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Diffstat (limited to 'DSP_Lib/Source/FilteringFunctions/arm_correlate_q7.c')
-rw-r--r-- | DSP_Lib/Source/FilteringFunctions/arm_correlate_q7.c | 790 |
1 files changed, 790 insertions, 0 deletions
diff --git a/DSP_Lib/Source/FilteringFunctions/arm_correlate_q7.c b/DSP_Lib/Source/FilteringFunctions/arm_correlate_q7.c new file mode 100644 index 0000000..6adef05 --- /dev/null +++ b/DSP_Lib/Source/FilteringFunctions/arm_correlate_q7.c @@ -0,0 +1,790 @@ +/* ---------------------------------------------------------------------- +* Copyright (C) 2010-2014 ARM Limited. All rights reserved. +* +* $Date: 19. March 2015 +* $Revision: V.1.4.5 +* +* Project: CMSIS DSP Library +* Title: arm_correlate_q7.c +* +* Description: Correlation of Q7 sequences. +* +* 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 Corr + * @{ + */ + +/** + * @brief Correlation of Q7 sequences. + * @param[in] *pSrcA points to the first input sequence. + * @param[in] srcALen length of the first input sequence. + * @param[in] *pSrcB points to the second input sequence. + * @param[in] srcBLen length of the second input sequence. + * @param[out] *pDst points to the location where the output result is written. Length 2 * max(srcALen, srcBLen) - 1. + * @return none. + * + * @details + * <b>Scaling and Overflow Behavior:</b> + * + * \par + * The function is implemented using a 32-bit internal accumulator. + * Both the inputs 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. + * This approach provides 17 guard bits and there is no risk of overflow as long as <code>max(srcALen, srcBLen)<131072</code>. + * The 18.14 result is then truncated to 18.7 format by discarding the low 7 bits and saturated to 1.7 format. + * + * \par + * Refer the function <code>arm_correlate_opt_q7()</code> for a faster implementation of this function. + * + */ + +void arm_correlate_q7( + q7_t * pSrcA, + uint32_t srcALen, + q7_t * pSrcB, + uint32_t srcBLen, + q7_t * pDst) +{ + + +#ifndef ARM_MATH_CM0_FAMILY + + /* Run the below code for Cortex-M4 and Cortex-M3 */ + + q7_t *pIn1; /* inputA pointer */ + q7_t *pIn2; /* inputB pointer */ + q7_t *pOut = pDst; /* output pointer */ + q7_t *px; /* Intermediate inputA pointer */ + q7_t *py; /* Intermediate inputB pointer */ + q7_t *pSrc1; /* Intermediate pointers */ + q31_t sum, acc0, acc1, acc2, acc3; /* Accumulators */ + q31_t input1, input2; /* temporary variables */ + q15_t in1, in2; /* temporary variables */ + q7_t x0, x1, x2, x3, c0, c1; /* temporary variables for holding input and coefficient values */ + uint32_t j, k = 0u, count, blkCnt, outBlockSize, blockSize1, blockSize2, blockSize3; /* loop counter */ + int32_t inc = 1; + + + /* The algorithm implementation is based on the lengths of the inputs. */ + /* srcB is always made to slide across srcA. */ + /* So srcBLen is always considered as shorter or equal to srcALen */ + /* But CORR(x, y) is reverse of CORR(y, x) */ + /* So, when srcBLen > srcALen, output pointer is made to point to the end of the output buffer */ + /* and the destination pointer modifier, inc is set to -1 */ + /* If srcALen > srcBLen, zero pad has to be done to srcB to make the two inputs of same length */ + /* But to improve the performance, + * we include zeroes in the output instead of zero padding either of the the inputs*/ + /* If srcALen > srcBLen, + * (srcALen - srcBLen) zeroes has to included in the starting of the output buffer */ + /* If srcALen < srcBLen, + * (srcALen - srcBLen) zeroes has to included in the ending of the output buffer */ + if(srcALen >= srcBLen) + { + /* Initialization of inputA pointer */ + pIn1 = (pSrcA); + + /* Initialization of inputB pointer */ + pIn2 = (pSrcB); + + /* Number of output samples is calculated */ + outBlockSize = (2u * srcALen) - 1u; + + /* When srcALen > srcBLen, zero padding is done to srcB + * to make their lengths equal. + * Instead, (outBlockSize - (srcALen + srcBLen - 1)) + * number of output samples are made zero */ + j = outBlockSize - (srcALen + (srcBLen - 1u)); + + /* Updating the pointer position to non zero value */ + pOut += j; + + } + else + { + /* Initialization of inputA pointer */ + pIn1 = (pSrcB); + + /* Initialization of inputB pointer */ + pIn2 = (pSrcA); + + /* srcBLen is always considered as shorter or equal to srcALen */ + j = srcBLen; + srcBLen = srcALen; + srcALen = j; + + /* CORR(x, y) = Reverse order(CORR(y, x)) */ + /* Hence set the destination pointer to point to the last output sample */ + pOut = pDst + ((srcALen + srcBLen) - 2u); + + /* Destination address modifier is set to -1 */ + inc = -1; + + } + + /* The function is internally + * divided into three parts according to the number of multiplications that has to be + * taken place between inputA samples and inputB samples. In the first part of the + * algorithm, the multiplications increase by one for every iteration. + * In the second part of the algorithm, srcBLen number of multiplications are done. + * In the third part of the algorithm, the multiplications decrease by one + * for every iteration.*/ + /* The algorithm is implemented in three stages. + * The loop counters of each stage is initiated here. */ + blockSize1 = srcBLen - 1u; + blockSize2 = srcALen - (srcBLen - 1u); + blockSize3 = blockSize1; + + /* -------------------------- + * Initializations of stage1 + * -------------------------*/ + + /* sum = x[0] * y[srcBlen - 1] + * sum = x[0] * y[srcBlen - 2] + x[1] * y[srcBlen - 1] + * .... + * sum = x[0] * y[0] + x[1] * y[1] +...+ x[srcBLen - 1] * y[srcBLen - 1] + */ + + /* In this stage the MAC operations are increased by 1 for every iteration. + The count variable holds the number of MAC operations performed */ + count = 1u; + + /* Working pointer of inputA */ + px = pIn1; + + /* Working pointer of inputB */ + pSrc1 = pIn2 + (srcBLen - 1u); + py = pSrc1; + + /* ------------------------ + * Stage1 process + * ----------------------*/ + + /* The first stage starts here */ + while(blockSize1 > 0u) + { + /* Accumulator is made zero for every iteration */ + sum = 0; + + /* Apply loop unrolling and compute 4 MACs simultaneously. */ + k = count >> 2; + + /* First part of the processing with loop unrolling. Compute 4 MACs at a time. + ** a second loop below computes MACs for the remaining 1 to 3 samples. */ + while(k > 0u) + { + /* x[0] , x[1] */ + in1 = (q15_t) * px++; + in2 = (q15_t) * px++; + input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* y[srcBLen - 4] , y[srcBLen - 3] */ + in1 = (q15_t) * py++; + in2 = (q15_t) * py++; + input2 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* x[0] * y[srcBLen - 4] */ + /* x[1] * y[srcBLen - 3] */ + sum = __SMLAD(input1, input2, sum); + + /* x[2] , x[3] */ + in1 = (q15_t) * px++; + in2 = (q15_t) * px++; + input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* y[srcBLen - 2] , y[srcBLen - 1] */ + in1 = (q15_t) * py++; + in2 = (q15_t) * py++; + input2 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* x[2] * y[srcBLen - 2] */ + /* x[3] * y[srcBLen - 1] */ + sum = __SMLAD(input1, input2, sum); + + + /* Decrement the loop counter */ + k--; + } + + /* If the count is not a multiple of 4, compute any remaining MACs here. + ** No loop unrolling is used. */ + k = count % 0x4u; + + while(k > 0u) + { + /* Perform the multiply-accumulates */ + /* x[0] * y[srcBLen - 1] */ + sum += (q31_t) ((q15_t) * px++ * *py++); + + /* Decrement the loop counter */ + k--; + } + + /* Store the result in the accumulator in the destination buffer. */ + *pOut = (q7_t) (__SSAT(sum >> 7, 8)); + /* Destination pointer is updated according to the address modifier, inc */ + pOut += inc; + + /* Update the inputA and inputB pointers for next MAC calculation */ + py = pSrc1 - count; + px = pIn1; + + /* Increment the MAC count */ + count++; + + /* Decrement the loop counter */ + blockSize1--; + } + + /* -------------------------- + * Initializations of stage2 + * ------------------------*/ + + /* sum = x[0] * y[0] + x[1] * y[1] +...+ x[srcBLen-1] * y[srcBLen-1] + * sum = x[1] * y[0] + x[2] * y[1] +...+ x[srcBLen] * y[srcBLen-1] + * .... + * sum = x[srcALen-srcBLen-2] * y[0] + x[srcALen-srcBLen-1] * y[1] +...+ x[srcALen-1] * y[srcBLen-1] + */ + + /* Working pointer of inputA */ + px = pIn1; + + /* Working pointer of inputB */ + py = pIn2; + + /* count is index by which the pointer pIn1 to be incremented */ + count = 0u; + + /* ------------------- + * Stage2 process + * ------------------*/ + + /* Stage2 depends on srcBLen as in this stage srcBLen number of MACS are performed. + * So, to loop unroll over blockSize2, + * srcBLen should be greater than or equal to 4 */ + if(srcBLen >= 4u) + { + /* Loop unroll over blockSize2, by 4 */ + blkCnt = blockSize2 >> 2u; + + while(blkCnt > 0u) + { + /* Set all accumulators to zero */ + acc0 = 0; + acc1 = 0; + acc2 = 0; + acc3 = 0; + + /* read x[0], x[1], x[2] samples */ + x0 = *px++; + x1 = *px++; + x2 = *px++; + + /* Apply loop unrolling and compute 4 MACs simultaneously. */ + k = srcBLen >> 2u; + + /* First part of the processing with loop unrolling. Compute 4 MACs at a time. + ** a second loop below computes MACs for the remaining 1 to 3 samples. */ + do + { + /* Read y[0] sample */ + c0 = *py++; + /* Read y[1] sample */ + c1 = *py++; + + /* Read x[3] sample */ + x3 = *px++; + + /* x[0] and x[1] are packed */ + in1 = (q15_t) x0; + in2 = (q15_t) x1; + + input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* y[0] and y[1] are packed */ + in1 = (q15_t) c0; + in2 = (q15_t) c1; + + input2 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* acc0 += x[0] * y[0] + x[1] * y[1] */ + acc0 = __SMLAD(input1, input2, acc0); + + /* x[1] and x[2] are packed */ + in1 = (q15_t) x1; + in2 = (q15_t) x2; + + input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* acc1 += x[1] * y[0] + x[2] * y[1] */ + acc1 = __SMLAD(input1, input2, acc1); + + /* x[2] and x[3] are packed */ + in1 = (q15_t) x2; + in2 = (q15_t) x3; + + input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* acc2 += x[2] * y[0] + x[3] * y[1] */ + acc2 = __SMLAD(input1, input2, acc2); + + /* Read x[4] sample */ + x0 = *(px++); + + /* x[3] and x[4] are packed */ + in1 = (q15_t) x3; + in2 = (q15_t) x0; + + input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* acc3 += x[3] * y[0] + x[4] * y[1] */ + acc3 = __SMLAD(input1, input2, acc3); + + /* Read y[2] sample */ + c0 = *py++; + /* Read y[3] sample */ + c1 = *py++; + + /* Read x[5] sample */ + x1 = *px++; + + /* x[2] and x[3] are packed */ + in1 = (q15_t) x2; + in2 = (q15_t) x3; + + input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* y[2] and y[3] are packed */ + in1 = (q15_t) c0; + in2 = (q15_t) c1; + + input2 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* acc0 += x[2] * y[2] + x[3] * y[3] */ + acc0 = __SMLAD(input1, input2, acc0); + + /* x[3] and x[4] are packed */ + in1 = (q15_t) x3; + in2 = (q15_t) x0; + + input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* acc1 += x[3] * y[2] + x[4] * y[3] */ + acc1 = __SMLAD(input1, input2, acc1); + + /* x[4] and x[5] are packed */ + in1 = (q15_t) x0; + in2 = (q15_t) x1; + + input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* acc2 += x[4] * y[2] + x[5] * y[3] */ + acc2 = __SMLAD(input1, input2, acc2); + + /* Read x[6] sample */ + x2 = *px++; + + /* x[5] and x[6] are packed */ + in1 = (q15_t) x1; + in2 = (q15_t) x2; + + input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* acc3 += x[5] * y[2] + x[6] * y[3] */ + acc3 = __SMLAD(input1, input2, acc3); + + } while(--k); + + /* If the srcBLen is not a multiple of 4, compute any remaining MACs here. + ** No loop unrolling is used. */ + k = srcBLen % 0x4u; + + while(k > 0u) + { + /* Read y[4] sample */ + c0 = *py++; + + /* Read x[7] sample */ + x3 = *px++; + + /* Perform the multiply-accumulates */ + /* acc0 += x[4] * y[4] */ + acc0 += ((q15_t) x0 * c0); + /* acc1 += x[5] * y[4] */ + acc1 += ((q15_t) x1 * c0); + /* acc2 += x[6] * y[4] */ + acc2 += ((q15_t) x2 * c0); + /* acc3 += x[7] * y[4] */ + acc3 += ((q15_t) x3 * c0); + + /* Reuse the present samples for the next MAC */ + x0 = x1; + x1 = x2; + x2 = x3; + + /* Decrement the loop counter */ + k--; + } + + /* Store the result in the accumulator in the destination buffer. */ + *pOut = (q7_t) (__SSAT(acc0 >> 7, 8)); + /* Destination pointer is updated according to the address modifier, inc */ + pOut += inc; + + *pOut = (q7_t) (__SSAT(acc1 >> 7, 8)); + pOut += inc; + + *pOut = (q7_t) (__SSAT(acc2 >> 7, 8)); + pOut += inc; + + *pOut = (q7_t) (__SSAT(acc3 >> 7, 8)); + pOut += inc; + + count += 4u; + /* Update the inputA and inputB pointers for next MAC calculation */ + px = pIn1 + count; + py = pIn2; + + /* Decrement the loop counter */ + blkCnt--; + } + + /* If the blockSize2 is not a multiple of 4, compute any remaining output samples here. + ** No loop unrolling is used. */ + blkCnt = blockSize2 % 0x4u; + + while(blkCnt > 0u) + { + /* Accumulator is made zero for every iteration */ + sum = 0; + + /* Apply loop unrolling and compute 4 MACs simultaneously. */ + k = srcBLen >> 2u; + + /* First part of the processing with loop unrolling. Compute 4 MACs at a time. + ** a second loop below computes MACs for the remaining 1 to 3 samples. */ + while(k > 0u) + { + /* Reading two inputs of SrcA buffer and packing */ + in1 = (q15_t) * px++; + in2 = (q15_t) * px++; + input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* Reading two inputs of SrcB buffer and packing */ + in1 = (q15_t) * py++; + in2 = (q15_t) * py++; + input2 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* Perform the multiply-accumulates */ + sum = __SMLAD(input1, input2, sum); + + /* Reading two inputs of SrcA buffer and packing */ + in1 = (q15_t) * px++; + in2 = (q15_t) * px++; + input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* Reading two inputs of SrcB buffer and packing */ + in1 = (q15_t) * py++; + in2 = (q15_t) * py++; + input2 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* Perform the multiply-accumulates */ + sum = __SMLAD(input1, input2, sum); + + /* Decrement the loop counter */ + k--; + } + + /* If the srcBLen is not a multiple of 4, compute any remaining MACs here. + ** No loop unrolling is used. */ + k = srcBLen % 0x4u; + + while(k > 0u) + { + /* Perform the multiply-accumulates */ + sum += ((q15_t) * px++ * *py++); + + /* Decrement the loop counter */ + k--; + } + + /* Store the result in the accumulator in the destination buffer. */ + *pOut = (q7_t) (__SSAT(sum >> 7, 8)); + /* Destination pointer is updated according to the address modifier, inc */ + pOut += inc; + + /* Increment the pointer pIn1 index, count by 1 */ + count++; + + /* Update the inputA and inputB pointers for next MAC calculation */ + px = pIn1 + count; + py = pIn2; + + /* Decrement the loop counter */ + blkCnt--; + } + } + else + { + /* If the srcBLen is not a multiple of 4, + * the blockSize2 loop cannot be unrolled by 4 */ + blkCnt = blockSize2; + + while(blkCnt > 0u) + { + /* Accumulator is made zero for every iteration */ + sum = 0; + + /* Loop over srcBLen */ + k = srcBLen; + + while(k > 0u) + { + /* Perform the multiply-accumulate */ + sum += ((q15_t) * px++ * *py++); + + /* Decrement the loop counter */ + k--; + } + + /* Store the result in the accumulator in the destination buffer. */ + *pOut = (q7_t) (__SSAT(sum >> 7, 8)); + /* Destination pointer is updated according to the address modifier, inc */ + pOut += inc; + + /* Increment the MAC count */ + count++; + + /* Update the inputA and inputB pointers for next MAC calculation */ + px = pIn1 + count; + py = pIn2; + + + /* Decrement the loop counter */ + blkCnt--; + } + } + + /* -------------------------- + * Initializations of stage3 + * -------------------------*/ + + /* sum += x[srcALen-srcBLen+1] * y[0] + x[srcALen-srcBLen+2] * y[1] +...+ x[srcALen-1] * y[srcBLen-1] + * sum += x[srcALen-srcBLen+2] * y[0] + x[srcALen-srcBLen+3] * y[1] +...+ x[srcALen-1] * y[srcBLen-1] + * .... + * sum += x[srcALen-2] * y[0] + x[srcALen-1] * y[1] + * sum += x[srcALen-1] * y[0] + */ + + /* In this stage the MAC operations are decreased by 1 for every iteration. + The count variable holds the number of MAC operations performed */ + count = srcBLen - 1u; + + /* Working pointer of inputA */ + pSrc1 = pIn1 + (srcALen - (srcBLen - 1u)); + px = pSrc1; + + /* Working pointer of inputB */ + py = pIn2; + + /* ------------------- + * Stage3 process + * ------------------*/ + + while(blockSize3 > 0u) + { + /* Accumulator is made zero for every iteration */ + sum = 0; + + /* Apply loop unrolling and compute 4 MACs simultaneously. */ + k = count >> 2u; + + /* First part of the processing with loop unrolling. Compute 4 MACs at a time. + ** a second loop below computes MACs for the remaining 1 to 3 samples. */ + while(k > 0u) + { + /* x[srcALen - srcBLen + 1] , x[srcALen - srcBLen + 2] */ + in1 = (q15_t) * px++; + in2 = (q15_t) * px++; + input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* y[0] , y[1] */ + in1 = (q15_t) * py++; + in2 = (q15_t) * py++; + input2 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* sum += x[srcALen - srcBLen + 1] * y[0] */ + /* sum += x[srcALen - srcBLen + 2] * y[1] */ + sum = __SMLAD(input1, input2, sum); + + /* x[srcALen - srcBLen + 3] , x[srcALen - srcBLen + 4] */ + in1 = (q15_t) * px++; + in2 = (q15_t) * px++; + input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* y[2] , y[3] */ + in1 = (q15_t) * py++; + in2 = (q15_t) * py++; + input2 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16); + + /* sum += x[srcALen - srcBLen + 3] * y[2] */ + /* sum += x[srcALen - srcBLen + 4] * y[3] */ + sum = __SMLAD(input1, input2, sum); + + /* Decrement the loop counter */ + k--; + } + + /* If the count is not a multiple of 4, compute any remaining MACs here. + ** No loop unrolling is used. */ + k = count % 0x4u; + + while(k > 0u) + { + /* Perform the multiply-accumulates */ + sum += ((q15_t) * px++ * *py++); + + /* Decrement the loop counter */ + k--; + } + + /* Store the result in the accumulator in the destination buffer. */ + *pOut = (q7_t) (__SSAT(sum >> 7, 8)); + /* Destination pointer is updated according to the address modifier, inc */ + pOut += inc; + + /* Update the inputA and inputB pointers for next MAC calculation */ + px = ++pSrc1; + py = pIn2; + + /* Decrement the MAC count */ + count--; + + /* Decrement the loop counter */ + blockSize3--; + } + +#else + +/* Run the below code for Cortex-M0 */ + + q7_t *pIn1 = pSrcA; /* inputA pointer */ + q7_t *pIn2 = pSrcB + (srcBLen - 1u); /* inputB pointer */ + q31_t sum; /* Accumulator */ + uint32_t i = 0u, j; /* loop counters */ + uint32_t inv = 0u; /* Reverse order flag */ + uint32_t tot = 0u; /* Length */ + + /* The algorithm implementation is based on the lengths of the inputs. */ + /* srcB is always made to slide across srcA. */ + /* So srcBLen is always considered as shorter or equal to srcALen */ + /* But CORR(x, y) is reverse of CORR(y, x) */ + /* So, when srcBLen > srcALen, output pointer is made to point to the end of the output buffer */ + /* and a varaible, inv is set to 1 */ + /* If lengths are not equal then zero pad has to be done to make the two + * inputs of same length. But to improve the performance, we include zeroes + * in the output instead of zero padding either of the the inputs*/ + /* If srcALen > srcBLen, (srcALen - srcBLen) zeroes has to included in the + * starting of the output buffer */ + /* If srcALen < srcBLen, (srcALen - srcBLen) zeroes has to included in the + * ending of the output buffer */ + /* Once the zero padding is done the remaining of the output is calcualted + * using convolution but with the shorter signal time shifted. */ + + /* Calculate the length of the remaining sequence */ + tot = ((srcALen + srcBLen) - 2u); + + if(srcALen > srcBLen) + { + /* Calculating the number of zeros to be padded to the output */ + j = srcALen - srcBLen; + + /* Initialise the pointer after zero padding */ + pDst += j; + } + + else if(srcALen < srcBLen) + { + /* Initialization to inputB pointer */ + pIn1 = pSrcB; + + /* Initialization to the end of inputA pointer */ + pIn2 = pSrcA + (srcALen - 1u); + + /* Initialisation of the pointer after zero padding */ + pDst = pDst + tot; + + /* Swapping the lengths */ + j = srcALen; + srcALen = srcBLen; + srcBLen = j; + + /* Setting the reverse flag */ + inv = 1; + + } + + /* Loop to calculate convolution for output length number of times */ + for (i = 0u; i <= tot; i++) + { + /* Initialize sum with zero to carry on MAC operations */ + sum = 0; + + /* Loop to perform MAC operations according to convolution equation */ + for (j = 0u; j <= i; j++) + { + /* Check the array limitations */ + if((((i - j) < srcBLen) && (j < srcALen))) + { + /* z[i] += x[i-j] * y[j] */ + sum += ((q15_t) pIn1[j] * pIn2[-((int32_t) i - j)]); + } + } + /* Store the output in the destination buffer */ + if(inv == 1) + *pDst-- = (q7_t) __SSAT((sum >> 7u), 8u); + else + *pDst++ = (q7_t) __SSAT((sum >> 7u), 8u); + } + +#endif /* #ifndef ARM_MATH_CM0_FAMILY */ + +} + +/** + * @} end of Corr group + */ |