Hi, I am trying to implement a low pass filter with cut off frequency 50kHz by using stm32f407. I sthere a document or a guide or manual that will help me to do the same?

Posted on May 07, 2018 at 11:39

Hi the example is arm_fir_example which is there in the following path:

C:\Keil_v5\ARM\CMSIS\DSP_Lib\Examples\arm_fir_example.

In this example they have done the following:

The input signal is a sum of two sine waves: 1 kHz and 15 kHz.

* This is processed by an FIR lowpass filter with cutoff frequency 6 kHz.

* The lowpass filter eliminates the 15 kHz signal leaving only the 1 kHz sine wave at the output.

The thing that is not clear is regarding the FIR coefficients generated.

They are using fir1() MATLAB function.

** fir1(28, 6/24) ,then storing the generated coefficients in the following buffer:

const float32_t firCoeffs32[NUM_TAPS] = {

-0.0018225230f, -0.0015879294f, +0.0000000000f, +0.0036977508f, +0.0080754303f, +0.0085302217f, -0.0000000000f, -0.0173976984f,

-0.0341458607f, -0.0333591565f, +0.0000000000f, +0.0676308395f, +0.1522061835f, +0.2229246956f, +0.2504960933f, +0.2229246956f,

+0.1522061835f, +0.0676308395f, +0.0000000000f, -0.0333591565f, -0.0341458607f, -0.0173976984f, -0.0000000000f, +0.0085302217f,

+0.0080754303f, +0.0036977508f, +0.0000000000f, -0.0015879294f, -0.0018225230f

};

However, if my input signal is different each time, how will i generate the FIR filter coefficients.