#define vTestPin       0
#define chargePin      13
#define dischargePin   11
#define resistorValue  10000.0F
#define ADC_RES        1023.0F
#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)
  // if it takes more than 2 seconds, assume it's not a capacitor
  while (true) {
    float charge = analogRead(vTestPin);
    elapsedTime = millis() - startTime;
    if (charge > (ADC_RES * .63)) {
      microFarads = ((float)elapsedTime / resistorValue) * 1000;
      break;
    }
    if (elapsedTime > 2000) {
      microFarads = 0;
      break;
    }
  }

  // ---- Resistance ----
  float vx = analogRead(vTestPin) * V_HIGH / ADC_RES;

  float ix = (V_HIGH - vx) / resistorValue;
  float rx = -1; // If this isn't overwritten, we have an open circuit
  if ( ix > 0) {
    float rx = vx / ix;
  }

  // If this was a capacitor, print its capacitance
  if ((microFarads > 0.1) && (microFarads < 30)) {
    Serial.println("The electronic component is a capacitor");

    // If it can be printed in microfarads, do so
    if (microFarads > 1) {
      Serial.print((long)microFarads);
      Serial.println(" microFarads is the value of the capacitor and");

      if (microFarads > 10) {
        Serial.println("falls into the category HIGH");
      }
      else {
        Serial.println("falls into the category MEDIUM");
      }
    }

    // Otherwise print in nanofarads
    else {
      nanoFarads = microFarads * 1000.0;
      Serial.print((long)nanoFarads);
      Serial.println(" nanoFarads is the value of the capacitor and falls into the category LOW");
    }
    delay(1600);
  }
  // If this was a resistor, print its resistance
  else if (rx > 0) {
    Serial.println("The electronic component is a resistor");
    Serial.print(rx);
    Serial.println(" ohms is the value of the resistor");
  }
  else {
    Serial.println("Insert component");
  }


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