Once you have written a driver based on iodrivers_base::Driver, you can think about integrating it in an oroGen component.

Rock contains a generic integration of such a component: the iodrivers_base oroGen package. This page is going to describe the usage of this class first, and then describe the component’s interface design.

Guidelines

• the oroGen project should have the same name than the corresponding library package.
• if the device is periodic, the component should use the TimestampEstimator to correct the timestamps
• use as much base data types as possible
• common type names have also common port names. In general, it is good to check devices of the same type and follow the same naming conventions.

• ports that output types in the /base/samples namespace must end with _samples, as e.g.

  position_samples
  orientation_samples
  

Usage

To create a new driver component, first create the corresponding package using the rock-create-orogen tool. This component should depend on the drivers/orogen/iodrivers_base package.

At the top of the oroGen file, add:

using_task_library "iodrivers_base"

Then, make your task a subclass of the iodrivers_base::Task task context:

task_context "Task" do
subclasses "iodrivers_base::Task"
end

There is two things left to do:

• configureHook: create the device driver, open the device and call the setDriver() method. The device’s “name” (i.e. device file, IP for network-based access, …) is provided in the io_port property. Note that it is legal for this property to be empty (see the next section for explanations).

setDriver(driver)

• process the incoming data in a “void processIO()” method that is going to be called by the base class from updateHook().

• cleanupHook: the device’s close() method is going to be called automatically by the base class. The pointer is not going to be deleted though, so you should take care of it if you want to recreate the object in cleanup/configure cycles.

For instance, one could have a setup looking like:

bool Task::configureHook()
{
Driver* driver = new Driver();
if (!_io_port.get().empty())
driver->openURI(_io_port.get());
setDriver(driver);

// This is MANDATORY and MUST be called after the setDriver but before you do
// anything with the driver
TaskBase::configureHook();

// If some device configuration was needed, it must be done after the
// setDriver and call to configureHook on TaskBase (i.e., here)
}
void Task::processIO()
{
mDriver->processSamples();
_samples.write(mDriver->getOrientationSample());
}

In addition, you might want to start data acquisition in the startHook and stop it in the stopHook. Whether the acquisition start/stop should be in startHook/stopHook or configureHook/cleanupHook is governed by the following factor:

• if starting/stopping acquisition is done a lot quicker than the whole device configuration, then do it in startHook/stopHook as you will not waste ressources doing acquisition while the data is not needed
• if it is slow (some people would even say: not deterministically fast, but YMMV), do it in the configureHook/cleanupHook to ensure the responsiveness of the system when start/stop cycles are needed but reconfiguration is not needed.

By default, the standard runtime management of oroGen tasks entails that you will have a full stop/cleanup/configure/start cycle if reconfiguration is needed. You should therefore not care about dynamic reconfiguration in first implementations.

Details about the iodrivers_base::Task interface

This interface provides two means of communication between the device and the driver.

• direct I/O access. This is done by setting io_port to a non-empty string. Acceptable values for io_port if the driver uses openURI (which it should do) are listed in the property’s documentation.
• port-based access. In this mode, the data is flowing through the io_raw_in and io_raw_out ports. The transfer of data between the ports and the Driver object is made by the iodrivers_base::Task class.

Other properties control the behaviour of the system in both modes (read timeout) and write statistics about the I/O. Some properties are specific to one mode, in which case this is documented in the property documentation directly.