/* ---------------------------------------------------------------------- * Copyright (C) 2010-2014 ARM Limited. All rights reserved. * * $Date: 19. March 2015 * $Revision: V.1.4.5 * * Project: CMSIS DSP Library * Title: arm_fir_init_q15.c * * Description: Q15 FIR filter initialization function. * * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * - Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * - Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * - Neither the name of ARM LIMITED nor the names of its contributors * may be used to endorse or promote products derived from this * software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ------------------------------------------------------------------- */ #include "arm_math.h" /** * @ingroup groupFilters */ /** * @addtogroup FIR * @{ */ /** * @param[in,out] *S points to an instance of the Q15 FIR filter structure. * @param[in] numTaps Number of filter coefficients in the filter. Must be even and greater than or equal to 4. * @param[in] *pCoeffs points to the filter coefficients buffer. * @param[in] *pState points to the state buffer. * @param[in] blockSize is number of samples processed per call. * @return The function returns ARM_MATH_SUCCESS if initialization is successful or ARM_MATH_ARGUMENT_ERROR if * numTaps is not greater than or equal to 4 and even. * * Description: * \par * pCoeffs points to the array of filter coefficients stored in time reversed order: *
    
 *    {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]}    
 * 
* Note that numTaps must be even and greater than or equal to 4. * To implement an odd length filter simply increase numTaps by 1 and set the last coefficient to zero. * For example, to implement a filter with numTaps=3 and coefficients *
    
 *     {0.3, -0.8, 0.3}    
 * 
* set numTaps=4 and use the coefficients: *
    
 *     {0.3, -0.8, 0.3, 0}.    
 * 
* Similarly, to implement a two point filter *
    
 *     {0.3, -0.3}    
 * 
* set numTaps=4 and use the coefficients: *
    
 *     {0.3, -0.3, 0, 0}.    
 * 
* \par * pState points to the array of state variables. * pState is of length numTaps+blockSize, when running on Cortex-M4 and Cortex-M3 and is of length numTaps+blockSize-1, when running on Cortex-M0 where blockSize is the number of input samples processed by each call to arm_fir_q15(). */ arm_status arm_fir_init_q15( arm_fir_instance_q15 * S, uint16_t numTaps, q15_t * pCoeffs, q15_t * pState, uint32_t blockSize) { arm_status status; #ifndef ARM_MATH_CM0_FAMILY /* Run the below code for Cortex-M4 and Cortex-M3 */ /* The Number of filter coefficients in the filter must be even and at least 4 */ if(numTaps & 0x1u) { status = ARM_MATH_ARGUMENT_ERROR; } else { /* Assign filter taps */ S->numTaps = numTaps; /* Assign coefficient pointer */ S->pCoeffs = pCoeffs; /* Clear the state buffer. The size is always (blockSize + numTaps ) */ memset(pState, 0, (numTaps + (blockSize)) * sizeof(q15_t)); /* Assign state pointer */ S->pState = pState; status = ARM_MATH_SUCCESS; } return (status); #else /* Run the below code for Cortex-M0 */ /* Assign filter taps */ S->numTaps = numTaps; /* Assign coefficient pointer */ S->pCoeffs = pCoeffs; /* Clear the state buffer. The size is always (blockSize + numTaps - 1) */ memset(pState, 0, (numTaps + (blockSize - 1u)) * sizeof(q15_t)); /* Assign state pointer */ S->pState = pState; status = ARM_MATH_SUCCESS; return (status); #endif /* #ifndef ARM_MATH_CM0_FAMILY */ } /** * @} end of FIR group */