Re: How to build an Orocos application

On Wednesday 15 January 2003 11:50, [email protected] 
wrote:
> I need to write a simple orocos application.
> I want to create:
>  3 RT processes (ZTT),
> 1 RT process (ZLT),
> 1 Not-RT process in user space.
> All ZTT processes must be connected with ZLT Process by fifo's,
> The not-RT process  must be connected to ZLT process,
> What are the guide lines that I need to follow to reach my goal?
> In the orocos core (0.9.0) there are some test file,but they are very hard
> to understand!
> What are the most important files for my purpose?


you could do the following :

write task 1 :

#include <TaskNonPreemptible.hpp>

class TaskOne : public TaskNonPreemptible
{
public:
	TaskOne() 
	: TaskNonPreemptible(0.001)   // period is 1ms
	{ // constructor, executed once on new ... }
	~TaskOne()        { // destructor, executed on delete ... }
	void initialise() { // your init code ... }
	void step()       { // your periodic task code ... }
	void finalise()   { // your finalise code .. }
}; // tada !

do the same for process 2 and 3
Do the same for the preemptible process but write :

class TaskFour : public TaskPreemptible
{ ...};

then in your startup file ( say example.cpp )


TaskOne* task1;
void initFunction()
{
	task1 = new TaskOne(); // constructor called
	task1->start();        // initialise is called once
				// step is executed periodically
}

void termFunction()
{
	task1->stop();         // step is no longer called, finalise is called.
	delete task1;          // call destructor
}	


now you only have to call these functions in your init_module and 
cleanup_module functions (take a look at moduleStartStop.c or so in the 
core/src directory )

The userspace process can have a main() function where it opens a fifo to 
communicate with the kernel.

to set up communication, i advise only to use fifos between kernel space and 
user space, and use the STL queue<YourType> for communication between two 
tasks. For fifos, look at the FifoRT[In/Out].hpp and FifoUS[In/Out].hpp files 
or documentation.

I am very aware of the lack of clear example programs, but i urge you to read 
the documentation and make sure you understand it. The online API (see link 
documentation on the orocos website) also helps you in discovering what's 
there.

Peter