/**
 * LF Inverter/UPS Firmware - Arduino Nano
 * V1.2.12-CHG (Integrated Synchronous Charger)
 * Logic: Unipolar Switching / Synchronous Buck Charging
 * Author: MNG proSystems South Africa
 */

#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <math.h>
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/pgmspace.h>

// ================= PINS CONFIGURATION =================
#define PIN_HI_LEFT   9   // OC1A (PWM)
#define PIN_HI_RIGHT 10   // OC1B (PWM)
#define PIN_LO_LEFT   7   // Steering
#define PIN_LO_RIGHT  8   // Steering
#define PIN_BAT_V    A2
#define PIN_AC_OUT   A6
#define PIN_SHUNT    A1   // 30A Shunt
#define PIN_NTC      A3   // 10k NTC
#define PIN_AC_IN    A0   // Analog Input
#define PIN_ZC       2    // Zero Cross (Moved to D2 for INT0)
#define PIN_RELAY    4    // Transfer Relay
#define PIN_FAN      6    // PWM Fan
#define PIN_BUZZER   5

// ================= CONSTANTS =================
#define ICR_MAX      639  // TOP for 25kHz
const int sineTable[] PROGMEM = {
  0, 20, 40, 60, 80, 100, 120, 139, 159, 178, 197, 216, 235, 253, 271, 289, 
  307, 324, 341, 357, 373, 389, 404, 419, 434, 448, 461, 475, 487, 500, 511, 522, 
  533, 543, 552, 561, 569, 577, 584, 591, 597, 603, 608, 612, 616, 620, 623, 625, 
  627, 628, 629, 628, 627, 625, 623, 620, 616, 612, 608, 603, 597, 591, 584, 577, 
  569, 561, 552, 543, 533, 522, 511, 500, 487, 475, 461, 448, 434, 419, 404, 389, 
  373, 357, 341, 324, 307, 289, 271, 253, 235, 216, 197, 178, 159, 139, 120, 100, 
  80, 60, 40, 20
};

// ================= SYSTEM VARIABLES =================
enum ChargeStage { BULK, ABSORPTION, FLOAT, OFF };
ChargeStage chargeState = OFF;
enum SysState { ST_CHECK_START, ST_SOFT_START, ST_INVERTER, ST_GRID_WAIT, ST_UPS_CHARGE, ST_ERROR };
SysState currentState = ST_CHECK_START;

volatile int sineIndex = 0;
volatile bool spwmEnabled = false;
volatile float modulationIndex = 0.0;
volatile int chargePWM = 0; // Duty cycle for charging

float batVolts = 0.0, acOutVolts = 0.0, acInVolts = 0.0;
float loadAmps = 0.0, loadWatts = 0.0, temperature = 0.0;

const float BULK_VOLTAGE = 14.4, FLOAT_VOLTAGE = 13.7;
const float CHG_CURRENT_LIMIT = 15.0; // Max Charging Amps
bool chargingActive = false;

unsigned long stateTimer = 0, softStartTimer = 0, lastScreenUpdate = 0;
const int AC_MIN = 180, AC_MAX = 260, MAX_LOAD_WATTS = 2000;

LiquidCrystal_I2C lcd(0x27, 20, 4);

// ================= SETUP =================
void setup() {
  Serial.begin(115200);
  pinMode(PIN_HI_LEFT, OUTPUT); pinMode(PIN_HI_RIGHT, OUTPUT);
  pinMode(PIN_LO_LEFT, OUTPUT); pinMode(PIN_LO_RIGHT, OUTPUT);
  pinMode(PIN_RELAY, OUTPUT); pinMode(PIN_FAN, OUTPUT);
  pinMode(PIN_BUZZER, OUTPUT); pinMode(PIN_ZC, INPUT);

  initSPWMTimer();
  attachInterrupt(digitalPinToInterrupt(PIN_ZC), zeroCrossISR, RISING);
  
  lcd.begin(20,4); lcd.backlight();
  lcd.print("MNG proSystems    ");
  delay(2000);
}

// ================= MAIN LOOP =================
void loop() {
  readSensors();
  thermalControl();
  stateMachine();
  manageCharging();
  updateLCD();
  
  if (currentState != ST_ERROR) digitalWrite(PIN_BUZZER, LOW);
}

// ================= SPWM & CHARGER ENGINE =================
void initSPWMTimer() {
  TCCR1A = _BV(COM1A1) | _BV(COM1B1) | _BV(WGM11); 
  TCCR1B = _BV(WGM13) | _BV(WGM12) | _BV(CS10); 
  ICR1 = ICR_MAX;
  
  TCCR2A = _BV(WGM21); // CTC Mode
  TCCR2B = _BV(CS21);  // Prescaler 8
  OCR2A = 199;         // 10kHz Interrupt
  TIMSK2 = _BV(OCIE2A);
}

ISR(TIMER2_COMPA_vect) {
  // --- MODE: CHARGING ---
  if (currentState == ST_UPS_CHARGE) {
    if (sineIndex < 100) { // Positive Grid Half
      digitalWrite(PIN_LO_LEFT, LOW);
      digitalWrite(PIN_LO_RIGHT, HIGH); // Path to GND
      OCR1A = chargePWM;                // Buck Switch
      OCR1B = 0;
    } else { // Negative Grid Half
      digitalWrite(PIN_LO_RIGHT, LOW);
      digitalWrite(PIN_LO_LEFT, HIGH);  // Path to GND
      OCR1A = 0;
      OCR1B = chargePWM;                // Buck Switch
    }
    sineIndex++;
    if (sineIndex >= 200) sineIndex = 0;
    return;
  }

  // --- MODE: INVERTER ---
  if (!spwmEnabled) {
    digitalWrite(PIN_LO_LEFT, LOW); digitalWrite(PIN_LO_RIGHT, LOW);
    OCR1A = 0; OCR1B = 0;
    return;
  }

  int val;
  if (sineIndex < 100) {
    val = pgm_read_word(&sineTable[sineIndex]);
    digitalWrite(PIN_LO_LEFT, LOW); digitalWrite(PIN_LO_RIGHT, HIGH);
    OCR1A = (int)(val * modulationIndex); OCR1B = 0;
  } else {
    val = pgm_read_word(&sineTable[sineIndex - 100]);
    digitalWrite(PIN_LO_RIGHT, LOW); digitalWrite(PIN_LO_LEFT, HIGH);
    OCR1A = 0; OCR1B = (int)(val * modulationIndex);
  }
  sineIndex++;
  if (sineIndex >= 200) sineIndex = 0;
}

// ================= CHARGING CONTROL =================

void manageCharging() {
  if (currentState != ST_UPS_CHARGE) {
    chargePWM = 0;
    chargingActive = false;
    return;
  }

  chargingActive = true;
  float vTarget = (chargeState == FLOAT) ? FLOAT_VOLTAGE : BULK_VOLTAGE;

  // Constant Current / Constant Voltage (CC/CV) Logic
  if (loadAmps > CHG_CURRENT_LIMIT) {
    if (chargePWM > 0) chargePWM--; // Current limiting
  } else if (batVolts < vTarget) {
    if (chargePWM < (ICR_MAX * 0.8)) chargePWM++; // Voltage ramp
  } else {
    if (chargePWM > 0) chargePWM--; // Voltage regulation
  }

  // Transitions
  if (chargeState == BULK && batVolts >= BULK_VOLTAGE - 0.1) chargeState = ABSORPTION;
  if (chargeState == ABSORPTION && batVolts >= BULK_VOLTAGE) chargeState = FLOAT;
}

// ================= STATE MACHINE =================
void stateMachine() {
  switch (currentState) {
    case ST_CHECK_START:
      if (acInVolts > AC_MIN && acInVolts < AC_MAX) {
        currentState = ST_GRID_WAIT;
        stateTimer = millis();
      } else {
        spwmEnabled = true;
        currentState = ST_SOFT_START;
      }
      break;

    case ST_SOFT_START:
      if (modulationIndex < 0.9) modulationIndex += 0.005;
      else currentState = ST_INVERTER;
      break;

    case ST_INVERTER:
      digitalWrite(PIN_RELAY, LOW);
      if (acInVolts > AC_MIN) currentState = ST_GRID_WAIT;
      if (batVolts < 10.5) triggerError("LOW BATT");
      break;

    case ST_GRID_WAIT:
      if (millis() - stateTimer > 2000) {
        spwmEnabled = false;
        digitalWrite(PIN_RELAY, HIGH);
        currentState = ST_UPS_CHARGE;
        chargeState = BULK;
      }
      break;

    case ST_UPS_CHARGE:
      if (acInVolts < AC_MIN) {
        currentState = ST_CHECK_START;
        digitalWrite(PIN_RELAY, LOW);
      }
      break;

    case ST_ERROR:
      spwmEnabled = false;
      chargePWM = 0;
      digitalWrite(PIN_RELAY, LOW);
      digitalWrite(PIN_BUZZER, HIGH);
      break;
  }
}

void zeroCrossISR() {
  sineIndex = 0; // Sync the internal wave to the grid
}

void readSensors() {
  batVolts = (analogRead(PIN_BAT_V) * 5.0 / 1023.0) * 4.0; // Adjust Divider
  acInVolts = (analogRead(PIN_AC_IN) * 5.0 / 1023.0) * 100.0;
  acOutVolts = (analogRead(PIN_AC_OUT) * 5.0 / 1023.0) * 100.0;
  loadAmps = (analogRead(PIN_SHUNT) * 5.0 / 1023.0) * 10.0; // Adjust for your shunt
  loadWatts = acOutVolts * loadAmps;
  temperature = map(analogRead(PIN_NTC), 0, 1023, 0, 100);
}

void thermalControl() {
  if (temperature > 50) analogWrite(PIN_FAN, 200);
  else analogWrite(PIN_FAN, 0);
  if (temperature > 85) triggerError("OVERHEAT");
}

void triggerError(const char* msg) {
  currentState = ST_ERROR;
  lcd.clear();
  lcd.print("ERR: "); lcd.print(msg);
}

void updateLCD() {
  if (millis() - lastScreenUpdate < 500) return;
  lastScreenUpdate = millis();
  if (currentState == ST_ERROR) return;

  lcd.setCursor(0,0);
  lcd.print(currentState == ST_UPS_CHARGE ? "MODE: CHARGER " : "MODE: INVERTER");
  lcd.setCursor(0,1);
  lcd.print("Bat:"); lcd.print(batVolts, 1); lcd.print("V ");
  lcd.print("Amps:"); lcd.print(loadAmps, 1);
  lcd.setCursor(0,2);
  lcd.print("PWM:"); lcd.print(chargePWM); lcd.print("  ");
}