#include <math.h>
int pinA = 4;  // First digital pin (Most Significant Bit)
int pinB = 5;  // Second digital pin
int pinC = 6;  // Third digital pin
int pinD = 7;  // Fourth digital pin (Least Significant Bit)
int value;
const int analogPin = A0;     // Analog pin to read data
const int numChannels = 4;   // Total number of channels
int analogValues[numChannels]; // Array to store analog values

float tdsValue;
float phValue;
float turbidityValue;

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

  // Initialize pins
  pinMode(pinA, OUTPUT);
  pinMode(pinB, OUTPUT);
  pinMode(pinC, OUTPUT);
  pinMode(pinD, OUTPUT);
}

void loop() {
  // Read and store analog values for all channels
  for (int a = 0; a < numChannels; a++) {
    value = a;

    // Convert the value to binary and output to the pins
    digitalWrite(pinA, bitRead(value, 0)); // Most significant bit
    digitalWrite(pinB, bitRead(value, 1));
    digitalWrite(pinC, bitRead(value, 2));
    digitalWrite(pinD, bitRead(value, 3)); // Least significant bit

    delay(1000); // Allow the analog multiplexer to stabilize

    // Read the analog value and store it in the array
    analogValues[a] = analogRead(analogPin);
  }

  // Assign sensor values
  int pHvoltage = analogValues[0];
  int tdsvoltage = analogValues[1];
  int turbidityvoltage = analogValues[2];

  // Calculate sensor values
  phValue = pH_Calculet(pHvoltage);
  tdsValue = tds_calculet(tdsvoltage);
  turbidityValue = turbidity_calculet(turbidityvoltage);

  // Print sensor values
  Serial.print("pH: ");  
  Serial.println(phValue, 2);
  Serial.print("TDS: ");  
  Serial.print(tdsValue, 2);
  Serial.println(" ppm");
  Serial.print("Turbidity: ");
  Serial.print(turbidityValue, 2);
  Serial.println(" NTU");
  delay(1000); // Add delay to make readings human-readable
}

float pH_Calculet(int pHvoltage) {
  long sensorSum = 0;  // Initialize the sum
  for (int m = 0; m < 50; m++) {
    sensorSum += pHvoltage; // Accumulate pH voltage readings
  }
  float sensorValue = sensorSum / 50.0;  // Calculate the average
  float phValue = 7 - (1000 * (sensorValue - 372) * 4.98 / 59.16 / 1023);
  return phValue;
}

float tds_calculet(int tdsvoltage) {
  float Voltage = tdsvoltage * 5.0 / 1023.0; // Convert analog reading to Voltage
  float tdsValue = (133.42 * Voltage * Voltage * Voltage - 255.86 * Voltage * Voltage + 857.39 * Voltage) * 0.5; // TDS formula
  return tdsValue;
}

float turbidity_calculet(int turbidityvoltage) { 
  float volt = 0;
  for (int i = 0; i < 800; i++) {
    volt += (float)turbidityvoltage / 1023 * 5.0;
  }
  volt = volt / 800;  // Calculate the average voltage
  volt = round_to_dp(volt, 2);  // Round to 2 decimal places
  if (volt < 2.5) {
    turbidityValue = 3000;  // High turbidity case
  } else {
    turbidityValue = -1120.4 * (volt * volt) + 5742.3 * volt - 4353.8;  // Turbidity formula
  }
  return turbidityValue;
}

float round_to_dp(float in_value, int decimal_place) {
  float multiplier = pow(10.0, decimal_place);
  return round(in_value * multiplier) / multiplier;
}