[etherlab-users] ethercat + xenomai on arm926 cpu system

[Ben Lewis]

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, paluan.luca at tiscali.it 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
>
>
>
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