ARDUINO - Capacimetro pF nF uF

//Capacimetro Digital
//Desde 0.000pF hasta 1000uF
const int OUT_PIN = A4;
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("Capacitor = ");
      Serial.print(capacitance, 3);// for the best precision
      Serial.println("pF ");
   }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("Capacitor =");
      if(capacitance > 1000.0){
         Serial.print(capacitance / 1000.0, 2);
         Serial.println("uF ");
      }else{
         Serial.print(capacitance, 2);
         Serial.println("nF ");
      }
      while (millis() % 1000 != 0);
   }
}