#define vTestPin       0
#define chargePin      13
#define dischargePin   11
#define resistorValue  10000.0F
#define ADC_RES        1024.0F
#define V_HIGH         5

unsigned long startTime;
unsigned long elapsedTime;
float microFarads;
float nanoFarads;

void setup(){
  pinMode(chargePin, OUTPUT);
  digitalWrite(chargePin, LOW);
  Serial.begin(9600);
}

void loop(){
  // ---- Capacitance ----
  // start charging capacitor, and record time
  digitalWrite(chargePin, HIGH);
  startTime = millis();

  // wait for capacitor to charge ~63% (one T = RC)
  while(analogRead(vTestPin) < (ADC_RES * .63)) {
  }

  // T = RC -> C = T / R
  elapsedTime= millis() - startTime;
  microFarads = ((float)elapsedTime / resistorValue) * 1000;
  Serial.print(elapsedTime);
  Serial.print(" mS    ");
  if (microFarads > 1){
    Serial.print((long)microFarads);
    Serial.println(" microFarads");
  }
  else{
    nanoFarads = microFarads * 1000.0;
    Serial.print((long)nanoFarads);
    Serial.println(" nanoFarads");
    delay(500);
  }

  float vx = analogRead(vTestPin) * V_HIGH * ADC_RES;
  Serial.print("vx: ");
  Serial.println(vx);

  float ix = (V_HIGH - vTest) / resistorValue;
    Serial.print("rx: ");
  if( ix > 0) {
    float rx = vx / ix;
    Serial.println(rx);
  }
  Serial.println("infinite!");


  // Allow capacitor to discharge
  digitalWrite(chargePin, LOW);
  pinMode(dischargePin, OUTPUT);
  digitalWrite(dischargePin, LOW);
  while(analogRead(vTestPin) > 0){
  }
  pinMode(dischargePin, INPUT);
}