arm_fir_decimate_init_q15.c

00001 /* ----------------------------------------------------------------------    
00002 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
00003 *    
00004 * $Date:        19. March 2015
00005 * $Revision:    V.1.4.5
00006 *    
00007 * Project:      CMSIS DSP Library    
00008 * Title:        arm_fir_decimate_init_q15.c    
00009 *    
00010 * Description:  Initialization function for the Q15 FIR Decimator.    
00011 *    
00012 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
00013 *  
00014 * Redistribution and use in source and binary forms, with or without 
00015 * modification, are permitted provided that the following conditions
00016 * are met:
00017 *   - Redistributions of source code must retain the above copyright
00018 *     notice, this list of conditions and the following disclaimer.
00019 *   - Redistributions in binary form must reproduce the above copyright
00020 *     notice, this list of conditions and the following disclaimer in
00021 *     the documentation and/or other materials provided with the 
00022 *     distribution.
00023 *   - Neither the name of ARM LIMITED nor the names of its contributors
00024 *     may be used to endorse or promote products derived from this
00025 *     software without specific prior written permission.
00026 *
00027 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
00028 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
00029 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
00030 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
00031 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
00032 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
00033 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
00034 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
00035 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
00036 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
00037 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
00038 * POSSIBILITY OF SUCH DAMAGE.    
00039 * ------------------------------------------------------------------- */
00040 
00041 #include "arm_math.h"
00042 
00043 /**    
00044  * @ingroup groupFilters    
00045  */
00046 
00047 /**    
00048  * @addtogroup FIR_decimate    
00049  * @{    
00050  */
00051 
00052 /**    
00053  * @brief  Initialization function for the Q15 FIR decimator.    
00054  * @param[in,out] *S points to an instance of the Q15 FIR decimator structure.    
00055  * @param[in] numTaps  number of coefficients in the filter.    
00056  * @param[in] M  decimation factor.    
00057  * @param[in] *pCoeffs points to the filter coefficients.    
00058  * @param[in] *pState points to the state buffer.    
00059  * @param[in] blockSize number of input samples to process per call.    
00060  * @return    The function returns ARM_MATH_SUCCESS if initialization was successful or ARM_MATH_LENGTH_ERROR if    
00061  * <code>blockSize</code> is not a multiple of <code>M</code>.    
00062  *    
00063  * <b>Description:</b>    
00064  * \par    
00065  * <code>pCoeffs</code> points to the array of filter coefficients stored in time reversed order:    
00066  * <pre>    
00067  *    {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]}    
00068  * </pre>    
00069  * \par    
00070  * <code>pState</code> points to the array of state variables.    
00071  * <code>pState</code> is of length <code>numTaps+blockSize-1</code> words where <code>blockSize</code> is the number of input samples    
00072  * to the call <code>arm_fir_decimate_q15()</code>.    
00073  * <code>M</code> is the decimation factor.    
00074  */
00075 
00076 arm_status arm_fir_decimate_init_q15(
00077   arm_fir_decimate_instance_q15 * S,
00078   uint16_t numTaps,
00079   uint8_t M,
00080   q15_t * pCoeffs,
00081   q15_t * pState,
00082   uint32_t blockSize)
00083 {
00084 
00085   arm_status status;
00086 
00087   /* The size of the input block must be a multiple of the decimation factor */
00088   if((blockSize % M) != 0u)
00089   {
00090     /* Set status as ARM_MATH_LENGTH_ERROR */
00091     status = ARM_MATH_LENGTH_ERROR;
00092   }
00093   else
00094   {
00095     /* Assign filter taps */
00096     S->numTaps = numTaps;
00097 
00098     /* Assign coefficient pointer */
00099     S->pCoeffs = pCoeffs;
00100 
00101     /* Clear the state buffer.  The size of buffer is always (blockSize + numTaps - 1) */
00102     memset(pState, 0, (numTaps + (blockSize - 1u)) * sizeof(q15_t));
00103 
00104     /* Assign state pointer */
00105     S->pState = pState;
00106 
00107     /* Assign Decimation factor */
00108     S->M = M;
00109 
00110     status = ARM_MATH_SUCCESS;
00111   }
00112 
00113   return (status);
00114 
00115 }
00116 
00117 /**    
00118  * @} end of FIR_decimate group    
00119  */