Hi, the ethernet emulation on Firewire (eth1394) has been ported to RTnet. The module stack consists of eth1394_rt.o, ieee1394_rt.o and ohci1394_rt.o. Another module, rtos_tasklet_scheduler.o needs also to be loaded, to make sure the tasklets triggered in the top half of interrupt handlers are executed in real-time manner.
So far, the round trip test can be run on Firewire. The results are compared with ethernet. With a low packetsize, the average round trip latency on Firewire is close to that on ethernet. But with a high packetsize, like 1400, Firewire shows its stronge point: the average is almost 100us less than on ethernet. This is because of the high data payload in Firewire packet. In Firewire asyn. transmission, depending on the hardware, the payload can be 512, 1024, 2048, corresponding to the speed: 100mb/s, 200mb/s, 400mb/s. It can even be higher in 1394b. The chip in my setup supports 400mb/s, i.e. 2048 bytes per packet. So another thing noteworthy is, on a Firewire chip supporting 2048 bytes per packet (which is quite common in the market), the mtu for eth1394 can be as high as 2044 bytes, subtracting encapsulation header for ipv4 on 1394. This means eth1394 provides a higher payload than normal ethernet (1500), but the question is how can we use this high payload, in which occasions? The next step could be using Firewire directly in real-time occasion, bypassing the ip protocol. To achieve this, there will be benefits, one is to increase payload, another is to save some processing power from the protocol conversion between ip and 1394. For this, I would like to have your suggestions: can I relate this to the rtdm framework, how? Best regards, Zhang Yuchen MSc Student Control Engineering Group University of Twente The Netherlands ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://productguide.itmanagersjournal.com/ _______________________________________________ RTnet-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/rtnet-developers
