QAds

Implements an object-orientated layer on top of Beckhoff ADS (TwinCAT2, TwinCAT3). The objects, implemented within the scope of this project, integrate nicely with Qt and Qml by using the Qt's signal/slot concept.

Prerequisites

This repository is using https://github.com/Beckhoff/ADS as submodule. Hence, in order to make use of this package, you should be familiar with ADS (setting up routes, etc.)

Usage

We provide two objects to communicate with TwinCAT devices.

• Tc3Manager connects to the TwinCAT device by constructing the object with the netid and port (e.g. 192.168.0.1.1.1:851). If the device is available, Tc3Manager will connect to the device and register a state-change callback. Whenever the state of the Twincat devices changes, Tc3Manager throws a qt signal, which can be connected to. Additionally, Tc3Manager takes care of reconnecting to the TwinCAT devices, if the connection to the device is lost at some point.

• Tc3Value represents a single instance on the TwinCAT device (e.g. MAIN.machineState). The object has methods to read and write values on the TwinCAT device. When constructing Tc3Value, we can optionally enable a valueChanged signal - Whenever the value of the variable on the TwinCAT devices changes, the valueChanged signal is send by the Tc3Value object. Tc3Value can read/write primitive datatypes (INT, DINT, REAL, LREAL, ...), but also reading/writing of DUTs (Structs, Enumerations, Unions) is implemented and demonstrated.

• Usually it is pretty tedious to write bindings from PLC structs to C++ structs by hand since one has to take care of alignment, use the correct datatypes and so on. Luckily zkbindings can we used to automatically generate bindings.

C++ example

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    Tc3Manager manager("192.168.0.1.1.1:851");
    Tc3Value *machineState = manager.value("MAIN.machineState");

    // EXAMPLE 1: single variable access
    //  change something on the PLC with the set method
    qDebug() << manager.value("MAIN.variable")->get();
    manager.value("MAIN.variable")->set("connected to plc");
    qDebug() << manager.value("MAIN.variable")->get();

    // EXAMPLE 2: struct variable access
    //  read "complex" struct from plc
    //  change something in the struct and write it to the plc
    //  read the struct again and let's check, if we actually change something
    Tc3Value *exampleStruct = manager.value("MAIN.struct1", sizeof(Plc::ExampleStruct));
    Plc::ExampleStruct exampleStructData = exampleStruct->get<Plc::ExampleStruct>();
    
    qDebug() << "Initial value" << exampleStructData.sub1.sub2.integer1;
    
    exampleStructData.sub1.sub2.integer1 += 1;
    exampleStruct->set<Plc::ExampleStruct>(exampleStructData);
    
    exampleStructData = exampleStruct->get<Plc::ExampleStruct>();
    qDebug() << "New value" << exampleStructData.sub1.sub2.integer1;

    return app.exec();
}

QML example

Window {
    title: sps.value("MAIN.somestring").value;
}

In main.cpp, we show how these objects can be made available for the Qml engine (see main.qml), such that variables of the TwinCAT device can be easily accessable in a qml gui. The main "trick" here is to implement a driver class that is made available as a context property to qml.