text: /**************************************************************************/
  /*!
    @file     RTClib.h
  
    Original library by JeeLabs http://news.jeelabs.org/code/, released to the
    public domain
  
    License: MIT (see LICENSE)
  
    This is a fork of JeeLab's fantastic real time clock library for Arduino.
  
    For details on using this library with an RTC module like the DS1307, PCF8523,
    or DS3231, see the guide at:
    https://learn.adafruit.com/ds1307-real-time-clock-breakout-board-kit/overview
  
    Adafruit invests time and resources providing this open source code,
    please support Adafruit and open-source hardware by purchasing
    products from Adafruit!
  */
  /**************************************************************************/
  
  #ifndef _RTCLIB_H_
  #define _RTCLIB_H_
  
  #include <Arduino.h>
  class TimeSpan;
  
  /** Registers */
  #define PCF8523_ADDRESS 0x68       ///< I2C address for PCF8523
  #define PCF8523_CLKOUTCONTROL 0x0F ///< Timer and CLKOUT control register
  #define PCF8523_CONTROL_1 0x00     ///< Control and status register 1
  #define PCF8523_CONTROL_2 0x01     ///< Control and status register 2
  #define PCF8523_CONTROL_3 0x02     ///< Control and status register 3
  #define PCF8523_TIMER_B_FRCTL 0x12 ///< Timer B source clock frequency control
  #define PCF8523_TIMER_B_VALUE 0x13 ///< Timer B value (number clock periods)
  #define PCF8523_OFFSET 0x0E        ///< Offset register
  #define PCF8523_STATUSREG 0x03     ///< Status register
  
  #define DS1307_ADDRESS 0x68 ///< I2C address for DS1307
  #define DS1307_CONTROL 0x07 ///< Control register
  #define DS1307_NVRAM 0x08   ///< Start of RAM registers - 56 bytes, 0x08 to 0x3f
  
  #define DS3231_ADDRESS 0x68   ///< I2C address for DS3231
  #define DS3231_TIME 0x00      ///< Time register
  #define DS3231_ALARM1 0x07    ///< Alarm 1 register
  #define DS3231_ALARM2 0x0B    ///< Alarm 2 register
  #define DS3231_CONTROL 0x0E   ///< Control register
  #define DS3231_STATUSREG 0x0F ///< Status register
  #define DS3231_TEMPERATUREREG                                                  \
    0x11 ///< Temperature register (high byte - low byte is at 0x12), 10-bit
         ///< temperature value
  
  /** Constants */
  #define SECONDS_PER_DAY 86400L ///< 60 * 60 * 24
  #define SECONDS_FROM_1970_TO_2000                                              \
    946684800 ///< Unixtime for 2000-01-01 00:00:00, useful for initialization
  
  /**************************************************************************/
  /*!
      @brief  Simple general-purpose date/time class (no TZ / DST / leap
              seconds).
  
      This class stores date and time information in a broken-down form, as a
      tuple (year, month, day, hour, minute, second). The day of the week is
      not stored, but computed on request. The class has no notion of time
      zones, daylight saving time, or
      [leap seconds](http://en.wikipedia.org/wiki/Leap_second): time is stored
      in whatever time zone the user chooses to use.
  
      The class supports dates in the range from 1 Jan 2000 to 31 Dec 2099
      inclusive.
  */
  /**************************************************************************/
  class DateTime {
  public:
    DateTime(uint32_t t = SECONDS_FROM_1970_TO_2000);
    DateTime(uint16_t year, uint8_t month, uint8_t day, uint8_t hour = 0,
             uint8_t min = 0, uint8_t sec = 0);
    DateTime(const DateTime &copy);
    DateTime(const char *date, const char *time);
    DateTime(const __FlashStringHelper *date, const __FlashStringHelper *time);
    DateTime(const char *iso8601date);
    bool isValid() const;
    char *toString(char *buffer);
  
    /*!
        @brief  Return the year.
        @return Year (range: 2000--2099).
    */
    uint16_t year() const { return 2000 + yOff; }
    /*!
        @brief  Return the month.
        @return Month number (1--12).
    */
    uint8_t month() const { return m; }
    /*!
        @brief  Return the day of the month.
        @return Day of the month (1--31).
    */
    uint8_t day() const { return d; }
    /*!
        @brief  Return the hour
        @return Hour (0--23).
    */
    uint8_t hour() const { return hh; }
  
    uint8_t twelveHour() const;
    /*!
        @brief  Return whether the time is PM.
        @return 0 if the time is AM, 1 if it's PM.
    */
    uint8_t isPM() const { return hh >= 12; }
    /*!
        @brief  Return the minute.
        @return Minute (0--59).
    */
    uint8_t minute() const { return mm; }
    /*!
        @brief  Return the second.
        @return Second (0--59).
    */
    uint8_t second() const { return ss; }
  
    uint8_t dayOfTheWeek() const;
  
    /* 32-bit times as seconds since 2000-01-01. */
    uint32_t secondstime() const;
  
    /* 32-bit times as seconds since 1970-01-01. */
    uint32_t unixtime(void) const;
  
    /*!
        Format of the ISO 8601 timestamp generated by `timestamp()`. Each
        option corresponds to a `toString()` format as follows:
    */
    enum timestampOpt {
      TIMESTAMP_FULL, //!< `YYYY-MM-DDThh:mm:ss`
      TIMESTAMP_TIME, //!< `hh:mm:ss`
      TIMESTAMP_DATE  //!< `YYYY-MM-DD`
    };
    String timestamp(timestampOpt opt = TIMESTAMP_FULL);
  
    DateTime operator+(const TimeSpan &span);
    DateTime operator-(const TimeSpan &span);
    TimeSpan operator-(const DateTime &right);
    bool operator<(const DateTime &right) const;
  
    /*!
        @brief  Test if one DateTime is greater (later) than another.
        @warning if one or both DateTime objects are invalid, returned value is
          meaningless
        @see use `isValid()` method to check if DateTime object is valid
        @param right DateTime object to compare
        @return True if the left DateTime is later than the right one,
          false otherwise
    */
    bool operator>(const DateTime &right) const { return right < *this; }
  
    /*!
        @brief  Test if one DateTime is less (earlier) than or equal to another
        @warning if one or both DateTime objects are invalid, returned value is
          meaningless
        @see use `isValid()` method to check if DateTime object is valid
        @param right DateTime object to compare
        @return True if the left DateTime is earlier than or equal to the
          right one, false otherwise
    */
    bool operator<=(const DateTime &right) const { return !(*this > right); }
  
    /*!
        @brief  Test if one DateTime is greater (later) than or equal to another
        @warning if one or both DateTime objects are invalid, returned value is
          meaningless
        @see use `isValid()` method to check if DateTime object is valid
        @param right DateTime object to compare
        @return True if the left DateTime is later than or equal to the right
          one, false otherwise
    */
    bool operator>=(const DateTime &right) const { return !(*this < right); }
    bool operator==(const DateTime &right) const;
  
    /*!
        @brief  Test if two DateTime objects are not equal.
        @warning if one or both DateTime objects are invalid, returned value is
          meaningless
        @see use `isValid()` method to check if DateTime object is valid
        @param right DateTime object to compare
        @return True if the two objects are not equal, false if they are
    */
    bool operator!=(const DateTime &right) const { return !(*this == right); }
  
  protected:
    uint8_t yOff; ///< Year offset from 2000
    uint8_t m;    ///< Month 1-12
    uint8_t d;    ///< Day 1-31
    uint8_t hh;   ///< Hours 0-23
    uint8_t mm;   ///< Minutes 0-59
    uint8_t ss;   ///< Seconds 0-59
  };
  
  /**************************************************************************/
  /*!
      @brief  Timespan which can represent changes in time with seconds accuracy.
  */
  /**************************************************************************/
  class TimeSpan {
  public:
    TimeSpan(int32_t seconds = 0);
    TimeSpan(int16_t days, int8_t hours, int8_t minutes, int8_t seconds);
    TimeSpan(const TimeSpan &copy);
  
    /*!
        @brief  Number of days in the TimeSpan
                e.g. 4
        @return int16_t days
    */
    int16_t days() const { return _seconds / 86400L; }
    /*!
        @brief  Number of hours in the TimeSpan
                This is not the total hours, it includes the days
                e.g. 4 days, 3 hours - NOT 99 hours
        @return int8_t hours
    */
    int8_t hours() const { return _seconds / 3600 % 24; }
    /*!
        @brief  Number of minutes in the TimeSpan
                This is not the total minutes, it includes days/hours
                e.g. 4 days, 3 hours, 27 minutes
        @return int8_t minutes
    */
    int8_t minutes() const { return _seconds / 60 % 60; }
    /*!
        @brief  Number of seconds in the TimeSpan
                This is not the total seconds, it includes the days/hours/minutes
                e.g. 4 days, 3 hours, 27 minutes, 7 seconds
        @return int8_t seconds
    */
    int8_t seconds() const { return _seconds % 60; }
    /*!
        @brief  Total number of seconds in the TimeSpan, e.g. 358027
        @return int32_t seconds
    */
    int32_t totalseconds() const { return _seconds; }
  
    TimeSpan operator+(const TimeSpan &right);
    TimeSpan operator-(const TimeSpan &right);
  
  protected:
    int32_t _seconds; ///< Actual TimeSpan value is stored as seconds
  };
  
  /** DS1307 SQW pin mode settings */
  enum Ds1307SqwPinMode {
    DS1307_OFF = 0x00,            // Low
    DS1307_ON = 0x80,             // High
    DS1307_SquareWave1HZ = 0x10,  // 1Hz square wave
    DS1307_SquareWave4kHz = 0x11, // 4kHz square wave
    DS1307_SquareWave8kHz = 0x12, // 8kHz square wave
    DS1307_SquareWave32kHz = 0x13 // 32kHz square wave
  };
  
  /**************************************************************************/
  /*!
      @brief  RTC based on the DS1307 chip connected via I2C and the Wire library
  */
  /**************************************************************************/
  class RTC_DS1307 {
  public:
    boolean begin(void);
    static void adjust(const DateTime &dt);
    uint8_t isrunning(void);
    static DateTime now();
    static Ds1307SqwPinMode readSqwPinMode();
    static void writeSqwPinMode(Ds1307SqwPinMode mode);
    uint8_t readnvram(uint8_t address);
    void readnvram(uint8_t *buf, uint8_t size, uint8_t address);
    void writenvram(uint8_t address, uint8_t data);
    void writenvram(uint8_t address, uint8_t *buf, uint8_t size);
  };
  
  /** DS3231 SQW pin mode settings */
  enum Ds3231SqwPinMode {
    DS3231_OFF = 0x01,            /**< Off */
    DS3231_SquareWave1Hz = 0x00,  /**<  1Hz square wave */
    DS3231_SquareWave1kHz = 0x08, /**<  1kHz square wave */
    DS3231_SquareWave4kHz = 0x10, /**<  4kHz square wave */
    DS3231_SquareWave8kHz = 0x18  /**<  8kHz square wave */
  };
  
  /** DS3231 Alarm modes for alarm 1 */
  enum Ds3231Alarm1Mode {
    DS3231_A1_PerSecond = 0x0F, /**< Alarm once per second */
    DS3231_A1_Second = 0x0E,    /**< Alarm when seconds match */
    DS3231_A1_Minute = 0x0C,    /**< Alarm when minutes and seconds match */
    DS3231_A1_Hour = 0x08,      /**< Alarm when hours, minutes
                                     and seconds match */
    DS3231_A1_Date = 0x00,      /**< Alarm when date (day of month), hours,
                                     minutes and seconds match */
    DS3231_A1_Day = 0x10        /**< Alarm when day (day of week), hours,
                                     minutes and seconds match */
  };
  /** DS3231 Alarm modes for alarm 2 */
  enum Ds3231Alarm2Mode {
    DS3231_A2_PerMinute = 0x7, /**< Alarm once per minute
                                    (whenever seconds are 0) */
    DS3231_A2_Minute = 0x6,    /**< Alarm when minutes match */
    DS3231_A2_Hour = 0x4,      /**< Alarm when hours and minutes match */
    DS3231_A2_Date = 0x0,      /**< Alarm when date (day of month), hours
                                    and minutes match */
    DS3231_A2_Day = 0x8        /**< Alarm when day (day of week), hours
                                    and minutes match */
  };
  
  /**************************************************************************/
  /*!
      @brief  RTC based on the DS3231 chip connected via I2C and the Wire library
  */
  /**************************************************************************/
  class RTC_DS3231 {
  public:
    boolean begin(void);
    static void adjust(const DateTime &dt);
    bool lostPower(void);
    static DateTime now();
    static Ds3231SqwPinMode readSqwPinMode();
    static void writeSqwPinMode(Ds3231SqwPinMode mode);
    bool setAlarm1(const DateTime &dt, Ds3231Alarm1Mode alarm_mode);
    bool setAlarm2(const DateTime &dt, Ds3231Alarm2Mode alarm_mode);
    void disableAlarm(uint8_t alarm_num);
    void clearAlarm(uint8_t alarm_num);
    bool alarmFired(uint8_t alarm_num);
    void enable32K(void);
    void disable32K(void);
    bool isEnabled32K(void);
    static float getTemperature(); // in Celcius degree
  };
  
  /** PCF8523 INT/SQW pin mode settings */
  enum Pcf8523SqwPinMode {
    PCF8523_OFF = 7,             /**< Off */
    PCF8523_SquareWave1HZ = 6,   /**< 1Hz square wave */
    PCF8523_SquareWave32HZ = 5,  /**< 32Hz square wave */
    PCF8523_SquareWave1kHz = 4,  /**< 1kHz square wave */
    PCF8523_SquareWave4kHz = 3,  /**< 4kHz square wave */
    PCF8523_SquareWave8kHz = 2,  /**< 8kHz square wave */
    PCF8523_SquareWave16kHz = 1, /**< 16kHz square wave */
    PCF8523_SquareWave32kHz = 0  /**< 32kHz square wave */
  };
  
  /** PCF8523 Timer Source Clock Frequencies for Timers A and B */
  enum PCF8523TimerClockFreq {
    PCF8523_Frequency4kHz = 0,   /**< 1/4096th second = 244 microseconds,
                                      max 62.256 milliseconds */
    PCF8523_Frequency64Hz = 1,   /**< 1/64th second = 15.625 milliseconds,
                                      max 3.984375 seconds */
    PCF8523_FrequencySecond = 2, /**< 1 second, max 255 seconds = 4.25 minutes */
    PCF8523_FrequencyMinute = 3, /**< 1 minute, max 255 minutes = 4.25 hours */
    PCF8523_FrequencyHour = 4,   /**< 1 hour, max 255 hours = 10.625 days */
  };
  
  /** PCF8523 Timer Interrupt Low Pulse Width options for Timer B only */
  enum PCF8523TimerIntPulse {
    PCF8523_LowPulse3x64Hz = 0,  /**<  46.875 ms   3/64ths second */
    PCF8523_LowPulse4x64Hz = 1,  /**<  62.500 ms   4/64ths second */
    PCF8523_LowPulse5x64Hz = 2,  /**<  78.125 ms   5/64ths second */
    PCF8523_LowPulse6x64Hz = 3,  /**<  93.750 ms   6/64ths second */
    PCF8523_LowPulse8x64Hz = 4,  /**< 125.000 ms   8/64ths second */
    PCF8523_LowPulse10x64Hz = 5, /**< 156.250 ms  10/64ths second */
    PCF8523_LowPulse12x64Hz = 6, /**< 187.500 ms  12/64ths second */
    PCF8523_LowPulse14x64Hz = 7  /**< 218.750 ms  14/64ths second */
  };
  
  /** PCF8523 Offset modes for making temperature/aging/accuracy adjustments */
  enum Pcf8523OffsetMode {
    PCF8523_TwoHours = 0x00, /**< Offset made every two hours */
    PCF8523_OneMinute = 0x80 /**< Offset made every minute */
  };
  
  /**************************************************************************/
  /*!
      @brief  RTC based on the PCF8523 chip connected via I2C and the Wire library
  */
  /**************************************************************************/
  class RTC_PCF8523 {
  public:
    boolean begin(void);
    void adjust(const DateTime &dt);
    boolean lostPower(void);
    boolean initialized(void);
    static DateTime now();
    void start(void);
    void stop(void);
    uint8_t isrunning();
    Pcf8523SqwPinMode readSqwPinMode();
    void writeSqwPinMode(Pcf8523SqwPinMode mode);
    void enableSecondTimer(void);
    void disableSecondTimer(void);
    void enableCountdownTimer(PCF8523TimerClockFreq clkFreq, uint8_t numPeriods,
                              uint8_t lowPulseWidth);
    void enableCountdownTimer(PCF8523TimerClockFreq clkFreq, uint8_t numPeriods);
    void disableCountdownTimer(void);
    void deconfigureAllTimers(void);
    void calibrate(Pcf8523OffsetMode mode, int8_t offset);
  };
  
  /**************************************************************************/
  /*!
      @brief  RTC using the internal millis() clock, has to be initialized before
     use. NOTE: this is immune to millis() rollover events.
  */
  /**************************************************************************/
  class RTC_Millis {
  public:
    /*!
        @brief  Start the RTC
        @param dt DateTime object with the date/time to set
    */
    static void begin(const DateTime &dt) { adjust(dt); }
    static void adjust(const DateTime &dt);
    static DateTime now();
  
  protected:
    static uint32_t lastUnix;   ///< Unix time from the previous call to now() -
                                ///< prevents rollover issues
    static uint32_t lastMillis; ///< the millis() value corresponding to the last
                                ///< **full second** of Unix time
  };
  
  /**************************************************************************/
  /*!
      @brief  RTC using the internal micros() clock, has to be initialized before
              use. Unlike RTC_Millis, this can be tuned in order to compensate for
              the natural drift of the system clock. Note that now() has to be
              called more frequently than the micros() rollover period, which is
              approximately 71.6 minutes.
  */
  /**************************************************************************/
  class RTC_Micros {
  public:
    /*!
        @brief  Start the RTC
        @param dt DateTime object with the date/time to set
    */
    static void begin(const DateTime &dt) { adjust(dt); }
    static void adjust(const DateTime &dt);
    static void adjustDrift(int ppm);
    static DateTime now();
  
  protected:
    static uint32_t microsPerSecond; ///< Number of microseconds reported by
                                     ///< micros() per "true" (calibrated) second
    static uint32_t lastUnix;   ///< Unix time from the previous call to now() -
                                ///< prevents rollover issues
    static uint32_t lastMicros; ///< micros() value corresponding to the last full
                                ///< second of Unix time
  };
  
  #endif // _RTCLIB_H_
  