nmea(3tcl) NMEA protocol implementation nmea(3tcl)______________________________________________________________________________NAMEnmea - 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::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
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, nmeaCATEGORY
Networking
COPYRIGHT
Copyright (c) 2006-2009, Aaron Faupell <afaupell@users.sourceforge.net>
nmea 1.0.0 nmea(3tcl)
