RHD:Plug-in architecture

Load a plug-in

Plugins are loaded when they are mentioned in the rhdconfig file, e.g. like

<?xml version="1.0" ?>
<rhd>
 <sheduler>
   <period value="3000000"/>
   <type value="itimer"/>
 </sheduler>
 <server>
   <port value="24902"/>
   <clients number="10" allwriters="1"/>
 </server>
 <plugins basepath="/usr/local/smr/lib/rhdplugin/">
   <joycontrol enable="true" lib="libjoycontrol.so.1" critical="false" safety="1">
       <joystick port="/dev/input/js0"/>
   </joycontrol>
   <sf9dof enable="true"
         lib="libsf9dof.so.1"
         critical="false"
         dev="/dev/ttyS1"
         baudrate="38400"
         debug="0">
   </sf9dof>
 </plugins>
</rhd>

Here the plugins section has an attribute basepath that states where the plug-in files are to be found.

Two plugins are loaded in this example, a joycontrol plug-in from the file libjoycontrol.so.1, in the joycontrol XML group is an embedded XML tag, called joystick with the needed configuration data.

Further is a sf9dof plugin, where the plugin configuration data is placed as attributes directly in the sf9dof tag.

Plug-in function

A plugin should read the configuration file, and all relevant configuration values should be controllable from the configuration file.

The plug-in is expected to have a function called initXML(char * filename) that reads the configuration file and initializes the plug-in as needed. If all went well, then the function should return 0.

At every sample time, just after data may have been received from weriter clients, a function called periodic(int tick) is called. This can be used to react on new variable values, or other regular tasks.