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CMSIS DSP library

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cmsis_dsp/FilteringFunctions/arm_biquad_cascade_df1_q31.c@2:da51fb522205, 2013-05-30 (annotated)

Committer:
emilmont
Date:
Thu May 30 17:10:11 2013 +0100
Revision:
2:da51fb522205
Parent:
1:fdd22bb7aa52
Child:
3:7a284390b0ce
Keep "cmsis-dsp" module in synch with its source

Who changed what in which revision?

UserRevisionLine numberNew contents of line
emilmont 1:fdd22bb7aa52 1 /* ----------------------------------------------------------------------
emilmont 1:fdd22bb7aa52 2 * Copyright (C) 2010 ARM Limited. All rights reserved.
emilmont 1:fdd22bb7aa52 3 *
emilmont 1:fdd22bb7aa52 4 * $Date: 15. February 2012
emilmont 2:da51fb522205 5 * $Revision: V1.1.0
emilmont 1:fdd22bb7aa52 6 *
emilmont 2:da51fb522205 7 * Project: CMSIS DSP Library
emilmont 2:da51fb522205 8 * Title: arm_biquad_cascade_df1_q31.c
emilmont 1:fdd22bb7aa52 9 *
emilmont 2:da51fb522205 10 * Description: Processing function for the
emilmont 2:da51fb522205 11 * Q31 Biquad cascade filter
emilmont 1:fdd22bb7aa52 12 *
emilmont 1:fdd22bb7aa52 13 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
emilmont 1:fdd22bb7aa52 14 *
emilmont 1:fdd22bb7aa52 15 * Version 1.1.0 2012/02/15
emilmont 1:fdd22bb7aa52 16 * Updated with more optimizations, bug fixes and minor API changes.
emilmont 1:fdd22bb7aa52 17 *
emilmont 1:fdd22bb7aa52 18 * Version 1.0.10 2011/7/15
emilmont 1:fdd22bb7aa52 19 * Big Endian support added and Merged M0 and M3/M4 Source code.
emilmont 1:fdd22bb7aa52 20 *
emilmont 1:fdd22bb7aa52 21 * Version 1.0.3 2010/11/29
emilmont 1:fdd22bb7aa52 22 * Re-organized the CMSIS folders and updated documentation.
emilmont 1:fdd22bb7aa52 23 *
emilmont 1:fdd22bb7aa52 24 * Version 1.0.2 2010/11/11
emilmont 1:fdd22bb7aa52 25 * Documentation updated.
emilmont 1:fdd22bb7aa52 26 *
emilmont 1:fdd22bb7aa52 27 * Version 1.0.1 2010/10/05
emilmont 1:fdd22bb7aa52 28 * Production release and review comments incorporated.
emilmont 1:fdd22bb7aa52 29 *
emilmont 1:fdd22bb7aa52 30 * Version 1.0.0 2010/09/20
emilmont 1:fdd22bb7aa52 31 * Production release and review comments incorporated.
emilmont 1:fdd22bb7aa52 32 *
emilmont 1:fdd22bb7aa52 33 * Version 0.0.5 2010/04/26
emilmont 2:da51fb522205 34 * incorporated review comments and updated with latest CMSIS layer
emilmont 1:fdd22bb7aa52 35 *
emilmont 1:fdd22bb7aa52 36 * Version 0.0.3 2010/03/10
emilmont 1:fdd22bb7aa52 37 * Initial version
emilmont 1:fdd22bb7aa52 38 * -------------------------------------------------------------------- */
emilmont 1:fdd22bb7aa52 39
emilmont 1:fdd22bb7aa52 40 #include "arm_math.h"
emilmont 1:fdd22bb7aa52 41
emilmont 1:fdd22bb7aa52 42 /**
emilmont 1:fdd22bb7aa52 43 * @ingroup groupFilters
emilmont 1:fdd22bb7aa52 44 */
emilmont 1:fdd22bb7aa52 45
emilmont 1:fdd22bb7aa52 46 /**
emilmont 1:fdd22bb7aa52 47 * @addtogroup BiquadCascadeDF1
emilmont 1:fdd22bb7aa52 48 * @{
emilmont 1:fdd22bb7aa52 49 */
emilmont 1:fdd22bb7aa52 50
emilmont 1:fdd22bb7aa52 51 /**
emilmont 1:fdd22bb7aa52 52 * @brief Processing function for the Q31 Biquad cascade filter.
emilmont 1:fdd22bb7aa52 53 * @param[in] *S points to an instance of the Q31 Biquad cascade structure.
emilmont 1:fdd22bb7aa52 54 * @param[in] *pSrc points to the block of input data.
emilmont 1:fdd22bb7aa52 55 * @param[out] *pDst points to the block of output data.
emilmont 1:fdd22bb7aa52 56 * @param[in] blockSize number of samples to process per call.
emilmont 1:fdd22bb7aa52 57 * @return none.
emilmont 1:fdd22bb7aa52 58 *
emilmont 1:fdd22bb7aa52 59 * <b>Scaling and Overflow Behavior:</b>
emilmont 1:fdd22bb7aa52 60 * \par
emilmont 1:fdd22bb7aa52 61 * The function is implemented using an internal 64-bit accumulator.
emilmont 1:fdd22bb7aa52 62 * The accumulator has a 2.62 format and maintains full precision of the intermediate multiplication results but provides only a single guard bit.
emilmont 1:fdd22bb7aa52 63 * Thus, if the accumulator result overflows it wraps around rather than clip.
emilmont 1:fdd22bb7aa52 64 * 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).
emilmont 1:fdd22bb7aa52 65 * After all 5 multiply-accumulates are performed, the 2.62 accumulator is shifted by <code>postShift</code> bits and the result truncated to
emilmont 1:fdd22bb7aa52 66 * 1.31 format by discarding the low 32 bits.
emilmont 1:fdd22bb7aa52 67 *
emilmont 1:fdd22bb7aa52 68 * \par
emilmont 1:fdd22bb7aa52 69 * 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.
emilmont 1:fdd22bb7aa52 70 */
emilmont 1:fdd22bb7aa52 71
emilmont 1:fdd22bb7aa52 72 void arm_biquad_cascade_df1_q31(
emilmont 1:fdd22bb7aa52 73 const arm_biquad_casd_df1_inst_q31 * S,
emilmont 1:fdd22bb7aa52 74 q31_t * pSrc,
emilmont 1:fdd22bb7aa52 75 q31_t * pDst,
emilmont 1:fdd22bb7aa52 76 uint32_t blockSize)
emilmont 1:fdd22bb7aa52 77 {
emilmont 1:fdd22bb7aa52 78 q63_t acc; /* accumulator */
emilmont 1:fdd22bb7aa52 79 uint32_t uShift = ((uint32_t) S->postShift + 1u);
emilmont 1:fdd22bb7aa52 80 uint32_t lShift = 32u - uShift; /* Shift to be applied to the output */
emilmont 1:fdd22bb7aa52 81 q31_t *pIn = pSrc; /* input pointer initialization */
emilmont 1:fdd22bb7aa52 82 q31_t *pOut = pDst; /* output pointer initialization */
emilmont 1:fdd22bb7aa52 83 q31_t *pState = S->pState; /* pState pointer initialization */
emilmont 1:fdd22bb7aa52 84 q31_t *pCoeffs = S->pCoeffs; /* coeff pointer initialization */
emilmont 1:fdd22bb7aa52 85 q31_t Xn1, Xn2, Yn1, Yn2; /* Filter state variables */
emilmont 1:fdd22bb7aa52 86 q31_t b0, b1, b2, a1, a2; /* Filter coefficients */
emilmont 1:fdd22bb7aa52 87 q31_t Xn; /* temporary input */
emilmont 1:fdd22bb7aa52 88 uint32_t sample, stage = S->numStages; /* loop counters */
emilmont 1:fdd22bb7aa52 89
emilmont 1:fdd22bb7aa52 90
emilmont 1:fdd22bb7aa52 91 #ifndef ARM_MATH_CM0
emilmont 1:fdd22bb7aa52 92
emilmont 1:fdd22bb7aa52 93 q31_t acc_l, acc_h; /* temporary output variables */
emilmont 1:fdd22bb7aa52 94
emilmont 1:fdd22bb7aa52 95 /* Run the below code for Cortex-M4 and Cortex-M3 */
emilmont 1:fdd22bb7aa52 96
emilmont 1:fdd22bb7aa52 97 do
emilmont 1:fdd22bb7aa52 98 {
emilmont 1:fdd22bb7aa52 99 /* Reading the coefficients */
emilmont 1:fdd22bb7aa52 100 b0 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 101 b1 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 102 b2 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 103 a1 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 104 a2 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 105
emilmont 1:fdd22bb7aa52 106 /* Reading the state values */
emilmont 1:fdd22bb7aa52 107 Xn1 = pState[0];
emilmont 1:fdd22bb7aa52 108 Xn2 = pState[1];
emilmont 1:fdd22bb7aa52 109 Yn1 = pState[2];
emilmont 1:fdd22bb7aa52 110 Yn2 = pState[3];
emilmont 1:fdd22bb7aa52 111
emilmont 1:fdd22bb7aa52 112 /* Apply loop unrolling and compute 4 output values simultaneously. */
emilmont 1:fdd22bb7aa52 113 /* The variable acc hold output values that are being computed:
emilmont 1:fdd22bb7aa52 114 *
emilmont 1:fdd22bb7aa52 115 * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
emilmont 1:fdd22bb7aa52 116 */
emilmont 1:fdd22bb7aa52 117
emilmont 1:fdd22bb7aa52 118 sample = blockSize >> 2u;
emilmont 1:fdd22bb7aa52 119
emilmont 1:fdd22bb7aa52 120 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
emilmont 1:fdd22bb7aa52 121 ** a second loop below computes the remaining 1 to 3 samples. */
emilmont 1:fdd22bb7aa52 122 while(sample > 0u)
emilmont 1:fdd22bb7aa52 123 {
emilmont 1:fdd22bb7aa52 124 /* Read the input */
emilmont 1:fdd22bb7aa52 125 Xn = *pIn++;
emilmont 1:fdd22bb7aa52 126
emilmont 1:fdd22bb7aa52 127 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 128
emilmont 1:fdd22bb7aa52 129 /* acc = b0 * x[n] */
emilmont 1:fdd22bb7aa52 130 acc = (q63_t) b0 *Xn;
emilmont 1:fdd22bb7aa52 131 /* acc += b1 * x[n-1] */
emilmont 1:fdd22bb7aa52 132 acc += (q63_t) b1 *Xn1;
emilmont 1:fdd22bb7aa52 133 /* acc += b[2] * x[n-2] */
emilmont 1:fdd22bb7aa52 134 acc += (q63_t) b2 *Xn2;
emilmont 1:fdd22bb7aa52 135 /* acc += a1 * y[n-1] */
emilmont 1:fdd22bb7aa52 136 acc += (q63_t) a1 *Yn1;
emilmont 1:fdd22bb7aa52 137 /* acc += a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 138 acc += (q63_t) a2 *Yn2;
emilmont 1:fdd22bb7aa52 139
emilmont 1:fdd22bb7aa52 140 /* The result is converted to 1.31 , Yn2 variable is reused */
emilmont 1:fdd22bb7aa52 141
emilmont 1:fdd22bb7aa52 142 /* Calc lower part of acc */
emilmont 1:fdd22bb7aa52 143 acc_l = acc & 0xffffffff;
emilmont 1:fdd22bb7aa52 144
emilmont 1:fdd22bb7aa52 145 /* Calc upper part of acc */
emilmont 1:fdd22bb7aa52 146 acc_h = (acc >> 32) & 0xffffffff;
emilmont 1:fdd22bb7aa52 147
emilmont 1:fdd22bb7aa52 148 /* Apply shift for lower part of acc and upper part of acc */
emilmont 1:fdd22bb7aa52 149 Yn2 = (uint32_t) acc_l >> lShift | acc_h << uShift;
emilmont 1:fdd22bb7aa52 150
emilmont 1:fdd22bb7aa52 151 /* Store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 152 *pOut++ = Yn2;
emilmont 1:fdd22bb7aa52 153
emilmont 1:fdd22bb7aa52 154 /* Read the second input */
emilmont 1:fdd22bb7aa52 155 Xn2 = *pIn++;
emilmont 1:fdd22bb7aa52 156
emilmont 1:fdd22bb7aa52 157 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 158
emilmont 1:fdd22bb7aa52 159 /* acc = b0 * x[n] */
emilmont 1:fdd22bb7aa52 160 acc = (q63_t) b0 *Xn2;
emilmont 1:fdd22bb7aa52 161 /* acc += b1 * x[n-1] */
emilmont 1:fdd22bb7aa52 162 acc += (q63_t) b1 *Xn;
emilmont 1:fdd22bb7aa52 163 /* acc += b[2] * x[n-2] */
emilmont 1:fdd22bb7aa52 164 acc += (q63_t) b2 *Xn1;
emilmont 1:fdd22bb7aa52 165 /* acc += a1 * y[n-1] */
emilmont 1:fdd22bb7aa52 166 acc += (q63_t) a1 *Yn2;
emilmont 1:fdd22bb7aa52 167 /* acc += a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 168 acc += (q63_t) a2 *Yn1;
emilmont 1:fdd22bb7aa52 169
emilmont 1:fdd22bb7aa52 170
emilmont 1:fdd22bb7aa52 171 /* The result is converted to 1.31, Yn1 variable is reused */
emilmont 1:fdd22bb7aa52 172
emilmont 1:fdd22bb7aa52 173 /* Calc lower part of acc */
emilmont 1:fdd22bb7aa52 174 acc_l = acc & 0xffffffff;
emilmont 1:fdd22bb7aa52 175
emilmont 1:fdd22bb7aa52 176 /* Calc upper part of acc */
emilmont 1:fdd22bb7aa52 177 acc_h = (acc >> 32) & 0xffffffff;
emilmont 1:fdd22bb7aa52 178
emilmont 1:fdd22bb7aa52 179
emilmont 1:fdd22bb7aa52 180 /* Apply shift for lower part of acc and upper part of acc */
emilmont 1:fdd22bb7aa52 181 Yn1 = (uint32_t) acc_l >> lShift | acc_h << uShift;
emilmont 1:fdd22bb7aa52 182
emilmont 1:fdd22bb7aa52 183 /* Store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 184 *pOut++ = Yn1;
emilmont 1:fdd22bb7aa52 185
emilmont 1:fdd22bb7aa52 186 /* Read the third input */
emilmont 1:fdd22bb7aa52 187 Xn1 = *pIn++;
emilmont 1:fdd22bb7aa52 188
emilmont 1:fdd22bb7aa52 189 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 190
emilmont 1:fdd22bb7aa52 191 /* acc = b0 * x[n] */
emilmont 1:fdd22bb7aa52 192 acc = (q63_t) b0 *Xn1;
emilmont 1:fdd22bb7aa52 193 /* acc += b1 * x[n-1] */
emilmont 1:fdd22bb7aa52 194 acc += (q63_t) b1 *Xn2;
emilmont 1:fdd22bb7aa52 195 /* acc += b[2] * x[n-2] */
emilmont 1:fdd22bb7aa52 196 acc += (q63_t) b2 *Xn;
emilmont 1:fdd22bb7aa52 197 /* acc += a1 * y[n-1] */
emilmont 1:fdd22bb7aa52 198 acc += (q63_t) a1 *Yn1;
emilmont 1:fdd22bb7aa52 199 /* acc += a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 200 acc += (q63_t) a2 *Yn2;
emilmont 1:fdd22bb7aa52 201
emilmont 1:fdd22bb7aa52 202 /* The result is converted to 1.31, Yn2 variable is reused */
emilmont 1:fdd22bb7aa52 203 /* Calc lower part of acc */
emilmont 1:fdd22bb7aa52 204 acc_l = acc & 0xffffffff;
emilmont 1:fdd22bb7aa52 205
emilmont 1:fdd22bb7aa52 206 /* Calc upper part of acc */
emilmont 1:fdd22bb7aa52 207 acc_h = (acc >> 32) & 0xffffffff;
emilmont 1:fdd22bb7aa52 208
emilmont 1:fdd22bb7aa52 209
emilmont 1:fdd22bb7aa52 210 /* Apply shift for lower part of acc and upper part of acc */
emilmont 1:fdd22bb7aa52 211 Yn2 = (uint32_t) acc_l >> lShift | acc_h << uShift;
emilmont 1:fdd22bb7aa52 212
emilmont 1:fdd22bb7aa52 213 /* Store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 214 *pOut++ = Yn2;
emilmont 1:fdd22bb7aa52 215
emilmont 1:fdd22bb7aa52 216 /* Read the forth input */
emilmont 1:fdd22bb7aa52 217 Xn = *pIn++;
emilmont 1:fdd22bb7aa52 218
emilmont 1:fdd22bb7aa52 219 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 220
emilmont 1:fdd22bb7aa52 221 /* acc = b0 * x[n] */
emilmont 1:fdd22bb7aa52 222 acc = (q63_t) b0 *Xn;
emilmont 1:fdd22bb7aa52 223 /* acc += b1 * x[n-1] */
emilmont 1:fdd22bb7aa52 224 acc += (q63_t) b1 *Xn1;
emilmont 1:fdd22bb7aa52 225 /* acc += b[2] * x[n-2] */
emilmont 1:fdd22bb7aa52 226 acc += (q63_t) b2 *Xn2;
emilmont 1:fdd22bb7aa52 227 /* acc += a1 * y[n-1] */
emilmont 1:fdd22bb7aa52 228 acc += (q63_t) a1 *Yn2;
emilmont 1:fdd22bb7aa52 229 /* acc += a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 230 acc += (q63_t) a2 *Yn1;
emilmont 1:fdd22bb7aa52 231
emilmont 1:fdd22bb7aa52 232 /* The result is converted to 1.31, Yn1 variable is reused */
emilmont 1:fdd22bb7aa52 233 /* Calc lower part of acc */
emilmont 1:fdd22bb7aa52 234 acc_l = acc & 0xffffffff;
emilmont 1:fdd22bb7aa52 235
emilmont 1:fdd22bb7aa52 236 /* Calc upper part of acc */
emilmont 1:fdd22bb7aa52 237 acc_h = (acc >> 32) & 0xffffffff;
emilmont 1:fdd22bb7aa52 238
emilmont 1:fdd22bb7aa52 239 /* Apply shift for lower part of acc and upper part of acc */
emilmont 1:fdd22bb7aa52 240 Yn1 = (uint32_t) acc_l >> lShift | acc_h << uShift;
emilmont 1:fdd22bb7aa52 241
emilmont 1:fdd22bb7aa52 242 /* Every time after the output is computed state should be updated. */
emilmont 1:fdd22bb7aa52 243 /* The states should be updated as: */
emilmont 1:fdd22bb7aa52 244 /* Xn2 = Xn1 */
emilmont 1:fdd22bb7aa52 245 /* Xn1 = Xn */
emilmont 1:fdd22bb7aa52 246 /* Yn2 = Yn1 */
emilmont 1:fdd22bb7aa52 247 /* Yn1 = acc */
emilmont 1:fdd22bb7aa52 248 Xn2 = Xn1;
emilmont 1:fdd22bb7aa52 249 Xn1 = Xn;
emilmont 1:fdd22bb7aa52 250
emilmont 1:fdd22bb7aa52 251 /* Store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 252 *pOut++ = Yn1;
emilmont 1:fdd22bb7aa52 253
emilmont 1:fdd22bb7aa52 254 /* decrement the loop counter */
emilmont 1:fdd22bb7aa52 255 sample--;
emilmont 1:fdd22bb7aa52 256 }
emilmont 1:fdd22bb7aa52 257
emilmont 1:fdd22bb7aa52 258 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
emilmont 1:fdd22bb7aa52 259 ** No loop unrolling is used. */
emilmont 1:fdd22bb7aa52 260 sample = (blockSize & 0x3u);
emilmont 1:fdd22bb7aa52 261
emilmont 1:fdd22bb7aa52 262 while(sample > 0u)
emilmont 1:fdd22bb7aa52 263 {
emilmont 1:fdd22bb7aa52 264 /* Read the input */
emilmont 1:fdd22bb7aa52 265 Xn = *pIn++;
emilmont 1:fdd22bb7aa52 266
emilmont 1:fdd22bb7aa52 267 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 268
emilmont 1:fdd22bb7aa52 269 /* acc = b0 * x[n] */
emilmont 1:fdd22bb7aa52 270 acc = (q63_t) b0 *Xn;
emilmont 1:fdd22bb7aa52 271 /* acc += b1 * x[n-1] */
emilmont 1:fdd22bb7aa52 272 acc += (q63_t) b1 *Xn1;
emilmont 1:fdd22bb7aa52 273 /* acc += b[2] * x[n-2] */
emilmont 1:fdd22bb7aa52 274 acc += (q63_t) b2 *Xn2;
emilmont 1:fdd22bb7aa52 275 /* acc += a1 * y[n-1] */
emilmont 1:fdd22bb7aa52 276 acc += (q63_t) a1 *Yn1;
emilmont 1:fdd22bb7aa52 277 /* acc += a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 278 acc += (q63_t) a2 *Yn2;
emilmont 1:fdd22bb7aa52 279
emilmont 1:fdd22bb7aa52 280 /* The result is converted to 1.31 */
emilmont 1:fdd22bb7aa52 281 acc = acc >> lShift;
emilmont 1:fdd22bb7aa52 282
emilmont 1:fdd22bb7aa52 283 /* Every time after the output is computed state should be updated. */
emilmont 1:fdd22bb7aa52 284 /* The states should be updated as: */
emilmont 1:fdd22bb7aa52 285 /* Xn2 = Xn1 */
emilmont 1:fdd22bb7aa52 286 /* Xn1 = Xn */
emilmont 1:fdd22bb7aa52 287 /* Yn2 = Yn1 */
emilmont 1:fdd22bb7aa52 288 /* Yn1 = acc */
emilmont 1:fdd22bb7aa52 289 Xn2 = Xn1;
emilmont 1:fdd22bb7aa52 290 Xn1 = Xn;
emilmont 1:fdd22bb7aa52 291 Yn2 = Yn1;
emilmont 1:fdd22bb7aa52 292 Yn1 = (q31_t) acc;
emilmont 1:fdd22bb7aa52 293
emilmont 1:fdd22bb7aa52 294 /* Store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 295 *pOut++ = (q31_t) acc;
emilmont 1:fdd22bb7aa52 296
emilmont 1:fdd22bb7aa52 297 /* decrement the loop counter */
emilmont 1:fdd22bb7aa52 298 sample--;
emilmont 1:fdd22bb7aa52 299 }
emilmont 1:fdd22bb7aa52 300
emilmont 1:fdd22bb7aa52 301 /* The first stage goes from the input buffer to the output buffer. */
emilmont 1:fdd22bb7aa52 302 /* Subsequent stages occur in-place in the output buffer */
emilmont 1:fdd22bb7aa52 303 pIn = pDst;
emilmont 1:fdd22bb7aa52 304
emilmont 1:fdd22bb7aa52 305 /* Reset to destination pointer */
emilmont 1:fdd22bb7aa52 306 pOut = pDst;
emilmont 1:fdd22bb7aa52 307
emilmont 1:fdd22bb7aa52 308 /* Store the updated state variables back into the pState array */
emilmont 1:fdd22bb7aa52 309 *pState++ = Xn1;
emilmont 1:fdd22bb7aa52 310 *pState++ = Xn2;
emilmont 1:fdd22bb7aa52 311 *pState++ = Yn1;
emilmont 1:fdd22bb7aa52 312 *pState++ = Yn2;
emilmont 1:fdd22bb7aa52 313
emilmont 1:fdd22bb7aa52 314 } while(--stage);
emilmont 1:fdd22bb7aa52 315
emilmont 1:fdd22bb7aa52 316 #else
emilmont 1:fdd22bb7aa52 317
emilmont 1:fdd22bb7aa52 318 /* Run the below code for Cortex-M0 */
emilmont 1:fdd22bb7aa52 319
emilmont 1:fdd22bb7aa52 320 do
emilmont 1:fdd22bb7aa52 321 {
emilmont 1:fdd22bb7aa52 322 /* Reading the coefficients */
emilmont 1:fdd22bb7aa52 323 b0 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 324 b1 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 325 b2 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 326 a1 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 327 a2 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 328
emilmont 1:fdd22bb7aa52 329 /* Reading the state values */
emilmont 1:fdd22bb7aa52 330 Xn1 = pState[0];
emilmont 1:fdd22bb7aa52 331 Xn2 = pState[1];
emilmont 1:fdd22bb7aa52 332 Yn1 = pState[2];
emilmont 1:fdd22bb7aa52 333 Yn2 = pState[3];
emilmont 1:fdd22bb7aa52 334
emilmont 1:fdd22bb7aa52 335 /* The variables acc holds the output value that is computed:
emilmont 1:fdd22bb7aa52 336 * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
emilmont 1:fdd22bb7aa52 337 */
emilmont 1:fdd22bb7aa52 338
emilmont 1:fdd22bb7aa52 339 sample = blockSize;
emilmont 1:fdd22bb7aa52 340
emilmont 1:fdd22bb7aa52 341 while(sample > 0u)
emilmont 1:fdd22bb7aa52 342 {
emilmont 1:fdd22bb7aa52 343 /* Read the input */
emilmont 1:fdd22bb7aa52 344 Xn = *pIn++;
emilmont 1:fdd22bb7aa52 345
emilmont 1:fdd22bb7aa52 346 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 347 /* acc = b0 * x[n] */
emilmont 1:fdd22bb7aa52 348 acc = (q63_t) b0 *Xn;
emilmont 1:fdd22bb7aa52 349
emilmont 1:fdd22bb7aa52 350 /* acc += b1 * x[n-1] */
emilmont 1:fdd22bb7aa52 351 acc += (q63_t) b1 *Xn1;
emilmont 1:fdd22bb7aa52 352 /* acc += b[2] * x[n-2] */
emilmont 1:fdd22bb7aa52 353 acc += (q63_t) b2 *Xn2;
emilmont 1:fdd22bb7aa52 354 /* acc += a1 * y[n-1] */
emilmont 1:fdd22bb7aa52 355 acc += (q63_t) a1 *Yn1;
emilmont 1:fdd22bb7aa52 356 /* acc += a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 357 acc += (q63_t) a2 *Yn2;
emilmont 1:fdd22bb7aa52 358
emilmont 1:fdd22bb7aa52 359 /* The result is converted to 1.31 */
emilmont 1:fdd22bb7aa52 360 acc = acc >> lShift;
emilmont 1:fdd22bb7aa52 361
emilmont 1:fdd22bb7aa52 362 /* Every time after the output is computed state should be updated. */
emilmont 1:fdd22bb7aa52 363 /* The states should be updated as: */
emilmont 1:fdd22bb7aa52 364 /* Xn2 = Xn1 */
emilmont 1:fdd22bb7aa52 365 /* Xn1 = Xn */
emilmont 1:fdd22bb7aa52 366 /* Yn2 = Yn1 */
emilmont 1:fdd22bb7aa52 367 /* Yn1 = acc */
emilmont 1:fdd22bb7aa52 368 Xn2 = Xn1;
emilmont 1:fdd22bb7aa52 369 Xn1 = Xn;
emilmont 1:fdd22bb7aa52 370 Yn2 = Yn1;
emilmont 1:fdd22bb7aa52 371 Yn1 = (q31_t) acc;
emilmont 1:fdd22bb7aa52 372
emilmont 1:fdd22bb7aa52 373 /* Store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 374 *pOut++ = (q31_t) acc;
emilmont 1:fdd22bb7aa52 375
emilmont 1:fdd22bb7aa52 376 /* decrement the loop counter */
emilmont 1:fdd22bb7aa52 377 sample--;
emilmont 1:fdd22bb7aa52 378 }
emilmont 1:fdd22bb7aa52 379
emilmont 1:fdd22bb7aa52 380 /* The first stage goes from the input buffer to the output buffer. */
emilmont 1:fdd22bb7aa52 381 /* Subsequent stages occur in-place in the output buffer */
emilmont 1:fdd22bb7aa52 382 pIn = pDst;
emilmont 1:fdd22bb7aa52 383
emilmont 1:fdd22bb7aa52 384 /* Reset to destination pointer */
emilmont 1:fdd22bb7aa52 385 pOut = pDst;
emilmont 1:fdd22bb7aa52 386
emilmont 1:fdd22bb7aa52 387 /* Store the updated state variables back into the pState array */
emilmont 1:fdd22bb7aa52 388 *pState++ = Xn1;
emilmont 1:fdd22bb7aa52 389 *pState++ = Xn2;
emilmont 1:fdd22bb7aa52 390 *pState++ = Yn1;
emilmont 1:fdd22bb7aa52 391 *pState++ = Yn2;
emilmont 1:fdd22bb7aa52 392
emilmont 1:fdd22bb7aa52 393 } while(--stage);
emilmont 1:fdd22bb7aa52 394
emilmont 1:fdd22bb7aa52 395 #endif /* #ifndef ARM_MATH_CM0 */
emilmont 1:fdd22bb7aa52 396 }
emilmont 1:fdd22bb7aa52 397
emilmont 1:fdd22bb7aa52 398 /**
emilmont 1:fdd22bb7aa52 399 * @} end of BiquadCascadeDF1 group
emilmont 1:fdd22bb7aa52 400 */