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Diffstat (limited to 'include/ntp_calgps.h')
| -rw-r--r-- | include/ntp_calgps.h | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/include/ntp_calgps.h b/include/ntp_calgps.h new file mode 100644 index 0000000000000..7b5d83d1305c5 --- /dev/null +++ b/include/ntp_calgps.h @@ -0,0 +1,151 @@ +/* + * ntp_calgps.h - calendar for GPS/GNSS based clocks + * + * Written by Juergen Perlinger (perlinger@ntp.org) for the NTP project. + * The contents of 'html/copyright.html' apply. + * + * -------------------------------------------------------------------- + * + * This module implements stuff often used with GPS/GNSS receivers + */ +#ifndef NTP_CALGPS_H +#define NTP_CALGPS_H + +#include <time.h> + +#include "ntp_types.h" +#include "ntp_fp.h" +#include "ntp_calendar.h" + +/* GPS week calendar (extended weeks) + * We use weeks based on 1899-31-12, which was the last Sunday before + * the begin of the NTP epoch. (Which is equivalent to saying 1900-01-01 + * was a Monday...) + * + * We simply pre-calculate the offsets and cycle shifts for the real GPS + * calendar, which starts at 1980-01-06, to simplyfy some expressions. + * + * This has a fringe benefit that should not be overlooked: Since week zero + * is around 1900, and we should never have to deal with dates before + * 1970 or 1980, a week number of zero can be easily used to indicate + * an invalid week time stamp. + */ +#define GPSNTP_WSHIFT 4175 /* weeks 1899-31-12 --> 1980-01-06 */ +#define GPSNTP_WCYCLE 79 /* above, modulo 1024 */ +#define GPSNTP_DSHIFT 1 /* day number of 1900-01-01 in week */ + +struct gpsdatum { + uint32_t weeks; /* weeks since GPS epoch */ + int32_t wsecs; /* seconds since week start */ + uint32_t frac; /* fractional seconds */ +}; +typedef struct gpsdatum TGpsDatum; +typedef struct gpsdatum const TcGpsDatum; + +/* NTP date/time in split representation */ +struct ntpdatum { + uint32_t days; /* since NTP epoch */ + int32_t secs; /* since midnight, denorm is ok */ + uint32_t frac; /* fractional seconds */ +}; +typedef struct ntpdatum TNtpDatum; +typedef struct ntpdatum const TcNtpDatum; + +/* + * GPS week/sec calendar functions + * + * see the implementation for details, especially the + * 'gpscal_from_weektime{1,2}()' + */ + +extern TGpsDatum +gpscal_fix_gps_era(TcGpsDatum *); + +extern void +gpscal_add_offset(TGpsDatum *datum, l_fp offset); + +extern TGpsDatum +gpscal_from_calendar_ex(TcCivilDate*, l_fp fofs, int/*BOOL*/ warp); + +static inline TGpsDatum +gpscal_from_calendar(TcCivilDate *pCiv, l_fp fofs) { + return gpscal_from_calendar_ex(pCiv, fofs, TRUE); +} + +extern TGpsDatum /* see source for semantic of the 'fofs' value! */ +gpscal_from_gpsweek(uint16_t w, int32_t s, l_fp fofs); + +extern TGpsDatum +gpscal_from_weektime1(int32_t wsecs, l_fp fofs, l_fp pivot); + +extern TGpsDatum +gpscal_from_weektime2(int32_t wsecs, l_fp fofs, TcGpsDatum *pivot); + +extern void +gpscal_to_calendar(TCivilDate*, TcGpsDatum*); + +extern TGpsDatum +gpscal_from_gpsntp(TcNtpDatum*); + +extern l_fp +ntpfp_from_gpsdatum(TcGpsDatum *); + +/* + * NTP day/sec calendar functions + * + * see the implementation for details, especially the + * 'gpscal_from_daytime{1,2}()' + */ +extern TNtpDatum +gpsntp_fix_gps_era(TcNtpDatum *); + +extern void +gpsntp_add_offset(TNtpDatum *datum, l_fp offset); + +extern TNtpDatum +gpsntp_from_calendar_ex(TcCivilDate*, l_fp fofs, int/*BOOL*/ warp); + +static inline TNtpDatum +gpsntp_from_calendar(TcCivilDate * pCiv, l_fp fofs) { + return gpsntp_from_calendar_ex(pCiv, fofs, TRUE); +} + +extern TNtpDatum +gpsntp_from_daytime1_ex(TcCivilDate *dt, l_fp fofs, l_fp pivot, int/*BOOL*/ warp); + +static inline TNtpDatum +gpsntp_from_daytime1(TcCivilDate *dt, l_fp fofs, l_fp pivot) { + return gpsntp_from_daytime1_ex(dt, fofs, pivot, TRUE); +} + +extern TNtpDatum +gpsntp_from_daytime2_ex(TcCivilDate *dt, l_fp fofs, TcNtpDatum *pivot, int/*BOOL*/ warp); + +static inline TNtpDatum +gpsntp_from_daytime2(TcCivilDate *dt, l_fp fofs, TcNtpDatum *pivot) { + return gpsntp_from_daytime2_ex(dt, fofs, pivot, TRUE); +} + +extern TNtpDatum +gpsntp_from_gpscal_ex(TcGpsDatum*, int/*BOOL*/ warp); + +static inline TNtpDatum +gpsntp_from_gpscal(TcGpsDatum *wd) { + return gpsntp_from_gpscal_ex(wd, FALSE); +} + +extern void +gpsntp_to_calendar(TCivilDate*, TcNtpDatum*); + +extern l_fp +ntpfp_from_ntpdatum(TcNtpDatum*); + +/* + * Some helpers + */ + +/* apply fudge to time stamp: *SUBTRACT* the given offset from an l_fp*/ +extern l_fp +ntpfp_with_fudge(l_fp lfp, double ofs); + +#endif /*!defined(NTP_CALGPS_H)*/ |