#include <stdio.h>
#include "pico/stdlib.h"
#include "hardware/i2c.h"

#define DS1307_ADDR 0x68
#define I2C_PORT i2c0

// 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));
}

// Set date and time on DS1307
void set_datetime() {
    uint8_t time_data[] = {
        0x00,  // Register address (start of time registers)
        dec_to_bcd(0),    // Seconds
        dec_to_bcd(27),   // Minutes
        dec_to_bcd(13),   // Hours (24-hour mode)
        dec_to_bcd(3),    // Day of week
        dec_to_bcd(24),   // Day of month
        dec_to_bcd(9),    // Month
        dec_to_bcd(24)    // Year
    };
    
    i2c_write_blocking(I2C_PORT, DS1307_ADDR, time_data, sizeof(time_data), false);
}

// Read date and time from DS1307
void read_datetime() {
    uint8_t reg = 0x00;  // Start from seconds register
    uint8_t buffer[7];

    // Set register pointer
    i2c_write_blocking(I2C_PORT, DS1307_ADDR, &reg, 1, true);
    
    // Read 7 bytes
    i2c_read_blocking(I2C_PORT, DS1307_ADDR, buffer, 7, false);

    // Extract and convert data
    uint8_t seconds = bcd_to_dec(buffer[0] & 0x7F);
    uint8_t minutes = bcd_to_dec(buffer[1]);
    uint8_t hours = bcd_to_dec(buffer[2] & 0x3F);
    uint8_t day_of_week = bcd_to_dec(buffer[3]);
    uint8_t day = bcd_to_dec(buffer[4]);
    uint8_t month = bcd_to_dec(buffer[5]);
    uint8_t year = bcd_to_dec(buffer[6]);

    // Print formatted date and time
    printf("Date: %02d/%02d/20%02d - Time: %02d:%02d:%02d\n", 
           day, month, year, hours, minutes, seconds);
}

int main() {
    // Initialize stdio and I2C
    stdio_init_all();
    i2c_init(I2C_PORT, 100 * 1000);  // 100 kHz

    // Set GPIO pins for I2C
    gpio_set_function(16, GPIO_FUNC_I2C);  // SDA
    gpio_set_function(17, GPIO_FUNC_I2C);  // SCL
    gpio_pull_up(16);
    gpio_pull_up(17);

    // Set initial datetime
    set_datetime();

    // Continuous reading
    while (1) {
        read_datetime();
        sleep_ms(5000);  // 5-second delay
    }

    return 0;
}