arm_fir_init_q15.c

00001 /* ----------------------------------------------------------------------    
00002 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.    
00003 *    
00004 * $Date:        17. January 2013
00005 * $Revision:    V1.4.1
00006 *    
00007 * Project:      CMSIS DSP Library    
00008 * Title:        arm_fir_init_q15.c    
00009 *    
00010 * Description:  Q15 FIR filter initialization function.    
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    
00049  * @{    
00050  */
00051 
00052 /**    
00053  * @param[in,out]  *S points to an instance of the Q15 FIR filter structure.    
00054  * @param[in]      numTaps  Number of filter coefficients in the filter. Must be even and greater than or equal to 4.    
00055  * @param[in]      *pCoeffs points to the filter coefficients buffer.    
00056  * @param[in]      *pState points to the state buffer.    
00057  * @param[in]      blockSize is number of samples processed per call.    
00058  * @return The function returns ARM_MATH_SUCCESS if initialization is successful or ARM_MATH_ARGUMENT_ERROR if    
00059  * <code>numTaps</code> is not greater than or equal to 4 and even.    
00060  *    
00061  * <b>Description:</b>    
00062  * \par    
00063  * <code>pCoeffs</code> points to the array of filter coefficients stored in time reversed order:    
00064  * <pre>    
00065  *    {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]}    
00066  * </pre>    
00067  * Note that <code>numTaps</code> must be even and greater than or equal to 4.    
00068  * To implement an odd length filter simply increase <code>numTaps</code> by 1 and set the last coefficient to zero.    
00069  * For example, to implement a filter with <code>numTaps=3</code> and coefficients    
00070  * <pre>    
00071  *     {0.3, -0.8, 0.3}    
00072  * </pre>    
00073  * set <code>numTaps=4</code> and use the coefficients:    
00074  * <pre>    
00075  *     {0.3, -0.8, 0.3, 0}.    
00076  * </pre>    
00077  * Similarly, to implement a two point filter    
00078  * <pre>    
00079  *     {0.3, -0.3}    
00080  * </pre>    
00081  * set <code>numTaps=4</code> and use the coefficients:    
00082  * <pre>    
00083  *     {0.3, -0.3, 0, 0}.    
00084  * </pre>    
00085  * \par    
00086  * <code>pState</code> points to the array of state variables.    
00087  * <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>.    
00088  */
00089 
00090 arm_status arm_fir_init_q15(
00091   arm_fir_instance_q15 * S,
00092   uint16_t numTaps,
00093   q15_t * pCoeffs,
00094   q15_t * pState,
00095   uint32_t blockSize)
00096 {
00097   arm_status status;
00098 
00099 
00100 #ifndef ARM_MATH_CM0_FAMILY
00101 
00102   /* Run the below code for Cortex-M4 and Cortex-M3 */
00103 
00104   /* The Number of filter coefficients in the filter must be even and at least 4 */
00105   if(numTaps & 0x1u)
00106   {
00107     status = ARM_MATH_ARGUMENT_ERROR;
00108   }
00109   else
00110   {
00111     /* Assign filter taps */
00112     S->numTaps = numTaps;
00113 
00114     /* Assign coefficient pointer */
00115     S->pCoeffs = pCoeffs;
00116 
00117     /* Clear the state buffer.  The size is always (blockSize + numTaps ) */
00118     memset(pState, 0, (numTaps + (blockSize)) * sizeof(q15_t));
00119 
00120     /* Assign state pointer */
00121     S->pState = pState;
00122 
00123     status = ARM_MATH_SUCCESS;
00124   }
00125 
00126   return (status);
00127 
00128 #else
00129 
00130   /* Run the below code for Cortex-M0 */
00131 
00132   /* Assign filter taps */
00133   S->numTaps = numTaps;
00134 
00135   /* Assign coefficient pointer */
00136   S->pCoeffs = pCoeffs;
00137 
00138   /* Clear the state buffer.  The size is always (blockSize + numTaps - 1) */
00139   memset(pState, 0, (numTaps + (blockSize - 1u)) * sizeof(q15_t));
00140 
00141   /* Assign state pointer */
00142   S->pState = pState;
00143 
00144   status = ARM_MATH_SUCCESS;
00145 
00146   return (status);
00147 
00148 #endif /*  #ifndef ARM_MATH_CM0_FAMILY */
00149 
00150 }
00151 
00152 /**    
00153  * @} end of FIR group    
00154  */