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>