| /* ---------------------------------------------------------------------- |
| * Copyright (C) 2010 ARM Limited. All rights reserved. |
| * |
| * $Date: 15. July 2011 |
| * $Revision: V1.0.10 |
| * |
| * Project: CMSIS DSP Library |
| * Title: arm_fir_f32.c |
| * |
| * Description: Floating-point FIR filter processing function. |
| * |
| * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 |
| * |
| * Version 1.0.10 2011/7/15 |
| * Big Endian support added and Merged M0 and M3/M4 Source code. |
| * |
| * Version 1.0.3 2010/11/29 |
| * Re-organized the CMSIS folders and updated documentation. |
| * |
| * Version 1.0.2 2010/11/11 |
| * Documentation updated. |
| * |
| * Version 1.0.1 2010/10/05 |
| * Production release and review comments incorporated. |
| * |
| * Version 1.0.0 2010/09/20 |
| * Production release and review comments incorporated. |
| * |
| * Version 0.0.5 2010/04/26 |
| * incorporated review comments and updated with latest CMSIS layer |
| * |
| * Version 0.0.3 2010/03/10 |
| * Initial version |
| * -------------------------------------------------------------------- */ |
| |
| #include "arm_math.h" |
| |
| /** |
| * @ingroup groupFilters |
| */ |
| |
| /** |
| * @defgroup FIR Finite Impulse Response (FIR) Filters |
| * |
| * This set of functions implements Finite Impulse Response (FIR) filters |
| * for Q7, Q15, Q31, and floating-point data types. |
| * Fast versions of Q15 and Q31 are also provided on Cortex-M4 and Cortex-M3. |
| * The functions operate on blocks of input and output data and each call to the function processes |
| * <code>blockSize</code> samples through the filter. <code>pSrc</code> and |
| * <code>pDst</code> points to input and output arrays containing <code>blockSize</code> values. |
| * |
| * \par Algorithm: |
| * The FIR filter algorithm is based upon a sequence of multiply-accumulate (MAC) operations. |
| * Each filter coefficient <code>b[n]</code> is multiplied by a state variable which equals a previous input sample <code>x[n]</code>. |
| * <pre> |
| * y[n] = b[0] * x[n] + b[1] * x[n-1] + b[2] * x[n-2] + ...+ b[numTaps-1] * x[n-numTaps+1] |
| * </pre> |
| * \par |
| * \image html FIR.gif "Finite Impulse Response filter" |
| * \par |
| * <code>pCoeffs</code> points to a coefficient array of size <code>numTaps</code>. |
| * Coefficients are stored in time reversed order. |
| * \par |
| * <pre> |
| * {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]} |
| * </pre> |
| * \par |
| * <code>pState</code> points to a state array of size <code>numTaps + blockSize - 1</code>. |
| * Samples in the state buffer are stored in the following order. |
| * \par |
| * <pre> |
| * {x[n-numTaps+1], x[n-numTaps], x[n-numTaps-1], x[n-numTaps-2]....x[0], x[1], ..., x[blockSize-1]} |
| * </pre> |
| * \par |
| * Note that the length of the state buffer exceeds the length of the coefficient array by <code>blockSize-1</code>. |
| * The increased state buffer length allows circular addressing, which is traditionally used in the FIR filters, |
| * to be avoided and yields a significant speed improvement. |
| * The state variables are updated after each block of data is processed; the coefficients are untouched. |
| * \par Instance Structure |
| * The coefficients and state variables for a filter are stored together in an instance data structure. |
| * A separate instance structure must be defined for each filter. |
| * Coefficient arrays may be shared among several instances while state variable arrays cannot be shared. |
| * There are separate instance structure declarations for each of the 4 supported data types. |
| * |
| * \par Initialization Functions |
| * There is also an associated initialization function for each data type. |
| * The initialization function performs the following operations: |
| * - Sets the values of the internal structure fields. |
| * - Zeros out the values in the state buffer. |
| * |
| * \par |
| * Use of the initialization function is optional. |
| * However, if the initialization function is used, then the instance structure cannot be placed into a const data section. |
| * To place an instance structure into a const data section, the instance structure must be manually initialized. |
| * Set the values in the state buffer to zeros before static initialization. |
| * The code below statically initializes each of the 4 different data type filter instance structures |
| * <pre> |
| *arm_fir_instance_f32 S = {numTaps, pState, pCoeffs}; |
| *arm_fir_instance_q31 S = {numTaps, pState, pCoeffs}; |
| *arm_fir_instance_q15 S = {numTaps, pState, pCoeffs}; |
| *arm_fir_instance_q7 S = {numTaps, pState, pCoeffs}; |
| * </pre> |
| * |
| * where <code>numTaps</code> is the number of filter coefficients in the filter; <code>pState</code> is the address of the state buffer; |
| * <code>pCoeffs</code> is the address of the coefficient buffer. |
| * |
| * \par Fixed-Point Behavior |
| * Care must be taken when using the fixed-point versions of the FIR filter functions. |
| * In particular, the overflow and saturation behavior of the accumulator used in each function must be considered. |
| * Refer to the function specific documentation below for usage guidelines. |
| */ |
| |
| /** |
| * @addtogroup FIR |
| * @{ |
| */ |
| |
| /** |
| * |
| * @param[in] *S points to an instance of the floating-point FIR filter structure. |
| * @param[in] *pSrc points to the block of input data. |
| * @param[out] *pDst points to the block of output data. |
| * @param[in] blockSize number of samples to process per call. |
| * @return none. |
| * |
| */ |
| |
| void arm_fir_f32( |
| const arm_fir_instance_f32 * S, |
| float32_t * pSrc, |
| float32_t * pDst, |
| uint32_t blockSize) |
| { |
| |
| float32_t *pState = S->pState; /* State pointer */ |
| float32_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| float32_t *pStateCurnt; /* Points to the current sample of the state */ |
| float32_t *px, *pb; /* Temporary pointers for state and coefficient buffers */ |
| uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */ |
| uint32_t i, tapCnt, blkCnt; /* Loop counters */ |
| |
| |
| #ifndef ARM_MATH_CM0 |
| |
| /* Run the below code for Cortex-M4 and Cortex-M3 */ |
| |
| float32_t acc0, acc1, acc2, acc3; /* Accumulators */ |
| float32_t x0, x1, x2, x3, c0; /* Temporary variables to hold state and coefficient values */ |
| |
| |
| /* S->pState points to state array which contains previous frame (numTaps - 1) samples */ |
| /* pStateCurnt points to the location where the new input data should be written */ |
| pStateCurnt = &(S->pState[(numTaps - 1u)]); |
| |
| /* Apply loop unrolling and compute 4 output values simultaneously. |
| * The variables acc0 ... acc3 hold output values that are being computed: |
| * |
| * acc0 = b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0] |
| * acc1 = b[numTaps-1] * x[n-numTaps] + b[numTaps-2] * x[n-numTaps-1] + b[numTaps-3] * x[n-numTaps-2] +...+ b[0] * x[1] |
| * acc2 = b[numTaps-1] * x[n-numTaps+1] + b[numTaps-2] * x[n-numTaps] + b[numTaps-3] * x[n-numTaps-1] +...+ b[0] * x[2] |
| * acc3 = b[numTaps-1] * x[n-numTaps+2] + b[numTaps-2] * x[n-numTaps+1] + b[numTaps-3] * x[n-numTaps] +...+ b[0] * x[3] |
| */ |
| blkCnt = blockSize >> 2; |
| |
| /* First part of the processing with loop unrolling. Compute 4 outputs at a time. |
| ** a second loop below computes the remaining 1 to 3 samples. */ |
| while(blkCnt > 0u) |
| { |
| /* Copy four new input samples into the state buffer */ |
| *pStateCurnt++ = *pSrc++; |
| *pStateCurnt++ = *pSrc++; |
| *pStateCurnt++ = *pSrc++; |
| *pStateCurnt++ = *pSrc++; |
| |
| /* Set all accumulators to zero */ |
| acc0 = 0.0f; |
| acc1 = 0.0f; |
| acc2 = 0.0f; |
| acc3 = 0.0f; |
| |
| /* Initialize state pointer */ |
| px = pState; |
| |
| /* Initialize coeff pointer */ |
| pb = (pCoeffs); |
| |
| /* Read the first three samples from the state buffer: x[n-numTaps], x[n-numTaps-1], x[n-numTaps-2] */ |
| x0 = *px++; |
| x1 = *px++; |
| x2 = *px++; |
| |
| /* Loop unrolling. Process 4 taps at a time. */ |
| tapCnt = numTaps >> 2u; |
| |
| /* Loop over the number of taps. Unroll by a factor of 4. |
| ** Repeat until we've computed numTaps-4 coefficients. */ |
| while(tapCnt > 0u) |
| { |
| /* Read the b[numTaps-1] coefficient */ |
| c0 = *(pb++); |
| |
| /* Read x[n-numTaps-3] sample */ |
| x3 = *(px++); |
| |
| /* acc0 += b[numTaps-1] * x[n-numTaps] */ |
| acc0 += x0 * c0; |
| |
| /* acc1 += b[numTaps-1] * x[n-numTaps-1] */ |
| acc1 += x1 * c0; |
| |
| /* acc2 += b[numTaps-1] * x[n-numTaps-2] */ |
| acc2 += x2 * c0; |
| |
| /* acc3 += b[numTaps-1] * x[n-numTaps-3] */ |
| acc3 += x3 * c0; |
| |
| /* Read the b[numTaps-2] coefficient */ |
| c0 = *(pb++); |
| |
| /* Read x[n-numTaps-4] sample */ |
| x0 = *(px++); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x1 * c0; |
| acc1 += x2 * c0; |
| acc2 += x3 * c0; |
| acc3 += x0 * c0; |
| |
| /* Read the b[numTaps-3] coefficient */ |
| c0 = *(pb++); |
| |
| /* Read x[n-numTaps-5] sample */ |
| x1 = *(px++); |
| |
| /* Perform the multiply-accumulates */ |
| acc0 += x2 * c0; |
| acc1 += x3 * c0; |
| acc2 += x0 * c0; |
| acc3 += x1 * c0; |
| |
| /* Read the b[numTaps-4] coefficient */ |
| c0 = *(pb++); |
| |
| /* Read x[n-numTaps-6] sample */ |
| x2 = *(px++); |
| |
| /* Perform the multiply-accumulates */ |
| acc0 += x3 * c0; |
| acc1 += x0 * c0; |
| acc2 += x1 * c0; |
| acc3 += x2 * c0; |
| |
| tapCnt--; |
| } |
| |
| /* If the filter length is not a multiple of 4, compute the remaining filter taps */ |
| tapCnt = numTaps % 0x4u; |
| |
| while(tapCnt > 0u) |
| { |
| /* Read coefficients */ |
| c0 = *(pb++); |
| |
| /* Fetch 1 state variable */ |
| x3 = *(px++); |
| |
| /* Perform the multiply-accumulates */ |
| acc0 += x0 * c0; |
| acc1 += x1 * c0; |
| acc2 += x2 * c0; |
| acc3 += x3 * c0; |
| |
| /* Reuse the present sample states for next sample */ |
| x0 = x1; |
| x1 = x2; |
| x2 = x3; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| /* Advance the state pointer by 4 to process the next group of 4 samples */ |
| pState = pState + 4; |
| |
| /* The results in the 4 accumulators, store in the destination buffer. */ |
| *pDst++ = acc0; |
| *pDst++ = acc1; |
| *pDst++ = acc2; |
| *pDst++ = acc3; |
| |
| blkCnt--; |
| } |
| |
| /* If the blockSize is not a multiple of 4, compute any remaining output samples here. |
| ** No loop unrolling is used. */ |
| blkCnt = blockSize % 0x4u; |
| |
| while(blkCnt > 0u) |
| { |
| /* Copy one sample at a time into state buffer */ |
| *pStateCurnt++ = *pSrc++; |
| |
| /* Set the accumulator to zero */ |
| acc0 = 0.0f; |
| |
| /* Initialize state pointer */ |
| px = pState; |
| |
| /* Initialize Coefficient pointer */ |
| pb = (pCoeffs); |
| |
| i = numTaps; |
| |
| /* Perform the multiply-accumulates */ |
| do |
| { |
| acc0 += *px++ * *pb++; |
| i--; |
| |
| } while(i > 0u); |
| |
| /* The result is store in the destination buffer. */ |
| *pDst++ = acc0; |
| |
| /* Advance state pointer by 1 for the next sample */ |
| pState = pState + 1; |
| |
| blkCnt--; |
| } |
| |
| /* Processing is complete. |
| ** Now copy the last numTaps - 1 samples to the satrt of the state buffer. |
| ** This prepares the state buffer for the next function call. */ |
| |
| /* Points to the start of the state buffer */ |
| pStateCurnt = S->pState; |
| |
| tapCnt = (numTaps - 1u) >> 2u; |
| |
| /* copy data */ |
| while(tapCnt > 0u) |
| { |
| *pStateCurnt++ = *pState++; |
| *pStateCurnt++ = *pState++; |
| *pStateCurnt++ = *pState++; |
| *pStateCurnt++ = *pState++; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| /* Calculate remaining number of copies */ |
| tapCnt = (numTaps - 1u) % 0x4u; |
| |
| /* Copy the remaining q31_t data */ |
| while(tapCnt > 0u) |
| { |
| *pStateCurnt++ = *pState++; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| #else |
| |
| /* Run the below code for Cortex-M0 */ |
| |
| float32_t acc; |
| |
| /* S->pState points to state array which contains previous frame (numTaps - 1) samples */ |
| /* pStateCurnt points to the location where the new input data should be written */ |
| pStateCurnt = &(S->pState[(numTaps - 1u)]); |
| |
| /* Initialize blkCnt with blockSize */ |
| blkCnt = blockSize; |
| |
| while(blkCnt > 0u) |
| { |
| /* Copy one sample at a time into state buffer */ |
| *pStateCurnt++ = *pSrc++; |
| |
| /* Set the accumulator to zero */ |
| acc = 0.0f; |
| |
| /* Initialize state pointer */ |
| px = pState; |
| |
| /* Initialize Coefficient pointer */ |
| pb = pCoeffs; |
| |
| i = numTaps; |
| |
| /* Perform the multiply-accumulates */ |
| do |
| { |
| /* acc = b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0] */ |
| acc += *px++ * *pb++; |
| i--; |
| |
| } while(i > 0u); |
| |
| /* The result is store in the destination buffer. */ |
| *pDst++ = acc; |
| |
| /* Advance state pointer by 1 for the next sample */ |
| pState = pState + 1; |
| |
| blkCnt--; |
| } |
| |
| /* Processing is complete. |
| ** Now copy the last numTaps - 1 samples to the starting of the state buffer. |
| ** This prepares the state buffer for the next function call. */ |
| |
| /* Points to the start of the state buffer */ |
| pStateCurnt = S->pState; |
| |
| /* Copy numTaps number of values */ |
| tapCnt = numTaps - 1u; |
| |
| /* Copy data */ |
| while(tapCnt > 0u) |
| { |
| *pStateCurnt++ = *pState++; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| #endif /* #ifndef ARM_MATH_CM0 */ |
| |
| } |
| |
| /** |
| * @} end of FIR group |
| */ |
