I am a beginner in Arduino, coding, and electrical engineering (learning on my own time) and am working on creating an EEG. I've got the hardware down and have managed to get numerical data output from the analog (A0) of Arduino. The next step is transforming these numbers to outputting dominant frequency and I have managed to find a code that uses FFT to find the dominant frequency from the input of A0. The following is the code:
#include "arduinoFFT.h"
#define SAMPLES 128 //Must be a power of 2
#define SAMPLING_FREQUENCY 1000 //Hz, must be less than 10000 due to ADC
arduinoFFT FFT = arduinoFFT();
unsigned int sampling_period_us;
unsigned long microseconds;
double vReal[SAMPLES];
double vImag[SAMPLES];
void setup() {
Serial.begin(115200);
sampling_period_us = round(1000000*(1.0/SAMPLING_FREQUENCY));
}
void loop() {
/*SAMPLING*/
for(int i=0; i<SAMPLES; i++)
{
microseconds = micros(); //Overflows after around 70 minutes!
vReal[i] = analogRead(0);
vImag[i] = 0;
while(micros() < (microseconds + sampling_period_us)){
}
}
/*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); //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
}
The problem I have is with the line microseconds = micros(). The comment state that this will overflow after 70 minutes and after some days of research, I sorta understand what is meant by this. However, I need this program to run over 9 hours, so I can log the dominant frequency of the brainwave throughout the night. Is that possible?