1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
|
/* ----------------------------------------------------------------------
* Copyright (C) 2010-2013 ARM Limited. All rights reserved.
*
* $Date: 17. January 2013
* $Revision: V1.4.1
*
* Project: CMSIS DSP Library
* Title: arm_biquad_cascade_df1_init_q31.c
*
* Description: Q31 Biquad cascade DirectFormI(DF1) filter initialization function.
*
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* - Neither the name of ARM LIMITED nor the names of its contributors
* may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* -------------------------------------------------------------------- */
#include "arm_math.h"
/**
* @ingroup groupFilters
*/
/**
* @addtogroup BiquadCascadeDF1
* @{
*/
/**
* @details
*
* @param[in,out] *S points to an instance of the Q31 Biquad cascade structure.
* @param[in] numStages number of 2nd order stages in the filter.
* @param[in] *pCoeffs points to the filter coefficients buffer.
* @param[in] *pState points to the state buffer.
* @param[in] postShift Shift to be applied after the accumulator. Varies according to the coefficients format
* @return none
*
* <b>Coefficient and State Ordering:</b>
*
* \par
* The coefficients are stored in the array <code>pCoeffs</code> in the following order:
* <pre>
* {b10, b11, b12, a11, a12, b20, b21, b22, a21, a22, ...}
* </pre>
* where <code>b1x</code> and <code>a1x</code> are the coefficients for the first stage,
* <code>b2x</code> and <code>a2x</code> are the coefficients for the second stage,
* and so on. The <code>pCoeffs</code> array contains a total of <code>5*numStages</code> values.
*
* \par
* The <code>pState</code> points to state variables array.
* Each Biquad stage has 4 state variables <code>x[n-1], x[n-2], y[n-1],</code> and <code>y[n-2]</code>.
* The state variables are arranged in the <code>pState</code> array as:
* <pre>
* {x[n-1], x[n-2], y[n-1], y[n-2]}
* </pre>
* The 4 state variables for stage 1 are first, then the 4 state variables for stage 2, and so on.
* The state array has a total length of <code>4*numStages</code> values.
* The state variables are updated after each block of data is processed; the coefficients are untouched.
*/
void arm_biquad_cascade_df1_init_q31(
arm_biquad_casd_df1_inst_q31 * S,
uint8_t numStages,
q31_t * pCoeffs,
q31_t * pState,
int8_t postShift)
{
/* Assign filter stages */
S->numStages = numStages;
/* Assign postShift to be applied to the output */
S->postShift = postShift;
/* Assign coefficient pointer */
S->pCoeffs = pCoeffs;
/* Clear state buffer and size is always 4 * numStages */
memset(pState, 0, (4u * (uint32_t) numStages) * sizeof(q31_t));
/* Assign state pointer */
S->pState = pState;
}
/**
* @} end of BiquadCascadeDF1 group
*/
|
