As described in Using ROS through EEROS HAL you can directly map EEROS signal onto ROS messages through the EEROS HAL. The wrapper library EEROS-ROS is used to connect the EEROS HAL with ROS topics.
The EEROS HAL digital and analog inputs and outputs can be defined as usual in a JSON file. In this file you specify into which message type these signals get packed. There are hundreds of different message types in ROS and it is possible to create custom types. For this reason, we currently support only a few by default. If one wishes to use other message types, the wrapper library can easily be extended.

The keywords for the EEROS-ROS wrapper library must be set as follows:

\end{tabular}

\end{table}

The \textit{additionalArguments} are special arguments which are parsed in the wrapper library \textit{ros-eeros}.

These arguments contain additional information which are necessary to communicate with a ROS network.

All arguments are separated with a semicolon.

The available arguments are listed in table \ref{tableAdditionalArgumentsEeros}.

An example for an additional argument could be:

\begin{snugshade*}

\textit{\char“22additionalArguments\char”22: \char“22topic=/testNode/TestTopic3; msgType=sensor\_msgs::LaserScan;

dataField=scan\_time; callOne=false; queueSize=100\char”22,}

\end{snugshade*}

Table \ref{tableAdditionalArgumentsEeros} shows all currently available \textit{additionalArguments}.

\textbf{Topic} and \textbf{msgType} are mandatory arguments.

\begin{table}

\centering

\caption{Additional arguments specific for ros-eeros}

\label{tableAdditionalArgumentsEeros}

\begin{tabular}{@{}lll@{}}

\toprule

Key & Typical value & Description
\midrule

\textbf{topic} & /testNode/TestTopic1 & Topic to listen / subscribe

\textbf{msgType } & sensor\_msgs::LaserScan & ROS message type of topic

dataField & scan\_time & Desired data member of message

callOne & true & Oldest, not yet fetched message is fetched

callOne & false & Newest available message is fetched

queueSize & 1000 & Size of buffer; queueSize=1000 if omitted

useEerosSystemTime & fals & Use system time or timestamp of received msg
\bottomrule

\end{tabular}

\end{table}

In table \ref{tableImplementedMsgTypes} are all currently implemented message types and associated data fields.

If your desired message type is not implemented yet, you can easily implement it yourself.

See chapter \ref{sectionImplementMsgType} for a guide to implement additional message types and data fields in \textit{ros-eeros}.

\begin{table}[]

\centering

\caption{Currently implemented message types in ros-eeros}

\label{tableImplementedMsgTypes}

\begin{tabular}{lll}

\cline{2-3}

HAL type & msgType & dataField
\cline{2-3}

AnalogIn & std\_msgs::Float64 & -

        & sensor\_msgs::LaserScan    & angle\_min       \\

        &                            & angle\_max       \\

        &                            & angle\_increment \\

        &                            & time\_increment  \\

        &                            & scan\_time       \\

        &                            & range\_min       \\

        &                            & range\_max       \\

AnalogOut & std\_msgs::Float64 & -

        & sensor\_msgs::LaserScan    & angle\_min       \\

        &                            & angle\_max       \\

        &                            & angle\_increment \\

        &                            & time\_increment  \\

        &                            & scan\_time       \\

        &                            & range\_min       \\

        &                            & range\_max       \\

DigIn & sensor\_msgs::BatteryState & present

DigOut & sensor\_msgs::BatteryState & present
\cline{2-3}

\end{tabular}

\end{table}

You can find a complete example, including a *.json file, in the eeros framework (/examples/hal/Ros*).

\subsection{How to use}

Refere to the documentation of the EEROS HAL\footnote{http://wiki.eeros.org/eeros\_architecture/hal/start?s[]=hal} and check the example in the eeros framework (/examples/ros).

First initialize the HAL in your main function:

\lstset{language=c}

\begin{lstlisting}

…

int main(int argc, char **argv) {

...

// HAL

// ////////////////////////////////////////////////////////////////////////

HAL& hal = HAL::instance();

hal.readConfigFromFile(&argc, argv);

...

\end{lstlisting}

Add the header file to your control system:

\lstset{language=c}

\begin{lstlisting}

#include <eeros/hal/HAL.hpp>

\end{lstlisting}

You can now declare \textit{PeripheralInputs} and \textit{PeripheralOutputs}:

\lstset{language=c}

\begin{lstlisting}

PeripheralInput<double>		analogIn0;

PeripheralInput<bool>		digitalIn0;

PeripheralOutput<double>	analogOut0;

PeripheralOutput<bool>		digitalOut0;

\end{lstlisting}

Call the constructor of the peripheral IOs with the \textit{signalID} used in the *.json file

\begin{lstlisting}

class MyControlSystem {

public:

MyControlSystem(double ts, ros::NodeHandle& rosNodeHandler):

	dt(ts),

	...

	analogIn0("scanTimeIn0"),		// argument has to match signalId of json

	digitalIn0("batteryPresent0"),

	analogOut0("scanTimeEchoOut0"),

	digitalOut0("batteryPresentEchoOut0"),

	...

}