3(3) GPSD Documentation 3(3)NAMElibgpsd - service library for GPS applications
SYNOPSIS
C:
#include <gpsd.h>
int gpsd_open_dgps(char * dgpsserver);
void gpsd_init(struct gps_device_t *session, struct * gps_context_t *,
char * device);
int gpsd_activate(struct gps_device_t *session);
void gpsd_deactivate(struct gps_device_t * session);
gps_mask_t gpsd_poll(struct gps_device_t * session);
void gpsd_wrap(struct gps_device_t * session);
DESCRIPTIONlibgpsd is a service library which supports querying GPS devices; link
it with the linker option -lgpsd. It is a set of low-level
device-handling calls, which gpsd(1) itself uses. See gpsd(3) for a
description of the high-level interface, which is almost certainly what
you want.
Calling gpsd_init() initializes a session structure to hold the data
collected by the GPS.
The second argument must be a context structure. The library will use
it for information that need to be shared between sessions; presently
this includes the leap-second correction and possibly a pointer to a
shared-memory segment used to communicate with the Network Time
Protocol daemon.
After the session structure has been set up, you may modify some of its
members.
gpsd_device
This member should hold the path name of the device.
baudrate
Communication speed in bits per second. For NMEA or SiRF devices,
the library automatically hunts through all plausible baud rates,
stopping on the one where it sees valid packets. By setting this
field you can designate a speed to be tried at the front of the
hunt queue
gpsd_activate() initializes the connection to the GPS.
gpsd_deactivate() closes the connection. These functions are provided
so that long-running programs can release a connection when there is no
activity requiring the GPS, and re-acquire it later.
gpsd_poll() queries the GPS and updates the part of the session
structure that holds position, speed, GPS signal quality, and other
data returned by the GPS. It returns a mask describing which fields
have changed.
gpsd_wrap() ends the session, implicitly performing a
gpsd_deactivate().
The calling application must define one additional function:
gpsd_report(). The library will use this to issue ordinary status
messages. See gpsd.h in the source distribution for the set of logging
levels.
The low-level functions do not allocate or free any dynamic storage.
They can thus be used in a long-running application (such as gpsd(8)
itself) with a guarantee that they won't cause memory leaks.
BUGS
Writes to the context structure members are not guarded by a mutex.
SEE ALSOgpsd(8), gps(1), libgps(3).
AUTHOR
Eric S. Raymond <esr@thyrsus.com> based partly on earlier work by Remco
Treffkorn, Derrick Brashear, and Russ Nelson.
The GPSD Project 14 Aug 2004 3(3)
