Am 10.11.2010 18:51, Anders Blomdell wrote: > On 2010-11-10 18.23, Vinzenz Bargsten wrote: >> Hi, >> >> can someone provide (more) information on how to run a RTnet >> in combination with in this case one non-Linux/non-RTnet, i.e. windows >> machines? >> >> The windows machine (robot controller), which runs some proprietary >> real-time >> software, >> sends a UDP packet with XML strings every 12ms to the Linux machine. >> The Linux machine receives and processes the data (<1ms) and has to answer >> in >> less than 12 ms. >> >> At the moment,the setup on the Linux machine is: >> kernel 2.6.32-7 x86_64 with xenomai 2.5.1, RTL8139 NIC >> The data processing is done in/via OROCOS in a real time task. >> There is no other machine on this network. >> >> However, the problem is that the real time requirement is not met, >> i.e. the answer from the linux machine sometimes takes more than 12ms. >> Using wireshark we found out, that normally the answer is sent after (packet >> receive time) + ~0.5ms, >> but after some time (minute(s)), it takes >40ms and several/the missing >> packets >> are sent at once. > Could it be that you are running a SMP machine? Then this might be of > interest: > > https://mail.gna.org/public/xenomai-core/2010-11/msg00053.html > > later kernel, but the bug might exist in earlier versions (Jan can you comment > on this)?
No, this particular issue was introduced with 2.5.5. > >> >> This is a big problem, as the packets, which are sent from the Linux machine >> contain position data, >> which should be commanded to a robot. >> If the packets are delayed, the robot will stop/hold its position for this >> time, >> which results in an non-smooth/impulsive movement, making the measurement >> useless. >> >> So, what is the correct procedure to make the network interface working in >> real >> time mode with a non-TDMA capable remote station? >> Is it possible with RTnet, does it make sense? >> As the communication is already working with a definite rhythm, I think the >> TDMA >> functionality is not necessarily required. Is this true? Yep, the setup sounds valid. There is something delaying the packet processing, and that needs to be found. The usual questions are: - any suspicious kernel logs? - what are the result of Xenomai latency tests (to evaluate the hardware)? - already tried a recent Xenomai & I-pipe combination? If that doesn't help, tracing is the next step. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux ------------------------------------------------------------------------------ The Next 800 Companies to Lead America's Growth: New Video Whitepaper David G. Thomson, author of the best-selling book "Blueprint to a Billion" shares his insights and actions to help propel your business during the next growth cycle. Listen Now! http://p.sf.net/sfu/SAP-dev2dev _______________________________________________ RTnet-users mailing list RTnet-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/rtnet-users
