/* =========================================================
   AXPERT-STYLE HYBRID INVERTER + MPPT (Arduino Nano)
   LiFePO4 | MPPT | UPS | Inverter | 2004 LCD
   ========================================================= */

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

/* ------------------- PIN MAP ------------------- */
#define MPPT_PWM_PIN     9

//#define INV_AH_PIN       5
//#define INV_AL_PIN       6
//#define INV_BH_PIN       10
//#define INV_BL_PIN       11

#define SOLAR_V_PIN      A0
#define SOLAR_I_PIN      A1
#define BATT_V_PIN       A2
#define BATT_I_PIN       A3

#define AC_DETECT_PIN    2
#define BYPASS_RELAY     3

/* ------------------- LCD ------------------- */
LiquidCrystal_I2C lcd(0x27, 20, 4);

/* ------------------- PWM ------------------- */
#define PWM_MAX 480
#define PWM_MIN 30
uint16_t mpptPWM = 150;

/* ------------------- BATTERY ------------------- */
float battV, battI;
uint8_t battSystem = 48;

struct BatteryProfile {
  float bulk;
  float absorb;
  float flt;
  float maxI;
} batt;

/* ------------------- MPPT ------------------- */
float pvV, pvI, pvPrevV, pvPrevI;

/* ------------------- STATES ------------------- */
enum ChargeState { BULK, ABSORB, FLOAT };
ChargeState chgState = BULK;

/* ------------------- TIMERS ------------------- */
unsigned long tMPPT, tCHG, tUPS, tUI;

/* =========================================================
   HARDWARE PWM (25kHz)
   ========================================================= */
void setupMPPTPWM() {
  pinMode(MPPT_PWM_PIN, OUTPUT);

  TCCR1A = 0;
  TCCR1B = 0;

  TCCR1A |= (1 << COM1A1) | (1 << WGM11);
  TCCR1B |= (1 << WGM13) | (1 << WGM12) | (1 << CS10);

  ICR1 = PWM_MAX;
  OCR1A = mpptPWM;
}

/* =========================================================
   SENSOR READ (SCALES MUST BE CALIBRATED)
   ========================================================= */
void readSensors() {
  pvV   = analogRead(SOLAR_V_PIN) * 0.10;
  pvI   = analogRead(SOLAR_I_PIN) * 0.05;
  battV = analogRead(BATT_V_PIN)  * 0.05;
  battI = analogRead(BATT_I_PIN)  * 0.05;
}

/* =========================================================
   BATTERY AUTO DETECT (LiFePO4)
   ========================================================= */
void detectBattery() {
  if (battV < 15) battSystem = 12;
  else if (battV < 30) battSystem = 24;
  else battSystem = 48;

  if (battSystem == 12)
    batt = {14.2, 14.2, 13.6, 50};
  else if (battSystem == 24)
    batt = {28.4, 28.4, 27.2, 50};
  else
    batt = {56.8, 56.8, 54.4, 50};
}

/* =========================================================
   INCREMENTAL CONDUCTANCE MPPT
   ========================================================= */
void taskMPPT() {
  float dV = pvV - pvPrevV;
  float dI = pvI - pvPrevI;

  if (dV != 0) {
    float slope = dI / dV;
    float ref   = -pvI / pvV;

    if (slope > ref) mpptPWM += 2;
    else mpptPWM -= 2;
  }

  mpptPWM = constrain(mpptPWM, PWM_MIN, PWM_MAX);
  OCR1A = mpptPWM;

  pvPrevV = pvV;
  pvPrevI = pvI;
}

/* =========================================================
   CHARGER CONTROL (AXPERT STYLE)
   ========================================================= */
void taskCharger() {

  if (battI > batt.maxI) mpptPWM -= 5;

  switch (chgState) {
    case BULK:
      if (battV >= batt.bulk) chgState = ABSORB;
      break;

    case ABSORB:
      if (battV > batt.absorb) mpptPWM--;
      if (battI < 0.05) chgState = FLOAT;
      break;

    case FLOAT:
      if (battV < batt.flt) chgState = BULK;
      break;
  }

  mpptPWM = constrain(mpptPWM, PWM_MIN, PWM_MAX);
  OCR1A = mpptPWM;
}

/* =========================================================
   UPS / GRID CONTROL
   ========================================================= */
void taskUPS() {
  bool grid = digitalRead(AC_DETECT_PIN);
  digitalWrite(BYPASS_RELAY, grid ? HIGH : LOW);
}

/* =========================================================
   LCD UI
   ========================================================= */
void taskUI() {
  lcd.setCursor(0,0);
  lcd.print("PV: ");
  lcd.print(pvV); lcd.print("V ");
  lcd.print(pvI); lcd.print("A  ");

  lcd.setCursor(0,1);
  lcd.print("BAT: ");
  lcd.print(battV); lcd.print("V ");
  lcd.print(battI); lcd.print("A  ");

  lcd.setCursor(0,2);
  lcd.print("PWM: ");
  lcd.print(mpptPWM);
  lcd.print(" SYS: ");
  lcd.print(battSystem);
  lcd.print("V ");

  lcd.setCursor(0,3);
  lcd.print("CHG: ");
  lcd.print(chgState == BULK ? "BULK " :
            chgState == ABSORB ? "ABS  " : "FLOAT");
}

/* =========================================================
   SETUP
   ========================================================= */
void setup() {
  pinMode(AC_DETECT_PIN, INPUT);
  pinMode(BYPASS_RELAY, OUTPUT);

  lcd.init();
  lcd.backlight();

  setupMPPTPWM();
  delay(1000);

  readSensors();
  detectBattery();
}

/* =========================================================
   MAIN LOOP (COOPERATIVE MULTITASKING)
   ========================================================= */
void loop() {

  if (millis() - tMPPT >= 30) {
    tMPPT = millis();
    readSensors();
    taskMPPT();
  }

  if (millis() - tCHG >= 10) {
    tCHG = millis();
    taskCharger();
  }

  if (millis() - tUPS >= 5) {
    tUPS = millis();
    taskUPS();
  }

  if (millis() - tUI >= 200) {
    tUI = millis();
    taskUI();
  }
}