Algobuilder IIR Filter a10/a20 coefficient

[DWind.1]

Hi!

I am using the IIR function block in Algobuilder. In the UI I can enter the coefficients manually or use a file. The implementation uses the CMSIS functions Biquad Cascade IIR Filters Using Direct Form I Structure (void arm_biquad_cascade_df1_init_f32). The init function expects the coefficients in the following order: {b10, b11, b12, a11, a12, b20, b21, b22, a21, a22, ...}

In Algobuilder I have to enter a a10/a20 coefficient in the user interface although the filter is not using it. What do I have to enter for this coefficient? Is it used anywhere?

Best wishes,

Dominik

[Miroslav BATEK]

Hi Dominik,

because the coefficients are normalized, the ax0 parameters are equal to 1. For details see here.

You can enter any value into the GUI, it is not used because the arm_biquad_cascade_df1_init_f32 expects it is equal to 1.