CMSIS DSP CFFT incorrect frequency analysis

Mavi · ‎2024-03-28

hi, I'm trying to do the FFT using the CMSIS DSP V1.15.0 libraries but I get a graph with random frequencies...
I have a CM4 microcontroller(without FPU) I implement the below code and get random frequencies.
I test the same code on a CM7 microcontroller(with FPU) and get the correct frequencies.
What am I doing wrong? since the CM4 microcontroller is without FPU I can't use the "arm_cfft_f32" function?

source code:

Spoiler

int16_t data_pcm[512];
float data_fft[1024];
float  data_fft_mag[512];
uint32_t ifftFlag = 0;
uint32_t doBitReverse = 1;

arm_status status;
status = ARM_MATH_SUCCESS;

arm_cfft_instance_f32 fftInstance;
status=arm_cfft_init_512_f32(&fftInstance);
if( status == ARM_MATH_SUCCESS)
{
    for(int i = 0; i < 512; i++)
    {
        data_fft[i * 2] = data_pcm[i];
        data_fft[i * 2 + 1] = 0;
    }
    arm_cfft_f32(&fftInstance, data_fft, ifftFlag, doBitReverse);
    arm_cmplx_mag_f32(data_fft, data_fft_mag, 512);
}

int16_t data_pcm[512]; float data_fft[1024]; float data_fft_mag[512]; uint32_t ifftFlag = 0; uint32_t doBitReverse = 1; arm_status status; status = ARM_MATH_SUCCESS; arm_cfft_instance_f32 fftInstance; status=arm_cfft_init_512_f32(&fftInstance); if( status == ARM_MATH_SUCCESS) { for(int i = 0; i < 512; i++) { data_fft[i * 2] = data_pcm[i]; data_fft[i * 2 + 1] = 0; } arm_cfft_f32(&fftInstance, data_fft, ifftFlag, doBitReverse); arm_cmplx_mag_f32(data_fft, data_fft_mag, 512); }

Mavi · ‎2024-03-29

Sorry, my mistake works correctly, the FFT is the input data that is noisy... I apologize for the inconvenience, can someone delete the topic please?