


nmea(n)            NMEA protocol implementation           nmea(n)


______________________________________________________________________________

NAME
       nmea - Process NMEA data

SYNOPSIS
       package require Tcl  8.4

       package require nmea  ?1.0.0?

       ::nmea::input sentence

       ::nmea::open_port port ?speed?

       ::nmea::close_port

       ::nmea::configure_port settings

       ::nmea::open_file file ?rate?

       ::nmea::close_file

       ::nmea::do_line

       ::nmea::rate

       ::nmea::log ?file?

       ::nmea::checksum data

       ::nmea::write sentence data

       ::nmea::event setence ?command?

_________________________________________________________________

DESCRIPTION
       This  package  provides a standard interface for writing software which
       recieves NMEA standard input data. It allows for reading data from  COM
       ports,  files, or programmatic input. It also supports the checksumming
       and logging of incoming data.  After parsing, input  is  dispatched  to
       user defined handler commands for processing.  To define a handler, see
       the event command. There are no GPS specific functions in this package.
       NMEA data consists of a sentence type, followed by a list of data.

COMMANDS
       ::nmea::input sentence
              Processes and dispatches the supplied sentence. If sentence con-
              tains no commas it is treated as a Tcl list, otherwise  it  must
              be standard comma delimited NMEA data, with an optional checksum
              and leading $.

              nmea::input {$GPGSA,A,3,04,05,,09,12,,,24,,,,,2.5,1.3,2.1*39}
              nmea::input [list GPGSA A 3 04 05  09 12 "" "" 24 "" "" ""  2.5 1.3 2.1]



nmea                          1.0.0                             1





nmea(n)            NMEA protocol implementation           nmea(n)


       ::nmea::open_port port ?speed?
              Open the specified COM port and read NMEA sentences when  avail-
              able. Port speed is set to 4800bps by default or to speed.

       ::nmea::close_port
              Close the com port connection if one is open.

       ::nmea::configure_port settings
              Changes  the current port settings. settings has the same format
              as fconfigure -mode.

       ::nmea::open_file file ?rate?
              Open file file and read NMEA sentences, one  per  line,  at  the
              rate  specified  by ?rate? in milliseconds.  The file format may
              omit the leading $ and/or the checksum. If rate  is  <=  0  (the
              default)  then  lines  will  only  be  processed  when a call to
              do_line is made.

       ::nmea::close_file
              Close the open file if one exists.

       ::nmea::do_line
              If there is a currently open file, this command  will  read  and
              process  a  single  line  from  it.  Returns the number of lines
              read.

       ::nmea::rate
              Sets the rate at which lines are processed from the  open  file,
              in milliseconds. The rate remains consistant across files, there
              does not need to be a file currently open to use  this  command.
              Set to 0 to disable automatic line processing.

       ::nmea::log ?file?
              Starts  or stops input logging. If a file name is specified then
              all NMEA data recieved on the open port will be  logged  to  the
              ?file?  in append mode. If file is an empty string then any log-
              ging will be stopped. If no file is  specified  then  returns  a
              boolean  value  indicating if logging is currently enabled. Data
              written to the port by write, data read  from  files,  or  input
              made using input, is not logged.

       ::nmea::checksum data
              Returns the checksum of the supplied data.

       ::nmea::write sentence data
              If  there  is a currently open port, this command will write the
              specified sentence and data to the port in  proper  NMEA  check-
              summed format.

       ::nmea::event setence ?command?
              Registers a handler proc for a given NMEA sentence. There may be
              at most one  handler  per  sentence,  any  existing  handler  is
              replaced.   If  no command is specified, returns the name of the
              current handler for the given setence or an empty string if none



nmea                          1.0.0                             2





nmea(n)            NMEA protocol implementation           nmea(n)


              exists.  In  addition  to  the  incoming  sentences  there are 2
              builtin types, EOF and DEFAULT.  The  handler  for  the  DEFAULT
              setence  is  invoked if there is not a specific handler for that
              sentence. The EOF handler is invoked when End Of File is reached
              on the open file or port.

              The  handler  procedures,  with  the  exception  of  the builtin
              types,must take exactly one argument, which is  a  list  of  the
              data values.  The DEFAULT handler should have two arguments, the
              sentence type and the data values.  The EOF handler has no argu-
              ments.

              nmea::event gpgsa parse_sat_detail
              nmea::event default handle_unknown

              proc parse_sat_detail {data} {
                  puts [lindex $data 1]
              }

              proc handle_unknown {name data} {
                  puts "unknown data type $name"
              }



BUGS, IDEAS, FEEDBACK
       This  document,  and the package it describes, will undoubtedly contain
       bugs and other problems.  Please report such in the  category  nmea  of
       the          Tcllib         SF         Trackers         [http://source-
       forge.net/tracker/?group_id=12883].  Please also report any  ideas  for
       enhancements you may have for either package and/or documentation.

KEYWORDS
       gps, nmea

CATEGORY
       Networking

COPYRIGHT
       Copyright (c) 2006-2009, Aaron Faupell <afaupell@users.sourceforge.net>

















nmea                          1.0.0                             3


