#define I2C_ADDR 0x27      // I2C address of the LCD

// I2C setup
void I2C_Init() {
    // Set SCL frequency to 100kHz with prescaler of 1 and assuming 16MHz clock
    TWSR = 0x00;                  // Set prescaler to 1
    TWBR = 72;                    // Set bit rate register (100kHz)
    TWCR = (1 << TWEN);           // Enable TWI (I2C)
}

// I2C Start Condition
void I2C_Start() {
    TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN);   // Send START condition
    while (!(TWCR & (1 << TWINT)));                     // Wait for TWINT flag set
}

// I2C Stop Condition
void I2C_Stop() {
    TWCR = (1 << TWINT) | (1 << TWSTO) | (1 << TWEN);   // Send STOP condition
    _delay_ms(1);
}

// I2C Write Byte
void I2C_Write(uint8_t data) {
    TWDR = data;                                        // Load data into TWDR register
    TWCR = (1 << TWINT) | (1 << TWEN);                  // Start transmission
    while (!(TWCR & (1 << TWINT)));                     // Wait for TWINT flag set
}

// Write data to LCD
void LCD_I2C_Write(uint8_t data, uint8_t control) {
    uint8_t highNibble = data & 0xF0;
    uint8_t lowNibble = (data << 4) & 0xF0;
    
    // Write high nibble
    I2C_Start();
    I2C_Write(I2C_ADDR << 1);   // LCD address + write bit (0)
    I2C_Write(highNibble | control | 0x04);  // Enable = 1
    I2C_Write(highNibble | control);         // Enable = 0
    I2C_Stop();

    // Write low nibble
    I2C_Start();
    I2C_Write(I2C_ADDR << 1);   // LCD address + write bit (0)
    I2C_Write(lowNibble | control | 0x04);  // Enable = 1
    I2C_Write(lowNibble | control);         // Enable = 0
    I2C_Stop();

    _delay_us(50);  // Wait for LCD to process the command
}

// Send command to LCD
void LCD_Send_Command(uint8_t command) {
    LCD_I2C_Write(command, 0x00);  // Command mode
}

// Send data to LCD
void LCD_Send_Data(uint8_t data) {
    LCD_I2C_Write(data, 0x01);     // Data mode
}

// Initialize the LCD
void LCD_Init() {
    _delay_ms(50);             // Wait for LCD to power up
    LCD_Send_Command(0x03);    // Initialize LCD in 4-bit mode (repeat 3 times)
    _delay_ms(5);
    LCD_Send_Command(0x03);
    _delay_us(150);
    LCD_Send_Command(0x03);
    LCD_Send_Command(0x02);    // Finally, set to 4-bit mode

    // Configure the LCD in 2-line, 5x7 matrix, and turn on display
    LCD_Send_Command(0x28);    // 4-bit, 2-line, 5x7 matrix
    LCD_Send_Command(0x0C);    // Display ON, Cursor OFF, Blink OFF
    LCD_Send_Command(0x01);    // Clear display
    _delay_ms(2);
    LCD_Send_Command(0x06);    // Increment cursor, no display shift
}

// Clear the LCD display
void LCD_Clear() {
    LCD_Send_Command(0x01);    // Clear display command
    _delay_ms(2);              // Wait for the command to complete
}

// Set cursor position (row 0 or 1, col 0-15)
void LCD_Set_Cursor(uint8_t row, uint8_t col) {
    uint8_t address = (row == 0) ? (0x80 + col) : (0xC0 + col);
    LCD_Send_Command(address);
}

// Write string to LCD
void LCD_Write_String(const char* str) {
    while (*str) {
        LCD_Send_Data(*str++);
    }
}

int main(void) {
    // Initialize I2C and LCD
    I2C_Init();
    LCD_Init();
    
    // Write "Hello, World!" to the LCD
    LCD_Clear();
    LCD_Set_Cursor(0, 0);
    LCD_Write_String("   I LOVE YOU");
    
    while (1) {
        // Main loop (LCD display remains active)
    }
}