14 Aug 2004
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The GPSD Project
GPSD Documentation
libgpsd
service library for GPS applications
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
DESCRIPTION
libgpsd
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
gpsd1
itself uses. See
gpsd3
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
gpsd8
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 ALSO
gpsd8,
gps1,
libgps3.
AUTHOR
Eric S. Raymond <esr@thyrsus.com> based partly on earlier work by
Remco Treffkorn, Derrick Brashear, and Russ Nelson.