// RTC DS1307 I2C address
#define DS1307_ADDRESS 0x68

// Initialize ports for seven-segment display
void init_ports() {
    DDRF = 0xFF;   // Set PORTF as output (for the segments)
    DDRK = 0x1F;   // Set lower 5 bits of PORTK as output (for digit select)
}

// Function to start I2C communication
void i2c_start() {
    TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN);
    while (!(TWCR & (1 << TWINT)));  // Wait for start to be transmitted
}

// Function to stop I2C communication
void i2c_stop() {
    TWCR = (1 << TWINT) | (1 << TWSTO) | (1 << TWEN);
}

// Function to write a byte over I2C
void i2c_write(uint8_t data) {
    TWDR = data;
    TWCR = (1 << TWINT) | (1 << TWEN);
    while (!(TWCR & (1 << TWINT)));  // Wait for the transmission to complete
}

// Function to read a byte from I2C (ack = 1 to acknowledge, ack = 0 for NACK)
uint8_t i2c_read(uint8_t ack) {
    TWCR = (1 << TWINT) | (1 << TWEN) | (ack << TWEA);
    while (!(TWCR & (1 << TWINT)));  // Wait for the data to be received
    return TWDR;
}

// Convert decimal to BCD
uint8_t dec_to_bcd(uint8_t val) {
    return ((val / 10 * 16) + (val % 10));
}

// Convert BCD to decimal
uint8_t bcd_to_dec(uint8_t val) {
    return ((val / 16 * 10) + (val % 16));
}

// Function to set time to 12:34:56 on the RTC DS1307
void rtc_set_time(uint8_t hours, uint8_t minutes, uint8_t seconds) {
    i2c_start();
    i2c_write(DS1307_ADDRESS << 1);  // Send address + write bit
    i2c_write(0x00);                 // Start at register 0x00 (seconds)
    
    i2c_write(dec_to_bcd(seconds));  // Set seconds in BCD format
    i2c_write(dec_to_bcd(minutes));  // Set minutes in BCD format
    i2c_write(dec_to_bcd(hours));    // Set hours in BCD format
    
    i2c_stop();
}

// Function to read time from RTC DS1307
void rtc_get_time(uint8_t *hours, uint8_t *minutes, uint8_t *seconds) {
    i2c_start();
    i2c_write(DS1307_ADDRESS << 1);  // Send address + write bit
    i2c_write(0x00);                 // Start reading at register 0x00 (seconds)
    i2c_start();
    i2c_write((DS1307_ADDRESS << 1) | 1);  // Send address + read bit
    
    *seconds = i2c_read(1);           // Read seconds
    *minutes = i2c_read(1);           // Read minutes
    *hours = i2c_read(0);             // Read hours
    i2c_stop();
}

// Seven-segment display digit patterns for 0-9
long seven_segment[] = {
    0x3F, // 0
    0x06, // 1
    0x5B, // 2
    0x4F, // 3
    0x66, // 4
    0x6D, // 5
    0x7D, // 6
    0x07, // 7
    0x7F, // 8
    0x6F  // 9
};

// Function to display a number on 4-digit seven-segment display
void display_time(uint8_t hours, uint8_t minutes) {
    int digits[4] = {0};
    digits[0] = seven_segment[hours / 10];
    digits[1] = seven_segment[hours % 10];
    digits[2] = seven_segment[minutes / 10];
    digits[3] = seven_segment[minutes % 10];

    int digit_select[4] = {0x1E, 0x1D, 0x1B, 0x17};

    for (int i = 0; i < 4; i++) {
        PORTF = digits[i];        // Output digit to seven-segment
        PORTK = digit_select[i];  // Select corresponding digit
        delay(5);                 // Short delay to allow multiplexing
        PORTK = 0x1F;             // Turn off all digits
    }
}

void setup() {
    init_ports();   // Initialize ports
    Serial.begin(9600);  // Initialize Serial for debugging
    
    // Set time to 12:34:56
    rtc_set_time(12, 34, 56);
    Serial.println("Time set to 12:34:56");
}

void loop() {
    uint8_t hours, minutes, seconds;
    
    // Get the current time from the RTC
    rtc_get_time(&hours, &minutes, &seconds);

    // Convert BCD to decimal
    hours = bcd_to_dec(hours);
    minutes = bcd_to_dec(minutes);
    seconds = bcd_to_dec(seconds);

    // Debug output to Serial to verify time
    Serial.print("Time: ");
    Serial.print(hours);
    Serial.print(":");
    Serial.print(minutes);
    Serial.print(":");
    Serial.println(seconds);

    // Display time on the 4-digit seven-segment display (hours and minutes)
    display_time(hours, minutes);

    delay(1000);  // Update every second
}