| /* ---------------------------------------------------------------------- |
| * Copyright (C) 2010 ARM Limited. All rights reserved. |
| * |
| * $Date: 15. July 2011 |
| * $Revision: V1.0.10 |
| * |
| * Project: CMSIS DSP Library |
| * Title: arm_biquad_cascade_df1_q31.c |
| * |
| * Description: Processing function for the |
| * Q31 Biquad cascade filter |
| * |
| * 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 0.0.5 2010/04/26 |
| * incorporated review comments and updated with latest CMSIS layer |
| * |
| * Version 0.0.3 2010/03/10 |
| * Initial version |
| * -------------------------------------------------------------------- */ |
| |
| #include "arm_math.h" |
| |
| /** |
| * @ingroup groupFilters |
| */ |
| |
| /** |
| * @addtogroup BiquadCascadeDF1 |
| * @{ |
| */ |
| |
| /** |
| * @brief Processing function for the Q31 Biquad cascade filter. |
| * @param[in] *S points to an instance of the Q31 Biquad cascade 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 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 |
| * Refer to the function <code>arm_biquad_cascade_df1_fast_q31()</code> for a faster but less precise implementation of this filter for Cortex-M3 and Cortex-M4. |
| */ |
| |
| void arm_biquad_cascade_df1_q31( |
| const arm_biquad_casd_df1_inst_q31 * S, |
| q31_t * pSrc, |
| q31_t * pDst, |
| uint32_t blockSize) |
| { |
| q31_t *pIn = pSrc; /* input pointer initialization */ |
| q31_t *pOut = pDst; /* output pointer initialization */ |
| q31_t *pState = S->pState; /* pState pointer initialization */ |
| q31_t *pCoeffs = S->pCoeffs; /* coeff pointer initialization */ |
| q63_t acc; /* accumulator */ |
| q31_t Xn1, Xn2, Yn1, Yn2; /* Filter state variables */ |
| q31_t b0, b1, b2, a1, a2; /* Filter coefficients */ |
| q31_t Xn; /* temporary input */ |
| uint32_t shift = 32u - ((uint32_t) S->postShift + 1u); /* Shift to be applied to the output */ |
| uint32_t sample, stage = S->numStages; /* loop counters */ |
| |
| |
| #ifndef ARM_MATH_CM0 |
| |
| /* Run the below code for Cortex-M4 and Cortex-M3 */ |
| |
| 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]; |
| |
| /* Apply loop unrolling and compute 4 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] |
| */ |
| |
| 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 */ |
| 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) b0 *Xn; |
| /* acc += b1 * x[n-1] */ |
| acc += (q63_t) b1 *Xn1; |
| /* acc += b[2] * x[n-2] */ |
| acc += (q63_t) b2 *Xn2; |
| /* acc += a1 * y[n-1] */ |
| acc += (q63_t) a1 *Yn1; |
| /* acc += a2 * y[n-2] */ |
| acc += (q63_t) a2 *Yn2; |
| |
| /* The result is converted to 1.31 , Yn2 variable is reused */ |
| Yn2 = (q31_t) (acc >> shift); |
| |
| /* Store the output in the destination buffer. */ |
| *pOut++ = Yn2; |
| |
| /* Read the second input */ |
| Xn2 = *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) b0 *Xn2; |
| /* acc += b1 * x[n-1] */ |
| acc += (q63_t) b1 *Xn; |
| /* acc += b[2] * x[n-2] */ |
| acc += (q63_t) b2 *Xn1; |
| /* acc += a1 * y[n-1] */ |
| acc += (q63_t) a1 *Yn2; |
| /* acc += a2 * y[n-2] */ |
| acc += (q63_t) a2 *Yn1; |
| |
| |
| /* The result is converted to 1.31, Yn1 variable is reused */ |
| Yn1 = (q31_t) (acc >> shift); |
| |
| /* Store the output in the destination buffer. */ |
| *pOut++ = Yn1; |
| |
| /* Read the third input */ |
| Xn1 = *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) b0 *Xn1; |
| /* acc += b1 * x[n-1] */ |
| acc += (q63_t) b1 *Xn2; |
| /* acc += b[2] * x[n-2] */ |
| acc += (q63_t) b2 *Xn; |
| /* acc += a1 * y[n-1] */ |
| acc += (q63_t) a1 *Yn1; |
| /* acc += a2 * y[n-2] */ |
| acc += (q63_t) a2 *Yn2; |
| |
| /* The result is converted to 1.31, Yn2 variable is reused */ |
| Yn2 = (q31_t) (acc >> shift); |
| |
| /* Store the output in the destination buffer. */ |
| *pOut++ = Yn2; |
| |
| /* Read the forth 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) b0 *Xn; |
| /* acc += b1 * x[n-1] */ |
| acc += (q63_t) b1 *Xn1; |
| /* acc += b[2] * x[n-2] */ |
| acc += (q63_t) b2 *Xn2; |
| /* acc += a1 * y[n-1] */ |
| acc += (q63_t) a1 *Yn2; |
| /* acc += a2 * y[n-2] */ |
| acc += (q63_t) a2 *Yn1; |
| |
| /* The result is converted to 1.31, Yn1 variable is reused */ |
| Yn1 = (q31_t) (acc >> shift); |
| |
| /* 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; |
| |
| /* Store the output in the destination buffer. */ |
| *pOut++ = Yn1; |
| |
| /* 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) b0 *Xn; |
| /* acc += b1 * x[n-1] */ |
| acc += (q63_t) b1 *Xn1; |
| /* acc += b[2] * x[n-2] */ |
| acc += (q63_t) b2 *Xn2; |
| /* acc += a1 * y[n-1] */ |
| acc += (q63_t) a1 *Yn1; |
| /* acc += a2 * y[n-2] */ |
| acc += (q63_t) a2 *Yn2; |
| |
| /* The result is converted to 1.31 */ |
| acc = acc >> shift; |
| |
| /* 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 = (q31_t) acc; |
| |
| /* Store the output in the destination buffer. */ |
| *pOut++ = (q31_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); |
| |
| #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 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 = (q63_t) b0 *Xn; |
| |
| /* acc += b1 * x[n-1] */ |
| acc += (q63_t) b1 *Xn1; |
| /* acc += b[2] * x[n-2] */ |
| acc += (q63_t) b2 *Xn2; |
| /* acc += a1 * y[n-1] */ |
| acc += (q63_t) a1 *Yn1; |
| /* acc += a2 * y[n-2] */ |
| acc += (q63_t) a2 *Yn2; |
| |
| /* The result is converted to 1.31 */ |
| acc = acc >> shift; |
| |
| /* 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 = (q31_t) acc; |
| |
| /* Store the output in the destination buffer. */ |
| *pOut++ = (q31_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 /* #ifndef ARM_MATH_CM0 */ |
| } |
| |
| /** |
| * @} end of BiquadCascadeDF1 group |
| */ |
