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_df2T_init_f32.c
10 * Description: Initialization function for the floating-point transposed
11 * direct form II Biquad cascade filter.
13 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
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40 * ---------------------------------------------------------------------------*/
45 * @ingroup groupFilters
49 * @addtogroup BiquadCascadeDF2T
54 * @brief Initialization function for the floating-point transposed direct form II Biquad cascade filter.
55 * @param[in,out] *S points to an instance of the filter data 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.
61 * <b>Coefficient and State Ordering:</b>
63 * The coefficients are stored in the array <code>pCoeffs</code> in the following order:
65 * {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> is a pointer to state array.
75 * Each Biquad stage has 2 state variables <code>d1,</code> and <code>d2</code>.
76 * The 2 state variables for stage 1 are first, then the 2 state variables for stage 2, and so on.
77 * The state array has a total length of <code>2*numStages</code> values.
78 * The state variables are updated after each block of data is processed; the coefficients are untouched.
81 void arm_biquad_cascade_df2T_init_f32(
82 arm_biquad_cascade_df2T_instance_f32
* S
,
87 /* Assign filter stages */
88 S
->numStages
= numStages
;
90 /* Assign coefficient pointer */
93 /* Clear state buffer and size is always 2 * numStages */
94 memset(pState
, 0, (2u * (uint32_t) numStages
) * sizeof(float32_t
));
96 /* Assign state pointer */
101 * @} end of BiquadCascadeDF2T group