#define F_CPU 16000000UL // Define the CPU frequency as 16 MHz
#include <avr/io.h>
#include <util/delay.h>

// Define LCD pins
#define LCD_E      PIN0_bm // Enable (PC0)
#define LCD_RS     PIN1_bm // Register Select (PC1)
#define LCD_D4     PIN3_bm // Data Bit 4 (PC3)
#define LCD_D5     PIN2_bm // Data Bit 5 (PC2)
#define LCD_D6     PIN5_bm // Data Bit 6 (PC5)
#define LCD_D7     PIN4_bm // Data Bit 7 (PC4)

// Helper macros
#define LCD_E_HIGH() (PORTC.OUTSET = LCD_E)
#define LCD_E_LOW()  (PORTC.OUTCLR = LCD_E)
#define LCD_RS_HIGH() (PORTC.OUTSET = LCD_RS)
#define LCD_RS_LOW()  (PORTC.OUTCLR = LCD_RS)

// Function Prototypes
void lcd_send_nibble(uint8_t nibble);
void lcd_send_byte(uint8_t data, uint8_t is_command);
void lcd_init();
void lcd_print(const char *str);
void lcd_set_cursor(uint8_t row, uint8_t col);

// Send a nibble (4 bits) to the LCD
void lcd_send_nibble(uint8_t nibble) {
	PORTC.OUTCLR = LCD_D4 | LCD_D5 | LCD_D6 | LCD_D7; // Clear D4-D7

	// Set data lines based on nibble
	if (nibble & 0x01) PORTC.OUTSET = LCD_D4;
	if (nibble & 0x02) PORTC.OUTSET = LCD_D5;
	if (nibble & 0x04) PORTC.OUTSET = LCD_D6;
	if (nibble & 0x08) PORTC.OUTSET = LCD_D7;

	// Pulse E pin
	LCD_E_HIGH(); // Set E high
	_delay_us(1); // Pulse duration
	LCD_E_LOW(); // Set E low
	_delay_us(100); // Command latch time
}

// Send a byte (8 bits) to the LCD
void lcd_send_byte(uint8_t data, uint8_t is_command) {
	if (is_command) {
		LCD_RS_LOW(); // Command mode
		} else {
		LCD_RS_HIGH(); // Data mode
	}

	lcd_send_nibble(data >> 4); // Send high nibble
	lcd_send_nibble(data & 0x0F); // Send low nibble
	_delay_us(50); // Command execution time
}

void lcd_init() {
	// Step 1: Initialize LCD pins
	PORTC.OUTCLR = LCD_E | LCD_RS | LCD_D4 | LCD_D5 | LCD_D6 | LCD_D7; // Clear pins
	PORTC.DIRSET = LCD_E | LCD_RS | LCD_D4 | LCD_D5 | LCD_D6 | LCD_D7; // Set as outputs

	LCD_E_LOW();
	LCD_RS_LOW();
	_delay_ms(50); // Wait for VDD stabilization (>40ms)

	// Step 2: Force 8-bit mode initialization (special sequence for 4-bit mode)
	lcd_send_nibble(0x03); // Upper nibble of 0x30
	_delay_ms(5);
	lcd_send_nibble(0x03); // Repeat initialization sequence
	_delay_us(200);
	lcd_send_nibble(0x03); // Repeat initialization sequence
	_delay_us(200);
	lcd_send_nibble(0x02); // Switch to 4-bit mode
	_delay_us(200);

	// Step 3: Function Set (4-bit, 2-line, instruction table 1)
	lcd_send_nibble(0x02); // Upper nibble of 0x28
	lcd_send_nibble(0x08); // Lower nibble of 0x28
	_delay_us(200);


	// Step 8: Display ON/OFF Control
	lcd_send_nibble(0x00); // Upper nibble of 0x0C
	lcd_send_nibble(0x0C); // Lower nibble of 0x0C
	_delay_us(200);

	// Step 9: Clear Display
	lcd_send_nibble(0x00); // Upper nibble of 0x01
	lcd_send_nibble(0x01); // Lower nibble of 0x01
	_delay_ms(2);

	// Step 10: Entry Mode Set
	lcd_send_nibble(0x00); // Upper nibble of 0x06
	lcd_send_nibble(0x06); // Lower nibble of 0x06
	_delay_us(200);
}





// Print a string to the LCD
void lcd_print(const char *str) {
	while (*str) {
		lcd_send_byte(*str++, 0); // Send characters in data mode
	}
}

// Set cursor to a specific position
void lcd_set_cursor(uint8_t row, uint8_t col) {
	uint8_t address = (row == 0) ? col : (0x40 + col);
	lcd_send_byte(0x80 | address, 1);
}

int main() {
	lcd_init(); // Initialize the LCD

	// Display a test message
	lcd_set_cursor(0, 0); // First row, first column
	lcd_print("Testing LCD");
	lcd_set_cursor(1, 0); // Second row, first column
	lcd_print("1234567890");

	while (1); // Infinite loop to hold the display
}