| /* ---------------------------------------------------------------------- |
| * Copyright (C) 2010 ARM Limited. All rights reserved. |
| * |
| * $Date: 15. July 2011 |
| * $Revision: V1.0.10 |
| * |
| * Project: CMSIS DSP Library |
| * Title: arm_iir_lattice_f32.c |
| * |
| * Description: Floating-point IIR Lattice 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 0.0.7 2010/06/10 |
| * Misra-C changes done |
| * -------------------------------------------------------------------- */ |
| |
| #include "arm_math.h" |
| |
| /** |
| * @ingroup groupFilters |
| */ |
| |
| /** |
| * @defgroup IIR_Lattice Infinite Impulse Response (IIR) Lattice Filters |
| * |
| * This set of functions implements lattice filters |
| * for Q15, Q31 and floating-point data types. Lattice filters are used in a |
| * variety of adaptive filter applications. The filter structure has feedforward and |
| * feedback components and the net impulse response is infinite length. |
| * 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> point to input and output arrays containing <code>blockSize</code> values. |
| |
| * \par Algorithm: |
| * \image html IIRLattice.gif "Infinite Impulse Response Lattice filter" |
| * <pre> |
| * fN(n) = x(n) |
| * fm-1(n) = fm(n) - km * gm-1(n-1) for m = N, N-1, ...1 |
| * gm(n) = km * fm-1(n) + gm-1(n-1) for m = N, N-1, ...1 |
| * y(n) = vN * gN(n) + vN-1 * gN-1(n) + ...+ v0 * g0(n) |
| * </pre> |
| * \par |
| * <code>pkCoeffs</code> points to array of reflection coefficients of size <code>numStages</code>. |
| * Reflection coefficients are stored in time-reversed order. |
| * \par |
| * <pre> |
| * {kN, kN-1, ....k1} |
| * </pre> |
| * <code>pvCoeffs</code> points to the array of ladder coefficients of size <code>(numStages+1)</code>. |
| * Ladder coefficients are stored in time-reversed order. |
| * \par |
| * <pre> |
| * {vN, vN-1, ...v0} |
| * </pre> |
| * <code>pState</code> points to a state array of size <code>numStages + blockSize</code>. |
| * The state variables shown in the figure above (the g values) are stored in the <code>pState</code> array. |
| * 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 3 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 and then manually initialize the instance structure as follows: |
| * <pre> |
| *arm_iir_lattice_instance_f32 S = {numStages, pState, pkCoeffs, pvCoeffs}; |
| *arm_iir_lattice_instance_q31 S = {numStages, pState, pkCoeffs, pvCoeffs}; |
| *arm_iir_lattice_instance_q15 S = {numStages, pState, pkCoeffs, pvCoeffs}; |
| * </pre> |
| * \par |
| * where <code>numStages</code> is the number of stages in the filter; <code>pState</code> points to the state buffer array; |
| * <code>pkCoeffs</code> points to array of the reflection coefficients; <code>pvCoeffs</code> points to the array of ladder coefficients. |
| * \par Fixed-Point Behavior |
| * Care must be taken when using the fixed-point versions of the IIR lattice 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 IIR_Lattice |
| * @{ |
| */ |
| |
| /** |
| * @brief Processing function for the floating-point IIR lattice filter. |
| * @param[in] *S points to an instance of the floating-point IIR lattice 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. |
| * @return none. |
| */ |
| |
| void arm_iir_lattice_f32( |
| const arm_iir_lattice_instance_f32 * S, |
| float32_t * pSrc, |
| float32_t * pDst, |
| uint32_t blockSize) |
| { |
| float32_t fcurr, fnext = 0, gcurr, gnext; /* Temporary variables for lattice stages */ |
| float32_t acc; /* Accumlator */ |
| uint32_t blkCnt, tapCnt; /* temporary variables for counts */ |
| float32_t *px1, *px2, *pk, *pv; /* temporary pointers for state and coef */ |
| uint32_t numStages = S->numStages; /* number of stages */ |
| float32_t *pState; /* State pointer */ |
| float32_t *pStateCurnt; /* State current pointer */ |
| |
| |
| #ifndef ARM_MATH_CM0 |
| |
| /* Run the below code for Cortex-M4 and Cortex-M3 */ |
| |
| gcurr = 0.0f; |
| blkCnt = blockSize; |
| |
| pState = &S->pState[0]; |
| |
| /* Sample processing */ |
| while(blkCnt > 0u) |
| { |
| /* Read Sample from input buffer */ |
| /* fN(n) = x(n) */ |
| fcurr = *pSrc++; |
| |
| /* Initialize state read pointer */ |
| px1 = pState; |
| /* Initialize state write pointer */ |
| px2 = pState; |
| /* Set accumulator to zero */ |
| acc = 0.0f; |
| /* Initialize Ladder coeff pointer */ |
| pv = &S->pvCoeffs[0]; |
| /* Initialize Reflection coeff pointer */ |
| pk = &S->pkCoeffs[0]; |
| |
| |
| /* Process sample for first tap */ |
| gcurr = *px1++; |
| /* fN-1(n) = fN(n) - kN * gN-1(n-1) */ |
| fnext = fcurr - ((*pk) * gcurr); |
| /* gN(n) = kN * fN-1(n) + gN-1(n-1) */ |
| gnext = (fnext * (*pk++)) + gcurr; |
| /* write gN(n) into state for next sample processing */ |
| *px2++ = gnext; |
| /* y(n) += gN(n) * vN */ |
| acc += (gnext * (*pv++)); |
| |
| /* Update f values for next coefficient processing */ |
| fcurr = fnext; |
| |
| /* Loop unrolling. Process 4 taps at a time. */ |
| tapCnt = (numStages - 1u) >> 2; |
| |
| while(tapCnt > 0u) |
| { |
| /* Process sample for 2nd, 6th ...taps */ |
| /* Read gN-2(n-1) from state buffer */ |
| gcurr = *px1++; |
| /* Process sample for 2nd, 6th .. taps */ |
| /* fN-2(n) = fN-1(n) - kN-1 * gN-2(n-1) */ |
| fnext = fcurr - ((*pk) * gcurr); |
| /* gN-1(n) = kN-1 * fN-2(n) + gN-2(n-1) */ |
| gnext = (fnext * (*pk++)) + gcurr; |
| /* y(n) += gN-1(n) * vN-1 */ |
| /* process for gN-5(n) * vN-5, gN-9(n) * vN-9 ... */ |
| acc += (gnext * (*pv++)); |
| /* write gN-1(n) into state for next sample processing */ |
| *px2++ = gnext; |
| |
| |
| /* Process sample for 3nd, 7th ...taps */ |
| /* Read gN-3(n-1) from state buffer */ |
| gcurr = *px1++; |
| /* Process sample for 3rd, 7th .. taps */ |
| /* fN-3(n) = fN-2(n) - kN-2 * gN-3(n-1) */ |
| fcurr = fnext - ((*pk) * gcurr); |
| /* gN-2(n) = kN-2 * fN-3(n) + gN-3(n-1) */ |
| gnext = (fcurr * (*pk++)) + gcurr; |
| /* y(n) += gN-2(n) * vN-2 */ |
| /* process for gN-6(n) * vN-6, gN-10(n) * vN-10 ... */ |
| acc += (gnext * (*pv++)); |
| /* write gN-2(n) into state for next sample processing */ |
| *px2++ = gnext; |
| |
| |
| /* Process sample for 4th, 8th ...taps */ |
| /* Read gN-4(n-1) from state buffer */ |
| gcurr = *px1++; |
| /* Process sample for 4th, 8th .. taps */ |
| /* fN-4(n) = fN-3(n) - kN-3 * gN-4(n-1) */ |
| fnext = fcurr - ((*pk) * gcurr); |
| /* gN-3(n) = kN-3 * fN-4(n) + gN-4(n-1) */ |
| gnext = (fnext * (*pk++)) + gcurr; |
| /* y(n) += gN-3(n) * vN-3 */ |
| /* process for gN-7(n) * vN-7, gN-11(n) * vN-11 ... */ |
| acc += (gnext * (*pv++)); |
| /* write gN-3(n) into state for next sample processing */ |
| *px2++ = gnext; |
| |
| |
| /* Process sample for 5th, 9th ...taps */ |
| /* Read gN-5(n-1) from state buffer */ |
| gcurr = *px1++; |
| /* Process sample for 5th, 9th .. taps */ |
| /* fN-5(n) = fN-4(n) - kN-4 * gN-1(n-1) */ |
| fcurr = fnext - ((*pk) * gcurr); |
| /* gN-4(n) = kN-4 * fN-5(n) + gN-5(n-1) */ |
| gnext = (fcurr * (*pk++)) + gcurr; |
| /* y(n) += gN-4(n) * vN-4 */ |
| /* process for gN-8(n) * vN-8, gN-12(n) * vN-12 ... */ |
| acc += (gnext * (*pv++)); |
| /* write gN-4(n) into state for next sample processing */ |
| *px2++ = gnext; |
| |
| tapCnt--; |
| |
| } |
| |
| fnext = fcurr; |
| |
| /* If the filter length is not a multiple of 4, compute the remaining filter taps */ |
| tapCnt = (numStages - 1u) % 0x4u; |
| |
| while(tapCnt > 0u) |
| { |
| gcurr = *px1++; |
| /* Process sample for last taps */ |
| fnext = fcurr - ((*pk) * gcurr); |
| gnext = (fnext * (*pk++)) + gcurr; |
| /* Output samples for last taps */ |
| acc += (gnext * (*pv++)); |
| *px2++ = gnext; |
| fcurr = fnext; |
| |
| tapCnt--; |
| |
| } |
| |
| |
| /* y(n) += g0(n) * v0 */ |
| acc += (fnext * (*pv)); |
| |
| *px2++ = fnext; |
| |
| /* write out into pDst */ |
| *pDst++ = acc; |
| |
| /* Advance the state pointer by 4 to process the next group of 4 samples */ |
| pState = pState + 1u; |
| blkCnt--; |
| |
| } |
| |
| /* Processing is complete. Now copy last S->numStages samples to start of the buffer |
| for the preperation of next frame process */ |
| |
| /* Points to the start of the state buffer */ |
| pStateCurnt = &S->pState[0]; |
| pState = &S->pState[blockSize]; |
| |
| tapCnt = numStages >> 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 = (numStages) % 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 */ |
| |
| blkCnt = blockSize; |
| |
| pState = &S->pState[0]; |
| |
| /* Sample processing */ |
| while(blkCnt > 0u) |
| { |
| /* Read Sample from input buffer */ |
| /* fN(n) = x(n) */ |
| fcurr = *pSrc++; |
| |
| /* Initialize state read pointer */ |
| px1 = pState; |
| /* Initialize state write pointer */ |
| px2 = pState; |
| /* Set accumulator to zero */ |
| acc = 0.0f; |
| /* Initialize Ladder coeff pointer */ |
| pv = &S->pvCoeffs[0]; |
| /* Initialize Reflection coeff pointer */ |
| pk = &S->pkCoeffs[0]; |
| |
| |
| /* Process sample for numStages */ |
| tapCnt = numStages; |
| |
| while(tapCnt > 0u) |
| { |
| gcurr = *px1++; |
| /* Process sample for last taps */ |
| fnext = fcurr - ((*pk) * gcurr); |
| gnext = (fnext * (*pk++)) + gcurr; |
| |
| /* Output samples for last taps */ |
| acc += (gnext * (*pv++)); |
| *px2++ = gnext; |
| fcurr = fnext; |
| |
| /* Decrementing loop counter */ |
| tapCnt--; |
| |
| } |
| |
| /* y(n) += g0(n) * v0 */ |
| acc += (fnext * (*pv)); |
| |
| *px2++ = fnext; |
| |
| /* write out into pDst */ |
| *pDst++ = acc; |
| |
| /* Advance the state pointer by 1 to process the next group of samples */ |
| pState = pState + 1u; |
| blkCnt--; |
| |
| } |
| |
| /* Processing is complete. Now copy last S->numStages samples to start of the buffer |
| for the preperation of next frame process */ |
| |
| /* Points to the start of the state buffer */ |
| pStateCurnt = &S->pState[0]; |
| pState = &S->pState[blockSize]; |
| |
| tapCnt = numStages; |
| |
| /* Copy the data */ |
| while(tapCnt > 0u) |
| { |
| *pStateCurnt++ = *pState++; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| #endif /* #ifndef ARM_MATH_CM0 */ |
| |
| } |
| |
| |
| |
| |
| /** |
| * @} end of IIR_Lattice group |
| */ |
