| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_biquad_cascade_df1_q15.c |
| * Description: Processing function for the Q15 Biquad cascade DirectFormI(DF1) filter |
| * |
| * $Date: 18. March 2019 |
| * $Revision: V1.6.0 |
| * |
| * Target Processor: Cortex-M cores |
| * -------------------------------------------------------------------- */ |
| /* |
| * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved. |
| * |
| * SPDX-License-Identifier: Apache-2.0 |
| * |
| * Licensed under the Apache License, Version 2.0 (the License); you may |
| * not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an AS IS BASIS, WITHOUT |
| * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #include "arm_math.h" |
| |
| /** |
| @ingroup groupFilters |
| */ |
| |
| /** |
| @addtogroup BiquadCascadeDF1 |
| @{ |
| */ |
| |
| /** |
| @brief Processing function for the Q15 Biquad cascade filter. |
| @param[in] S points to an instance of the Q15 Biquad cascade structure |
| @param[in] pSrc points to the block of input data |
| @param[out] pDst points to the location where the output result is written |
| @param[in] blockSize number of samples to process |
| @return none |
| |
| @par Scaling and Overflow Behavior |
| The function is implemented using a 64-bit internal accumulator. |
| Both coefficients and state variables are represented in 1.15 format and multiplications yield a 2.30 result. |
| The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format. |
| There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved. |
| The accumulator is then shifted by <code>postShift</code> bits to truncate the result to 1.15 format by discarding the low 16 bits. |
| Finally, the result is saturated to 1.15 format. |
| @remark |
| Refer to \ref arm_biquad_cascade_df1_fast_q15() for a faster but less precise implementation of this filter. |
| */ |
| |
| void arm_biquad_cascade_df1_q15( |
| const arm_biquad_casd_df1_inst_q15 * S, |
| const q15_t * pSrc, |
| q15_t * pDst, |
| uint32_t blockSize) |
| { |
| |
| |
| #if defined (ARM_MATH_DSP) |
| |
| const q15_t *pIn = pSrc; /* Source pointer */ |
| q15_t *pOut = pDst; /* Destination pointer */ |
| q31_t in; /* Temporary variable to hold input value */ |
| q31_t out; /* Temporary variable to hold output value */ |
| q31_t b0; /* Temporary variable to hold bo value */ |
| q31_t b1, a1; /* Filter coefficients */ |
| q31_t state_in, state_out; /* Filter state variables */ |
| q31_t acc_l, acc_h; |
| q63_t acc; /* Accumulator */ |
| q15_t *pState = S->pState; /* State pointer */ |
| const q15_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| int32_t lShift = (15 - (int32_t) S->postShift); /* Post shift */ |
| uint32_t sample, stage = (uint32_t) S->numStages; /* Stage loop counter */ |
| int32_t uShift = (32 - lShift); |
| |
| do |
| { |
| /* Read the b0 and 0 coefficients using SIMD */ |
| b0 = read_q15x2_ia ((q15_t **) &pCoeffs); |
| |
| /* Read the b1 and b2 coefficients using SIMD */ |
| b1 = read_q15x2_ia ((q15_t **) &pCoeffs); |
| |
| /* Read the a1 and a2 coefficients using SIMD */ |
| a1 = read_q15x2_ia ((q15_t **) &pCoeffs); |
| |
| /* Read the input state values from the state buffer: x[n-1], x[n-2] */ |
| state_in = read_q15x2_ia (&pState); |
| |
| /* Read the output state values from the state buffer: y[n-1], y[n-2] */ |
| state_out = read_q15x2_da (&pState); |
| |
| /* Apply loop unrolling and compute 2 output values simultaneously. */ |
| /* The variable acc hold output values that are being computed: |
| * |
| * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] |
| * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] |
| */ |
| sample = blockSize >> 1U; |
| |
| /* First part of the processing with loop unrolling. Compute 2 outputs at a time. |
| ** a second loop below computes the remaining 1 sample. */ |
| while (sample > 0U) |
| { |
| |
| /* Read the input */ |
| in = read_q15x2_ia ((q15_t **) &pIn); |
| |
| /* out = b0 * x[n] + 0 * 0 */ |
| out = __SMUAD(b0, in); |
| |
| /* acc += b1 * x[n-1] + b2 * x[n-2] + out */ |
| acc = __SMLALD(b1, state_in, out); |
| /* acc += a1 * y[n-1] + a2 * y[n-2] */ |
| acc = __SMLALD(a1, state_out, acc); |
| |
| /* The result is converted from 3.29 to 1.31 if postShift = 1, and then saturation is applied */ |
| /* 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 */ |
| out = (uint32_t) acc_l >> lShift | acc_h << uShift; |
| |
| out = __SSAT(out, 16); |
| |
| /* 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 */ |
| /* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */ |
| /* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */ |
| |
| #ifndef ARM_MATH_BIG_ENDIAN |
| state_in = __PKHBT(in, state_in, 16); |
| state_out = __PKHBT(out, state_out, 16); |
| #else |
| state_in = __PKHBT(state_in >> 16, (in >> 16), 16); |
| state_out = __PKHBT(state_out >> 16, (out), 16); |
| #endif /* #ifndef ARM_MATH_BIG_ENDIAN */ |
| |
| /* out = b0 * x[n] + 0 * 0 */ |
| out = __SMUADX(b0, in); |
| /* acc += b1 * x[n-1] + b2 * x[n-2] + out */ |
| acc = __SMLALD(b1, state_in, out); |
| /* acc += a1 * y[n-1] + a2 * y[n-2] */ |
| acc = __SMLALD(a1, state_out, acc); |
| |
| /* The result is converted from 3.29 to 1.31 if postShift = 1, and then saturation is applied */ |
| /* 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 */ |
| out = (uint32_t) acc_l >> lShift | acc_h << uShift; |
| |
| out = __SSAT(out, 16); |
| |
| /* Store the output in the destination buffer. */ |
| #ifndef ARM_MATH_BIG_ENDIAN |
| write_q15x2_ia (&pOut, __PKHBT(state_out, out, 16)); |
| #else |
| write_q15x2_ia (&pOut, __PKHBT(out, state_out >> 16, 16)); |
| #endif /* #ifndef ARM_MATH_BIG_ENDIAN */ |
| |
| /* 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 */ |
| /* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */ |
| /* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */ |
| #ifndef ARM_MATH_BIG_ENDIAN |
| state_in = __PKHBT(in >> 16, state_in, 16); |
| state_out = __PKHBT(out, state_out, 16); |
| #else |
| state_in = __PKHBT(state_in >> 16, in, 16); |
| state_out = __PKHBT(state_out >> 16, out, 16); |
| #endif /* #ifndef ARM_MATH_BIG_ENDIAN */ |
| |
| /* Decrement loop counter */ |
| sample--; |
| } |
| |
| /* If the blockSize is not a multiple of 2, compute any remaining output samples here. |
| ** No loop unrolling is used. */ |
| |
| if ((blockSize & 0x1U) != 0U) |
| { |
| /* Read the input */ |
| in = *pIn++; |
| |
| /* out = b0 * x[n] + 0 * 0 */ |
| #ifndef ARM_MATH_BIG_ENDIAN |
| out = __SMUAD(b0, in); |
| #else |
| out = __SMUADX(b0, in); |
| #endif /* #ifndef ARM_MATH_BIG_ENDIAN */ |
| |
| /* acc = b1 * x[n-1] + b2 * x[n-2] + out */ |
| acc = __SMLALD(b1, state_in, out); |
| /* acc += a1 * y[n-1] + a2 * y[n-2] */ |
| acc = __SMLALD(a1, state_out, acc); |
| |
| /* The result is converted from 3.29 to 1.31 if postShift = 1, and then saturation is applied */ |
| /* 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 */ |
| out = (uint32_t) acc_l >> lShift | acc_h << uShift; |
| |
| out = __SSAT(out, 16); |
| |
| /* Store the output in the destination buffer. */ |
| *pOut++ = (q15_t) out; |
| |
| /* 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 */ |
| /* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */ |
| /* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */ |
| #ifndef ARM_MATH_BIG_ENDIAN |
| state_in = __PKHBT(in, state_in, 16); |
| state_out = __PKHBT(out, state_out, 16); |
| #else |
| state_in = __PKHBT(state_in >> 16, in, 16); |
| state_out = __PKHBT(state_out >> 16, out, 16); |
| #endif /* #ifndef ARM_MATH_BIG_ENDIAN */ |
| } |
| |
| /* The first stage goes from the input wire to the output wire. */ |
| /* Subsequent numStages occur in-place in the output wire */ |
| pIn = pDst; |
| |
| /* Reset the output pointer */ |
| pOut = pDst; |
| |
| /* Store the updated state variables back into the state array */ |
| write_q15x2_ia (&pState, state_in); |
| write_q15x2_ia (&pState, state_out); |
| |
| /* Decrement loop counter */ |
| stage--; |
| |
| } while (stage > 0U); |
| |
| #else |
| |
| const q15_t *pIn = pSrc; /* Source pointer */ |
| q15_t *pOut = pDst; /* Destination pointer */ |
| q15_t b0, b1, b2, a1, a2; /* Filter coefficients */ |
| q15_t Xn1, Xn2, Yn1, Yn2; /* Filter state variables */ |
| q15_t Xn; /* temporary input */ |
| q63_t acc; /* Accumulator */ |
| int32_t shift = (15 - (int32_t) S->postShift); /* Post shift */ |
| q15_t *pState = S->pState; /* State pointer */ |
| const q15_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| uint32_t sample, stage = (uint32_t) S->numStages; /* Stage loop counter */ |
| |
| do |
| { |
| /* Reading the coefficients */ |
| b0 = *pCoeffs++; |
| pCoeffs++; // skip the 0 coefficient |
| 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 variables acc holds the output value that is computed: |
| * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] |
| */ |
| |
| sample = blockSize; |
| |
| 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 = (q31_t) b0 *Xn; |
| |
| /* acc += b1 * x[n-1] */ |
| acc += (q31_t) b1 *Xn1; |
| /* acc += b[2] * x[n-2] */ |
| acc += (q31_t) b2 *Xn2; |
| /* acc += a1 * y[n-1] */ |
| acc += (q31_t) a1 *Yn1; |
| /* acc += a2 * y[n-2] */ |
| acc += (q31_t) a2 *Yn2; |
| |
| /* The result is converted to 1.31 */ |
| acc = __SSAT((acc >> shift), 16); |
| |
| /* 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; |
| Yn1 = (q15_t) acc; |
| |
| /* Store the output in the destination buffer. */ |
| *pOut++ = (q15_t) acc; |
| |
| /* decrement the loop counter */ |
| sample--; |
| } |
| |
| /* The first stage goes from the input buffer to the output buffer. */ |
| /* Subsequent stages occur in-place in the output buffer */ |
| pIn = pDst; |
| |
| /* Reset to destination pointer */ |
| pOut = pDst; |
| |
| /* Store the updated state variables back into the pState array */ |
| *pState++ = Xn1; |
| *pState++ = Xn2; |
| *pState++ = Yn1; |
| *pState++ = Yn2; |
| |
| } while (--stage); |
| |
| #endif /* #if defined (ARM_MATH_DSP) */ |
| |
| } |
| |
| /** |
| @} end of BiquadCascadeDF1 group |
| */ |