#include <avr/io.h>

const int dataSamp = 200;

void setup() {
  // setup for leads off detection LO +, LO -
  PORTB = (0<<PB3)|(0<<PB2);
  DDRB = (0<<PB3)|(0<<PB2);
  // setup ADC
  ADMUX = (0<<REFS1)|(0<<REFS0)|(0<<MUX3)|(0<<MUX2)|(0<<MUX1)|(0<<MUX0);
  ADCSRA = (1<<ADEN)|(1<<ADSC)|(1<<ADPS2)|(0<<ADPS1)|(0<<ADPS0);
  DIDR0 = (1<<ADC0D);
  // initialize the serial communication
  UBRR0L = 103;
  UBRR0H = 0;
  UCSR0B = (1<<RXEN0)|(1<<TXEN0);
  UCSR0C = (0<<UMSEL01)|(0<<UMSEL00)|(0<<UPM01)|(0<<UPM00)|(0<<USBS0)|(3<<UCSZ00);
}

void loop() {
  int analogBuffer[dataSamp];
  unsigned long timeBuffer[dataSamp];
  
  // sampling the ECG signal and saving it in buffer
  for (int i = 0; i < dataSamp; i++)
  {
    if ((PINB & (1<<PINB2)) || (PINB & (1<<PINB3)))
      analogBuffer[i] = '!';
    else
      analogBuffer[i] = analogRead(A0);
    
    timeBuffer[i] = micros(); // timestamp
  }
  // then sending saved data for processing in csv format
  for (int i = 0; i < dataSamp; i++)
  {
    Serial.print(timeBuffer[i]);
    Serial.print(",");
    Serial.println(analogBuffer[i]);
  }
}