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       gpsctl - control the modes of a GPS


       gpsctl [-h] [-b | -n] [-x control] [-e] [-f] [-l] [-s speed]
              [-t devicetype] [-D debuglevel] [-V] [serial-port]


       gpsctl can switch a dual-mode GPS between NMEA and vendor-binary modes.
       It can also be used to set the device baudrate. Note: Not all devices
       have these capabilities.

       If you have only one GPS attached to your machine, and gpsd is running,
       it is not necessary to specify the device; gpsctl does its work through
       gpsd, which will locate it for you.

       When gpsd is not running, the device specification is required, and you
       will almost certainly need to be running as root in order to have write
       access to the device.

       The program accepts the following options:

           Put the GPS into binary mode. After the GPS resets itself, autobaud
           to the new speed.

           Change the GPS's cycle time. Units are seconds. Note, most GPSes
           have a fixed cycle time of 1 second.

           Generate the packet from any other arguments specified and ship it
           to standard output instead of the device. This switch can be used
           with the -t option without specifying a device. Note: the packet
           data for a binary prototype will be raw, not ASCII-ized in any way.

           Force low-level access (not through the daemon).

           List a table showing which option switches can be applied to which
           device types, and exit.

           Put GPS into NMEA mode. After the GPS resets itself autobaud to its
           new speed.

           Set the baud rate at which the GPS emits packets.

           Use this option with caution. On USB and Bluetooth GPSes it is also
           possible for serial mode setting to fail either because the serial
           adaptor chip does not support non-8N1 modes or because the device
           firmware does not properly synchronize the serrial adaptor chip
           with the UART on the GPS chipset whjen the speed changes. These
           failures can hang your device, possibly requiring a GPS power cycle
           or (in extreme cases) physically disconnecting the NVRAM backup

           Force the device type.

           Send a specified control string to the GPS; gpsctl will provide
           packet headers and trailers and checksum as appropriate for binary
           packet types, and whatever checksum and trailer is required for
           text packet types. (You must include the leading $ for NMEA
           packets.) When sending to a UBX device, the first two bytes of the
           string supplied will become the message class and type, and the
           remainder the payload. When sending to a Navcom NCT or Trimble TSIP
           device, the first byte is interpreted as the command ID and the
           rest as payload. When sending to a Zodiac device, the first two
           bytes are used as a message ID of type little-endian short, and the
           remainder as payload in byte pairs interpreted as little-endian
           short. C-style backslash escapes in the string, notably \xNN for
           hex, will be interpreted; additionally, \e will be replaced with
           ESC. This switch implies -f.

           Change the sampling timeout. Defaults to 4 seconds, which should
           always be sufficient to get a packet from a device emitting at the
           normal rate of 1 per second.

           Display program usage and exit.

           Set level of debug messages.

           Display program version and exit.

       The argument of the forcing option.  -t, should be a string which
       should be contained in exactly one of the known driver names; for a
       list, do gpsctl -l.

       Forcing the device type behaves somewhat differently depending on
       whether this tool is going through the daemon or not. In high-level
       mode, if the device that daemon selects for you doesn't match the
       driver you specified, gpsctl exits with a warning. (This may be useful
       in scripts.)

       In low-level mode, if the device identifies as a Generic NMEA, use the
       selected driver instead. This will be useful if you have a GPS device
       of known type that is in NMEA mode and not responding to probes. (This
       option was originally implemented for talking to SiRFStar I chips,
       which don't respond to the normal SiRF ID probe.)

       If no options are given, the program will display a message identifying
       the GPS type of the selected device and exit.

       Reset (-r) operations must stand alone; others can be combined.
       Multiple opations will be executed in tis order: mode changes (-b and
       -n) first, speed changes (-s) second, and control-string sends (-c)


       gpsctl /dev/ttyUSB0
           Attempt to identify the device on USB serial device 0. Time out
           after the default number of seconds. Adding the -f will force
           low-level access and suppress the normal complaint when this tool
           can't find a GPSD to work through.

       gpsctl -f -n -s 9600 /dev/ttyUSB0
           Use low-level operations (not going through a gpsd instance) to
           switch a GPS to NMEA mode at 9600bps. The tool will identify the
           GPS type itself.


       SiRF GPSes can only be identified by the success of an attempt to flip
       them into SiRF binary mode. Thus, the process of probing one of these
       running in NMEA will change its behavior.


       gpsd(8), gps(1), libgps(3), libgpsd(3), gpsprof(1), gpsfake(1).


       Eric S. Raymond There is a project page for gpsd


        1. here