7a284390b0ce 210 multAcc_32x32_keep32_R(acc, b1, Xn1);
emilmont 1:fdd22bb7aa52 211 /* acc += b[2] * x[n-2] */
mbed_official 5:3762170b6d4d 212 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32);*/
mbed_official 3:7a284390b0ce 213 multAcc_32x32_keep32_R(acc, b2, Xn2);
emilmont 1:fdd22bb7aa52 214 /* acc += a1 * y[n-1] */
mbed_official 5:3762170b6d4d 215 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn2))) >> 32);*/
mbed_official 3:7a284390b0ce 216 multAcc_32x32_keep32_R(acc, a1, Yn2);
emilmont 1:fdd22bb7aa52 217 /* acc += a2 * y[n-2] */
mbed_official 5:3762170b6d4d 218 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn1))) >> 32);*/
mbed_official 3:7a284390b0ce 219 multAcc_32x32_keep32_R(acc, a2, Yn1);
emilmont 1:fdd22bb7aa52 220
emilmont 1:fdd22bb7aa52 221 /* Every time after the output is computed state should be updated. */
emilmont 1:fdd22bb7aa52 222 /* The states should be updated as: */
emilmont 1:fdd22bb7aa52 223 /* Xn2 = Xn1 */
emilmont 1:fdd22bb7aa52 224 Xn2 = Xn1;
emilmont 1:fdd22bb7aa52 225
emilmont 1:fdd22bb7aa52 226 /* The result is converted to 1.31, Yn1 variable is reused */
emilmont 1:fdd22bb7aa52 227 Yn1 = acc << shift;
emilmont 1:fdd22bb7aa52 228
emilmont 1:fdd22bb7aa52 229 /* Xn1 = Xn */
emilmont 1:fdd22bb7aa52 230 Xn1 = Xn;
emilmont 1:fdd22bb7aa52 231
emilmont 1:fdd22bb7aa52 232 /* Store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 233 *(pOut + 3u) = Yn1;
emilmont 1:fdd22bb7aa52 234 pOut += 4u;
emilmont 1:fdd22bb7aa52 235
emilmont 1:fdd22bb7aa52 236 /* decrement the loop counter */
emilmont 1:fdd22bb7aa52 237 sample--;
emilmont 1:fdd22bb7aa52 238 }
emilmont 1:fdd22bb7aa52 239
emilmont 1:fdd22bb7aa52 240 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
emilmont 1:fdd22bb7aa52 241 ** No loop unrolling is used. */
emilmont 1:fdd22bb7aa52 242 sample = (blockSize & 0x3u);
emilmont 1:fdd22bb7aa52 243
mbed_official 3:7a284390b0ce 244 while(sample > 0u)
mbed_official 3:7a284390b0ce 245 {
emilmont 1:fdd22bb7aa52 246 /* Read the input */
emilmont 1:fdd22bb7aa52 247 Xn = *pIn++;
emilmont 1:fdd22bb7aa52 248
emilmont 1:fdd22bb7aa52 249 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 250 /* acc = b0 * x[n] */
mbed_official 5:3762170b6d4d 251 /*acc = (q31_t) (((q63_t) b0 * (Xn)) >> 32);*/
mbed_official 3:7a284390b0ce 252 mult_32x32_keep32_R(acc, b0, Xn);
emilmont 1:fdd22bb7aa52 253 /* acc += b1 * x[n-1] */
mbed_official 5:3762170b6d4d 254 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn1))) >> 32);*/
mbed_official 3:7a284390b0ce 255 multAcc_32x32_keep32_R(acc, b1, Xn1);
emilmont 1:fdd22bb7aa52 256 /* acc += b[2] * x[n-2] */
mbed_official 5:3762170b6d4d 257 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32);*/
mbed_official 3:7a284390b0ce 258 multAcc_32x32_keep32_R(acc, b2, Xn2);
emilmont 1:fdd22bb7aa52 259 /* acc += a1 * y[n-1] */
mbed_official 5:3762170b6d4d 260 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32);*/
mbed_official 3:7a284390b0ce 261 multAcc_32x32_keep32_R(acc, a1, Yn1);
emilmont 1:fdd22bb7aa52 262 /* acc += a2 * y[n-2] */
mbed_official 5:3762170b6d4d 263 /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32);*/
mbed_official 3:7a284390b0ce 264 multAcc_32x32_keep32_R(acc, a2, Yn2);
mbed_official 3:7a284390b0ce 265
emilmont 1:fdd22bb7aa52 266 /* The result is converted to 1.31 */
emilmont 1:fdd22bb7aa52 267 acc = acc << shift;
emilmont 1:fdd22bb7aa52 268
emilmont 1:fdd22bb7aa52 269 /* Every time after the output is computed state should be updated. */
emilmont 1:fdd22bb7aa52 270 /* The states should be updated as: */
emilmont 1:fdd22bb7aa52 271 /* Xn2 = Xn1 */
emilmont 1:fdd22bb7aa52 272 /* Xn1 = Xn */
emilmont 1:fdd22bb7aa52 273 /* Yn2 = Yn1 */
emilmont 1:fdd22bb7aa52 274 /* Yn1 = acc */
emilmont 1:fdd22bb7aa52 275 Xn2 = Xn1;
emilmont 1:fdd22bb7aa52 276 Xn1 = Xn;
emilmont 1:fdd22bb7aa52 277 Yn2 = Yn1;
emilmont 1:fdd22bb7aa52 278 Yn1 = acc;
emilmont 1:fdd22bb7aa52 279
emilmont 1:fdd22bb7aa52 280 /* Store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 281 *pOut++ = acc;
emilmont 1:fdd22bb7aa52 282
emilmont 1:fdd22bb7aa52 283 /* decrement the loop counter */
emilmont 1:fdd22bb7aa52 284 sample--;
mbed_official 3:7a284390b0ce 285 }
emilmont 1:fdd22bb7aa52 286
emilmont 1:fdd22bb7aa52 287 /* The first stage goes from the input buffer to the output buffer. */
emilmont 1:fdd22bb7aa52 288 /* Subsequent stages occur in-place in the output buffer */
emilmont 1:fdd22bb7aa52 289 pIn = pDst;
emilmont 1:fdd22bb7aa52 290
emilmont 1:fdd22bb7aa52 291 /* Reset to destination pointer */
emilmont 1:fdd22bb7aa52 292 pOut = pDst;
emilmont 1:fdd22bb7aa52 293
emilmont 1:fdd22bb7aa52 294 /* Store the updated state variables back into the pState array */
emilmont 1:fdd22bb7aa52 295 *pState++ = Xn1;
emilmont 1:fdd22bb7aa52 296 *pState++ = Xn2;
emilmont 1:fdd22bb7aa52 297 *pState++ = Yn1;
emilmont 1:fdd22bb7aa52 298 *pState++ = Yn2;
emilmont 1:fdd22bb7aa52 299
emilmont 1:fdd22bb7aa52 300 } while(--stage);
emilmont 1:fdd22bb7aa52 301 }
emilmont 1:fdd22bb7aa52 302
emilmont 1:fdd22bb7aa52 303 /**
emilmont 1:fdd22bb7aa52 304 * @} end of BiquadCascadeDF1 group
emilmont 1:fdd22bb7aa52 305 */