Build a Machine project – voltage rectifier and integrator

//
// machine.ino - voltage rectifier and integrator circuit
// for the DT009/1 EEPP build-a-machine project
// Written by Ted Burke, 11-2-2019
//

unsigned long t_start, t1, t2;
int n;

void setup()
{
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);

  Serial.begin(9600);

  for(n=0 ; n<3 ; ++n)
  {
    digitalWrite(3, HIGH);
    delay(200);
    digitalWrite(3, LOW);
    delay(800);
  }

  for(n=0 ; n<25 ; ++n)
  {
    digitalWrite(3, HIGH);
    delay(20);
    digitalWrite(3, LOW);
    delay(20);
  }

  digitalWrite(2, HIGH);
  digitalWrite(3, LOW);

  t_start = micros();
  t1 = t_start;
  t2 = t_start;
}

void loop()
{
  int v1, v2, v_rect;
  double Vs = 0;

  while(1)
  {
    v1 = analogRead(6);
    v2 = analogRead(7);
  
    v_rect = v1 > v2 ? v1 : v2;
  
    t2 = micros();  
    Vs += (t2 - t1) * 1e-6 * v_rect * (5.0 / 1023.0);
    t1 = t2;
  
    //Serial.print("0 1024 ");
    Serial.print(v1);
    Serial.print(" ");
    Serial.print(v2);
    Serial.print(" ");
    Serial.print(v_rect);  
    Serial.print(" ");
    Serial.println(Vs);

    if (t2 - t_start > 10000000L) break;
  }

  digitalWrite(2, LOW);
  for(n=0 ; n<75 ; ++n)
  {
    digitalWrite(3, HIGH);
    delay(20);
    digitalWrite(3, LOW);
    delay(20);
  }

  while(1)
  {
    Serial.print("Integrated output voltage = ");
    Serial.print(Vs);
    Serial.println(" Vs");
    digitalWrite(3, HIGH);
    delay(200);
    digitalWrite(3, LOW);
    delay(800);
  }
}