#define F_CPU 16000000UL  // CPU Frequency 16 MHz
#define SCL_CLOCK 100000L // I2C clock frequency 100 kHz

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

void I2C_Init(void);
void I2C_Start(void);
void I2C_Stop(void);
void I2C_Write(uint8_t data);
uint8_t I2C_Read_ACK(void);
uint8_t I2C_Read_NACK(void);
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);
void Print_Day_of_Week(uint8_t day);
uint8_t BCD_to_Decimal(uint8_t bcd);

int main(void) {
    uint8_t seconds, minutes, hours, day, date, month, year;

    // Initialize I2C and Serial communication
    I2C_Init();
    Serial.begin(9600);  // Initialize Serial at 9600 baud rate

    while (1) {
        // Read the time and date from DS1307
        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);

        // Serial.print("Current time: ");
        Serial.print("Current time: 20");  // Printing year (e.g., 20XX)
        if (year < 10) Serial.print("0");  // Add leading zero for single digit year
        Serial.print(year);

        // Print Date in format YYYY/MM/DD
        Serial.print('/');
        if (month < 10) Serial.print("0"); // Add leading zero for single digit month
        Serial.print(month);
        Serial.print('/');
        if (date < 10) Serial.print("0");  // Add leading zero for single digit date
        Serial.print(date);

        // Print Day of the Week
        Serial.print(" (");
        Print_Day_of_Week(day);  // Convert numeric day to text (e.g., Friday)
        Serial.print(") ");

        // Print Time in format HH:MM:SS
        if (hours < 10) Serial.print("0");
        Serial.print(hours);
        Serial.print(':');
        if (minutes < 10) Serial.print("0");
        Serial.print(minutes);
        Serial.print(':');
        if (seconds < 10) Serial.print("0");
        Serial.print(seconds);

        Serial.println();  // Move to the next line for the next reading

        _delay_ms(1000);  // Wait for 1 second before reading again
    }

    return 0;
}

// I2C Initialization
void I2C_Init(void) {
    TWSR = 0x00; // Set prescaler bits to 0
    TWBR = ((F_CPU / SCL_CLOCK) - 16) / 2; // Set bit rate register
}

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

// I2C Stop Condition
void I2C_Stop(void) {
    TWCR = (1 << TWSTO) | (1 << TWEN) | (1 << TWINT); // Send STOP condition
    while (TWCR & (1 << TWSTO)); // Wait until STOP condition is executed
}

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

// I2C Read Byte with ACK
uint8_t I2C_Read_ACK(void) {
    TWCR = (1 << TWEN) | (1 << TWINT) | (1 << TWEA); // Enable ACK generation
    while (!(TWCR & (1 << TWINT))); // Wait for TWINT flag to be set
    return TWDR; // Return received data
}

// I2C Read Byte with NACK
uint8_t I2C_Read_NACK(void) {
    TWCR = (1 << TWEN) | (1 << TWINT); // No ACK after reception
    while (!(TWCR & (1 << TWINT))); // Wait for TWINT flag to be set
    return TWDR; // Return received data
}

// 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();              // Start I2C communication
    I2C_Write(DS1307_ADDRESS); // DS1307 address + write bit
    I2C_Write(0x00);          // Set register pointer to seconds (0x00)
    I2C_Start();              // Repeated start
    I2C_Write(DS1307_READ);    // DS1307 address + read bit

    *seconds = I2C_Read_ACK();  // Read seconds with ACK
    *minutes = I2C_Read_ACK();  // Read minutes with ACK
    *hours   = I2C_Read_ACK();  // Read hours with ACK
    *day     = I2C_Read_ACK();  // Read day with ACK
    *date    = I2C_Read_ACK();  // Read date with ACK
    *month   = I2C_Read_ACK();  // Read month with ACK
    *year    = I2C_Read_NACK(); // Read year with NACK

    I2C_Stop();               // Stop I2C communication
}

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

// Function to Print Day of the Week
void Print_Day_of_Week(uint8_t day) {
    switch(day) {
        case 1: Serial.print("Sunday"); break;
        case 2: Serial.print("Monday"); break;
        case 3: Serial.print("Tuesday"); break;
        case 4: Serial.print("Wednesday"); break;
        case 5: Serial.print("Thursday"); break;
        case 6: Serial.print("Friday"); break;
        case 7: Serial.print("Saturday"); break;
        default: Serial.print("Invalid"); break;
    }
}