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6 libgpsd - service library for GPS applications
7
9 C:
10 #include <gpsd.h>
12 int gpsd_open_dgps (char * dgpsserver);
17 void gpsd_init (struct gps_device_t *session, struct * gps_context_t *,
19 char * device);
20 int gpsd_activate (struct gps_device_t *session, bool reconfigurable);
22 void gpsd_deactivate (struct gps_device_t * session);
24 gps_mask_t gpsd_poll (struct gps_device_t * session);
26 void gpsd_wrap (struct gps_device_t * session);
28 void gpsd_report (int d, const char * fmt, ...);
30
33 libgps is a service library which supports querying GPS devices; link
34 it with the linker option -lgps. There are two interfaces supported in
35 it; one high-level interface that goes through gpsd(1) and is intended
36 for concurrent use by several applications, and one low-level interface
37 that speaks directly with the serial or USB device to which the GPS is
38 attached. This page describes the low-level interface, which gpsd(1)
39 itself uses. See gpsd(3) for a description of the high-level interface,
40 which is almost certainly what you want.
41 Calling gpsd_init() initializes a session structure to hold the data
44 collected by the GPS.
45 You may optionally specify a DGPS server, either as a string containing
48 a server name or a string containining server name followed by a colon
49 and a port name or number. To specify no DGPS, pass the null pointer.
50 The second argument must be a context structure. The library will use
53 it for information that need to be shared between sessions; presently
54 this includes the leap-second correction and possibly a pointer to a
55 shared-memory segment used to communicate with the Network Time Proto‐
56 col daemon.
57 After the session structure has been set up, you may modify some of its
60 members.
61 gpsd_device
64 This member should hold the path name of the device.
65 baudrate
68 Communication speed in bits per second. For NMEA or SiRF de‐
69 vices, the library automatically hunts through all plausible
70 baud rates, stopping on the one where it sees valid packets. By
71 setting this field you can designate a speed to be tried at the
72 front of the hunt queue
73 raw_hook
76 A hook function to be executed on each NMEA sentence or as it is
77 read from the GPS. The data from non-NMEA GPSes like the Earth‐
78 Mate will be translated to an NMEA sentence before being passed
79 to the hook. Parameters are a pointer to a gps_data structure
80 full of parsed data, the sentence, the length of the sentence,
81 and a rawness level.
82 gpsd_activate() initializes the connection to the GPS. gpsd_deacti‐
85 vate() closes the connection. These functions are provided so that
86 long-running programs can release a connection when there is no activi‐
87 ty requiring the GPS, and re-acquire it later.
88 gpsd_poll() queries the GPS and updates the part of the session struc‐
91 ture that holds position, speed, GPS signal quality, and other data re‐
92 turned by the GPS. It returns a mask describing which fields have
93 changed.
94 gpsd_wrap() ends the session, implicitly performing a gpsd_deacti‐
97 vate().
98 The calling application must define one additional function: gpsd_re‐
101 port(). The library will use this to issue ordinary status messages.
102 Use first argument of 0 for errors, 1 for ordinary status messages, and
103 2 or higher for debugging messages.
104 The low-level functions do not allocate or free any dynamic storage.
107 They can thus be used in a long-running application (such as gpsd(8)
108 itself) with a guarantee that they won't cause memory leaks.
109
112 Writes to the context structure members are not guarded by a mutex.
113
116 gpsd(8), gps(1), libgpsd(3).
117
120 Eric S. Raymond <esr@thyrsus.com> based partly on earlier work by Remco
121 Treffkorn, Derrick Brashear, and Russ Nelson.
122 14 Aug 2004 3(3)