Hi everybody,
I just play around with the 0.6.0 version of rtnet. One thing is interesting - I think it is different from previous versions: I have a point-to-point (full duplex) connection from my Intel eepro100 board (using the rtnet driver) and a non-PC device. They communicate via UDP, this works fine. However, when I do not use a point-to-point connection but add a Hub to monitor the Ethernet traffic with a second PC, the communication between the real time PC and the non-PC device does not work as stable as it should work. It looks, as if there are collisions that are not handled by the system. With an older version of rtnet (0.2.10) this seemed to work fine as well.
Is the monitoring PC actually quiet (no DHCP, no IPv6 router discovery)?
I do not use rtmac - as I think it is not required in my setup.
Well, with a non-RTnet device on one side you don't even have the possibility to use RTmac.
But, as I often explained :), RTmac/TDMA provides more than "just" protection against collisions/congestions. By limiting the bandwidth, it gives you the chance to calculate the resource requirements (formost CPU time) of every attached node while still allowing undeterministic traffic over the VNIC devices.
My question is now: If there are collisions on the Ethernet, is it the task of the eepro100 hardware to do the detection of collisions and re-sending of data or is this part of RTMac and this fails in my
Unfortunately it's a built-in feature of the NIC. If not, this would open much more possibilities in designing RTmac mechanisms.
So, if there is actually a collision (watch the hub LEDs!), your cards should deal with it. Are you sure that the hub works correctly with your NICs? Do you have the chance to test a different model/manufacturer? We observed such effects with rather old and cheap devices.
setup as I do not use RTMac? Does the usage of RTMac slow down the communication?
Nothing's for free :). Of course RTmac/TDMA adds some overhead to the communication as everything is handled by software. And there is also the latency dictated by the cycle time.
Jan
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