#define F_CPU 16000000UL
#include <avr/io.h>
#include <util/delay.h>
#include <math.h> // Required for log function
#include <stdio.h> // Required for snprintf function

#define LCD_I2C_ADDR 0x27  // I2C address of PCF8574 LCD backpack
#define LCD_BACKLIGHT 0x08 // Backlight control bit
#define LCD_EN 0x04        // Enable bit
#define LCD_RW 0x02        // Read/Write bit
#define LCD_RS 0x01        // Register select bit
const float BETA = 3950;   // Beta coefficient of the thermistor

#define DS1307_ADDRESS 0xD0 // DS1307 address for write (0x68 << 1)
#define DS1307_READ 0xD1    // DS1307 address for read (0x68 << 1 | 1)

// Function prototypes
void init_ADC(void);
unsigned char start_ADC(void);
uint16_t read_ADC(void);
void Temp(uint16_t value);
void I2C_Init(void);
uint8_t I2C_Start(void);
void I2C_Stop(void);
uint8_t I2C_Write(uint8_t data);
uint8_t I2C_Read_ACK(void);
uint8_t I2C_Read_NACK(void);
void LCD_Write(uint8_t data);
void LCD_Enable_Pulse(uint8_t data);
void LCD_Send_Nibble(uint8_t data, uint8_t rs);
void LCD_Send_Byte(uint8_t data, uint8_t rs);
void LCD_Command(uint8_t cmd);
void LCD_Data(uint8_t data);
void LCD_Init(void);
void LCD_Clear(void);
void LCD_Set_Cursor(uint8_t row, uint8_t col);
void LCD_Write_String(const char* str);
void DS1307_Read_DateTime(uint8_t *seconds, uint8_t *minutes, uint8_t *hours, 
uint8_t *day, uint8_t *date, uint8_t *month, uint8_t *year);
uint8_t BCD_to_Decimal(uint8_t bcd);
void Display_DateTime(uint8_t seconds, uint8_t minutes, uint8_t hours, 
uint8_t day, uint8_t date, uint8_t month, uint8_t year);

// I2C setup for 100kHz
void I2C_Init(void) {
    TWSR = 0x00;                    // Prescaler = 1
    TWBR = ((F_CPU / 100000UL) - 16) / 2; // Set bit rate for 100kHz
    TWCR = (1 << TWEN);             // Enable I2C
}

// I2C Start condition
uint8_t I2C_Start(void) {
    TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN);
    while (!(TWCR & (1 << TWINT)));
    if ((TWSR & 0xF8) != 0x08)
        return 0;
    return 1;
}

// I2C Stop condition
void I2C_Stop(void) {
    TWCR = (1 << TWINT) | (1 << TWSTO) | (1 << TWEN);
    while (TWCR & (1 << TWSTO));
}

// I2C Write byte with ACK checking
uint8_t I2C_Write(uint8_t data) {
    TWDR = data;
    TWCR = (1 << TWINT) | (1 << TWEN);
    while (!(TWCR & (1 << TWINT)));
    if ((TWSR & 0xF8) != 0x28)
        return 0;
    return 1;
}

// I2C Read Byte with ACK
uint8_t I2C_Read_ACK(void) {
    TWCR = (1 << TWEN) | (1 << TWINT) | (1 << TWEA);
    while (!(TWCR & (1 << TWINT)));
    return TWDR;
}

// I2C Read Byte with NACK
uint8_t I2C_Read_NACK(void) {
    TWCR = (1 << TWEN) | (1 << TWINT);
    while (!(TWCR & (1 << TWINT)));
    return TWDR;
}

// Write to LCD with backlight control
void LCD_Write(uint8_t data) {
    I2C_Start();
    I2C_Write(LCD_I2C_ADDR << 1);
    I2C_Write(data | LCD_BACKLIGHT);
    I2C_Stop();
}

// Send pulse to Enable pin
void LCD_Enable_Pulse(uint8_t data) {
    LCD_Write(data | LCD_EN);
    _delay_us(1);
    LCD_Write(data & ~LCD_EN);
    _delay_us(50);
}

// Send 4-bit data to LCD
void LCD_Send_Nibble(uint8_t data, uint8_t rs) {
    uint8_t high_nibble = (data & 0xF0) | rs | LCD_BACKLIGHT;
    LCD_Enable_Pulse(high_nibble);
}

// Send 8-bit data to LCD
void LCD_Send_Byte(uint8_t data, uint8_t rs) {
    LCD_Send_Nibble(data & 0xF0, rs);
    LCD_Send_Nibble((data << 4) & 0xF0, rs);
}

// Send command to LCD
void LCD_Command(uint8_t cmd) {
    LCD_Send_Byte(cmd, 0);
}

// Send data to LCD
void LCD_Data(uint8_t data) {
    LCD_Send_Byte(data, LCD_RS);
}
// Initialize LCD
void LCD_Init(void) {
    _delay_ms(50);
    LCD_Send_Nibble(0x30, 0);
    _delay_ms(5);
    LCD_Send_Nibble(0x30, 0);
    _delay_ms(1);
    LCD_Send_Nibble(0x30, 0);
    _delay_ms(1);
    LCD_Send_Nibble(0x20, 0);
    _delay_ms(1);
    LCD_Command(0x28);
    LCD_Command(0x0C);
    LCD_Command(0x06);
    LCD_Command(0x01);
    _delay_ms(2);
}

// Clear LCD display
void LCD_Clear(void) {
    LCD_Command(0x01);
    _delay_ms(2);
}

// Set cursor position
void LCD_Set_Cursor(uint8_t row, uint8_t col) {
    const uint8_t row_offsets[] = {0x00, 0x40, 0x14, 0x54};
    LCD_Command(0x80 | (row_offsets[row] + col));
}

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

// ADC initialization
void init_ADC() {
    ADMUX = 0x40;  // Use AVcc as reference, select ADC0
    ADCSRA = 0x87; // Enable ADC, set prescaler to 128
}

// Start ADC conversion
unsigned char start_ADC() {
    ADCSRA |= (1 << ADSC);
}

// Read ADC value
uint16_t read_ADC() {
    while (!(ADCSRA & (1 << ADIF)));
    ADCSRA |= (1 << ADIF);
    return ADC;
}

// Calculate and display temperature
void Temp(uint16_t value) {
    //char debugStr[16];
    //sprintf(debugStr, "ADC: %u", value);
    //LCD_Set_Cursor(2, 0);
    //LCD_Write_String(debugStr);

    float analogValue = (float)value;
    float celsius = 1 / (log(1 / (1023.0 / analogValue - 1)) / BETA + 1.0 / 298.15) - 273.15;

    char tempStr[16];
    if (celsius > -100.0 && celsius < 100.0) {
        int16_t temp_whole = (int16_t)celsius;
        int16_t temp_frac = (int16_t)((celsius - temp_whole) * 100);
        if (temp_frac < 0) temp_frac = -temp_frac;
        
        sprintf(tempStr, "Temp:%d.%02d C", temp_whole, temp_frac);
        LCD_Set_Cursor(3, 0);
        LCD_Write_String(tempStr);
    } else {
        LCD_Set_Cursor(3, 0);
        LCD_Write_String("Temp: Invalid");
    }
}

// DS1307 Read Date and Time Function
void DS1307_Read_DateTime(uint8_t *seconds, uint8_t *minutes, uint8_t *hours,uint8_t *day, uint8_t *date, uint8_t *month, uint8_t *year) {
    I2C_Start();
    I2C_Write(DS1307_ADDRESS);
    I2C_Write(0x00);
    I2C_Start();
    I2C_Write(DS1307_READ);

    *seconds = I2C_Read_ACK();
    *minutes = I2C_Read_ACK();
    *hours = I2C_Read_ACK();
    *day = I2C_Read_ACK();
    *date = I2C_Read_ACK();
    *month = I2C_Read_ACK();
    *year = I2C_Read_NACK();

    I2C_Stop();
}

// BCD to Decimal Conversion
uint8_t BCD_to_Decimal(uint8_t bcd) {
    return ((bcd / 16) * 10) + (bcd % 16);
}

// Display Date and Time on LCD
void Display_DateTime(uint8_t seconds, uint8_t minutes, uint8_t hours,uint8_t day, uint8_t date, uint8_t month, uint8_t year) {
    char dateStr[16];
    
    // Display day of week on row 0
    LCD_Set_Cursor(0, 0);
    switch(day) {
        case 1: LCD_Write_String("Day: Sunday");
          break;
        case 2: LCD_Write_String("Day: Monday");
          break;
        case 3: LCD_Write_String("Day: Tuesday"); 
          break;
        case 4: LCD_Write_String("Day: Wednesday"); 
          break;
        case 5: LCD_Write_String("Day: Thursday");
          break;
        case 6: LCD_Write_String("Day: Friday"); 
          break;
        case 7: LCD_Write_String("Day: Saturday"); 
          break;
        default: LCD_Write_String("Day: Invalid Day"); 
          break;
    }
    
    // Display date on row 1
    LCD_Set_Cursor(1, 0);
    sprintf(dateStr, "Date: %02d/%02d/%02d", date, month, year);
    LCD_Write_String(dateStr);
}

// Main function
// Main function
int main(void) {
    uint8_t seconds, minutes, hours, day, date, month, year;
    init_ADC();
    I2C_Init();
    _delay_ms(100);
    LCD_Init();
    LCD_Clear();
    
    while (1) {
        // Read and display time
        DS1307_Read_DateTime(&seconds, &minutes, &hours, &day, &date, &month, &year);
        
        // Convert BCD to decimal
        seconds = BCD_to_Decimal(seconds);
        minutes = BCD_to_Decimal(minutes);
        hours = BCD_to_Decimal(hours);
        day = BCD_to_Decimal(day);
        date = BCD_to_Decimal(date);
        month = BCD_to_Decimal(month);
        year = BCD_to_Decimal(year);
        
        // Display time on row 2
        Temp(hours, minutes, seconds);

        // Read and display temperature
        start_ADC();
        uint16_t adcValue = read_ADC();
        Temp(adcValue); // Display temperature on row 3
        
        // Display day and date
        Display_DateTime(seconds, minutes, hours, day, date, month, year);
        
        _delay_ms(1000);
    }
    return 0;
}

// Calculate and display time
void Temp(uint8_t hours, uint8_t minutes, uint8_t seconds) {
    char timeStr[16];

    // Format and display time in HH:MM:SS format
    sprintf(timeStr, "Time: %02d:%02d:%02d", hours, minutes, seconds);
    LCD_Set_Cursor(2, 0);
    LCD_Write_String(timeStr);
}



//*This complete code now:
//1. Displays the day of the week on row 0
//2. Displays the date (DD/MM/YY) on row 1
//3. Shows ADC value on row 2
//4. Shows temperature on row 3

//The code has been cleaned up to remove all Arduino-specific functions (Serial) and properly implements the RTC and temperature monitoring functionality using pure AVR-C. All necessary I2C communication functions for both the LCD and RTC are included.

//Let me know if you need any modifications or have questions about specific parts of the code!/*