DS1307RTC.cpp

/*
 * DS1307RTC.h - library for DS1307 RTC
  
  Copyright (c) Michael Margolis 2009
  This library is intended to be uses with Arduino Time.h library functions

  The library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  
  30 Dec 2009 - Initial release
  5 Sep 2011 updated for Arduino 1.0
 */

#include <I2C.h>
#include "DS1307RTC.h"

#define DS1307_CTRL_ID 0x68 

DS1307RTC::DS1307RTC()
{
    I2c.begin();
}

// PUBLIC FUNCTIONS
time_t DS1307RTC::get()   // Aquire data from buffer and convert to time_t
{
  tmElements_t tm;
  if (read(tm) == false) return 0;
  return(makeTime(tm));
}

bool DS1307RTC::set(time_t t)
{
  tmElements_t tm;
  breakTime(t, tm);
  tm.Second |= 0x80;  // stop the clock 
  write(tm); 
  tm.Second &= 0x7f;  // start the clock
  write(tm); 
}

// Aquire data from the RTC chip in BCD format
bool DS1307RTC::read(tmElements_t &tm)
{
  uint8_t sec;
  if (I2c.write(DS1307_CTRL_ID, 0x00) != 0)
  {
    exists = false;
    return false;
  }
  exists = true;

  // request the 7 data fields   (secs, min, hr, dow, date, mth, yr)
  I2c.read(DS1307_CTRL_ID, tmNbrFields);
  if (I2c.available() < tmNbrFields) return false;
  sec = I2c.receive();
  tm.Second = bcd2dec(sec & 0x7f);   
  tm.Minute = bcd2dec(I2c.receive() );
  tm.Hour =   bcd2dec(I2c.receive() & 0x3f);  // mask assumes 24hr clock
  tm.Wday = bcd2dec(I2c.receive() );
  tm.Day = bcd2dec(I2c.receive() );
  tm.Month = bcd2dec(I2c.receive() );
  tm.Year = y2kYearToTm((bcd2dec(I2c.receive())));
  if (sec & 0x80) return false; // clock is halted
  return true;
}

bool DS1307RTC::write(tmElements_t &tm)
{
  uint8_t message[7];
  message[0]=(dec2bcd(tm.Second)) ;   
  message[1]=(dec2bcd(tm.Minute));
  message[2]=(dec2bcd(tm.Hour));      // sets 24 hour format
  message[3]=(dec2bcd(tm.Wday));   
  message[4]=(dec2bcd(tm.Day));
  message[5]=(dec2bcd(tm.Month));
  message[6]=(dec2bcd(tmYearToY2k(tm.Year))); 

  if(I2c.write(DS1307_CTRL_ID, 0x00, message, 7) != 0)
  {
    exists = false;
    return false;
  }
  exists = true;
  return true;
}

// PRIVATE FUNCTIONS

// Convert Decimal to Binary Coded Decimal (BCD)
uint8_t DS1307RTC::dec2bcd(uint8_t num)
{
  return ((num/10 * 16) + (num % 10));
}

// Convert Binary Coded Decimal (BCD) to Decimal
uint8_t DS1307RTC::bcd2dec(uint8_t num)
{
  return ((num/16 * 10) + (num % 16));
}

bool DS1307RTC::exists = false;

DS1307RTC RTC = DS1307RTC(); // create an instance for the user