Hello, I also agrree. The arm926 is known to have a bad realtime performance. Please have a look at www.osadl.de https://www.osadl.org/Latency-plot-of-system-in-rack-2-slot.qa-latencyplot-r2s1.0.html
Please check your realtime performace or try a cylic task with 100Hz. I you have the choice please use preempt rt because this will be the future for realtime systems based on linux. Best regards Andreas -------- Original-Nachricht -------- > Datum: Thu, 30 Aug 2012 09:35:28 +1000 > Von: Ben Lewis <[email protected]> > An: [email protected] > Betreff: Re: [etherlab-users] ethercat + xenomai on arm926 cpu system > Hi Luca, > > First I must say that I have just joined this list and I have not used > Etherlab. > > I've recently completed an EtherCAT application on an ARM based processor > (IXP420, 533MHz). > > Hardware specifications here: > http://www.beckhoff.com/english.asp?industrial_pc/cp66xx.htm > > My I/O requirements were small: > > * DI: 4 > * DO: 4 > * AI:5 > * AO:2 > * PWM: 2 > > I used TwinCAT for EtherCAT master. > > I was not able to achieve a 1 ms cycle time. > > A 2 ms cycle time was possible but with high real time usage and regular > cycle time exceeds in low > priority tasks. > > In the end I had to settle on a 3 ms cycle time. This gave me enough > overhead to run lower priority > tasks (such as updating the visualisation) reliably. > > On the face of it, it looks like your processor runs at about half the > frequency as the one I was > using, therefore it would not surprise me if you are not able to achieve a > cycle time below 4 ms. > > I'm not sure if this is of any relevance to you, I'm just providing it as > another point of reference. > > Regards, Ben > > > On 30/08/2012 3:20 AM, [email protected] wrote: > > Hello everyone, > > I'm trying to develop a real time server on the arm > > (arm926) cpu and on a real time linux with xenomai. > > Unfortunatly even > > the basic examples seem not to work on such a system: the real time > > task is set to work with a 2ms period like the 2 servos connected to > > the ethercat net (even though 1ms would definetly be the best). > > With a > > bare example I immediatly receive warning from ethercat master of > > skipped frames and if the real task has to do something more the server > > crashes... > > I tried various compile time optimizations and I tried to > > give up with real time task using hrtimer without results. > > My system is > > using the generic ethernet driver too, but could anyone give me some > > advice about whether the cpu power is enough to manage the ethercat > > driver in a real time environment? > > Thanks in advance, Best Regards Luca > > > > > > > > Invita i tuoi amici e Tiscali ti premia! Il consiglio di un amico vale > più di uno spot in TV. Per ogni nuovo abbonato 30 € di premio per te e > per lui! Un amico al mese e parli e navighi sempre gratis: > http://freelosophy.tiscali.it/ > > _______________________________________________ > > etherlab-users mailing list > > [email protected] > > http://lists.etherlab.org/mailman/listinfo/etherlab-users > _______________________________________________ etherlab-users mailing list [email protected] http://lists.etherlab.org/mailman/listinfo/etherlab-users
