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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 han-dler handler
       dler 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  mil-liseconds. milliseconds.
              liseconds.   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  sen-
              tence,  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 argu-ment, argument,
              ment, 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   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                                            nmea(n)