Provided by: avr-libc_2.0.0+Atmel3.6.0-1_all bug

NAME

       avr_time

SYNOPSIS

   Data Structures
       struct tm
       struct week_date

   Macros
       #define ONE_HOUR   3600
       #define ONE_DEGREE   3600
       #define ONE_DAY   86400
       #define UNIX_OFFSET   946684800
       #define NTP_OFFSET   3155673600

   Typedefs
       typedef uint32_t time_t

   Enumerations
       enum _WEEK_DAYS_ { SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY }
       enum _MONTHS_ { JANUARY, FEBRUARY, MARCH, APRIL, MAY, JUNE, JULY, AUGUST, SEPTEMBER,
           OCTOBER, NOVEMBER, DECEMBER }

   Functions
       time_t time (time_t *timer)
       int32_t difftime (time_t time1, time_t time0)
       time_t mktime (struct tm *timeptr)
       time_t mk_gmtime (const struct tm *timeptr)
       struct tm * gmtime (const time_t *timer)
       void gmtime_r (const time_t *timer, struct tm *timeptr)
       struct tm * localtime (const time_t *timer)
       void localtime_r (const time_t *timer, struct tm *timeptr)
       char * asctime (const struct tm *timeptr)
       void asctime_r (const struct tm *timeptr, char *buf)
       char * ctime (const time_t *timer)
       void ctime_r (const time_t *timer, char *buf)
       char * isotime (const struct tm *tmptr)
       void isotime_r (const struct tm *, char *)
       size_t strftime (char *s, size_t maxsize, const char *format, const struct tm *timeptr)
       void set_dst (int(*)(const time_t *, int32_t *))
       void set_zone (int32_t)
       void set_system_time (time_t timestamp)
       void system_tick (void)
       uint8_t is_leap_year (int16_t year)
       uint8_t month_length (int16_t year, uint8_t month)
       uint8_t week_of_year (const struct tm *timeptr, uint8_t start)
       uint8_t week_of_month (const struct tm *timeptr, uint8_t start)
       struct week_date * iso_week_date (int year, int yday)
       void iso_week_date_r (int year, int yday, struct week_date *)
       uint32_t fatfs_time (const struct tm *timeptr)
       void set_position (int32_t latitude, int32_t longitude)
       int16_t equation_of_time (const time_t *timer)
       int32_t daylight_seconds (const time_t *timer)
       time_t solar_noon (const time_t *timer)
       time_t sun_rise (const time_t *timer)
       time_t sun_set (const time_t *timer)
       double solar_declination (const time_t *timer)
       int8_t moon_phase (const time_t *timer)
       unsigned long gm_sidereal (const time_t *timer)
       unsigned long lm_sidereal (const time_t *timer)

Detailed Description

       #include <time.h>

   Introduction to the Time functions
       This file declares the time functions implemented in avr-libc.

       The implementation aspires to conform with ISO/IEC 9899 (C90). However, due to limitations
       of the target processor and the nature of its development environment, a practical
       implementation must of necessity deviate from the standard.

       Section 7.23.2.1 clock() The type clock_t, the macro CLOCKS_PER_SEC, and the function
       clock() are not implemented. We consider these items belong to operating system code, or
       to application code when no operating system is present.

       Section 7.23.2.3 mktime() The standard specifies that mktime() should return (time_t) -1,
       if the time cannot be represented. This implementation always returns a 'best effort'
       representation.

       Section 7.23.2.4 time() The standard specifies that time() should return (time_t) -1, if
       the time is not available. Since the application must initialize the time system, this
       functionality is not implemented.

       Section 7.23.2.2, difftime() Due to the lack of a 64 bit double, the function difftime()
       returns a long integer. In most cases this change will be invisible to the user, handled
       automatically by the compiler.

       Section 7.23.1.4 struct tm Per the standard, struct tm->tm_isdst is greater than zero when
       Daylight Saving time is in effect. This implementation further specifies that, when
       positive, the value of tm_isdst represents the amount time is advanced during Daylight
       Saving time.

       Section 7.23.3.5 strftime() Only the 'C' locale is supported, therefore the modifiers 'E'
       and 'O' are ignored. The 'Z' conversion is also ignored, due to the lack of time zone
       name.

       In addition to the above departures from the standard, there are some behaviors which are
       different from what is often expected, though allowed under the standard.

       There is no 'platform standard' method to obtain the current time, time zone, or daylight
       savings 'rules' in the AVR environment. Therefore the application must initialize the time
       system with this information. The functions set_zone(), set_dst(), and set_system_time()
       are provided for initialization. Once initialized, system time is maintained by calling
       the function system_tick() at one second intervals.

       Though not specified in the standard, it is often expected that time_t is a signed integer
       representing an offset in seconds from Midnight Jan 1 1970... i.e. 'Unix time'. This
       implementation uses an unsigned 32 bit integer offset from Midnight Jan 1 2000. The use of
       this 'epoch' helps to simplify the conversion functions, while the 32 bit value allows
       time to be properly represented until Tue Feb 7 06:28:15 2136 UTC. The macros UNIX_OFFSET
       and NTP_OFFSET are defined to assist in converting to and from Unix and NTP time stamps.

       Unlike desktop counterparts, it is impractical to implement or maintain the 'zoneinfo'
       database. Therefore no attempt is made to account for time zone, daylight saving, or leap
       seconds in past dates. All calculations are made according to the currently configured
       time zone and daylight saving 'rule'.

       In addition to C standard functions, re-entrant versions of ctime(), asctime(), gmtime()
       and localtime() are provided which, in addition to being re-entrant, have the property of
       claiming less permanent storage in RAM. An additional time conversion, isotime() and its
       re-entrant version, uses far less storage than either ctime() or asctime().

       Along with the usual smattering of utility functions, such as is_leap_year(), this library
       includes a set of functions related the sun and moon, as well as sidereal time functions.

Macro Definition Documentation

   #define NTP_OFFSET   3155673600
       Difference between the Y2K and the NTP epochs, in seconds. To convert a Y2K timestamp to
       NTP...

       unsigned long ntp;
       time_t y2k;

       y2k = time(NULL);
       ntp = y2k + NTP_OFFSET;

   #define ONE_DAY   86400
       One day, expressed in seconds

   #define ONE_DEGREE   3600
       Angular degree, expressed in arc seconds

   #define ONE_HOUR   3600
       One hour, expressed in seconds

   #define UNIX_OFFSET   946684800
       Difference between the Y2K and the UNIX epochs, in seconds. To convert a Y2K timestamp to
       UNIX...

       long unix;
       time_t y2k;

       y2k = time(NULL);
       unix = y2k + UNIX_OFFSET;

Typedef Documentation

   typedef uint32_t time_t
       time_t represents seconds elapsed from Midnight, Jan 1 2000 UTC (the Y2K 'epoch'). Its
       range allows this implementation to represent time up to Tue Feb 7 06:28:15 2136 UTC.

Enumeration Type Documentation

   enum _MONTHS_
       Enumerated labels for the months.

   enum _WEEK_DAYS_
       Enumerated labels for the days of the week.

Function Documentation

   char* asctime (const struct tm * timeptr)
       The asctime function converts the broken-down time of timeptr, into an ascii string in the
       form

       Sun Mar 23 01:03:52 2013

   void asctime_r (const struct tm * timeptr, char * buf)
       Re entrant version of asctime().

   char* ctime (const time_t * timer)
       The ctime function is equivalent to asctime(localtime(timer))

   void ctime_r (const time_t * timer, char * buf)
       Re entrant version of ctime().

   int32_t daylight_seconds (const time_t * timer)
       Computes the amount of time the sun is above the horizon, at the location of the observer.

       NOTE: At observer locations inside a polar circle, this value can be zero during the
       winter, and can exceed ONE_DAY during the summer.

       The returned value is in seconds.

   int32_t difftime (time_t time1, time_t time0)
       The difftime function returns the difference between two binary time stamps, time1 -
       time0.

   int16_t equation_of_time (const time_t * timer)
       Computes the difference between apparent solar time and mean solar time. The returned
       value is in seconds.

   uint32_t fatfs_time (const struct tm * timeptr)
       Convert a Y2K time stamp into a FAT file system time stamp.

   unsigned long gm_sidereal (const time_t * timer)
       Returns Greenwich Mean Sidereal Time, as seconds into the sidereal day. The returned value
       will range from 0 through 86399 seconds.

   struct tm* gmtime (const time_t * timer)
       The gmtime function converts the time stamp pointed to by timer into broken-down time,
       expressed as UTC.

   void gmtime_r (const time_t * timer, struct tm * timeptr)
       Re entrant version of gmtime().

   uint8_t is_leap_year (int16_t year)
       Return 1 if year is a leap year, zero if it is not.

   struct week_date* iso_week_date (int year, int yday)
       Return a week_date structure with the ISO_8601 week based date corresponding to the given
       year and day of year. See http://en.wikipedia.org/wiki/ISO_week_date for more information.

   void iso_week_date_r (int year, int yday, struct week_date *)
       Re-entrant version of iso-week_date.

   char* isotime (const struct tm * tmptr)
       The isotime function constructs an ascii string in the form

       2013-03-23 01:03:52

   void isotime_r (const struct tm *, char *)
       Re entrant version of isotime()

   unsigned long lm_sidereal (const time_t * timer)
       Returns Local Mean Sidereal Time, as seconds into the sidereal day. The returned value
       will range from 0 through 86399 seconds.

   struct tm* localtime (const time_t * timer)
       The localtime function converts the time stamp pointed to by timer into broken-down time,
       expressed as Local time.

   void localtime_r (const time_t * timer, struct tm * timeptr)
       Re entrant version of localtime().

   time_t mk_gmtime (const struct tm * timeptr)
       This function 'compiles' the elements of a broken-down time structure, returning a binary
       time stamp. The elements of timeptr are interpreted as representing UTC.

       The original values of the tm_wday and tm_yday elements of the structure are ignored, and
       the original values of the other elements are not restricted to the ranges stated for
       struct tm.

       Unlike mktime(), this function DOES NOT modify the elements of timeptr.

   time_t mktime (struct tm * timeptr)
       This function 'compiles' the elements of a broken-down time structure, returning a binary
       time stamp. The elements of timeptr are interpreted as representing Local Time.

       The original values of the tm_wday and tm_yday elements of the structure are ignored, and
       the original values of the other elements are not restricted to the ranges stated for
       struct tm.

       On successful completion, the values of all elements of timeptr are set to the appropriate
       range.

   uint8_t month_length (int16_t year, uint8_t month)
       Return the length of month, given the year and month, where month is in the range 1 to 12.

   int8_t moon_phase (const time_t * timer)
       Returns an approximation to the phase of the moon. The sign of the returned value
       indicates a waning or waxing phase. The magnitude of the returned value indicates the
       percentage illumination.

   void set_dst (int(*)(const time_t *, int32_t *))
       Specify the Daylight Saving function.

       The Daylight Saving function should examine its parameters to determine whether Daylight
       Saving is in effect, and return a value appropriate for tm_isdst.

       Working examples for the USA and the EU are available..

       #include <util/eu_dst.h>

        for the European Union, and

       #include <util/usa_dst.h>

        for the United States

       If a Daylight Saving function is not specified, the system will ignore Daylight Saving.

   void set_position (int32_t latitude, int32_t longitude)
       Set the geographic coordinates of the 'observer', for use with several of the following
       functions. Parameters are passed as seconds of North Latitude, and seconds of East
       Longitude.

       For New York City...

       set_position( 40.7142 * ONE_DEGREE, -74.0064 * ONE_DEGREE);

   void set_system_time (time_t timestamp)
       Initialize the system time. Examples are...

       From a Clock / Calendar type RTC:

       struct tm rtc_time;

       read_rtc(&rtc_time);
       rtc_time.tm_isdst = 0;
       set_system_time( mktime(&rtc_time) );

       From a Network Time Protocol time stamp:

       set_system_time(ntp_timestamp - NTP_OFFSET);

       From a UNIX time stamp:

       set_system_time(unix_timestamp - UNIX_OFFSET);

   void set_zone (int32_t)
       Set the 'time zone'. The parameter is given in seconds East of the Prime Meridian. Example
       for New York City:

       set_zone(-5 * ONE_HOUR);

       If the time zone is not set, the time system will operate in UTC only.

   double solar_declination (const time_t * timer)
       Returns the declination of the sun in radians.

   time_t solar_noon (const time_t * timer)
       Computes the time of solar noon, at the location of the observer.

   size_t strftime (char * s, size_t maxsize, const char * format, const struct tm * timeptr)
       A complete description of strftime() is beyond the pale of this document. Refer to ISO/IEC
       document 9899 for details.

       All conversions are made using the 'C Locale', ignoring the E or O modifiers. Due to the
       lack of a time zone 'name', the 'Z' conversion is also ignored.

   time_t sun_rise (const time_t * timer)
       Return the time of sunrise, at the location of the observer. See the note about
       daylight_seconds().

   time_t sun_set (const time_t * timer)
       Return the time of sunset, at the location of the observer. See the note about
       daylight_seconds().

   void system_tick (void)
       Maintain the system time by calling this function at a rate of 1 Hertz.

       It is anticipated that this function will typically be called from within an Interrupt
       Service Routine, (though that is not required). It therefore includes code which makes it
       simple to use from within a 'Naked' ISR, avoiding the cost of saving and restoring all the
       cpu registers.

       Such an ISR may resemble the following example...

       ISR(RTC_OVF_vect, ISR_NAKED)
       {
           system_tick();
           reti();
       }

   time_t time (time_t * timer)
       The time function returns the systems current time stamp. If timer is not a null pointer,
       the return value is also assigned to the object it points to.

   uint8_t week_of_month (const struct tm * timeptr, uint8_t start)
       Return the calendar week of month, where the first week is considered to begin on the day
       of week specified by 'start'. The returned value may range from zero to 5.

   uint8_t week_of_year (const struct tm * timeptr, uint8_t start)
       Return the calendar week of year, where week 1 is considered to begin on the day of week
       specified by 'start'. The returned value may range from zero to 52.

Author

       Generated automatically by Doxygen for avr-libc from the source code.