[etherlab-users] Multiple SDO requests

[Jordan Palacios]

I have repeated the test with “ethercat debug 1” (see attachment with the
output).

I does look to me from this that once the SDO for slave 1 is successful the
one for slave 2 is queued. And when the later is finished the one from
slave 1 is queued again. The SDO request of slave 3 is never processed. So
it seems that, at least in our version of the ethercat master, only one SDO
can be processed at the time. Even across different slaves.

I forgot to mention that we are currently using the default branch of the
master.

We will definitely check the unofficial patchset. Specially the
parallel-slave features.

Thanks a lot for your help Gavin.

Kind regards.

On 30 August 2017 at 02:02, Gavin Lambert <gavinl at compacsort.com> wrote:

> First off, note that using printfs inside your cyclic task is going to
> kill your latency.  By itself this shouldn’t cause any issues with SDOs,
> unless it’s sufficient to trigger the timeout.
>
>
>
> The master does support a limited number of concurrent SDO requests,
> provided that they are always to different slaves.  By default it will only
> process up to 16 concurrent requests at a time, however.  So if you might
> have larger networks it’s a good idea to allow some downtime, perhaps only
> scheduling a read request once per second or even slower (depending how
> many slaves you have and how often you really need the data).
>
>
>
> I didn’t spot anything obviously wrong in your code.  To diagnose further
> you should probably set “ethercat debug 1” and then examine your syslog
> after running your application; this will contain additional information
> about the progress of requests.
>
>
>
> Another thing you might want to consider is trying out the unofficial
> patchset at https://sourceforge.net/u/uecasm/etherlab-patches/ci/
> default/tree/#readme; this includes a number of patches to enhance
> mailbox stability and increase slave concurrency.
>
>
>
> *From:* Jordan Palacios
> *Sent:* Wednesday, 30 August 2017 02:03
> *To:* etherlab-users at etherlab.org
> *Subject:* [etherlab-users] Multiple SDO requests
>
>
>
> Dear Etherlab users,
>
>
>
> I have a setup with some Elmo Gold boards where I wish to access some data
> objects that unfortunately are not mappable. The information from these
> data objects is not really required each cycle, though it should be
> requested regularly.
>
>
>
> I'm attaching a sample test code where I try to read the same data object
> in three different slaves each cycle. The result is that the sdo request
> for the third slave is never successful.
>
>
>
> It is as if the master could not serve more than one SDO request at a
> time. Is this correct? I am doing something wrong?
>
>
>
> Kinds regards.
>
>
>
> Jordán.
>



-- 

Jordán Palacios

Software Engineer

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