[etherlab-users] cycle frequency and unmatched datagrams

Andreas Stewering-Bone Andreas.Stewering-Bone at gmx.de
Mon Apr 19 21:53:33 CEST 2010

Hello Juri,

Please note, the user space example is only a user space example. Let me 
explain. you have no realtime deterministic on a rtai system for an user 
space example. The programm is schedulded by the normal linux system. A 
normal debian kernel has a cycle freuency of 1000 Hz. If your process freq is 
equal or higher you will get problems. 

For RTAI examples, please have a look at the rtai kernel example.

If you use a rt-preempt kernel, you will get a proper system behavior for the 
userspace example.



Am Monday 19 April 2010 13:36:50 schrieb Juri Gerke:
> Hi,
> I try to set the maximum  cycle frequency using the user example.
> The master is connected with one EK1110(coupler) and one EL3102(analog
> input) from Beckhoff. If the define: frequency is set to 100, the cycle
> operation works fine. But at a frequency of 1000 and above I get warnings
> about unmatched datagrams. If the  frequency is set to 1000, does it mean
> that the function cyclic_task() will be execute every 1ms? It doesn`t
> matter which value I choose for frequency , I never get  output warnigs
> about "skipped"  datagrams. Any Hints what`s wrong with my system?
> My system:
> Intel Pentium M 1,8GHz
> 512 MB Memory
> Debian 5.0.4
> Kernel with rtai
> e100 PRO/100 Network Driver
> Kind regards
> Juri Gerke
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