| #include "ref.h" |
| |
| void ref_biquad_cascade_df2T_f32( |
| const arm_biquad_cascade_df2T_instance_f32 * S, |
| float32_t * pSrc, |
| float32_t * pDst, |
| uint32_t blockSize) |
| { |
| float32_t *pIn = pSrc; /* source pointer */ |
| float32_t *pOut = pDst; /* destination pointer */ |
| float32_t *pState = S->pState; /* State pointer */ |
| const float32_t *pCoeffs = S->pCoeffs; /* coefficient pointer */ |
| float32_t acc; /* accumulator */ |
| float32_t b0, b1, b2, a1, a2; /* Filter coefficients */ |
| float32_t Xn; /* temporary input */ |
| float32_t d1, d2; /* state variables */ |
| uint32_t sample, stage = S->numStages; /* loop counters */ |
| |
| do |
| { |
| /* Reading the coefficients */ |
| b0 = *pCoeffs++; |
| b1 = *pCoeffs++; |
| b2 = *pCoeffs++; |
| a1 = *pCoeffs++; |
| a2 = *pCoeffs++; |
| |
| /*Reading the state values */ |
| d1 = pState[0]; |
| d2 = pState[1]; |
| |
| sample = blockSize; |
| |
| while (sample > 0U) |
| { |
| /* Read the input */ |
| Xn = *pIn++; |
| |
| /* y[n] = b0 * x[n] + d1 */ |
| acc = (b0 * Xn) + d1; |
| |
| /* Store the result in the accumulator in the destination buffer. */ |
| *pOut++ = acc; |
| |
| /* Every time after the output is computed state should be updated. */ |
| /* d1 = b1 * x[n] + a1 * y[n] + d2 */ |
| d1 = (b1 * Xn + a1 * acc) + d2; |
| |
| /* d2 = b2 * x[n] + a2 * y[n] */ |
| d2 = (b2 * Xn) + (a2 * acc); |
| |
| /* decrement the loop counter */ |
| sample--; |
| } |
| |
| /* Store the updated state variables back into the state array */ |
| *pState++ = d1; |
| *pState++ = d2; |
| |
| /* The current stage input is given as the output to the next stage */ |
| pIn = pDst; |
| |
| /*Reset the output working pointer */ |
| pOut = pDst; |
| |
| /* decrement the loop counter */ |
| stage--; |
| |
| } while (stage > 0U); |
| } |
| |
| |
| void ref_biquad_cascade_stereo_df2T_f32( |
| const arm_biquad_cascade_stereo_df2T_instance_f32 * S, |
| float32_t * pSrc, |
| float32_t * pDst, |
| uint32_t blockSize) |
| { |
| float32_t *pIn = pSrc; /* source pointer */ |
| float32_t *pOut = pDst; /* destination pointer */ |
| float32_t *pState = S->pState; /* State pointer */ |
| const float32_t *pCoeffs = S->pCoeffs; /* coefficient pointer */ |
| float32_t acc1a, acc1b; /* accumulator */ |
| float32_t b0, b1, b2, a1, a2; /* Filter coefficients */ |
| float32_t Xn1a, Xn1b; /* temporary input */ |
| float32_t d1a, d2a, d1b, d2b; /* state variables */ |
| uint32_t sample, stage = S->numStages; /* loop counters */ |
| |
| do |
| { |
| /* Reading the coefficients */ |
| b0 = *pCoeffs++; |
| b1 = *pCoeffs++; |
| b2 = *pCoeffs++; |
| a1 = *pCoeffs++; |
| a2 = *pCoeffs++; |
| |
| /*Reading the state values */ |
| d1a = pState[0]; |
| d2a = pState[1]; |
| d1b = pState[2]; |
| d2b = pState[3]; |
| |
| sample = blockSize; |
| |
| while (sample > 0U) |
| { |
| /* Read the input */ |
| Xn1a = *pIn++; //Channel a |
| Xn1b = *pIn++; //Channel b |
| |
| /* y[n] = b0 * x[n] + d1 */ |
| acc1a = (b0 * Xn1a) + d1a; |
| acc1b = (b0 * Xn1b) + d1b; |
| |
| /* Store the result in the accumulator in the destination buffer. */ |
| *pOut++ = acc1a; |
| *pOut++ = acc1b; |
| |
| /* Every time after the output is computed state should be updated. */ |
| /* d1 = b1 * x[n] + a1 * y[n] + d2 */ |
| d1a = ((b1 * Xn1a) + (a1 * acc1a)) + d2a; |
| d1b = ((b1 * Xn1b) + (a1 * acc1b)) + d2b; |
| |
| /* d2 = b2 * x[n] + a2 * y[n] */ |
| d2a = (b2 * Xn1a) + (a2 * acc1a); |
| d2b = (b2 * Xn1b) + (a2 * acc1b); |
| |
| /* decrement the loop counter */ |
| sample--; |
| } |
| |
| /* Store the updated state variables back into the state array */ |
| *pState++ = d1a; |
| *pState++ = d2a; |
| *pState++ = d1b; |
| *pState++ = d2b; |
| |
| /* The current stage input is given as the output to the next stage */ |
| pIn = pDst; |
| |
| /*Reset the output working pointer */ |
| pOut = pDst; |
| |
| /* decrement the loop counter */ |
| stage--; |
| |
| } while (stage > 0U); |
| |
| } |
| |
| void ref_biquad_cascade_df2T_f64( |
| const arm_biquad_cascade_df2T_instance_f64 * S, |
| float64_t * pSrc, |
| float64_t * pDst, |
| uint32_t blockSize) |
| { |
| float64_t *pIn = pSrc; /* source pointer */ |
| float64_t *pOut = pDst; /* destination pointer */ |
| float64_t *pState = S->pState; /* State pointer */ |
| float64_t *pCoeffs = S->pCoeffs; /* coefficient pointer */ |
| float64_t acc; /* accumulator */ |
| float64_t b0, b1, b2, a1, a2; /* Filter coefficients */ |
| float64_t Xn; /* temporary input */ |
| float64_t d1, d2; /* state variables */ |
| uint32_t sample, stage = S->numStages; /* loop counters */ |
| |
| do |
| { |
| /* Reading the coefficients */ |
| b0 = *pCoeffs++; |
| b1 = *pCoeffs++; |
| b2 = *pCoeffs++; |
| a1 = *pCoeffs++; |
| a2 = *pCoeffs++; |
| |
| /*Reading the state values */ |
| d1 = pState[0]; |
| d2 = pState[1]; |
| |
| sample = blockSize; |
| |
| while (sample > 0U) |
| { |
| /* Read the input */ |
| Xn = *pIn++; |
| |
| /* y[n] = b0 * x[n] + d1 */ |
| acc = (b0 * Xn) + d1; |
| |
| /* Store the result in the accumulator in the destination buffer. */ |
| *pOut++ = acc; |
| |
| /* Every time after the output is computed state should be updated. */ |
| /* d1 = b1 * x[n] + a1 * y[n] + d2 */ |
| d1 = (b1 * Xn + a1 * acc) + d2; |
| |
| /* d2 = b2 * x[n] + a2 * y[n] */ |
| d2 = (b2 * Xn) + (a2 * acc); |
| |
| /* decrement the loop counter */ |
| sample--; |
| } |
| |
| /* Store the updated state variables back into the state array */ |
| *pState++ = d1; |
| *pState++ = d2; |
| |
| /* The current stage input is given as the output to the next stage */ |
| pIn = pDst; |
| |
| /*Reset the output working pointer */ |
| pOut = pDst; |
| |
| /* decrement the loop counter */ |
| stage--; |
| |
| } while (stage > 0U); |
| } |
| |
| void ref_biquad_cascade_df1_f32( |
| const arm_biquad_casd_df1_inst_f32 * S, |
| float32_t * pSrc, |
| float32_t * pDst, |
| uint32_t blockSize) |
| { |
| float32_t *pIn = pSrc; /* source pointer */ |
| float32_t *pOut = pDst; /* destination pointer */ |
| float32_t *pState = S->pState; /* pState pointer */ |
| const float32_t *pCoeffs = S->pCoeffs; /* coefficient pointer */ |
| float32_t acc; /* Simulates the accumulator */ |
| float32_t b0, b1, b2, a1, a2; /* Filter coefficients */ |
| float32_t Xn1, Xn2, Yn1, Yn2; /* Filter pState variables */ |
| float32_t Xn; /* temporary input */ |
| uint32_t sample, stage = S->numStages; /* loop counters */ |
| |
| do |
| { |
| /* Reading the coefficients */ |
| b0 = *pCoeffs++; |
| b1 = *pCoeffs++; |
| b2 = *pCoeffs++; |
| a1 = *pCoeffs++; |
| a2 = *pCoeffs++; |
| |
| /* Reading the pState 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 * Xn) + (b1 * Xn1) + (b2 * Xn2) + (a1 * Yn1) + (a2 * Yn2); |
| |
| /* Store the result in the accumulator in the destination buffer. */ |
| *pOut++ = acc; |
| |
| /* 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 = acc; |
| |
| /* decrement the loop counter */ |
| sample--; |
| } |
| |
| /* Store the updated state variables back into the pState array */ |
| *pState++ = Xn1; |
| *pState++ = Xn2; |
| *pState++ = Yn1; |
| *pState++ = Yn2; |
| |
| /* The first stage goes from the input buffer to the output buffer. */ |
| /* Subsequent numStages occur in-place in the output buffer */ |
| pIn = pDst; |
| |
| /* Reset the output pointer */ |
| pOut = pDst; |
| |
| /* decrement the loop counter */ |
| stage--; |
| |
| } while (stage > 0U); |
| } |
| |
| void ref_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 *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 |
| { |
| /* 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]; |
| |
| 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 = (q63_t)Xn*b0 + (q63_t)Xn1*b1 + (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. */ |
| 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; |
| |
| /* decrement the 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 */ |
| *pState++ = (q63_t) Xn1; |
| *pState++ = (q63_t) Xn2; |
| *pState++ = Yn1; |
| *pState++ = Yn2; |
| |
| } while (--stage); |
| } |
| |
| void ref_biquad_cascade_df1_q31( |
| const arm_biquad_casd_df1_inst_q31 * S, |
| q31_t * pSrc, |
| q31_t * pDst, |
| uint32_t blockSize) |
| { |
| q63_t acc; /* accumulator */ |
| uint32_t uShift = ((uint32_t) S->postShift + 1U); |
| uint32_t lShift = 32U - uShift; /* Shift to be applied to the output */ |
| q31_t *pIn = pSrc; /* input pointer initialization */ |
| q31_t *pOut = pDst; /* output pointer initialization */ |
| q31_t *pState = S->pState; /* pState pointer initialization */ |
| const q31_t *pCoeffs = S->pCoeffs; /* coeff pointer initialization */ |
| 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 sample, stage = S->numStages; /* loop counters */ |
| |
| 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 >> lShift; |
| |
| /* 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); |
| } |
| |
| |
| void ref_biquad_cascade_df1_fast_q31( |
| const arm_biquad_casd_df1_inst_q31 * S, |
| q31_t * pSrc, |
| q31_t * pDst, |
| uint32_t blockSize) |
| { |
| q31_t acc = 0; /* accumulator */ |
| q31_t Xn1, Xn2, Yn1, Yn2; /* Filter state variables */ |
| q31_t b0, b1, b2, a1, a2; /* Filter coefficients */ |
| q31_t *pIn = pSrc; /* input pointer initialization */ |
| q31_t *pOut = pDst; /* output pointer initialization */ |
| q31_t *pState = S->pState; /* pState pointer initialization */ |
| const q31_t *pCoeffs = S->pCoeffs; /* coeff pointer initialization */ |
| 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 */ |
| |
| 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]; |
| |
| 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] */ |
| mult_32x32_keep32_R(acc, b0, Xn); |
| multAcc_32x32_keep32_R(acc, b1, Xn1); |
| multAcc_32x32_keep32_R(acc, b2, Xn2); |
| multAcc_32x32_keep32_R(acc, a1, Yn1); |
| multAcc_32x32_keep32_R(acc, a2, Yn2); |
| |
| /* The result is converted to 1.31 */ |
| acc <<= shift; |
| |
| /* Every time after the output is computed state should be updated. */ |
| Xn2 = Xn1; |
| Xn1 = Xn; |
| Yn2 = Yn1; |
| Yn1 = acc; |
| |
| /* Store the output in the destination buffer. */ |
| *pOut++ = 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); |
| } |
| |
| void ref_biquad_cascade_df1_fast_q15( |
| const arm_biquad_casd_df1_inst_q15 * S, |
| q15_t * pSrc, |
| q15_t * pDst, |
| uint32_t blockSize) |
| { |
| 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 */ |
| q31_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]; |
| |
| 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 = (q31_t)b0*Xn + (q31_t)b1*Xn1 + (q31_t)b2*Xn2 + (q31_t)a1*Yn1 + (q31_t)a2*Yn2; |
| |
| /* The result is converted to 1.15 */ |
| acc = ref_sat_q15(acc >> shift); |
| |
| /* Every time after the output is computed state should be updated. */ |
| 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); |
| } |
| |
| void ref_biquad_cascade_df1_q15( |
| const arm_biquad_casd_df1_inst_q15 * S, |
| q15_t * pSrc, |
| q15_t * pDst, |
| uint32_t blockSize) |
| { |
| 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]; |
| |
| 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 = (q31_t)b0*Xn + (q31_t)b1*Xn1 + (q31_t)b2*Xn2 + (q31_t)a1*Yn1 + (q31_t)a2*Yn2; |
| |
| /* The result is converted to 1.15 */ |
| acc = ref_sat_q15(acc >> shift); |
| |
| /* Every time after the output is computed state should be updated. */ |
| 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); |
| } |
