[etherlab-users] hard-realtime using rtai-lxrt and IGH userspace API

Florian Pose fp at igh-essen.com
Wed Apr 14 15:17:23 CEST 2010

On Tue, Apr 06, 2010 at 09:14:53PM +0200, Stefan Kohlbrecher wrote:
> Hi,
> my group is developing a robot control application using EtherCAT for
> communication between controller and devices. For being flexible and
> interoperable we are looking into using OROCOS together with the IGH
> EtherCAT master for maximum flexibility. Under the hood, OROCOS is
> using rtai-lxrt or xenomai for hard-realtime. Is the userspace API of
> the IGH master hard-realtime compatible using these two realtime
> systems? Preliminary testing suggested that ioctl calls in the
> userspace API lead to switching out of hard realtime.

See last thread.

> Being new to hard realtime systems, I was also wondering why normal
> locking ( down(&master->io_sem); etc.) seems to be used for example in
> master.c. Shouldn't the corresponding RTOS structures
> (rt_sem_wait(&master->master_sem); etc. ) be used?

Th io_sem is only used in idle mode, when not in realtime context.
Moreover the master code is not able to know, whether is is called in
RTAI context, therefore it can not use RTAI code (that's a feature!).

Best regards,
Florian Pose


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