File content as of revision 2:6d8d35a5b3f2:

#include "mbed.h"
#include "DS1307.h"

DS1307::DS1307(PinName sda, PinName scl) : ds1307_i2c(sda, scl)
{
    ds1307_i2c.frequency(DS1307_FREQ);
}

time_t DS1307::now()
{
    struct tm now;
    char addr = 0x00; // memory address
    char buffer[7];

    if (ds1307_i2c.write(DS1307_ADDR, &addr, 1) != 0) return 0;
    if (ds1307_i2c.read(DS1307_ADDR, buffer, 7) != 0) return 0;
    
    if (buffer[0] & 0x80) return 0; // clock stopped
    if (!(buffer[2] & 0x40)) return 0; // 12-hour format not supported
    now.tm_sec = bcdToDecimal(buffer[0] & 0x7F);
    now.tm_min = bcdToDecimal(buffer[1]);
    now.tm_hour = bcdToDecimal(buffer[2] & 0x3F);
    now.tm_mday = bcdToDecimal(buffer[4]);
    now.tm_mon = bcdToDecimal(buffer[5]) - 1;
    now.tm_year = bcdToDecimal(buffer[6]) + 2000 - 1900;
    
    return mktime(&now);
}

bool DS1307::set_time(time_t t)
{
    struct tm *now;
    char buffer[9];

    now = localtime(&t);

    buffer[0] = 0x00; // memory address
    buffer[1] = decimalToBcd(now->tm_sec) & 0x7f; // CH = 0
    buffer[2] = decimalToBcd(now->tm_min);
    buffer[3] = 0x40 | (decimalToBcd(now->tm_hour) & 0x3F); // 24-hour format
    buffer[4] = now->tm_wday + 1;
    buffer[5] = decimalToBcd(now->tm_mday);
    buffer[6] = decimalToBcd(now->tm_mon+1);
    buffer[7] = decimalToBcd(now->tm_year + 1900 - 2000);
    buffer[8] = 0x00; // OUT = 0
    if (ds1307_i2c.write(DS1307_ADDR, buffer, 9) != 0) return false;

    return true;
}