nmea.qdoc

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// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
 
/*!
\page position-plugin-nmea.html
\title Qt Positioning NMEA plugin
\ingroup QtPositioning-plugins
 
\brief Reads the NMEA stream to provide position updates.
 
\section1 Overview
 
Included with Qt Positioning is a position plugin which parses NMEA sentences
into position updates. This plugin can use serial port, socket or file as a
source.
 
This plugin can be loaded by using the provider name \b nmea.
 
\section1 Parameters
 
The following table lists parameters that \e can be passed to the nmea plugin.
 
\table
\header
    \li Parameter
    \li Description
\row
    \li nmea.source
    \li The source that will be used to get NMEA data.
\row
    \li nmea.baudrate
    \li The baud rate to be used by the serial port connection, expressed with
        a positive integer number. Typically it should be one of the values
        from the \l QSerialPort::BaudRate enum. If the parameter is not
        specified or does not contain a positive integer, the default value
        of \c 4800 is used.
\row
    \li nmea.satellite_info_simulation_interval
    \li The interval for reading satellite information data from the file in
        simulation mode.
\endtable
 
Different sources require different ways of providing the data. The following
table lists different ways of providing \c {nmea.source} parameter for socket,
serial port and file inputs.
 
\table
\header
    \li Scheme
    \li Example
    \li Description
\row
    \li socket://hostname:port
    \li \c {socket://localhost:12345}
    \li Use \b {socket:} keyword to specify that you want to get the nmea data
        from the socket. A TCP socket will be created, which will try to connect
        to host \c hostname using port \c port. Upon successful connection
        a text NMEA stream is expected to be received from the server.
\row
    \li {1, 3} serial:portname
    \li \c {serial:/dev/ttyUSB0}
    \li {1, 3} Use \b {serial:} keyword to specify that you want to get the nmea
        data from the serial port. The plugin will try to establish a connection
        to port \c portname with a default baudrate = 4800 Bd (the baudrate
        value can be specified using \b {nmea.baudrate} parameter). Upon
        successful connection
        a text NMEA stream is expected to be received from the serial port.
        If you use \b {serial:} without any port name, the plugin will try to
        find one of the well known serial devices using vendor identifier. Note
        however that this is not a recommended way of using the serial port
        connection, as the list of well-known devices is small and most probably
        does not include your hardware.
\row
    \li \c {serial:COM1}
\row
    \li \c {serial:}
\row
    \li filepath
    \li \c {/home/user/nmealog.txt}
    \li {1, 2} Use \b {file:///} or just full file path to specify a path to a
        local file.
\row
    \li file:///filepath
    \li \c {file:///home/user/nmealog.txt}
\row
    \li qrc:///filepath
    \li \c {qrc:///nmealog.txt}
    \li Use \b {qrc:///} prefix to specify a path to a file in the application
        resources.
\endtable
 
\note If \c {nmea.source} parameter is not specified, the plugin will try to
locate one of the well-known serial devices (as if \c {nmea.source = serial:}
was specified).
 
\section1 Position source usage example
 
The following examples show how to create a \b nmea PositionSource
using different data sources.
 
\section2 QML
 
\code
// text file
PositionSource {
    name: "nmea"
    PluginParameter { name: "nmea.source"; value: "qrc:///nmealog.txt" }
}
 
// socket
PositionSource {
    name: "nmea"
    PluginParameter { name: "nmea.source"; value: "socket://localhost:22222" }
}
 
// serial port
PositionSource {
    name: "nmea"
    PluginParameter { name: "nmea.source"; value: "serial:/dev/ttyACM0" }
    PluginParameter { name: "nmea.baudrate"; value: 4800 }
}
\endcode
 
\section2 C++
 
\code
// text file
QVariantMap params;
params["nmea.source"] = "qrc:///nmealog.txt";
QGeoPositionInfoSource *textPositionSource = QGeoPositionInfoSource::createSource("nmea", params, this);
 
// socket
params["nmea.source"] = "socket://localhost:22222";
QGeoPositionInfoSource *socketPositionSource = QGeoPositionInfoSource::createSource("nmea", params, this);
 
// serial port
params["nmea.source"] = "serial:/dev/ttyACM0";
params["nmea.baudrate"] = 4800;
QGeoPositionInfoSource *serialPositionSource = QGeoPositionInfoSource::createSource("nmea", params, this);
\endcode
 
\note Once a PositionSource is created, it can't be reconfigured to use other
type of source data.
 
\section1 Satellite information source usage example
 
Apart from the position information, \b nmea plugin is also capable of providing
satellite information.
 
\section2 QML
 
\code
// serial port
SatelliteSource {
    name: "nmea"
    PluginParameter { name: "nmea.source"; value: "serial:/dev/ttyUSB0" }
    PluginParameter { name: "nmea.baudrate"; value: 9600 }
}
 
// socket
SatelliteSource {
    name: "nmea"
    PluginParameter { name: "nmea.source"; value: "socket://localhost:22222" }
}
\endcode
 
\section2 C++
 
\code
// serial port
QVariantMap parameters;
parameters["nmea.source"] = "serial:/dev/ttyUSB0";
params["nmea.baudrate"] = 9600;
QGeoSatelliteInfoSource *serialSource = QGeoSatelliteInfoSource::createSource("nmea", parameters, this);
 
// socket
parameters["nmea.source"] = "socket://localhost:22222";
QGeoSatelliteInfoSource *socketSource = QGeoSatelliteInfoSource::createSource("nmea", parameters, this);
\endcode
 
\section2 Settings Custom Simulation Speed
 
If you want to use \l QGeoSatelliteInfoSource to read file with NMEA stream, you
can also use additional parameter \c "nmea.satellite_info_simulation_interval".
This parameter is used to specify the playback rate (in milliseconds) for the
satellite info messages. The minimum allowed frequency is specified by
\l {QGeoSatelliteInfoSource::}{minimumUpdateInterval()}. If you specify a
smaller value, it will be ignored. If no value is specified, the default value
is \c {qMax(100, minimumUpdateInterval())}.
At runtime \l {QNmeaSatelliteInfoSource::setBackendProperty()} method can be
used to update this parameter.
 
\code
// file
QVariantMap parameters;
parameters["nmea.source"] = "qrc:///nmealog.txt";
parameters["nmea.satellite_info_simulation_interval"] = 1000;
QGeoSatelliteInfoSource *fileSource = QGeoSatelliteInfoSource::createSource("nmea", parameters, this);
\endcode
 
This parameter is not applicable to position source because NMEA protocol
already has timestamps in position messages. These timestamps are used to
simulate the correct message rate while using \l QGeoPositionInfoSource with
file as a data source.
 
\note Once a \l QGeoSatelliteInfoSource is created, it can't be reconfigured to
use other type of source data.
 
*/