Capacitometro

const int OUT_PIN = A2;
const int IN_PIN = A0;
const float IN_STRAY_CAP_TO_GND = 24.48;
const float IN_CAP_TO_GND  = IN_STRAY_CAP_TO_GND;
const float R_PULLUP = 34.8; 
const int MAX_ADC_VALUE = 1023;

void setup()
{
  pinMode(OUT_PIN, OUTPUT);
  pinMode(IN_PIN, OUTPUT);
  Serial.begin(9600);
}

void loop()
{
    pinMode(IN_PIN, INPUT);
    digitalWrite(OUT_PIN, HIGH);
    int val = analogRead(IN_PIN);
    digitalWrite(OUT_PIN, LOW);

    if (val < 1000){
      pinMode(IN_PIN, OUTPUT);
      float capacitance = (float)val * IN_CAP_TO_GND / (float)(MAX_ADC_VALUE - val);

      Serial.print(F("C= "));
      Serial.print(capacitance, 3);
      Serial.println(F(" pF"));
      //Serial.print(val);
      //Serial.println(F(") "));
      }
 
      else{
      pinMode(IN_PIN, OUTPUT);
      delay(1);
      pinMode(OUT_PIN, INPUT_PULLUP);
      unsigned long u1 = micros();
      unsigned long t;
      int digVal;

      do{
        digVal = digitalRead(OUT_PIN);
        unsigned long u2 = micros();
        t = u2 > u1 ? u2 - u1 : u1 - u2;
        }
     
      while ((digVal < 1) && (t < 400000L));

      pinMode(OUT_PIN, INPUT); 
      val = analogRead(OUT_PIN);
      digitalWrite(IN_PIN, HIGH);
      int dischargeTime = (int)(t / 1000L) * 5;
      delay(dischargeTime);  
      pinMode(OUT_PIN, OUTPUT); 
      digitalWrite(OUT_PIN, LOW);
      digitalWrite(IN_PIN, LOW);

      float capacitance = -(float)t / R_PULLUP / log(1.0 - (float)val / (float)MAX_ADC_VALUE);

      Serial.print(F("C= "));
      if (capacitance > 1000.0){
        Serial.print(capacitance / 1000.0, 2);
        Serial.println(F(" uF"));
      }
      else{
        Serial.print(capacitance, 2);
        Serial.println(F(" nF"));
      }
      }
    while (millis() % 80 != 0);     
}