#include <LiquidCrystal_I2C.h>

#define I2C_ADDR    0x27
#define LCD_COLUMNS 20
#define LCD_LINES   4
int started = 0;

LiquidCrystal_I2C lcd(I2C_ADDR, LCD_COLUMNS, LCD_LINES);


// Constants
#define MAX485_PIN 5  // PIN to control MAX485 direction
#define SLAVE_ID 1
#define MODBUS_TIMEOUT 1000

// Modbus function codes
#define READ_HOLDING_REGISTERS 0x03
#define WRITE_SINGLE_REGISTER 0x06

// Register addresses
#define TEMP_REG 0x00
#define HUM_REG 0x01
#define RELAY1_REG 0x02
#define RELAY2_REG 0x03





uint8_t humheatdata[9];
uint8_t crdone[8];
char placeholder[10];

// CRC calculation function
uint16_t calculateCRC(uint8_t* buffer, int length) {
    uint16_t crc = 0xFFFF;
    
    for (int pos = 0; pos < length; pos++) {
        crc ^= (uint16_t)buffer[pos];
        
        for (int i = 8; i != 0; i--) {
            if ((crc & 0x0001) != 0) {
                crc >>= 1;
                crc ^= 0xA001;
            } else {
                crc >>= 1;
            }
        }
    }
    return crc;
}

void sendModbusRequest(uint8_t* request, int length) {
    digitalWrite(MAX485_PIN, HIGH);  // Set MAX485 to transmit mode
    delay(10);

    Serial.write(request, length);
    Serial.flush();
    
    digitalWrite(MAX485_PIN, LOW);  // Set MAX485 to receive mode
}

void readSensorData() {
    uint8_t request[8] = {
        SLAVE_ID,
        READ_HOLDING_REGISTERS,
        0x00,  // Starting address high byte
        0x00,  // Starting address low byte
        0x00,  // Number of registers high byte
        0x02   // Number of registers low byte (reading 2 registers)
    };
    
    uint16_t crc = calculateCRC(request, 6);
    request[6] = crc & 0xFF;
    request[7] = (crc >> 8) & 0xFF;

    if (started == 0){delay(4000); started = 1;}
    
    sendModbusRequest(request, 8);
    
    // Wait for response
    
    while (Serial.available() < 9) {delay(20);};  // Minimum request length
    Serial.readBytes(humheatdata, 9);

    uint16_t receivedCRC = (humheatdata[8] << 8) | humheatdata[7];
    uint16_t calculatedCRC = calculateCRC(humheatdata, 7);
    while (receivedCRC != calculatedCRC) {Serial.println("qerror");};

}

void controlRelay(uint8_t relay, bool state) {
    uint8_t request[8] = {
        SLAVE_ID,
        WRITE_SINGLE_REGISTER,
        0x00,
        (relay == 0) ? RELAY1_REG : RELAY2_REG,  // Register address
        0x00,
        state ? 0x01 : 0x00  // Value to write
    };
    
    uint16_t crc = calculateCRC(request, 6);
    request[6] = crc & 0xFF;
    request[7] = (crc >> 8) & 0xFF;


    sendModbusRequest(request, 8);
    while (Serial.available() < 8) {delay(20);};  // Minimum request length
    Serial.readBytes(crdone, 8);

    lcd.setCursor(0, 0);
    lcd.print(crdone[0]);
    lcd.setCursor(4, 0);
    lcd.print(crdone[1]);
    lcd.setCursor(8, 0);
    lcd.print(crdone[2]);

    lcd.setCursor(0, 1);
    lcd.print(crdone[3]);
    lcd.setCursor(4, 1);
    lcd.print(crdone[4]);
    lcd.setCursor(8, 1);
    lcd.print(crdone[5]);

    lcd.setCursor(0, 2);
    lcd.print(crdone[6]);
    lcd.setCursor(4, 2);
    lcd.print(crdone[7]);


    uint16_t receivedCRC = (humheatdata[8] << 8) | humheatdata[7];
    uint16_t calculatedCRC = calculateCRC(humheatdata, 7);
    while (receivedCRC != calculatedCRC) {Serial.println("error");};

}

void setup() {
    // Init
    lcd.init();
    lcd.backlight();
    Serial.begin(9600);
    
    pinMode(MAX485_PIN, OUTPUT);
    digitalWrite(MAX485_PIN, LOW);  // Start in receive mode
}

void loop() {
    readSensorData();
    delay(100);  // Read every .1 seconds
 
    int16_t temperature = (humheatdata[3] << 8) | humheatdata[4];
    int16_t humidity = (humheatdata[5] << 8) |humheatdata[6];
    
    
    // Example: Toggle relays based on some condition
    if (temperature < 20) {controlRelay(0, true);}
    
    if (temperature > 25) {controlRelay(0, false);}
    
    if (humidity < 30) {controlRelay(1, true);}
    
    if (humidity > 50) {controlRelay(1, false);}
 
}