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 contains 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::open_port port ?speed?
              Open the specified COM port and read NMEA sentences when available. 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 logging 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 checksummed 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 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
              arguments.

              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  Trackers
       [http://core.tcl.tk/tcllib/reportlist].  Please also report any ideas for enhancements you
       may have for either package and/or documentation.

       When proposing code changes, please provide unified diffs, i.e the output of diff -u.

       Note further that attachments are strongly preferred over inlined patches. Attachments can
       be made by going to the Edit form of the ticket immediately after its creation,  and  then
       using the left-most button in the secondary navigation bar.

KEYWORDS

       gps, nmea

CATEGORY

       Networking

COPYRIGHT

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