/*
  Aircraft Cabin Pressure Monitoring and Automated Relief System
  Target: STM32F103C8T6 "Blue Pill" (Wokwi)
  Peripherals: ADC, TIM2 (Timer+Interrupt), UART, PWM (servo), I2C (LCD)
  Three-tier severity indication:
    Normal   - LED off, buzzer silent
    Caution  - LED blinking (gradual pressure drop)
    Emergency- Buzzer sounding (rapid decompression)
*/

#include <Servo.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

const int pressurePin   = PA0;
const int ledPin        = PB0;
const int buzzerPin     = PB1;
const int valveServoPin = PA6;

HardwareTimer *sampleTimer;
volatile bool sampleFlag = false;

Servo valveServo;
LiquidCrystal_I2C lcd(0x27, 16, 2);  // SDA=PB7, SCL=PB6 (this board's default I2C1 pins)

float previousPressure = 1013.0;
bool ledBlinkState = false;

const float RATE_EMERGENCY_THRESHOLD = -100.0;

void onTimerTick(void) {
  sampleFlag = true;
}

void setup() {
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);
  pinMode(buzzerPin, OUTPUT);
  digitalWrite(ledPin, LOW);
  noTone(buzzerPin);

  valveServo.attach(valveServoPin);
  valveServo.write(0);

  Wire.begin();
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Cabin Pressure");
  lcd.setCursor(0, 1);
  lcd.print("Booting...");

  Serial.println("Cabin Pressure Monitoring System - Boot OK");

  //sampleTimer = new HardwareTimer(TIM2);
  //sampleTimer->setOverflow(500000, MICROSEC_FORMAT);
  //sampleTimer->attachInterrupt(onTimerTick);
  //sampleTimer->resume();
}

void loop() {
  if (sampleFlag) {
    sampleFlag = false;

    int rawPressure = analogRead(pressurePin);
    float pressure = 600.0 + (rawPressure / 1023.0) * (1013.0 - 600.0);

    float rate = (pressure - previousPressure) / 0.5;
    previousPressure = pressure;
    bool rapidDrop = (rate < RATE_EMERGENCY_THRESHOLD);
    bool belowThreshold = (pressure < 750.0);

    Serial.print("Pressure: ");
    Serial.print((int)pressure);
    Serial.print(" hPa | Rate: ");
    Serial.print((int)rate);
    Serial.println(" hPa/s");

    // --- Proportional valve control ---
    float openFraction = (750.0 - pressure) / (750.0 - 600.0);
    openFraction = constrain(openFraction, 0.0, 1.0);
    int valveAngle = (int)(openFraction * 90.0);
    if (rapidDrop) {
      valveAngle = 90;
    }
    valveServo.write(valveAngle);

    // --- Three-tier severity: LED = caution, buzzer = emergency ---
    const char* statusText;

    if (rapidDrop) {
      digitalWrite(ledPin, LOW);
      ledBlinkState = false;
      tone(buzzerPin, 2000);
      Serial.println("EMERGENCY: RAPID DECOMPRESSION DETECTED!");
      statusText = "EMERGENCY!";
    } else if (belowThreshold) {
      ledBlinkState = !ledBlinkState;
      digitalWrite(ledPin, ledBlinkState ? HIGH : LOW);
      noTone(buzzerPin);
      Serial.println("CAUTION: CABIN PRESSURE LOW!");
      statusText = "CAUTION: LOW";
    } else {
      ledBlinkState = false;
      digitalWrite(ledPin, LOW);
      noTone(buzzerPin);
      statusText = "Status: Normal";
    }

    Serial.print("Valve angle: ");
    Serial.print(valveAngle);
    Serial.println(" deg");

    // --- LCD status ---
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("P: ");
    lcd.print((int)pressure);
    lcd.print(" hPa");
    lcd.setCursor(0, 1);
    lcd.print(statusText);
  }
}