[etherlab-users] CoE mailbox problem: "Received unknown response while uploading SDO"

[Jun Yuan]

Hi Frank,

thank you very much for your mail. Your patches are very precious for me.
I'll test them as soon as I can.

Regards,
Jun


On 5 June 2014 17:02, Frank Heckenbach <f.heckenbach at fh-soft.de> wrote:

> Jun Yuan wrote:
>
> > The CoE mailbox communication between the master and slave is like the
> > following:
> > 1) the master sends a request datagram to the slave, and receives the
> > acknowledge from the slave;
> > 2) the master sends a mailbox check datagram to the slave, asking if the
> > slave has a reply mail prepared for him;
> > 3) If the slave says no, go to 2) send another check datagram; otherwise,
> > go to 4);
> > 4) the master sends a fetch-response datagram to fetch the reply mail
> from
> > the slave.
> >
> > The problem I discovered with the etherlabmaster is, when the bus
> topology
> > changes and a bus rescan is required, the state machine of the CoE
> mailbox
> > communication will be interrupted/stopped and later be reset to START
> > state. And this causes the problem.
>
> I had similar issues and I fixed them. I now sent my patches (a bit
> late, sorry) to etherlab-dev. I hope they'll help with your problems
> as well. (However, my patches are against 1.5.0, so if you need
> 1.5.1 or 1.5.2 you may need to port them or wait for someone else to
> do it.)
>
> > Take an example, the master sends a request A to the slave, and the slave
> > acknowledges, and prepares the reply A, which takes a while. At that time
> > we attach a new slave to the bus, the bus topology changes, which stops
> the
> > CoE mailbox communication. No the master scans the bus, and begins to use
> > CoE mailbox to fetch the SDO 1C12:00 for SM2 of the slave. He sends the
> > request, then checks the mailbox and find a reply mail. He fetches the
> mail
> > from the slave, opens it and it's the reply A, not the reply for the SDO
> > 1C12:00 which he's waiting for.
>
> Looks like the issue from my patch #26.
>
> > Is there any command in the EtherCAT standard for the master to ask the
> > slaves to clear their mailbox? Why doesn't the mail have any id, so the
> > master can tell which reply is for which request? Is simultaneous
> multiple
> > request allowed?
> >
> > What should the master do when he receives a wrong reply from the slave?
> > How can it tell whether it is a wrong reply or a outdated reply for the
> > last request?
>
> These more general questions are the focus of my bigger patches
> (in particular #09-#15 and #27). Those should also fix (hopefully)
> the issues you mentioned in another mail ("BUG in the mailbox
> handling").
>
> > Without answering the questions above, I find the following possible
> > solutions:
> > 1) Before send the request datagram, send a check datagram at first to
> see
> > if there is any outdated response there, and clean it if it exists. But
> > what if the slave finishes the old response after the check datagram?
>
> What I do in #26 is to just fetch the mailbox and ignore the result
> (success or error).
>
> > 2) If the master receives a wrong reply, instead of giving up and
> returning
> > an error, he keeps checking until timeout. That's what I did in my patch,
> > but is there any side effects?
>
> I haven't looked at your patch, but if the reply is meant for some
> other part of the code and you just throw it away, there will be
> side effects. ;) Therefore I use internal buffers to dispatch the
> replies, see my patches.
>
> Regards,
> Frank
>
> --
> Dipl.-Math. Frank Heckenbach <f.heckenbach at fh-soft.de>
> Stubenlohstr. 6, 91052 Erlangen, Germany, +49-9131-21359
> Systems Programming, Software Development, IT Consulting
> _______________________________________________
> etherlab-users mailing list
> etherlab-users at etherlab.org
> http://lists.etherlab.org/mailman/listinfo/etherlab-users
>



-- 
Jun Yuan
[Aussprache: Djün Üän]

Robotics Technology Leaders GmbH
Am Loferfeld 58, D-81249 München
Tel: +49 89 189 0465 24
Fax: +49 89 189 0465 11
mailto: j.yuan at rtleaders.com

Umlautregel in der chinesischen Lautschrift Pinyin: Nach den Anlauten y, j,
q, und x wird u als ü ausgesprochen, z.B. yu => ü,  ju => dschü,  qu =>
tschü,  xu => schü.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.etherlab.org/pipermail/etherlab-users/attachments/20140605/22eb9d21/attachment-0003.htm>