diff options
Diffstat (limited to 'Drivers/CMSIS/DSP/Source/FilteringFunctions/arm_biquad_cascade_df1_32x64_q31.c')
| -rw-r--r-- | Drivers/CMSIS/DSP/Source/FilteringFunctions/arm_biquad_cascade_df1_32x64_q31.c | 479 |
1 files changed, 194 insertions, 285 deletions
diff --git a/Drivers/CMSIS/DSP/Source/FilteringFunctions/arm_biquad_cascade_df1_32x64_q31.c b/Drivers/CMSIS/DSP/Source/FilteringFunctions/arm_biquad_cascade_df1_32x64_q31.c index c77cc8e4e..9a284b8a9 100644 --- a/Drivers/CMSIS/DSP/Source/FilteringFunctions/arm_biquad_cascade_df1_32x64_q31.c +++ b/Drivers/CMSIS/DSP/Source/FilteringFunctions/arm_biquad_cascade_df1_32x64_q31.c @@ -3,13 +3,13 @@ * Title: arm_biquad_cascade_df1_32x64_q31.c * Description: High precision Q31 Biquad cascade filter processing function * - * $Date: 27. January 2017 - * $Revision: V.1.5.1 + * $Date: 18. March 2019 + * $Revision: V1.6.0 * * Target Processor: Cortex-M cores * -------------------------------------------------------------------- */ /* - * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved. + * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved. * * SPDX-License-Identifier: Apache-2.0 * @@ -29,174 +29,169 @@ #include "arm_math.h" /** - * @ingroup groupFilters + @ingroup groupFilters */ /** - * @defgroup BiquadCascadeDF1_32x64 High Precision Q31 Biquad Cascade Filter - * - * This function implements a high precision Biquad cascade filter which operates on - * Q31 data values. The filter coefficients are in 1.31 format and the state variables - * are in 1.63 format. The double precision state variables reduce quantization noise - * in the filter and provide a cleaner output. - * These filters are particularly useful when implementing filters in which the - * singularities are close to the unit circle. This is common for low pass or high - * pass filters with very low cutoff frequencies. - * - * The function operates 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> Q31 values. - * - * \par Algorithm - * Each Biquad stage implements a second order filter using the difference equation: - * <pre> - * y[n] = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] - * </pre> - * A Direct Form I algorithm is used with 5 coefficients and 4 state variables per stage. - * \image html Biquad.gif "Single Biquad filter stage" - * Coefficients <code>b0, b1, and b2 </code> multiply the input signal <code>x[n]</code> and are referred to as the feedforward coefficients. - * Coefficients <code>a1</code> and <code>a2</code> multiply the output signal <code>y[n]</code> and are referred to as the feedback coefficients. - * Pay careful attention to the sign of the feedback coefficients. - * Some design tools use the difference equation - * <pre> - * y[n] = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] - a1 * y[n-1] - a2 * y[n-2] - * </pre> - * In this case the feedback coefficients <code>a1</code> and <code>a2</code> must be negated when used with the CMSIS DSP Library. - * - * \par - * Higher order filters are realized as a cascade of second order sections. - * <code>numStages</code> refers to the number of second order stages used. - * For example, an 8th order filter would be realized with <code>numStages=4</code> second order stages. - * \image html BiquadCascade.gif "8th order filter using a cascade of Biquad stages" - * A 9th order filter would be realized with <code>numStages=5</code> second order stages with the coefficients for one of the stages configured as a first order filter (<code>b2=0</code> and <code>a2=0</code>). - * - * \par - * The <code>pState</code> points to state variables array . - * Each Biquad stage has 4 state variables <code>x[n-1], x[n-2], y[n-1],</code> and <code>y[n-2]</code> and each state variable in 1.63 format to improve precision. - * The state variables are arranged in the array as: - * <pre> - * {x[n-1], x[n-2], y[n-1], y[n-2]} - * </pre> - * - * \par - * The 4 state variables for stage 1 are first, then the 4 state variables for stage 2, and so on. - * The state array has a total length of <code>4*numStages</code> values of data in 1.63 format. - * 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. - * - * \par Init Function - * There is also an associated initialization function which performs the following operations: - * - Sets the values of the internal structure fields. - * - Zeros out the values in the state buffer. - * To do this manually without calling the init function, assign the follow subfields of the instance structure: - * numStages, pCoeffs, postShift, pState. Also set all of the values in pState to zero. - * - * \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. - * For example, to statically initialize the filter instance structure use - * <pre> - * arm_biquad_cas_df1_32x64_ins_q31 S1 = {numStages, pState, pCoeffs, postShift}; - * </pre> - * where <code>numStages</code> is the number of Biquad stages in the filter; <code>pState</code> is the address of the state buffer; - * <code>pCoeffs</code> is the address of the coefficient buffer; <code>postShift</code> shift to be applied which is described in detail below. - * \par Fixed-Point Behavior - * Care must be taken while using Biquad Cascade 32x64 filter function. - * Following issues must be considered: - * - Scaling of coefficients - * - Filter gain - * - Overflow and saturation - * - * \par - * Filter coefficients are represented as fractional values and - * restricted to lie in the range <code>[-1 +1)</code>. - * The processing function has an additional scaling parameter <code>postShift</code> - * which allows the filter coefficients to exceed the range <code>[+1 -1)</code>. - * At the output of the filter's accumulator is a shift register which shifts the result by <code>postShift</code> bits. - * \image html BiquadPostshift.gif "Fixed-point Biquad with shift by postShift bits after accumulator" - * This essentially scales the filter coefficients by <code>2^postShift</code>. - * For example, to realize the coefficients - * <pre> - * {1.5, -0.8, 1.2, 1.6, -0.9} - * </pre> - * set the Coefficient array to: - * <pre> - * {0.75, -0.4, 0.6, 0.8, -0.45} - * </pre> - * and set <code>postShift=1</code> - * - * \par - * The second thing to keep in mind is the gain through the filter. - * The frequency response of a Biquad filter is a function of its coefficients. - * It is possible for the gain through the filter to exceed 1.0 meaning that the filter increases the amplitude of certain frequencies. - * This means that an input signal with amplitude < 1.0 may result in an output > 1.0 and these are saturated or overflowed based on the implementation of the filter. - * To avoid this behavior the filter needs to be scaled down such that its peak gain < 1.0 or the input signal must be scaled down so that the combination of input and filter are never overflowed. - * - * \par - * The third item to consider is the overflow and saturation behavior of the fixed-point Q31 version. - * This is described in the function specific documentation below. + @defgroup BiquadCascadeDF1_32x64 High Precision Q31 Biquad Cascade Filter + + This function implements a high precision Biquad cascade filter which operates on + Q31 data values. The filter coefficients are in 1.31 format and the state variables + are in 1.63 format. The double precision state variables reduce quantization noise + in the filter and provide a cleaner output. + These filters are particularly useful when implementing filters in which the + singularities are close to the unit circle. This is common for low pass or high + pass filters with very low cutoff frequencies. + + The function operates 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> Q31 values. + + @par Algorithm + Each Biquad stage implements a second order filter using the difference equation: + <pre> + y[n] = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] + </pre> + A Direct Form I algorithm is used with 5 coefficients and 4 state variables per stage. + \image html Biquad.gif "Single Biquad filter stage" + Coefficients <code>b0, b1 and b2 </code> multiply the input signal <code>x[n]</code> and are referred to as the feedforward coefficients. + Coefficients <code>a1</code> and <code>a2</code> multiply the output signal <code>y[n]</code> and are referred to as the feedback coefficients. + Pay careful attention to the sign of the feedback coefficients. + Some design tools use the difference equation + <pre> + y[n] = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] - a1 * y[n-1] - a2 * y[n-2] + </pre> + In this case the feedback coefficients <code>a1</code> and <code>a2</code> must be negated when used with the CMSIS DSP Library. + @par + Higher order filters are realized as a cascade of second order sections. + <code>numStages</code> refers to the number of second order stages used. + For example, an 8th order filter would be realized with <code>numStages=4</code> second order stages. + \image html BiquadCascade.gif "8th order filter using a cascade of Biquad stages" + A 9th order filter would be realized with <code>numStages=5</code> second order stages + with the coefficients for one of the stages configured as a first order filter + (<code>b2=0</code> and <code>a2=0</code>). + @par + The <code>pState</code> points to state variables array. + Each Biquad stage has 4 state variables <code>x[n-1], x[n-2], y[n-1],</code> and <code>y[n-2]</code> and each state variable in 1.63 format to improve precision. + The state variables are arranged in the array as: + <pre> + {x[n-1], x[n-2], y[n-1], y[n-2]} + </pre> + @par + The 4 state variables for stage 1 are first, then the 4 state variables for stage 2, and so on. + The state array has a total length of <code>4*numStages</code> values of data in 1.63 format. + 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. + + @par Init Function + There is also an associated initialization function which performs the following operations: + - Sets the values of the internal structure fields. + - Zeros out the values in the state buffer. + To do this manually without calling the init function, assign the follow subfields of the instance structure: + numStages, pCoeffs, postShift, pState. Also set all of the values in pState to zero. + + @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. + For example, to statically initialize the filter instance structure use + <pre> + arm_biquad_cas_df1_32x64_ins_q31 S1 = {numStages, pState, pCoeffs, postShift}; + </pre> + where <code>numStages</code> is the number of Biquad stages in the filter; + <code>pState</code> is the address of the state buffer; + <code>pCoeffs</code> is the address of the coefficient buffer; + <code>postShift</code> shift to be applied which is described in detail below. + @par Fixed-Point Behavior + Care must be taken while using Biquad Cascade 32x64 filter function. + Following issues must be considered: + - Scaling of coefficients + - Filter gain + - Overflow and saturation + + @par + Filter coefficients are represented as fractional values and + restricted to lie in the range <code>[-1 +1)</code>. + The processing function has an additional scaling parameter <code>postShift</code> + which allows the filter coefficients to exceed the range <code>[+1 -1)</code>. + At the output of the filter's accumulator is a shift register which shifts the result by <code>postShift</code> bits. + \image html BiquadPostshift.gif "Fixed-point Biquad with shift by postShift bits after accumulator" + This essentially scales the filter coefficients by <code>2^postShift</code>. + For example, to realize the coefficients + <pre> + {1.5, -0.8, 1.2, 1.6, -0.9} + </pre> + set the Coefficient array to: + <pre> + {0.75, -0.4, 0.6, 0.8, -0.45} + </pre> + and set <code>postShift=1</code> + @par + The second thing to keep in mind is the gain through the filter. + The frequency response of a Biquad filter is a function of its coefficients. + It is possible for the gain through the filter to exceed 1.0 meaning that the + filter increases the amplitude of certain frequencies. + This means that an input signal with amplitude < 1.0 may result in an output > 1.0 + and these are saturated or overflowed based on the implementation of the filter. + To avoid this behavior the filter needs to be scaled down such that its peak gain < 1.0 + or the input signal must be scaled down so that the combination of input and filter are never overflowed. + @par + The third item to consider is the overflow and saturation behavior of the fixed-point Q31 version. + This is described in the function specific documentation below. */ /** - * @addtogroup BiquadCascadeDF1_32x64 - * @{ + @addtogroup BiquadCascadeDF1_32x64 + @{ */ /** - * @details - - * @param[in] *S points to an instance of the high precision Q31 Biquad cascade filter. - * @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. - * - * \par - * The function is implemented using an internal 64-bit accumulator. - * The accumulator has a 2.62 format and maintains full precision of the intermediate multiplication results but provides only a single guard bit. - * Thus, if the accumulator result overflows it wraps around rather than clip. - * In order to avoid overflows completely the input signal must be scaled down by 2 bits and lie in the range [-0.25 +0.25). - * After all 5 multiply-accumulates are performed, the 2.62 accumulator is shifted by <code>postShift</code> bits and the result truncated to - * 1.31 format by discarding the low 32 bits. - * - * \par - * Two related functions are provided in the CMSIS DSP library. - * <code>arm_biquad_cascade_df1_q31()</code> implements a Biquad cascade with 32-bit coefficients and state variables with a Q63 accumulator. - * <code>arm_biquad_cascade_df1_fast_q31()</code> implements a Biquad cascade with 32-bit coefficients and state variables with a Q31 accumulator. + @brief Processing function for the Q31 Biquad cascade 32x64 filter. + @param[in] S points to an instance of the high precision Q31 Biquad cascade filter + @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 + + @par Details + The function is implemented using an internal 64-bit accumulator. + The accumulator has a 2.62 format and maintains full precision of the intermediate multiplication results but provides only a single guard bit. + Thus, if the accumulator result overflows it wraps around rather than clip. + In order to avoid overflows completely the input signal must be scaled down by 2 bits and lie in the range [-0.25 +0.25). + After all 5 multiply-accumulates are performed, the 2.62 accumulator is shifted by <code>postShift</code> bits and the result truncated to + 1.31 format by discarding the low 32 bits. + @par + Two related functions are provided in the CMSIS DSP library. + - \ref arm_biquad_cascade_df1_q31() implements a Biquad cascade with 32-bit coefficients and state variables with a Q63 accumulator. + - \ref arm_biquad_cascade_df1_fast_q31() implements a Biquad cascade with 32-bit coefficients and state variables with a Q31 accumulator. */ void arm_biquad_cas_df1_32x64_q31( const arm_biquad_cas_df1_32x64_ins_q31 * S, - q31_t * pSrc, - q31_t * pDst, - uint32_t blockSize) + q31_t * pSrc, + q31_t * pDst, + uint32_t blockSize) { - q31_t *pIn = pSrc; /* input pointer initialization */ - q31_t *pOut = pDst; /* output pointer initialization */ - q63_t *pState = S->pState; /* state pointer initialization */ - q31_t *pCoeffs = S->pCoeffs; /* coeff pointer initialization */ - q63_t acc; /* accumulator */ - q31_t Xn1, Xn2; /* Input Filter state variables */ - q63_t Yn1, Yn2; /* Output Filter state variables */ - q31_t b0, b1, b2, a1, a2; /* Filter coefficients */ - q31_t Xn; /* temporary input */ - int32_t shift = (int32_t) S->postShift + 1; /* Shift to be applied to the output */ - uint32_t sample, stage = S->numStages; /* loop counters */ - q31_t acc_l, acc_h; /* temporary output */ - uint32_t uShift = ((uint32_t) S->postShift + 1U); - uint32_t lShift = 32U - uShift; /* Shift to be applied to the output */ - - -#if defined (ARM_MATH_DSP) - - /* Run the below code for Cortex-M4 and Cortex-M3 */ + q31_t *pIn = pSrc; /* input pointer initialization */ + q31_t *pOut = pDst; /* output pointer initialization */ + q63_t *pState = S->pState; /* state pointer initialization */ + const q31_t *pCoeffs = S->pCoeffs; /* coeff pointer initialization */ + q63_t acc; /* accumulator */ + q31_t Xn1, Xn2; /* Input Filter state variables */ + q63_t Yn1, Yn2; /* Output Filter state variables */ + q31_t b0, b1, b2, a1, a2; /* Filter coefficients */ + q31_t Xn; /* temporary input */ + int32_t shift = (int32_t) S->postShift + 1; /* Shift to be applied to the output */ + uint32_t sample, stage = S->numStages; /* loop counters */ + q31_t acc_l, acc_h; /* temporary output */ + uint32_t uShift = ((uint32_t) S->postShift + 1U); + uint32_t lShift = 32U - uShift; /* Shift to be applied to the output */ do { @@ -213,16 +208,16 @@ void arm_biquad_cas_df1_32x64_q31( Yn1 = pState[2]; Yn2 = pState[3]; +#if defined (ARM_MATH_LOOPUNROLL) + /* Apply loop unrolling and compute 4 output values simultaneously. */ - /* The variable acc hold output value that is being computed and - * stored in the destination buffer + /* Variable acc hold output value that is being computed and stored in destination buffer * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ + /* Loop unrolling: Compute 4 outputs at a time */ sample = blockSize >> 2U; - /* 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 (sample > 0U) { /* Read the input */ @@ -231,13 +226,13 @@ void arm_biquad_cas_df1_32x64_q31( /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ /* acc = b0 * x[n] */ - acc = (q63_t) Xn *b0; + acc = (q63_t) Xn * b0; /* acc += b1 * x[n-1] */ - acc += (q63_t) Xn1 *b1; + acc += (q63_t) Xn1 * b1; /* acc += b[2] * x[n-2] */ - acc += (q63_t) Xn2 *b2; + acc += (q63_t) Xn2 * b2; /* acc += a1 * y[n-1] */ acc += mult32x64(Yn1, a1); @@ -266,13 +261,13 @@ void arm_biquad_cas_df1_32x64_q31( /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ /* acc += b1 * x[n-1] */ - acc = (q63_t) Xn *b1; + acc = (q63_t) Xn * b1; /* acc = b0 * x[n] */ - acc += (q63_t) Xn2 *b0; + acc += (q63_t) Xn2 * b0; /* acc += b[2] * x[n-2] */ - acc += (q63_t) Xn1 *b2; + acc += (q63_t) Xn1 * b2; /* acc += a1 * y[n-1] */ acc += mult32x64(Yn2, a1); @@ -302,13 +297,13 @@ void arm_biquad_cas_df1_32x64_q31( /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ /* acc = b0 * x[n] */ - acc = (q63_t) Xn1 *b0; + acc = (q63_t) Xn1 * b0; /* acc += b1 * x[n-1] */ - acc += (q63_t) Xn2 *b1; + acc += (q63_t) Xn2 * b1; /* acc += b[2] * x[n-2] */ - acc += (q63_t) Xn *b2; + acc += (q63_t) Xn * b2; /* acc += a1 * y[n-1] */ acc += mult32x64(Yn1, a1); @@ -336,13 +331,13 @@ void arm_biquad_cas_df1_32x64_q31( /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ /* acc = b0 * x[n] */ - acc = (q63_t) Xn *b0; + acc = (q63_t) Xn * b0; /* acc += b1 * x[n-1] */ - acc += (q63_t) Xn1 *b1; + acc += (q63_t) Xn1 * b1; /* acc += b[2] * x[n-2] */ - acc += (q63_t) Xn2 *b2; + acc += (q63_t) Xn2 * b2; /* acc += a1 * y[n-1] */ acc += mult32x64(Yn2, a1); @@ -366,139 +361,55 @@ void arm_biquad_cas_df1_32x64_q31( *(pOut + 3U) = acc_h; /* Every time after the output is computed state should be updated. */ - /* The states should be updated as: */ - /* Xn2 = Xn1 */ - /* Xn1 = Xn */ - /* Yn2 = Yn1 */ - /* Yn1 = acc */ + /* The states should be updated as: */ + /* Xn2 = Xn1 */ + /* Xn1 = Xn */ + /* Yn2 = Yn1 */ + /* Yn1 = acc */ Xn2 = Xn1; Xn1 = Xn; /* update output pointer */ pOut += 4U; - /* decrement the loop counter */ - sample--; - } - - /* If the blockSize is not a multiple of 4, compute any remaining output samples here. - ** No loop unrolling is used. */ - sample = (blockSize & 0x3U); - - while (sample > 0U) - { - /* Read the input */ - Xn = *pIn++; - - /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ - - /* acc = b0 * x[n] */ - acc = (q63_t) Xn *b0; - /* acc += b1 * x[n-1] */ - acc += (q63_t) Xn1 *b1; - /* acc += b[2] * x[n-2] */ - acc += (q63_t) Xn2 *b2; - /* acc += a1 * y[n-1] */ - acc += mult32x64(Yn1, a1); - /* acc += a2 * y[n-2] */ - acc += mult32x64(Yn2, a2); - - /* Every time after the output is computed state should be updated. */ - /* The states should be updated as: */ - /* Xn2 = Xn1 */ - /* Xn1 = Xn */ - /* Yn2 = Yn1 */ - /* Yn1 = acc */ - Xn2 = Xn1; - Xn1 = Xn; - Yn2 = Yn1; - /* The result is converted to 1.63, Yn1 variable is reused */ - Yn1 = acc << shift; - - /* Calc lower part of acc */ - acc_l = acc & 0xffffffff; - - /* Calc upper part of acc */ - acc_h = (acc >> 32) & 0xffffffff; - - /* Apply shift for lower part of acc and upper part of acc */ - acc_h = (uint32_t) acc_l >> lShift | acc_h << uShift; - - /* Store the output in the destination buffer in 1.31 format. */ - *pOut++ = acc_h; - /* Yn1 = acc << shift; */ - - /* Store the output in the destination buffer in 1.31 format. */ -/* *pOut++ = (q31_t) (acc >> (32 - shift)); */ - - /* decrement the loop counter */ + /* decrement loop counter */ sample--; } - /* The first stage output is given as input to the second stage. */ - pIn = pDst; - - /* Reset to destination buffer working pointer */ - pOut = pDst; - - /* Store the updated state variables back into the pState array */ - /* Store the updated state variables back into the pState array */ - *pState++ = (q63_t) Xn1; - *pState++ = (q63_t) Xn2; - *pState++ = Yn1; - *pState++ = Yn2; - - } while (--stage); + /* Loop unrolling: Compute remaining outputs */ + sample = blockSize & 0x3U; #else - /* Run the below code for Cortex-M0 */ - - do - { - /* Reading the coefficients */ - b0 = *pCoeffs++; - b1 = *pCoeffs++; - b2 = *pCoeffs++; - a1 = *pCoeffs++; - a2 = *pCoeffs++; - - /* Reading the state values */ - Xn1 = pState[0]; - Xn2 = pState[1]; - Yn1 = pState[2]; - Yn2 = pState[3]; - - /* The variable acc hold output value that is being computed and - * stored in the destination buffer - * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] - */ - + /* Initialize blkCnt with number of samples */ sample = blockSize; +#endif /* #if defined (ARM_MATH_LOOPUNROLL) */ + while (sample > 0U) { /* Read the input */ Xn = *pIn++; /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ + /* acc = b0 * x[n] */ - acc = (q63_t) Xn *b0; + acc = (q63_t) Xn * b0; /* acc += b1 * x[n-1] */ - acc += (q63_t) Xn1 *b1; + acc += (q63_t) Xn1 * b1; /* acc += b[2] * x[n-2] */ - acc += (q63_t) Xn2 *b2; + acc += (q63_t) Xn2 * b2; /* acc += a1 * y[n-1] */ acc += mult32x64(Yn1, a1); /* acc += a2 * y[n-2] */ acc += mult32x64(Yn2, a2); /* Every time after the output is computed state should be updated. */ - /* The states should be updated as: */ - /* Xn2 = Xn1 */ - /* Xn1 = Xn */ - /* Yn2 = Yn1 */ - /* Yn1 = acc */ + /* The states should be updated as: */ + /* Xn2 = Xn1 */ + /* Xn1 = Xn */ + /* Yn2 = Yn1 */ + /* Yn1 = acc */ Xn2 = Xn1; Xn1 = Xn; Yn2 = Yn1; @@ -517,17 +428,16 @@ void arm_biquad_cas_df1_32x64_q31( /* Store the output in the destination buffer in 1.31 format. */ *pOut++ = acc_h; - /* Yn1 = acc << shift; */ /* Store the output in the destination buffer in 1.31 format. */ - /* *pOut++ = (q31_t) (acc >> (32 - shift)); */ +/* *pOut++ = (q31_t) (acc >> (32 - shift)); */ - /* decrement the loop counter */ + /* decrement loop counter */ sample--; } - /* The first stage output is given as input to the second stage. */ + /* The first stage output is given as input to the second stage. */ pIn = pDst; /* Reset to destination buffer working pointer */ @@ -541,9 +451,8 @@ void arm_biquad_cas_df1_32x64_q31( } while (--stage); -#endif /* #if defined (ARM_MATH_DSP) */ } - /** - * @} end of BiquadCascadeDF1_32x64 group - */ +/** + @} end of BiquadCascadeDF1_32x64 group + */ |