RFXCOM RFXtrx433 Especificaciones descargar pdf (Pagina 54)

Chapter 4. Implementation 47

4.2. Software Basics

The next sections cover the implementation of the three ROS Nodes: gateway driver, device

manager and visualization. In order to improve the general understanding, this section provides a

short introduction of the used software and the Qt signal/slot mechanism.

All nodes are implemented in C++ using the following external software:

QT framework: Qt is a multi lingual, cross-platform application and UI framework. It covers

that many ﬁelds of application that except the software listed below, no other third-party

programs had to be used. Of particular interest is the signal and slot concept, which allows

thread-safe data exchange within the diﬀerent objects of the software. Used version: 4.81

QextSerialPort: A multi-platform library for serial port communication. Since it is based on the

Qt framework, it can be easily integrated using its signals and slots. Used version: 1.2 beta1

QtCreator: An IDE from the QT SDK, which is specially designed for use with the QT framework.

It was chosen to speed up the development and for convenience, as it oﬀers functions such

as debugging, auto completion, graphic designer tools and many more. Used version: 2.5

ROS Fuerte: The latest ROS release. For more information, go to section 2.4.2 on page 23.

The signal/slot mechanism is a central feature of Qt. It is used for communication between objects

and consists of signals and slots. Similar to ROS topics, it provides a type safe, decoupled and

many-to-many data exchange method, but only within a single program. A signal is emitted when

a particular event occurs and if it is connected to a slot, the slot will be called and executed.

Qt widgets oﬀers many predeﬁned signals and slots, such as the close()-signal, when a window

is closed, or the click()-signal, when a button is pressed. However, they are usually sub-classed

to add custom slots that allow handling signals the user is interested in. Slots are normal C++

functions which can be called normally; their special feature is that signals can connect to them.

Data can be exchanged by passing parameters or accessing a predeﬁned common storage.

Please note, the diﬀerent .msg and .srv ﬁles of each node are listed in appendix A on 71.

4.3. Gateway driver

The gateway driver is the ﬁrst abstraction level in our abstraction model (ﬁgure 3.3 on page 29).

It aims to provide a uniﬁed interface between ROS and the gateways WiﬁCtrl and MiniCtrl, so that

other nodes can communicate with HA hardware through ROS topics. The gateway is hidden by

the gateway driver, consequently no knowledge about its exact communication process is required.

That allows connecting multiple gateways over ROS as well as linking diﬀerent gateway types.

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RFXCOM RFXtrx433 Especificaciones Pagina 54