#include <Arduino.h>
#include <cfloat>  // Include this to use FLT_MAX

// Define the multiplexer control pins
#define S0 32
#define S1 33
#define S2 25
#define S3 26

// Define the multiplexer SIG pin connected to the ADC
#define SIG_PIN 34

// Reference resistors array (values in ohms)
const float referenceResistors[16] = {100, 220, 330, 470, 560, 680, 820, 1000, 1200, 1500, 1800, 2200, 2700, 3300, 3900, 4700};

// Function to set the multiplexer channel
void setMuxChannel(byte channel) {
  digitalWrite(S0, channel & 0x01);
  digitalWrite(S1, (channel >> 1) & 0x01);
  digitalWrite(S2, (channel >> 2) & 0x01);
  digitalWrite(S3, (channel >> 3) & 0x01);
}

void setup() {
  // Initialize serial communication
  Serial.begin(115200);

  // Set multiplexer control pins as output
  pinMode(S0, OUTPUT);
  pinMode(S1, OUTPUT);
  pinMode(S2, OUTPUT);
  pinMode(S3, OUTPUT);

  // Set the ADC pin
  pinMode(SIG_PIN, INPUT);

  // Ensure the multiplexer is enabled by connecting EN to GND
  // Assuming EN is connected to GND directly
  // Set all multiplexer channels to low initially
  setMuxChannel(0);
}

void loop() {
  float measuredVoltage;
  float unknownResistance;
  float closestReference = referenceResistors[0];
  float minDifference = FLT_MAX;

  // Loop through all reference resistors
  for (byte i = 0; i < 16; i++) {
    setMuxChannel(i);
    delay(50);  // Allow time for the multiplexer to switch

    // Read the voltage from the ADC
    int adcValue = analogRead(SIG_PIN);
    measuredVoltage = (adcValue / 4095.0) * 3.3;  // Assuming a 3.3V ADC reference voltage

    // Calculate the resistance
    if (measuredVoltage != 0) {
      unknownResistance = referenceResistors[i] * ((3.3 / measuredVoltage) - 1);
    } else {
      unknownResistance = FLT_MAX;  // Avoid division by zero
    }

    // Debug prints to troubleshoot
    Serial.print("Channel: ");
    Serial.print(i);
    Serial.print(" (S0=");
    Serial.print(digitalRead(S0));
    Serial.print(", S1=");
    Serial.print(digitalRead(S1));
    Serial.print(", S2=");
    Serial.print(digitalRead(S2));
    Serial.print(", S3=");
    Serial.print(digitalRead(S3));
    Serial.print("), Ref Resistor: ");
    Serial.print(referenceResistors[i]);
    Serial.print(", ADC Value: ");
    Serial.print(adcValue);
    Serial.print(", Measured Voltage: ");
    Serial.print(measuredVoltage);
    Serial.print(", Calculated Resistance: ");
    Serial.println(unknownResistance);

    // Find the closest reference resistor
    float difference = fabs(unknownResistance - referenceResistors[i]);
    if (difference < minDifference) {
      minDifference = difference;
      closestReference = referenceResistors[i];
    }
  }

  // Print the closest reference resistor value
  Serial.print("Closest Reference Resistor: ");
  Serial.print(closestReference);
  Serial.print(" Ohms, Min Difference: ");
  Serial.print(minDifference);
  Serial.print(" Ohms, Calculated Resistance: ");
  Serial.print(unknownResistance);
  Serial.println(" Ohms");

  delay(1000);  // Delay for readability
}