arm_fir_decimate_init_q15.c

00001 /* ----------------------------------------------------------------------  
00002 * Copyright (C) 2010 ARM Limited. All rights reserved.  
00003 *  
00004 * $Date:        29. November 2010  
00005 * $Revision:    V1.0.3  
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
00013 *  
00014 * Version 1.0.3 2010/11/29 
00015 *    Re-organized the CMSIS folders and updated documentation.  
00016 *   
00017 * Version 1.0.2 2010/11/11  
00018 *    Documentation updated.   
00019 *  
00020 * Version 1.0.1 2010/10/05   
00021 *    Production release and review comments incorporated.  
00022 *  
00023 * Version 1.0.0 2010/09/20   
00024 *    Production release and review comments incorporated  
00025 *  
00026 * Version 0.0.7  2010/06/10   
00027 *    Misra-C changes done  
00028 * ------------------------------------------------------------------- */ 
00029  
00030 #include "arm_math.h" 
00031  
00032 /**  
00033  * @ingroup groupFilters  
00034  */ 
00035  
00036 /**  
00037  * @addtogroup FIR_decimate  
00038  * @{  
00039  */ 
00040  
00041 /**  
00042  * @brief  Initialization function for the Q15 FIR decimator.  
00043  * @param[in,out] *S points to an instance of the Q15 FIR decimator structure.  
00044  * @param[in] numTaps  number of coefficients in the filter.  
00045  * @param[in] M  decimation factor.  
00046  * @param[in] *pCoeffs points to the filter coefficients.  
00047  * @param[in] *pState points to the state buffer.  
00048  * @param[in] blockSize number of input samples to process per call.  
00049  * @return    The function returns ARM_MATH_SUCCESS if initialization was successful or ARM_MATH_LENGTH_ERROR if  
00050  * <code>blockSize</code> is not a multiple of <code>M</code>.  
00051  *  
00052  * <b>Description:</b>  
00053  * \par  
00054  * <code>pCoeffs</code> points to the array of filter coefficients stored in time reversed order:  
00055  * <pre>  
00056  *    {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]}  
00057  * </pre>  
00058  * \par  
00059  * <code>pState</code> points to the array of state variables.  
00060  * <code>pState</code> is of length <code>numTaps+blockSize-1</code> words where <code>blockSize</code> is the number of input samples  
00061  * to the call <code>arm_fir_decimate_q15()</code>.  
00062  * <code>M</code> is the decimation factor.  
00063  */ 
00064  
00065 arm_status arm_fir_decimate_init_q15( 
00066   arm_fir_decimate_instance_q15 * S, 
00067   uint16_t numTaps, 
00068   uint8_t M, 
00069   q15_t * pCoeffs, 
00070   q15_t * pState, 
00071   uint32_t blockSize) 
00072 { 
00073  
00074   arm_status status; 
00075  
00076   /* The size of the input block must be a multiple of the decimation factor */ 
00077   if((blockSize % M) != 0u) 
00078   { 
00079     /* Set status as ARM_MATH_LENGTH_ERROR */ 
00080     status = ARM_MATH_LENGTH_ERROR; 
00081   } 
00082   else 
00083   { 
00084     /* Assign filter taps */ 
00085     S->numTaps = numTaps; 
00086  
00087     /* Assign coefficient pointer */ 
00088     S->pCoeffs = pCoeffs; 
00089  
00090     /* Clear the state buffer.  The size of buffer is always (blockSize + numTaps - 1) */ 
00091     memset(pState, 0, (numTaps + (blockSize - 1u)) * sizeof(q15_t)); 
00092  
00093     /* Assign state pointer */ 
00094     S->pState = pState; 
00095  
00096     /* Assign Decimation factor */ 
00097     S->M = M; 
00098  
00099     status = ARM_MATH_SUCCESS; 
00100   } 
00101  
00102   return (status); 
00103  
00104 } 
00105  
00106 /**  
00107  * @} end of FIR_decimate group  
00108  */