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

#define I2C_PORT i2c0
#define SDA_PIN 20
#define SCL_PIN 21
#define DS1307_ADDRESS 0x68

uint8_t dec_to_bcd(uint8_t val) {
    return ((val / 10) << 4) | (val % 10);
}

uint8_t bcd_to_dec(uint8_t val) {
    return ((val >> 4) * 10) + (val & 0x0F);
}

void set_rtc_datetime() {
    uint8_t data[7];
    data[0] = 0x00;                      
    data[1] = dec_to_bcd(0);             
    data[2] = dec_to_bcd(27);            
    data[3] = dec_to_bcd(13);            
    data[4] = dec_to_bcd(24);            
    data[5] = dec_to_bcd(9);             
    data[6] = dec_to_bcd(24);            

    i2c_write_blocking(I2C_PORT, DS1307_ADDRESS, data, 7, false);
    sleep_ms(10);
}

void read_rtc_datetime() {
    uint8_t buffer[6];
    uint8_t reg = 0x00;
    i2c_write_blocking(I2C_PORT, DS1307_ADDRESS, &reg, 1, true);
    i2c_read_blocking(I2C_PORT, DS1307_ADDRESS, buffer, 6, false);

    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     = bcd_to_dec(buffer[3]);
    uint8_t month   = bcd_to_dec(buffer[4]);
    uint16_t year   = bcd_to_dec(buffer[5]) + 2000;

    printf("Date: %02d/%02d/%04d - Time: %02d:%02d:%02d\n",
           day, month, year, hours, minutes, seconds);
}

int main() {
    stdio_init_all();
    i2c_init(I2C_PORT, 100000); 
    gpio_set_function(SDA_PIN, GPIO_FUNC_I2C);
    gpio_set_function(SCL_PIN, GPIO_FUNC_I2C);
    gpio_pull_up(SDA_PIN);
    gpio_pull_up(SCL_PIN);

    sleep_ms(2000); 

    printf("Setting up RTC...\n");
    set_rtc_datetime();

    while (1) {
        read_rtc_datetime();
        sleep_ms(5000);
    }
    return 0;
}