1GPSCTL(1) GPSD Documentation GPSCTL(1)
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6 gpsctl - control the modes of a GPS
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9 gpsctl [-h] [-b | -n] [-x control] [-e] [-f] [-l] [-s speed]
10 [-t devicetype] [-R] [-D debuglevel] [-V] [serial-port]
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13 gpsctl can switch a dual-mode GPS between NMEA and vendor-binary modes.
14 It can also be used to set the device baudrate. Note: Not all devices
15 have these capabilities.
16 If you have only one GPS attached to your machine, and gpsd is running,
18 it is not necessary to specify the device; gpsctl does its work through
19 gpsd, which will locate it for you.
20 When gpsd is not running, the device specification is required, and you
22 will need to be running as root or be a member of the device's owning
23 group in order to have write access to the device. On many Unix
24 variants the owning group will be named 'dialout'.
25 The program accepts the following options:
27 -b
29 Put the GPS into native (binary) mode.
30 -c
32 Change the GPS's cycle time. Units are seconds. Note, most GPSes
33 have a fixed cycle time of 1 second.
34 -e
36 Generate the packet from any other arguments specified and ship it
37 to standard output instead of the device. This switch can be used
38 with the -t option without specifying a device. Note: the packet
39 data for a binary prototype will be raw, not ASCII-ized in any way.
40 -f
42 Force low-level access (not through the daemon).
43 -l
45 List a table showing which option switches can be applied to which
46 device types, and exit.
47 -n
49 Put GPS into NMEA mode.
50 -s
52 Set the baud rate at which the GPS emits packets.
53 Use this option with caution. On USB and Bluetooth GPSes it is also
55 possible for serial mode setting to fail either because the serial
56 adaptor chip does not support non-8N1 modes or because the device
57 firmware does not properly synchronize the serial adaptor chip with
58 the UART on the GPS chipset when the speed changes. These failures
59 can hang your device, possibly requiring a GPS power cycle or (in
60 extreme cases) physically disconnecting the NVRAM backup battery.
61 -t
63 Force the device type.
64 -x
66 Send a specified control string to the GPS; gpsctl will provide
67 packet headers and trailers and checksum as appropriate for binary
68 packet types, and whatever checksum and trailer is required for
69 text packet types. (You must include the leading $ for NMEA
70 packets.) When sending to a UBX device, the first two bytes of the
71 string supplied will become the message class and type, and the
72 remainder the payload. When sending to a Navcom NCT or Trimble TSIP
73 device, the first byte is interpreted as the command ID and the
74 rest as payload. When sending to a Zodiac device, the first two
75 bytes are used as a message ID of type little-endian short, and the
76 remainder as payload in byte pairs interpreted as little-endian
77 short. For all other supported binary GPSes (notably including
78 SiRF) the string is taken as the entire message payload and wrapped
79 with appropriate header, trailer and checksum bytes. C-style
80 backslash escapes in the string, notably \xNN for hex, will be
81 interpreted; additionally, \e will be replaced with ESC. This
82 switch implies -f.
83 -T
85 Change the sampling timeout. Defaults to 8 seconds, which should
86 always be sufficient to get an identifying packet from a device
87 emitting at the normal rate of 1 per second.
88 -R
90 Remove the GPSD shared-memory segment used for SHM export. This
91 option will normally only be of interest to GPSD developers.
92 -h
94 Display program usage and exit.
95 -D
97 Set level of debug messages.
98 -V
100 Display program version and exit.
101 The argument of the forcing option, -t, should be a string which is
103 contained in exactly one of the known driver names; for a list, do
104 gpsctl -l.
105 Forcing the device type behaves somewhat differently depending on
107 whether this tool is going through the daemon or not. In high-level
108 mode, if the device that daemon selects for you doesn't match the
109 driver you specified, gpsctl exits with a warning. (This may be useful
110 in scripts.)
111 In low-level mode, if the device identifies as a Generic NMEA, use the
113 selected driver instead. This will be useful if you have a GPS device
114 of known type that is in NMEA mode and not responding to probes. (This
115 option was originally implemented for talking to SiRFStar I chips,
116 which don't respond to the normal SiRF ID probe.)
117 If no options are given, the program will display a message identifying
119 the GPS type of the selected device and exit.
120 Reset (-r) operations must stand alone; others can be combined.
122 Multiple options will be executed in this order: mode changes (-b and
123 -n) first, speed changes (-s) second, and control-string sends (-c)
124 last.
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127 By setting the environment variable GPSD_SHM_KEY, you can control the
128 key value used to designate the shared-memory segment removed with the
129 -R option. This will be useful mainly when isolating test instances of
130 gpsd from production ones.
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133 gpsctl /dev/ttyUSB0
134 Attempt to identify the device on USB serial device 0. Time out
135 after the default number of seconds. Adding the -f will force
136 low-level access and suppress the normal complaint when this tool
137 can't find a GPSD to work through.
138 gpsctl -f -n -s 9600 /dev/ttyUSB0
140 Use low-level operations (not going through a gpsd instance) to
141 switch a GPS to NMEA mode at 9600bps. The tool will identify the
142 GPS type itself.
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145 SiRF GPSes can only be identified by the success of an attempt to flip
146 them into SiRF binary mode. Thus, the process of probing one of these
147 running in NMEA will change its behavior.
148 Baud rate and mode changes work in direct mode but are not reliable in
150 client mode. This will be fixed in a future release.
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153 gpsd(8), gpsdctl(8), gps(1), libgps(3), libgpsmm(3), gpsprof(1),
154 gpsfake(1).
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157 Eric S. Raymond <esr@thyrsus.com>.
158The GPSD Project 29 Oct 2006 GPSCTL(1)