Connecting CMSIS-DSP Biquad Filters

What I checked first

The 250 Hz ECG sources implement 40 Hz low-pass and 0.5 Hz high-pass stages using DF1 or DF2T cascades. The PPG source instead separates a 0.5 Hz high-pass and 8 Hz low-pass, so I do not reuse ECG coefficients unchanged.

Source view

• ARM_MATH_CM4, FPU settings, source files, and include paths must all agree.
• I separate the filter instance, coefficient array, state buffer, and blocksize=1 roles.
• The sources preserve coefficient structures, but I did not recreate a measured frequency response.

Code path

arm_biquad_cascade_df2T_init_f32(
    &ECG_Filter, numStage_ECG,
    IIR_Coeffs_ECG, pState_ECG);
arm_biquad_cascade_df2T_f32(
    &ECG_Filter, &Raw_Voltage,
    &ECG_Filtered, 1);

Key terms

1. CMSIS-DSP
2. DF2T
3. coefficient
4. state buffer

Review sequence

1. CMSIS-DSP
2. DF2T → coefficient
3. state buffer