Question
CMSIS DSP CFFT incorrect frequency analysis
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);
}