v2.6.0

Link management part, management of different links

Currently supported UDP,TCP,serial

1. Create a single instance linkmanager

IMPLEMENT_QGC_SINGLETON(LinkManager, LinkManager)

#define IMPLEMENT_QGC_SINGLETON(className, interfaceName) \
    interfaceName* className::_instance = NULL; \
    interfaceName* className::_mockInstance = NULL; \
    interfaceName* className::_realInstance = NULL; \
    \
    interfaceName* className::_createSingleton(void) \
    { \
        Q_ASSERT(_instance == NULL); \
        _instance = new className(qgcApp()); \
        return _instance; \
    } \
    \

send data

1. Send heartbeat package

void MAVLinkProtocol::sendHeartbeat()

1. send message

sendMessage(beat);

1. Transmit link

 link->writeBytes((const char*)buffer, len);

1. IO write function of send link

void SerialLink::writeBytes(const char* data, qint64 size)
{
    if(_port && _port->isOpen()) {
        _logOutputDataRate(size, QDateTime::currentMSecsSinceEpoch());
        _port->write(data, size);
    } else {
        // Error occured
        _emitLinkError(tr("Could not send data - link %1 is disconnected!").arg(getName()));
    }
}

receive data

1. First find the location to parse the mavlink package

void MAVLinkProtocol::receiveBytes(LinkInterface* link, QByteArray b)
    for (int position = 0; position < b.size(); position++) {
        unsigned int decodeState = mavlink_parse_char(mavlinkChannel, (uint8_t)(b[position]), &message, &status);

1. Find that location and call the receive byte method
   Here is where receiveBytes is called. The best design in qt is the signal / slot function

src/comm/LinkManager.cc:153:    connect(link, &LinkInterface::bytesReceived, mavlink, &MAVLinkProtocol::receiveBytes);

1. Find where slot function triggers

void SerialLink::readBytes()
        qint64 numBytes = _port->bytesAvailable();
            emit bytesReceived(this, b);
     
    }
}

1. Find out which bit called SerialLink::readBytes()

QObject::connect(_port, &QIODevice::readyRead, this, &SerialLink::_readBytes);