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Diffstat (limited to 'DSP_Lib/Source/FilteringFunctions/arm_fir_q7.c')
-rw-r--r-- | DSP_Lib/Source/FilteringFunctions/arm_fir_q7.c | 397 |
1 files changed, 397 insertions, 0 deletions
diff --git a/DSP_Lib/Source/FilteringFunctions/arm_fir_q7.c b/DSP_Lib/Source/FilteringFunctions/arm_fir_q7.c new file mode 100644 index 0000000..24a50dc --- /dev/null +++ b/DSP_Lib/Source/FilteringFunctions/arm_fir_q7.c @@ -0,0 +1,397 @@ +/* ---------------------------------------------------------------------- +* 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_q7.c +* +* Description: Q7 FIR filter processing 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] *S points to an instance of the Q7 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. + * + * <b>Scaling and Overflow Behavior:</b> + * \par + * The function is implemented using a 32-bit internal accumulator. + * Both coefficients and state variables are represented in 1.7 format and multiplications yield a 2.14 result. + * The 2.14 intermediate results are accumulated in a 32-bit accumulator in 18.14 format. + * There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved. + * The accumulator is converted to 18.7 format by discarding the low 7 bits. + * Finally, the result is truncated to 1.7 format. + */ + +void arm_fir_q7( + const arm_fir_instance_q7 * S, + q7_t * pSrc, + q7_t * pDst, + uint32_t blockSize) +{ + +#ifndef ARM_MATH_CM0_FAMILY + + /* Run the below code for Cortex-M4 and Cortex-M3 */ + + q7_t *pState = S->pState; /* State pointer */ + q7_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ + q7_t *pStateCurnt; /* Points to the current sample of the state */ + q7_t x0, x1, x2, x3; /* Temporary variables to hold state */ + q7_t c0; /* Temporary variable to hold coefficient value */ + q7_t *px; /* Temporary pointer for state */ + q7_t *pb; /* Temporary pointer for coefficient buffer */ + q31_t acc0, acc1, acc2, acc3; /* Accumulators */ + uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */ + uint32_t i, tapCnt, blkCnt; /* Loop counters */ + + /* 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; + acc1 = 0; + acc2 = 0; + acc3 = 0; + + /* Initialize state pointer */ + px = pState; + + /* Initialize coefficient 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 >> 2; + i = tapCnt; + + while(i > 0u) + { + /* Read the b[numTaps] coefficient */ + c0 = *pb; + + /* Read x[n-numTaps-3] sample */ + x3 = *px; + + /* acc0 += b[numTaps] * x[n-numTaps] */ + acc0 += ((q15_t) x0 * c0); + + /* acc1 += b[numTaps] * x[n-numTaps-1] */ + acc1 += ((q15_t) x1 * c0); + + /* acc2 += b[numTaps] * x[n-numTaps-2] */ + acc2 += ((q15_t) x2 * c0); + + /* acc3 += b[numTaps] * x[n-numTaps-3] */ + acc3 += ((q15_t) x3 * c0); + + /* Read the b[numTaps-1] coefficient */ + c0 = *(pb + 1u); + + /* Read x[n-numTaps-4] sample */ + x0 = *(px + 1u); + + /* Perform the multiply-accumulates */ + acc0 += ((q15_t) x1 * c0); + acc1 += ((q15_t) x2 * c0); + acc2 += ((q15_t) x3 * c0); + acc3 += ((q15_t) x0 * c0); + + /* Read the b[numTaps-2] coefficient */ + c0 = *(pb + 2u); + + /* Read x[n-numTaps-5] sample */ + x1 = *(px + 2u); + + /* Perform the multiply-accumulates */ + acc0 += ((q15_t) x2 * c0); + acc1 += ((q15_t) x3 * c0); + acc2 += ((q15_t) x0 * c0); + acc3 += ((q15_t) x1 * c0); + + /* Read the b[numTaps-3] coefficients */ + c0 = *(pb + 3u); + + /* Read x[n-numTaps-6] sample */ + x2 = *(px + 3u); + + /* Perform the multiply-accumulates */ + acc0 += ((q15_t) x3 * c0); + acc1 += ((q15_t) x0 * c0); + acc2 += ((q15_t) x1 * c0); + acc3 += ((q15_t) x2 * c0); + + /* update coefficient pointer */ + pb += 4u; + px += 4u; + + /* Decrement the loop counter */ + i--; + } + + /* If the filter length is not a multiple of 4, compute the remaining filter taps */ + + i = numTaps - (tapCnt * 4u); + while(i > 0u) + { + /* Read coefficients */ + c0 = *(pb++); + + /* Fetch 1 state variable */ + x3 = *(px++); + + /* Perform the multiply-accumulates */ + acc0 += ((q15_t) x0 * c0); + acc1 += ((q15_t) x1 * c0); + acc2 += ((q15_t) x2 * c0); + acc3 += ((q15_t) x3 * c0); + + /* Reuse the present sample states for next sample */ + x0 = x1; + x1 = x2; + x2 = x3; + + /* Decrement the loop counter */ + i--; + } + + /* Advance the state pointer by 4 to process the next group of 4 samples */ + pState = pState + 4; + + /* The results in the 4 accumulators are in 2.62 format. Convert to 1.31 + ** Then store the 4 outputs in the destination buffer. */ + acc0 = __SSAT((acc0 >> 7u), 8); + *pDst++ = acc0; + acc1 = __SSAT((acc1 >> 7u), 8); + *pDst++ = acc1; + acc2 = __SSAT((acc2 >> 7u), 8); + *pDst++ = acc2; + acc3 = __SSAT((acc3 >> 7u), 8); + *pDst++ = acc3; + + /* Decrement the samples loop counter */ + blkCnt--; + } + + + /* If the blockSize is not a multiple of 4, compute any remaining output samples here. + ** No loop unrolling is used. */ + blkCnt = blockSize % 4u; + + while(blkCnt > 0u) + { + /* Copy one sample at a time into state buffer */ + *pStateCurnt++ = *pSrc++; + + /* Set the accumulator to zero */ + acc0 = 0; + + /* Initialize state pointer */ + px = pState; + + /* Initialize Coefficient pointer */ + pb = (pCoeffs); + + i = numTaps; + + /* Perform the multiply-accumulates */ + do + { + acc0 += (q15_t) * (px++) * (*(pb++)); + i--; + } while(i > 0u); + + /* The result is in 2.14 format. Convert to 1.7 + ** Then store the output in the destination buffer. */ + *pDst++ = __SSAT((acc0 >> 7u), 8); + + /* Advance state pointer by 1 for the next sample */ + pState = pState + 1; + + /* Decrement the samples loop counter */ + 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 */ + + uint32_t numTaps = S->numTaps; /* Number of taps in the filter */ + uint32_t i, blkCnt; /* Loop counters */ + q7_t *pState = S->pState; /* State pointer */ + q7_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ + q7_t *px, *pb; /* Temporary pointers to state and coeff */ + q31_t acc = 0; /* Accumlator */ + q7_t *pStateCurnt; /* Points to the current sample of the state */ + + + /* 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; + + /* Perform filtering upto BlockSize - BlockSize%4 */ + while(blkCnt > 0u) + { + /* Copy one sample at a time into state buffer */ + *pStateCurnt++ = *pSrc++; + + /* Set accumulator to zero */ + acc = 0; + + /* Initialize state pointer of type q7 */ + px = pState; + + /* Initialize coeff pointer of type q7 */ + pb = pCoeffs; + + + i = numTaps; + + while(i > 0u) + { + /* 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 += (q15_t) * px++ * *pb++; + i--; + } + + /* Store the 1.7 format filter output in destination buffer */ + *pDst++ = (q7_t) __SSAT((acc >> 7), 8); + + /* Advance the state pointer by 1 to process the next sample */ + pState = pState + 1; + + /* Decrement the loop counter */ + 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; + + + /* Copy numTaps number of values */ + i = (numTaps - 1u); + + /* Copy q7_t data */ + while(i > 0u) + { + *pStateCurnt++ = *pState++; + i--; + } + +#endif /* #ifndef ARM_MATH_CM0_FAMILY */ + +} + +/** + * @} end of FIR group + */ |