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Orocos stands for Open Robot Control Software and was a EU funded project to write Free Software for robots. This FAQ is about the Real-Time Toolkit library for writing hard real-time control applications in C++. It supports hard real-time RTAI/LXRT and Xenomai and normal GNU/Linux programs.

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In the Orocos in 3 slides Overview Presentation.

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In the Manuals Section of the Orocos website, you can find all on-line documents (and this FAQ). Also, the RTT Documentation Section contains links to the manuals.

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In the Download Section of the Orocos website and the Orocos Installation Manual.

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On the Orocos-dev mailing list (medium traffic) or the forum.

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On the Orocos mailing list (very low traffic ).

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In the Orocos RTT Installation Manual.

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The RTT works with vanilla Linux 2.4 and 2.6 kernels.

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The RTT works with RTAI 3.0r5 ( you need to apply a patch if you use 3.0r(1-4) ), RTAI 3.1, 3.2, 3.3 and 3.4 (no patching required).

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Disable anything that is remotely 'Experimental' or not necessarily needed. The following Linux options must be disabled to guarantee the most stable performance:

The following Linux options must be enabled to guarantee the most stable performance:

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The following RTAI options must be enabled (and modules must be loaded):

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Use the cmake .. command in your build directory , which will pop-up the configuration menu. See the the Installation Manual .

Or, use ../configure --help in your build directory for configuring only basic options.

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For compiling the RTT, you need a very fast machine with minimum 256MB RAM, and 512MB RAM to be comfortable.

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For running a full-featured Orocos application, you need an Intel Pentium-like or PowerPC processor with minimum 32MB RAM if all options are enabled, but much depends on the application itself.

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You can download the Orocos Component Library (OCL), install it and check out the examples you can download on the Orocos RTT page as well.

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Did you read the README ? Did you install Orocos in /usr/local/orocos ? Otherwise, set ORO_PATH to the correct location in the Makefile or specify it in make ORO_PATH=/path/to/install

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Maybe you are mixing C++ libraries or compiler versions. In this case, the linker shows a warning, which most users ignore though. In order to check if your libraries are correctly setup, do:

$ cd build/tests;
$ ldd core-test
        linux-gate.so.1 =>  (0xffffe000)
        libcppunit-1.10.so.2 => /usr/lib/libcppunit-1.10.so.2 (0xb7f54000)
        libdl.so.2 => /lib/tls/i686/cmov/libdl.so.2 (0xb7f4f000)
        libpthread.so.0 => /lib/tls/i686/cmov/libpthread.so.0 (0xb7f3c000)
        libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0xb7e56000)
        libm.so.6 => /lib/tls/i686/cmov/libm.so.6 (0xb7e33000)
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0xb7e28000)
        libc.so.6 => /lib/tls/i686/cmov/libc.so.6 (0xb7cfa000)
        /lib/ld-linux.so.2 (0xb7fcc000)

You should only see one libstdc++ library listed, thus if you see:

  ....
        libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0xb78a9000)
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0xb789e000)
        libc.so.6 => /lib/tls/i686/cmov/libc.so.6 (0xb7770000)
        libstdc++.so.5 => /usr/lib/libstdc++.so.5 (0xb76b6000)
        ....

the double occurence of 'libstdc++' is the cause of the crash.

Compile all your libraries (cppunit, Orocos,...) with the same compiler.

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Check if your rtai_lxrt and rtai_sem kernel modules are loaded and rtai_up is not loaded.

If that does not help, set

export ORO_LOGLEVEL=6

and send the output to the Orocos-dev mailing list.

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Check if the LXRT user space tests work. Orocos should be compiled with the same compiler as RTAI and Linux. RTAI/LXRT is quite sensitive about the chosen compiler. Problems have been reported with Red Hat's GCC 3.4 compiler for example.

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You tried to use RTAI's functions while RTAI was not yet initialised. This happens if you use global objects which contain Mutexes. Examples are Event and some DataObjects, Buffers and the Logger class. The solution is not to use global objects, but use global pointers and create the objects in ORO_main() with new.

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You did not put your program in the ORO_main() function. ( see The Installation Manual and The Orocos OS Manual. )

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Well, that is not a question really, but anyway... Did you read the section about Priority Inversions in the RTT CoreLib Manual ?

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Are you calling Linux system calls from a hard-real-time thread ? See this document for what you can and can't do within hard-real-time LXRT tasks.

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The RTT test cases test the system to its limits and may crash RTAI if not properly configured. Especially RTAI 3.0 and older. Also, verify that the RTAI/LXRT (aka 'user space') test programs work before blaming Orocos. Choosing a different compiler ( GCC 3.3 ) mostly solves that problem.

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Orocos is targeted at 32bit or 64bit systems and can run on systems with < 1MB of RAM (for code&data & application code) although with reduced functionality.

Orocos has an 'Embedded Systems' flag which disables C++ exceptions in order to save in terms of memory footprint. However, this means that the 'Scripting' language of Orocos can not be used.

Orocos contains tiny XML for parsing XML scripts on embedded systems as well, but you can disable XML completely.

The Orocos Logger can be disabled at compile time to save on memory footprint.

Various parts of the Execution Engine can be disabled at compile time to save on memory footprint.

It can be cross compiled. See the installation manual..

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Orocos RTT runs on eCos, standard GNU/Linux, Xenomai and RTAI and supports cross-compiling. For eCos, you need to create a specially crafted C++ GNU tool chain, see libstdc++ for eCos.

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The minimum requirements for running the RTT on a different target are for the CPU: floating point unit (FPU) or FPU emulation (will degrade performance), compare-and-swap instruction ( CAS, cmpxch ), and is targeted at 32 or 64 bit processors. The target Operating System (OS) must support the GNU C/C++ compiler with the Standard Template Library, periodic threads, semaphores and recursive mutexes.

The RTT has a very thin wrapper around the above OS functions in the 'OS' package, this is the only place of the RTT you need to port, where the 'gnulinux' package is a good starting point if you intend to port to a POSIX compliant OS. See also The OS Reference.

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The Orocos developers are very willing to assist you in porting the RTT to your Operating System.

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C++ is a fundamental pillar of Orocos' design. If you need to be convinced that this actually works, take a look at Demonstration movies , and read a Technical Report on C++ Performance , but Google can point you to lots more documents. We are still finding ways to measure the overhead of using Orocos itself, and much depends on the application, but the minimum system requirements to run it are a Pentium-class processor or PowerPC with 32 MB of RAM.