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CMSIS-DSP
Version 1.4.7
CMSIS DSP Software Library
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Functions | |
| LOW_OPTIMIZATION_ENTER void | arm_biquad_cascade_df2T_f32 (const arm_biquad_cascade_df2T_instance_f32 *S, float32_t *pSrc, float32_t *pDst, uint32_t blockSize) |
| Processing function for the floating-point transposed direct form II Biquad cascade filter. | |
| LOW_OPTIMIZATION_ENTER void | arm_biquad_cascade_df2T_f64 (const arm_biquad_cascade_df2T_instance_f64 *S, float64_t *pSrc, float64_t *pDst, uint32_t blockSize) |
| Processing function for the floating-point transposed direct form II Biquad cascade filter. | |
| void | arm_biquad_cascade_df2T_init_f32 (arm_biquad_cascade_df2T_instance_f32 *S, uint8_t numStages, float32_t *pCoeffs, float32_t *pState) |
| Initialization function for the floating-point transposed direct form II Biquad cascade filter. | |
| void | arm_biquad_cascade_df2T_init_f64 (arm_biquad_cascade_df2T_instance_f64 *S, uint8_t numStages, float64_t *pCoeffs, float64_t *pState) |
| Initialization function for the floating-point transposed direct form II Biquad cascade filter. | |
| LOW_OPTIMIZATION_ENTER void | arm_biquad_cascade_stereo_df2T_f32 (const arm_biquad_cascade_stereo_df2T_instance_f32 *S, float32_t *pSrc, float32_t *pDst, uint32_t blockSize) |
| Processing function for the floating-point transposed direct form II Biquad cascade filter. | |
| void | arm_biquad_cascade_stereo_df2T_init_f32 (arm_biquad_cascade_stereo_df2T_instance_f32 *S, uint8_t numStages, float32_t *pCoeffs, float32_t *pState) |
| Initialization function for the floating-point transposed direct form II Biquad cascade filter. | |
This set of functions implements arbitrary order recursive (IIR) filters using a transposed direct form II structure. The filters are implemented as a cascade of second order Biquad sections. These functions provide a slight memory savings as compared to the direct form I Biquad filter functions. Only floating-point data is supported.
This function operate on blocks of input and output data and each call to the function processes blockSize samples through the filter. pSrc points to the array of input data and pDst points to the array of output data. Both arrays contain blockSize values.
y[n] = b0 * x[n] + d1 d1 = b1 * x[n] + a1 * y[n] + d2 d2 = b2 * x[n] + a2 * y[n]where d1 and d2 represent the two state values.
b0, b1, and b2 multiply the input signal x[n] and are referred to as the feedforward coefficients. Coefficients a1 and a2 multiply the output signal y[n] and are referred to as the feedback coefficients. Pay careful attention to the sign of the feedback coefficients. Some design tools flip the sign of the feedback coefficients: y[n] = b0 * x[n] + d1; d1 = b1 * x[n] - a1 * y[n] + d2; d2 = b2 * x[n] - a2 * y[n];In this case the feedback coefficients
a1 and a2 must be negated when used with the CMSIS DSP Library.numStages refers to the number of second order stages used. For example, an 8th order filter would be realized with numStages=4 second order stages. A 9th order filter would be realized with numStages=5 second order stages with the coefficients for one of the stages configured as a first order filter (b2=0 and a2=0).pState points to the state variable array. Each Biquad stage has 2 state variables d1 and d2. The state variables are arranged in the pState array as:
{d11, d12, d21, d22, ...}
where d1x refers to the state variables for the first Biquad and d2x refers to the state variables for the second Biquad. The state array has a total length of 2*numStages values. The state variables are updated after each block of data is processed; the coefficients are untouched.d1 and d2. Because of this, the CMSIS library only has a floating-point version of the Direct Form II Biquad. The advantage of the Direct Form II Biquad is that it requires half the number of state variables, 2 rather than 4, per Biquad stage.
arm_biquad_cascade_df2T_instance_f32 S1 = {numStages, pState, pCoeffs};
where numStages is the number of Biquad stages in the filter; pState is the address of the state buffer. pCoeffs is the address of the coefficient buffer;This set of functions implements arbitrary order recursive (IIR) filters using a transposed direct form II structure. The filters are implemented as a cascade of second order Biquad sections. These functions provide a slight memory savings as compared to the direct form I Biquad filter functions. Only floating-point data is supported.
This function operate on blocks of input and output data and each call to the function processes blockSize samples through the filter. pSrc points to the array of input data and pDst points to the array of output data. Both arrays contain blockSize values.
y[n] = b0 * x[n] + d1 d1 = b1 * x[n] + a1 * y[n] + d2 d2 = b2 * x[n] + a2 * y[n]where d1 and d2 represent the two state values.
b0, b1, and b2 multiply the input signal x[n] and are referred to as the feedforward coefficients. Coefficients a1 and a2 multiply the output signal y[n] and are referred to as the feedback coefficients. Pay careful attention to the sign of the feedback coefficients. Some design tools flip the sign of the feedback coefficients: y[n] = b0 * x[n] + d1; d1 = b1 * x[n] - a1 * y[n] + d2; d2 = b2 * x[n] - a2 * y[n];In this case the feedback coefficients
a1 and a2 must be negated when used with the CMSIS DSP Library.numStages refers to the number of second order stages used. For example, an 8th order filter would be realized with numStages=4 second order stages. A 9th order filter would be realized with numStages=5 second order stages with the coefficients for one of the stages configured as a first order filter (b2=0 and a2=0).pState points to the state variable array. Each Biquad stage has 2 state variables d1 and d2. The state variables are arranged in the pState array as:
{d11, d12, d21, d22, ...}
where d1x refers to the state variables for the first Biquad and d2x refers to the state variables for the second Biquad. The state array has a total length of 2*numStages values. The state variables are updated after each block of data is processed; the coefficients are untouched.d1 and d2. Because of this, the CMSIS library only has a floating-point version of the Direct Form II Biquad. The advantage of the Direct Form II Biquad is that it requires half the number of state variables, 2 rather than 4, per Biquad stage.
arm_biquad_cascade_df2T_instance_f64 S1 = {numStages, pState, pCoeffs};
where numStages is the number of Biquad stages in the filter; pState is the address of the state buffer. pCoeffs is the address of the coefficient buffer; | LOW_OPTIMIZATION_ENTER void arm_biquad_cascade_df2T_f32 | ( | const arm_biquad_cascade_df2T_instance_f32 * | S, |
| float32_t * | pSrc, | ||
| float32_t * | pDst, | ||
| uint32_t | blockSize | ||
| ) |
| [in] | *S | points to an instance of the filter data structure. |
| [in] | *pSrc | points to the block of input data. |
| [out] | *pDst | points to the block of output data |
| [in] | blockSize | number of samples to process. |
References blockSize, arm_biquad_cascade_df2T_instance_f32::numStages, arm_biquad_cascade_df2T_instance_f32::pCoeffs, and arm_biquad_cascade_df2T_instance_f32::pState.
| LOW_OPTIMIZATION_ENTER void arm_biquad_cascade_df2T_f64 | ( | const arm_biquad_cascade_df2T_instance_f64 * | S, |
| float64_t * | pSrc, | ||
| float64_t * | pDst, | ||
| uint32_t | blockSize | ||
| ) |
| [in] | *S | points to an instance of the filter data structure. |
| [in] | *pSrc | points to the block of input data. |
| [out] | *pDst | points to the block of output data |
| [in] | blockSize | number of samples to process. |
References blockSize, arm_biquad_cascade_df2T_instance_f64::numStages, arm_biquad_cascade_df2T_instance_f64::pCoeffs, and arm_biquad_cascade_df2T_instance_f64::pState.
| void arm_biquad_cascade_df2T_init_f32 | ( | arm_biquad_cascade_df2T_instance_f32 * | S, |
| uint8_t | numStages, | ||
| float32_t * | pCoeffs, | ||
| float32_t * | pState | ||
| ) |
| [in,out] | *S | points to an instance of the filter data structure. |
| [in] | numStages | number of 2nd order stages in the filter. |
| [in] | *pCoeffs | points to the filter coefficients. |
| [in] | *pState | points to the state buffer. |
Coefficient and State Ordering:
pCoeffs in the following order:
{b10, b11, b12, a11, a12, b20, b21, b22, a21, a22, ...}
b1x and a1x are the coefficients for the first stage, b2x and a2x are the coefficients for the second stage, and so on. The pCoeffs array contains a total of 5*numStages values.pState is a pointer to state array. Each Biquad stage has 2 state variables d1, and d2. The 2 state variables for stage 1 are first, then the 2 state variables for stage 2, and so on. The state array has a total length of 2*numStages values. The state variables are updated after each block of data is processed; the coefficients are untouched. References arm_biquad_cascade_df2T_instance_f32::numStages, arm_biquad_cascade_df2T_instance_f32::pCoeffs, and arm_biquad_cascade_df2T_instance_f32::pState.
| void arm_biquad_cascade_df2T_init_f64 | ( | arm_biquad_cascade_df2T_instance_f64 * | S, |
| uint8_t | numStages, | ||
| float64_t * | pCoeffs, | ||
| float64_t * | pState | ||
| ) |
| [in,out] | *S | points to an instance of the filter data structure. |
| [in] | numStages | number of 2nd order stages in the filter. |
| [in] | *pCoeffs | points to the filter coefficients. |
| [in] | *pState | points to the state buffer. |
Coefficient and State Ordering:
pCoeffs in the following order:
{b10, b11, b12, a11, a12, b20, b21, b22, a21, a22, ...}
b1x and a1x are the coefficients for the first stage, b2x and a2x are the coefficients for the second stage, and so on. The pCoeffs array contains a total of 5*numStages values.pState is a pointer to state array. Each Biquad stage has 2 state variables d1, and d2. The 2 state variables for stage 1 are first, then the 2 state variables for stage 2, and so on. The state array has a total length of 2*numStages values. The state variables are updated after each block of data is processed; the coefficients are untouched. References arm_biquad_cascade_df2T_instance_f64::numStages, arm_biquad_cascade_df2T_instance_f64::pCoeffs, and arm_biquad_cascade_df2T_instance_f64::pState.
| LOW_OPTIMIZATION_ENTER void arm_biquad_cascade_stereo_df2T_f32 | ( | const arm_biquad_cascade_stereo_df2T_instance_f32 * | S, |
| float32_t * | pSrc, | ||
| float32_t * | pDst, | ||
| uint32_t | blockSize | ||
| ) |
Processing function for the floating-point transposed direct form II Biquad cascade filter. 2 channels.
| [in] | *S | points to an instance of the filter data structure. |
| [in] | *pSrc | points to the block of input data. |
| [out] | *pDst | points to the block of output data |
| [in] | blockSize | number of samples to process. |
References blockSize, arm_biquad_cascade_stereo_df2T_instance_f32::numStages, arm_biquad_cascade_stereo_df2T_instance_f32::pCoeffs, and arm_biquad_cascade_stereo_df2T_instance_f32::pState.
| void arm_biquad_cascade_stereo_df2T_init_f32 | ( | arm_biquad_cascade_stereo_df2T_instance_f32 * | S, |
| uint8_t | numStages, | ||
| float32_t * | pCoeffs, | ||
| float32_t * | pState | ||
| ) |
| [in,out] | *S | points to an instance of the filter data structure. |
| [in] | numStages | number of 2nd order stages in the filter. |
| [in] | *pCoeffs | points to the filter coefficients. |
| [in] | *pState | points to the state buffer. |
Coefficient and State Ordering:
pCoeffs in the following order:
{b10, b11, b12, a11, a12, b20, b21, b22, a21, a22, ...}
b1x and a1x are the coefficients for the first stage, b2x and a2x are the coefficients for the second stage, and so on. The pCoeffs array contains a total of 5*numStages values.pState is a pointer to state array. Each Biquad stage has 2 state variables d1, and d2 for each channel. The 2 state variables for stage 1 are first, then the 2 state variables for stage 2, and so on. The state array has a total length of 2*numStages values. The state variables are updated after each block of data is processed; the coefficients are untouched. References arm_biquad_cascade_stereo_df2T_instance_f32::numStages, arm_biquad_cascade_stereo_df2T_instance_f32::pCoeffs, and arm_biquad_cascade_stereo_df2T_instance_f32::pState.