Apply FFT on a Real Time signal

Projects Programming
1

Hi everyone, I'm trying to do a Timegrapher and I want to analyse the output samples[n].
I'm trying to apply the FFT on the output before printing it, without success. Any help will be welcome.
Thanks in advance.

#include <SPI.h>    
#define SS 5   

int16_t* samples;
uint32_t n = 0;
int count = 0;
unsigned long start_time;
unsigned long end_time;
const unsigned long event = 10000;
const uint32_t max_samples=50000;

void setup() {
  Serial.begin(115200);                     /* initialization of serial communication */
  SPI.begin();                            /* initialization of SPI port */
  SPI.setDataMode(SPI_MODE0);             /* configuration of SPI communication in mode 0 */
  SPI.setClockDivider(SPI_CLOCK_DIV64);   /* configuration of clock at 1MHz */
  pinMode(SS, OUTPUT);
  Serial.println("Start");
  
  samples = (int16_t*)malloc(sizeof(int16_t)*max_samples);
  if(samples == NULL){
      Serial.print("insufficient memory");
    }
    else{
      Serial.print("malloc ok.");   
    }
}

void loop() {
  start_time = millis();
  for (n=0; n<max_samples; n++)
  {
    samples[n] = Sound();
  }
  end_time = millis();
  Serial.print("Dauer [ms]: ");
  Serial.print((end_time-start_time));
  Serial.print(" ||| ");
  Serial.print("Beats: ");
  Serial.print(n);
  Serial.println(" ||| ");
  for (n = 0; n < max_samples; n++)
  {
    Serial.print(samples[n]);
    //Serial.print(",-35000,35000");
    Serial.println();
  }
}


int16_t Sound(void) {
  digitalWrite(SS, LOW);                                        //activate chip select
  int sound = SPI.transfer(0) | (SPI.transfer(0) << 8);         //reconstruct 12-bit data
  digitalWrite(SS, HIGH);                                       //deactivate chip select
  return sound;
}
2

Not in the posted code.

What is connected to the SPI pins?

3

the Mic, for real time input

4

Does the microphone input work as you expect?

What Arduino do you have? Most have very limited memory.

const uint32_t max_samples=50000;
5

yes the mic (Pmod MIC3) work as expected, I'm using ESP32

6

Try the Arduino_FFT library, starting with the library examples.

7

That's the point Remington, I really don't know how to use those examples on my case

8

The examples should run "out of the box". You collect some data, and transform it.

What is it that you don't understand?