#include <Arduino.h>

const int vinPin = A5; // Analog input pin for voltage measurement
const float referenceVoltage = 5.0; // Voltage reference (5V)
const float resistors[] = {10000.0, 1000.0, 100.0}; // Array of reference resistor values
const int numResistors = sizeof(resistors) / sizeof(resistors[0]); // Number of reference resistors

void setup() {
  Serial.begin(9600); // Start serial communication
}

void loop() {
  for (int i = 0; i < numResistors; i++) {
    float resistance = measureResistance(resistors[i]);
    if (resistance > 0.0) {
      Serial.print("Resistance: ");
      Serial.print(resistance);
      Serial.print(" Ohms (using ");
      Serial.print(resistors[i]);
      Serial.println(" ohm reference)");
      break; // Stop loop after finding valid measurement
    }
  }
  delay(1000); // Delay between measurements
}

float measureResistance(float referenceResistor) {
  // Read voltage from analog input pin
 //int analogValue = analogRead(vinPin);
  int analogValue = 100;

  // Calculate voltage based on reference voltage and resolution
  float voltage = (analogValue / 1023.0) * referenceVoltage;

  // Check if voltage is within valid range for this reference resistor
  if (voltage < 0.1 || voltage > 4.9) {
    return 0.0; // Invalid measurement, return 0
  }

  // Calculate resistance using voltage divider formula
  return referenceResistor * (referenceVoltage - voltage) / voltage;
}