DS3231RTC.cpp

/*
  DS3231RTC.cpp - library for DS3231 RTC
  
  Copyright (c) Wagner Sartori Junior 2011
  Copyright (c) Michael Margolis 2009
  This library is intended to be uses with Arduino Time.h library functions

  This file is part of TrunetClock.

  TrunetClock program is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  This program 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 General Public License for more details.

  You should have received a copy of the GNU General Public License
*/
#if ARDUINO >= 100
#include <Arduino.h>
#else
#include <WProgram.h>
#endif

#include <Wire.h>
#include "DS3231RTC.h"

#define DS3231_CTRL_ID 104

DS3231RTC::DS3231RTC()
{
  Wire.begin();
}
  
// PUBLIC FUNCTIONS
time_t DS3231RTC::get()   // Aquire data from buffer and convert to time_t
{
  tmElements_t tm;
  read(tm);
  return(makeTime(tm));
}

void  DS3231RTC::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
void DS3231RTC::read( tmElements_t &tm)
{
  Wire.beginTransmission(DS3231_CTRL_ID);
  Wire.write((uint8_t)0);
  Wire.endTransmission();

  // request the 7 data fields   (secs, min, hr, dow, date, mth, yr)
  Wire.requestFrom(DS3231_CTRL_ID, tmNbrFields);
  
  tm.Second = bcd2dec(Wire.read() & 0x7f);   
  tm.Minute = bcd2dec(Wire.read() );
  tm.Hour =   bcd2dec(Wire.read() & 0x3f);  // mask assumes 24hr clock
  tm.Wday = bcd2dec(Wire.read() );
  tm.Day = bcd2dec(Wire.read() );
  tm.Month = bcd2dec(Wire.read() );
  tm.Year = y2kYearToTm((bcd2dec(Wire.read())));
}

void DS3231RTC::write(tmElements_t &tm)
{
  Wire.beginTransmission(DS3231_CTRL_ID);
  Wire.write((uint8_t)0); // reset register pointer
  
  Wire.write(dec2bcd(tm.Second)) ;   
  Wire.write(dec2bcd(tm.Minute));
  Wire.write(dec2bcd(tm.Hour));      // sets 24 hour format
  Wire.write(dec2bcd(tm.Wday));   
  Wire.write(dec2bcd(tm.Day));
  Wire.write(dec2bcd(tm.Month));
  Wire.write(dec2bcd(tmYearToY2k(tm.Year)));   

  Wire.endTransmission();  
}

float DS3231RTC::getTemp()
{
  byte tMSB, tLSB;
  float temp3231;

  //temp registers (11h-12h) get updated automatically every 64s
  Wire.beginTransmission(DS3231_CTRL_ID);
  Wire.write(0x11);
  Wire.endTransmission();
  Wire.requestFrom(DS3231_CTRL_ID, 2);
  
  if(Wire.available()) {
    tMSB = Wire.read(); //2's complement int portion
    tLSB = Wire.read(); //fraction portion
    
    temp3231 = (tMSB & B01111111); //do 2's math on Tmsb
    temp3231 += ( (tLSB >> 6) * 0.25 ); //only care about bits 7 & 8
	//temp3231 = ((((short)tMSB << 8) | (short)tLSB) >> 6) / 4.0;
    //temp3231 = (temp3231 * 1.8) + 32.0;
    return temp3231;
  }
  else {
    //oh noes, no data!
  }
    
  return 0;
}
// PRIVATE FUNCTIONS

// Convert Decimal to Binary Coded Decimal (BCD)
uint8_t DS3231RTC::dec2bcd(uint8_t num)
{
  return ((num/10 * 16) + (num % 10));
}

// Convert Binary Coded Decimal (BCD) to Decimal
uint8_t DS3231RTC::bcd2dec(uint8_t num)
{
  return ((num/16 * 10) + (num % 16));
}

// PROTECTED FUNCTIONS

void set_sreg(uint8_t val) {
	Wire.beginTransmission(DS3231_CTRL_ID);
	Wire.write(DS3231_STATUS_ADDR);
	Wire.write(val);
	Wire.endTransmission();
}

uint8_t get_sreg() {
	uint8_t rv;

	Wire.beginTransmission(DS3231_CTRL_ID);
	Wire.write(DS3231_STATUS_ADDR);
	Wire.endTransmission();

	Wire.requestFrom(DS3231_CTRL_ID, 1);
	rv = Wire.read();

	return rv;
}

void set_creg(uint8_t val) {
	Wire.beginTransmission(DS3231_CTRL_ID);
	Wire.write(DS3231_CONTROL_ADDR);
	Wire.write(val);
	Wire.endTransmission();
}

uint8_t get_creg() {
	uint8_t rv;

	Wire.beginTransmission(DS3231_CTRL_ID);
	Wire.write(DS3231_CONTROL_ADDR);
	Wire.endTransmission();

	Wire.requestFrom(DS3231_CTRL_ID, 1);
	rv = Wire.read();

	return rv;
}

DS3231RTC RTC = DS3231RTC(); // create an instance for the user