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git.gir.st - tmk_keyboard.git/blob - tmk_core/tool/mbed/mbed-sdk/libraries/dsp/cmsis_dsp/FilteringFunctions/arm_fir_init_q15.c
1 /* ----------------------------------------------------------------------
2 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.
4 * $Date: 17. January 2013
7 * Project: CMSIS DSP Library
8 * Title: arm_fir_init_q15.c
10 * Description: Q15 FIR filter initialization function.
12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions
17 * - Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 * - Redistributions in binary form must reproduce the above copyright
20 * notice, this list of conditions and the following disclaimer in
21 * the documentation and/or other materials provided with the
23 * - Neither the name of ARM LIMITED nor the names of its contributors
24 * may be used to endorse or promote products derived from this
25 * software without specific prior written permission.
27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
30 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
31 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
33 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
34 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
35 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
37 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
38 * POSSIBILITY OF SUCH DAMAGE.
39 * ------------------------------------------------------------------- */
44 * @ingroup groupFilters
53 * @param[in,out] *S points to an instance of the Q15 FIR filter structure.
54 * @param[in] numTaps Number of filter coefficients in the filter. Must be even and greater than or equal to 4.
55 * @param[in] *pCoeffs points to the filter coefficients buffer.
56 * @param[in] *pState points to the state buffer.
57 * @param[in] blockSize is number of samples processed per call.
58 * @return The function returns ARM_MATH_SUCCESS if initialization is successful or ARM_MATH_ARGUMENT_ERROR if
59 * <code>numTaps</code> is not greater than or equal to 4 and even.
63 * <code>pCoeffs</code> points to the array of filter coefficients stored in time reversed order:
65 * {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]}
67 * Note that <code>numTaps</code> must be even and greater than or equal to 4.
68 * To implement an odd length filter simply increase <code>numTaps</code> by 1 and set the last coefficient to zero.
69 * For example, to implement a filter with <code>numTaps=3</code> and coefficients
73 * set <code>numTaps=4</code> and use the coefficients:
75 * {0.3, -0.8, 0.3, 0}.
77 * Similarly, to implement a two point filter
81 * set <code>numTaps=4</code> and use the coefficients:
86 * <code>pState</code> points to the array of state variables.
87 * <code>pState</code> is of length <code>numTaps+blockSize</code>, when running on Cortex-M4 and Cortex-M3 and is of length <code>numTaps+blockSize-1</code>, when running on Cortex-M0 where <code>blockSize</code> is the number of input samples processed by each call to <code>arm_fir_q15()</code>.
90 arm_status
arm_fir_init_q15 (
91 arm_fir_instance_q15
* S
,
100 #ifndef ARM_MATH_CM0_FAMILY
102 /* Run the below code for Cortex-M4 and Cortex-M3 */
104 /* The Number of filter coefficients in the filter must be even and at least 4 */
107 status
= ARM_MATH_ARGUMENT_ERROR
;
111 /* Assign filter taps */
112 S
-> numTaps
= numTaps
;
114 /* Assign coefficient pointer */
115 S
-> pCoeffs
= pCoeffs
;
117 /* Clear the state buffer. The size is always (blockSize + numTaps ) */
118 memset ( pState
, 0 , ( numTaps
+ ( blockSize
)) * sizeof ( q15_t
));
120 /* Assign state pointer */
123 status
= ARM_MATH_SUCCESS
;
130 /* Run the below code for Cortex-M0 */
132 /* Assign filter taps */
133 S
-> numTaps
= numTaps
;
135 /* Assign coefficient pointer */
136 S
-> pCoeffs
= pCoeffs
;
138 /* Clear the state buffer. The size is always (blockSize + numTaps - 1) */
139 memset ( pState
, 0 , ( numTaps
+ ( blockSize
- 1u )) * sizeof ( q15_t
));
141 /* Assign state pointer */
144 status
= ARM_MATH_SUCCESS
;
148 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
153 * @} end of FIR group