Hi folks,

I have a question about ArduinoFFT.h. I use it on a perfect sine wave sampled with 32*Fb the base frequency of 60Hz with no DC component and no harmonics. The array vReal[SAMPLES] is loaded with the 32 values, one sine cycle period I have generated in excel. The FFT seems to see a DC component in the Bin0 and harmonic in Bin2. Neither are the amplitudes right. The signal has a peak of 165 and the FFT calculates a peak of 1374 at bin 1 =60Hz and second harmonic at 120Hz at Bin2 with and amplitude of 620?

The same FFT in excel with the same data produces correct results.

Is there a problem with ArduinoFFT.h or am I missing something here. Anyone that give me a helping hand?

```
#include <Arduino.h>
#include <arduinoFFT.h>
#define SAMPLES 32 //Must be a power of 2
#define SAMPLING_FREQUENCY 1920 //Hz, must be less than 10000 due to ADC
arduinoFFT FFT = arduinoFFT();
unsigned int sampling_period_us;
unsigned long microseconds;
double vReal[SAMPLES]={
0.0000 ,
32.1899 ,
63.1428 ,
91.6691 ,
116.6726 ,
137.1925 ,
152.4401 ,
161.8296 ,
165.0000 ,
161.8296 ,
152.4401 ,
137.1925 ,
116.6726 ,
91.6691 ,
63.1428 ,
32.1899 ,
0.0000 ,
-32.1899 ,
-63.1428 ,
-91.6691 ,
-116.6726 ,
-137.1925 ,
-152.4401 ,
-161.8296 ,
-165.0000 ,
-161.8296 ,
-152.4401 ,
-137.1925 ,
-116.6726 ,
-91.6691 ,
-63.1428 ,
-32.1899
};
double vImag[SAMPLES];
void setup() {
Serial.begin(115200);
sampling_period_us = round(1000000.0/SAMPLING_FREQUENCY);
}
void loop() {
/*SAMPLING*/
// for(int i=0; i<SAMPLES; i++)
// {
// microseconds = micros(); //Overflows after around 70 minutes!
// vReal[i] = analogRead(A0);
// vReal[i] -= 511;
// vImag[i] = 0;
// while(micros() < (microseconds + sampling_period_us)){
// }
// }
for (int i=0; i<SAMPLES;i++) { Serial.print(vReal[i], 1); Serial.print("\n"); }
Serial.print("\n");
/*FFT*/
FFT.Windowing(vReal, SAMPLES, FFT_WIN_TYP_HAMMING, FFT_FORWARD);
FFT.Compute(vReal, vImag, SAMPLES, FFT_FORWARD);
FFT.ComplexToMagnitude(vReal, vImag, SAMPLES);
double peak = FFT.MajorPeak(vReal, SAMPLES, SAMPLING_FREQUENCY);
/*PRINT RESULTS*/
Serial.println(peak); Serial.println("\n"); //Print out what frequency is the most dominant.
for(int i=0; i<(SAMPLES/2); i++)
{
/*View all these three lines in serial terminal to see which frequencies has which amplitudes*/
//Serial.print((i * 1.0 * SAMPLING_FREQUENCY) / SAMPLES, 1);
//Serial.print(" ");
Serial.println(vReal[i], 1); //View only this line in serial plotter to visualize the bins
}
//delay(1000); //Repeat the process every second OR:
while(1); //Run code once
}
```