> Kate Alhola wrote: >> Is it possible to use RTnet without specially ported network drivers >> and routing trafick via standard Linux network driver ? > > Nope, that is not possible ATM. [I may become feasible in the far future > when PREEMPT_RT matured and netchannels or something similar > materialised and we make use of it.] > >> In my mind something like using RTmac and rt_loobback drivers >> or is there siome other way ? > > No, this has nothing to do with it. The rt_loopback driver provides a > RTnet-internal loop. And RTmac is the framework to add software-based > media access control to RTnet's NIC drivers.
I had in my mind http://www.rts.uni-hannover.de/rtnet/images/network.gif image. The leftmost Linux box has both normal linux ethernet card and rtnet interface. If we just replace the rtnet interface with loopback, should the routing functionality still exist ? I don't even consider any user mode solution, then there comes ann contxt switch and scheduling latensies and with them 1ms is about inpossible. >> I understand that TDMA and hardest real time is lost but >> at the moment, my target is just get 1ms cyckle time >> from RTAI. My goal is just use microcontroller as >> I/O module for RTAI. > > Hard RT has nothing to do with 1 ms vs. 0.1 ms or whatever. It's about > if you can tolerate deadline misses or not. Even a 1 ms loop can already > be stressing for a loaded low-end processors. I understand this and understand also that with loaded ethernet there is no possibility to hard real time. My idea was just have dedicated lightly loaded machine and no-load or just administrative wery light load ethernet interface. 100Mbit ethernet interface can still send 6 full sized 1500 byte packets or hundred small ssh etc packets per second so with no-load or light load there liest will bee free slots to send my packets with 1ms loop. > So, do you have hard requirements to meet your 1-ms deadline? I need to have this 1ms, the net can be dedicated and machine light loaded but i can't be fixed in some specific network card. As other solution i had in my mind just to use ip_finish_output(skb) to send udp packets from RTAI and dev_add_pack() to add my own packet handler. Or may be just use them to implement pseudodriver for RTnet that just sends and receives packets via Linux stack. > Jan > > > PS: Just read your RTAI posting: Don't assume user-mode==non-RT. > Execution context (RT/non-RT) and mode (kernel/user) are orthogonal. In > fact, hardly anyone should start new RT application designs in kernel > space today. I am somihow familiar with this, i have also user Ingo Molnar Pre-Empt/low latency patches. At this time i just need to make Ethernet interface to microcontroller from EMC Kate ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ RTnet-users mailing list RTnet-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/rtnet-users
