1 /* ----------------------------------------------------------------------
2 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.
4 * $Date: 17. January 2013
7 * Project: CMSIS DSP Library
8 * Title: arm_biquad_cascade_df1_32x64_init_q31.c
10 * Description: High precision Q31 Biquad cascade filter initialization function.
12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
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15 * modification, are permitted provided that the following conditions
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21 * the documentation and/or other materials provided with the
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25 * software without specific prior written permission.
27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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39 * -------------------------------------------------------------------- */
44 * @ingroup groupFilters
48 * @addtogroup BiquadCascadeDF1_32x64
55 * @param[in,out] *S points to an instance of the high precision Q31 Biquad cascade filter structure.
56 * @param[in] numStages number of 2nd order stages in the filter.
57 * @param[in] *pCoeffs points to the filter coefficients.
58 * @param[in] *pState points to the state buffer.
59 * @param[in] postShift Shift to be applied after the accumulator. Varies according to the coefficients format.
62 * <b>Coefficient and State Ordering:</b>
65 * The coefficients are stored in the array <code>pCoeffs</code> in the following order:
67 * {b10, b11, b12, a11, a12, b20, b21, b22, a21, a22, ...}
69 * where <code>b1x</code> and <code>a1x</code> are the coefficients for the first stage,
70 * <code>b2x</code> and <code>a2x</code> are the coefficients for the second stage,
71 * and so on. The <code>pCoeffs</code> array contains a total of <code>5*numStages</code> values.
74 * The <code>pState</code> points to state variables array and size of each state variable is 1.63 format.
75 * Each Biquad stage has 4 state variables <code>x[n-1], x[n-2], y[n-1],</code> and <code>y[n-2]</code>.
76 * The state variables are arranged in the state array as:
78 * {x[n-1], x[n-2], y[n-1], y[n-2]}
80 * The 4 state variables for stage 1 are first, then the 4 state variables for stage 2, and so on.
81 * The state array has a total length of <code>4*numStages</code> values.
82 * The state variables are updated after each block of data is processed; the coefficients are untouched.
85 void arm_biquad_cas_df1_32x64_init_q31(
86 arm_biquad_cas_df1_32x64_ins_q31
* S
,
92 /* Assign filter stages */
93 S
->numStages
= numStages
;
95 /* Assign postShift to be applied to the output */
96 S
->postShift
= postShift
;
98 /* Assign coefficient pointer */
101 /* Clear state buffer and size is always 4 * numStages */
102 memset(pState
, 0, (4u * (uint32_t) numStages
) * sizeof(q63_t
));
104 /* Assign state pointer */
109 * @} end of BiquadCascadeDF1_32x64 group