A collection of GNU Octave scripts to design IIR filters that can be HW accelerated on ARM Cortex cores via CMSIS DSP.
These filters have been written by Silex Embedded and Elimo Engineering
These scripts compute the coefficients for IIR filters implementented as biquad cascade using a Direct Form II transposed structure. This is the IIR implementation that is used by ARM's CMSIS DSP, which means they can run optimally on ARM Cortex cores over floating point data.
See the examples file for usage examples. After running each of those examples, you will get the coefficients array in the format CMSIS expects.
Example 1 will output:
coeffs =
0.99799
-1.99597
0.99799
1.99597
-0.99598
That array of coefficients can be directly used in ARM code like the following:
#define IIR_ORDER 2
#define IIR_NUMSTAGES (IIR_ORDER/2)
static float32_t m_biquad_state[IIR_ORDER];
static float32_t m_biquad_coeffs[5*IIR_NUMSTAGES] =
{
0.99799,
-1.99597,
0.99799,
1.99597,
-0.99598
};
arm_biquad_cascade_df2T_instance_f32 const iir_inst =
{
IIR_ORDER/2,
m_biquad_state,
m_biquad_coeffs
};
extern float32_t* pSrc;
extern float32_t* pDst;
extern uint16_t blockSize;
arm_biquad_cascade_df2T_f32(&iir_inst, pSrc, pDst, blockSize);