int N=0,freq=0;
float Re=0,Im=0,Xk[100],Xn[100];
long time1=0;
int analogPin = A1;

void setup() 
{
  Serial.begin(57600);
  Serial.print("system starts now...");
  Serial.print("\n");

}

void loop() 
{
   if (Serial.available() > 0) 
  {
  Serial.print("insert your frequency: ");
  Serial.print("\n");
  delay(1000);
  freq = Serial.parseInt();
  Serial.print("insert your number of Samples: ");
  Serial.print("\n");
  delay(1000);
  N= Serial.parseInt();
  }
  if (N!=0)
  {
    for (int n=0;n<N;n++)
    {
      Xn[n]=analogRead(analogPin);
      delay(1000/(freq));
    } 

  for (int i=0;i<100;i++)
  {
    Serial.print(Xn[i]*5/1024);
    Serial.print("\n");
  }
  Serial.print("\n\n\n");

  //FFT
 for (int k=0;k<N;k++)
 {
  Re=0;
  Im=0;
  for (int n=0;n<N;n++)
  {
    Re=Re+Xn[n]*cos(2*M_PI*k*n/N);
    Im=Im+Xn[n]*sin(2*M_PI*k*n/N);
  }
  Xk[k]=sqrt(Re*Re+Im*Im);
 }
  for (int k=0;k<N;k++)
  {
    Serial.print(Xk[k]);
    Serial.print("\n");
  }
  N=0;
  }
}