PaciSense_Arduino_Code

// Pin Definitions
#define RX_PIN 5             // UART Receive pin for pH probe
#define TX_PIN 4             // UART Transmit pin for pH probe
#define RED_LED_PIN 6        // Red LED for high acidity warning
#define GREEN_LED_PIN 7      // Green LED for normal pH
#define THERMISTOR_PIN A0    // Analog pin for thermistor input
#define THRESHOLD_TEMP 30.0  // Temperature threshold in °C for activation
#define PH_THRESHOLD 5.5     // pH threshold for ECC risk

// Timing Variables
unsigned long samplingDuration = 0;  // Total accumulated sampling time
unsigned long totalAcidicTime = 0;   // Time spent below pH threshold
unsigned long totalNeutralTime = 0;  // Time spent above pH threshold
unsigned long lastSamplingTime = 0;  // Last recorded time for sampling
bool samplingEnabled = false;        // Tracks if sampling is active
bool intervalComplete = false;       // Tracks if the 1-minute interval is complete
bool ledStateSet = false;            // Tracks if LED state has been updated

void setup() {
  // Initialize Serial communication for debugging
  Serial.begin(9600);
  Serial1.begin(9600, SERIAL_8N1, RX_PIN, TX_PIN);

  // Initialize pins
  pinMode(RED_LED_PIN, OUTPUT);
  pinMode(GREEN_LED_PIN, OUTPUT);
  pinMode(THERMISTOR_PIN, INPUT);

  // Ensure LEDs are off initially
  digitalWrite(RED_LED_PIN, LOW);
  digitalWrite(GREEN_LED_PIN, LOW);

  // Serial Monitor Header
  Serial.println("Time (s),pH,Threshold,Temperature (°C)");

  Serial.println("System Initialized. Place the device in the mouth to activate.");
}

void loop() {
  unsigned long currentMillis = millis();

  // Read temperature from thermistor
  float temperature = readThermistor();
  Serial.print("Temperature: ");
  Serial.print(temperature);
  Serial.println(" °C");

  // Check if the device is in the mouth (temperature above threshold)
  if (temperature >= THRESHOLD_TEMP) {
    if (!samplingEnabled) {
      samplingEnabled = true;
      Serial.println("Device activated: Sampling Enabled");
    }
  } else {
    if (samplingEnabled) {
      samplingEnabled = false;
      Serial.println("Device removed: Sampling Paused");
    }
    delay(500); // Debounce delay
    return;
  }

  // Perform sampling only when activated
  if (samplingEnabled && !intervalComplete) {
    // Increment accumulated sampling time
    samplingDuration += currentMillis - lastSamplingTime;

    // Request pH reading
    Serial1.print("R\r");
    delay(500);

    // Read the pH response
    String response = "";
    while (Serial1.available()) {
      response += (char)Serial1.read();
    }

    if (response.length() > 0 && isdigit(response[0])) {
      float pH = response.toFloat();

      // Output data to Serial Monitor
      Serial.print(samplingDuration / 1000.0); // Time in seconds
      Serial.print(",");
      Serial.print(pH);                        // pH value
      Serial.print(",");
      Serial.print(PH_THRESHOLD);              // Threshold line for Serial Plotter
      Serial.print(",");
      Serial.println(temperature);             // Current temperature

      // Track time spent above or below pH threshold
      if (pH < PH_THRESHOLD) {
        totalAcidicTime += currentMillis - lastSamplingTime;
      } else {
        totalNeutralTime += currentMillis - lastSamplingTime;
      }
    }

    // Check if the 1-minute interval is complete
    if (samplingDuration >= 60000) {
      intervalComplete = true;

      // Calculate results
      float totalTime = totalAcidicTime + totalNeutralTime;
      float acidicPercentage = 0.0;

      if (totalTime > 0) {  // Avoid division by zero
        acidicPercentage = (float)totalAcidicTime / totalTime * 100.0;
      }

      Serial.print("Acidic Percentage: ");
      Serial.print(acidicPercentage);
      Serial.println("%");

      // Determine LED state
      if (acidicPercentage >= 25.0) {
        digitalWrite(RED_LED_PIN, HIGH);  // Turn Red LED ON
        digitalWrite(GREEN_LED_PIN, LOW);
        Serial.println("1 Minute Complete: LED RED (Acidic)");
      } else {
        digitalWrite(RED_LED_PIN, LOW);
        digitalWrite(GREEN_LED_PIN, HIGH);  // Turn Green LED ON
        Serial.println("1 Minute Complete: LED GREEN (Neutral)");
      }

      // Set LED state and reset for the next interval
      ledStateSet = true;
      delay(10000); // Hold LED state for 10 seconds
      resetInterval();
    }
  }

  // Update the last sampling time
  lastSamplingTime = currentMillis;
}

// Function to read temperature from the thermistor
float readThermistor() {
  int analogValue = analogRead(THERMISTOR_PIN);
  float resistance = (1023.0 / analogValue) - 1.0;  // Convert to resistance
  resistance = 10000.0 / resistance;               // 10kΩ reference resistor

  // Use the Steinhart-Hart equation to convert resistance to temperature
  float steinhart;
  steinhart = resistance / 10000.0;       // (R/R0)
  steinhart = log(steinhart);             // ln(R/R0)
  steinhart /= 3950.0;                    // 1/Beta * ln(R/R0)
  steinhart += 1.0 / (25 + 273.15);       // + (1/T0)
  steinhart = 1.0 / steinhart;            // Invert
  steinhart -= 273.15;                    // Convert to Celsius

  return steinhart;
}

// Function to reset variables for the next interval
void resetInterval() {
  samplingDuration = 0;
  totalAcidicTime = 0;
  totalNeutralTime = 0;
  intervalComplete = false;
  ledStateSet = false;
  Serial.println("Ready for next interval.");
}