#include <SPI.h>

// ADC ADS8345 connections
const int CS_PIN = 10; // Chip Select pin for ADS8345
const int ADC_CHANNEL = 2; // Channel 2 for ADS8345

// Calibration values
const int numCalPoints = 5;
float knownSalinities[numCalPoints] = {0.00, 10.00, 20.00, 30.00, 35.00}; // Known salinities in g/L
float rawValues[numCalPoints]; // Raw ADC values for calibration points

// Temperature compensation
float temperature = 25.0; // Default temperature in Celsius

// Function to read ADC value
float readADC(int channel) {
    // Select ADC channel
    digitalWrite(CS_PIN, LOW);
    SPI.transfer(0x80 | (channel << 4));
    uint16_t result = SPI.transfer(0x00) << 8;
    result |= SPI.transfer(0x00);
    digitalWrite(CS_PIN, HIGH);
    
    return result * 5.0 / 65536.0; // Convert ADC value to voltage (assuming 5V reference)
}

// Function to calibrate the electrode
void calibrateElectrode() {
    for (int i = 0; i < numCalPoints; i++) {
        Serial.print("Immerse the electrode in the solution with ");
        Serial.print(knownSalinities[i]);
        Serial.println(" g/L salinity.");
        delay(10000); // Wait for the user to immerse the electrode
        rawValues[i] = readADC(ADC_CHANNEL);
        Serial.print("Calibration value for ");
        Serial.print(knownSalinities[i]);
        Serial.print(" g/L: ");
        Serial.println(rawValues[i]);
    }
}

// Function to calculate salinity using linear interpolation
float calculateSalinity(float rawValue, float temp) {
    // Find the two calibration points surrounding the raw value
    float salinity = 0.0;
    for (int i = 0; i < numCalPoints - 1; i++) {
        if (rawValue >= rawValues[i] && rawValue <= rawValues[i + 1]) {
            // Linear interpolation
            salinity = (rawValue - rawValues[i]) * (knownSalinities[i + 1] - knownSalinities[i]) / (rawValues[i + 1] - rawValues[i]) + knownSalinities[i];
            break;
        }
    }

    // Temperature compensation (using a simple linear model)
    float tempCoefficient = 0.02; // Change this coefficient based on your electrode's characteristics
    salinity *= 1.0 + tempCoefficient * (temp - 25.0);
    
    return salinity;
}

void setup() {
    Serial.begin(9600);
    SPI.begin();
    pinMode(CS_PIN, OUTPUT);
    digitalWrite(CS_PIN, HIGH);
    
    calibrateElectrode();
}

void loop() {
    float rawValue = readADC(ADC_CHANNEL);
    float salinity = calculateSalinity(rawValue, temperature);
    
    Serial.print("Raw ADC value: ");
    Serial.print(rawValue);
    Serial.print(", Salinity: ");
    Serial.print(salinity);
    Serial.println(" g/L");
    
    delay(1000); // Read every second
}
