[manpage_begin nmea n 1.0.0]
[copyright {2006-2009, Aaron Faupell <afaupell@users.sourceforge.net>}]
[moddesc   {NMEA protocol implementation}]
[titledesc {Process NMEA data}]
[category Networking]
[require Tcl 8.4]
[require nmea [opt 1.0.0]]
[description]
[para]

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 [cmd event] command. There are no GPS specific functions
in this package. NMEA data consists of a sentence type, followed by a list of data.

[section COMMANDS]
[list_begin definitions]

[call [cmd ::nmea::input] [arg sentence]]
Processes and dispatches the supplied sentence. If [arg 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 [const \$].

[example {
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]
}]

[call [cmd ::nmea::open_port] [arg port] [opt speed]]
Open the specified COM port and read NMEA sentences when available. Port speed is set to
4800bps by default or to [arg speed].

[call [cmd ::nmea::close_port]]
Close the com port connection if one is open.

[call [cmd ::nmea::configure_port] [arg settings]]
Changes the current port settings. [arg settings] has the same format as fconfigure -mode.

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

[call [cmd ::nmea::close_file]]
Close the open file if one exists.

[call [cmd ::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.

[call [cmd ::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.

[call [cmd ::nmea::log] [opt 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 [opt 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 [cmd write], 
 data read from files, or input made using [cmd input], is not logged.

[call [cmd ::nmea::checksum] [arg data]]
Returns the checksum of the supplied data.

[call [cmd ::nmea::write] [arg sentence] [arg 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.

[call [cmd ::nmea::event] [arg setence] [opt command]]
Registers a handler proc for a given NMEA [arg 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 [arg 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.
[para]
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.

[example {
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"
}
}]

[list_end]

[section {BUGS, IDEAS, FEEDBACK}]

This document, and the package it describes, will undoubtedly contain
bugs and other problems.

Please report such in the category [emph nmea] of the
[uri {http://sourceforge.net/tracker/?group_id=12883} {Tcllib SF Trackers}].

Please also report any ideas for enhancements you may have for either
package and/or documentation.


[keywords nmea gps]
[manpage_end]